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Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.
Auxins are of two types :
(1) Natural auxins : These are naturally occuring auxins, isolated from plants and are regarded as phytohormones e.g. IAA. NAA etc.
(2) Synthetic auxins : These are synthesized by artificially e.g. IBA 2,4-D etc.
How can we quantitatively compare the growth of living system?
Quantitative comparisons between the growth of living system can be done in two ways :
(i) By measuring and comparing the total
growth per unit time that is the absolute growth rate.
(ii) By comparing the growth of the given system per unit time expressed on a common basis that is the the relative growth rate.
The ability to follow different pathways in response to environment or phases of life to form different kinds of structure is called plasticity. For example heterophylly in coriander.
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Photoperiodism is the response of plants to periods of day/night. the flowering of the plants depends not only on the combination of light and dark exposures but also on their relative duration.
Dormancy is a period when growth, development, and activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy and survive the unfavourable condition.
(2) Inhibition of abscission of leaves and fruits.
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Writes notes on following :
(a) Senescence (b) Abscission
(c) Quiescence (d) Vivipary.
(a) Senescence : Senescence is the process of ageing in plants. It is the period between maturity and death.
(b) Abscission: It is the natural falling of leaves, foliage branches, fruits, floral parts etc.
(c) Quiescence : It is the suspension of growth due to external factors. It is a period during which development is suspended.
(d) Vivipary : It is the process when seeds germinate inside fruits which are still attached to the mother plant.
Vernalization ; It is the treatment of low temperature for reducing vegetative phase and hastening the reproductive phase. It was first discovered by Lysenko.
Vernalisation refers specially to the promotion of flowering by a period of low temperature. For example - Subjecting the growing of a biennial plant to a cold treatment stimulates a subsequent photoperiodic flowering response.
Significance of vernalization :
1. The reproductive phase can be quickened.
2. The yield is increased.
3. The plants become more resistant towards diseases.
4. It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.
Seed germination : It is the process by which the seed resumes its metabolic activities and grows under favourable conditions.
The following steps are involved in seed germination :
1. Imbibition of water : The seeds imbibe or uptake water and swell. Imbibition takes place against great compressive forces. Due to the imbibition pressure seed coats ruptures.
3. Resumption of metabolic activities : As the protoplast is rehydrated, the metabolic activties resume. The respiration is in the beginning anerobic which later becomes aerobic When the anerobic respiration reaches peak then mitoehondria differentrates in the embryo cell.
4. Mobilisation of reserve food : Activated embryo has long lived RNAs. They induce the production of hormones which synthesise hydrolytic enzymes like amylases, proteases, lipases. The enzymes move into the storage cells and digest the nutrients which are translocated to the tips of embryo axis.
6. Growth of the embryo : On receiving the food the embryo cells metabolise actively. DNA replicates and transcribe RNAs. The cells divide. The radical end enlarges, ruptures the seed coat and passes downward to form primary root which later on forms the root system.The plmule elongates to form the stem, new leaves are formed and cotyledons fall.
Seed germination
What structural changes do the cells undergo during differentiation as tracheary elements?
The cells undergo the following structural changes during the process of differentiation as tracheary elements.
i. The cells lose their protoplasm to form tracheary elements.
ii. They also develop a very strong, elastic,
lignocellulosic secondary cell walls, to carry water to long distances even under extreme tension.
Growth is most important phenomenon because of following reasons :
1. Due to growth, size of the organism, increases.
2. The growth results in increase in weight, mass and size of the organism.
3. Growth allows the cells to be differentiated. e.g. In roots, the cells first elongate in the zone of elongation and then in the zone of differentiation they are differentiated into tissues and organs.
4. It is due to growth that radical forms root and plumule forms the stem during germination of the seeds.
5. It is due to growth that buds sprout to form the branches.
8. It is due to the growth that floral buds sprout to form flowers.
9. It is due to the growth of pollen grains and functional megaspore cells that male and female gametophytes are formed respectively.
10. It is due to the growth that pollen tubes grow and siphonogamy occurs.
11. The fruits are formed due to the growth of the ovary.
1. They bring growth.
2. They stimulate cell division.
3. They bring opening of stomata.
4. They check abscission of leaves except ethylene.
5. They break seed dormancy.
6. They induce formation of fruits and flowers in all types of plants.
7. Gibberellins overcome vernalization.
Inhibitor hormones :
1. They retard growth.
2. They inhibit cell division.
3. They bring closing of stomata.
4. They bring abscission of leaves.
5. They induce seed dormancy.
6. They generally do not induce fruit and flower formation.
7. They have no impact.
Quantitative comparisons between the growth of living system can be made in two ways :
(i) By measuring and comparing the total growth per unit time. This is called the absolute growth rate.
(ii) The growth of the given system per unit time expressed on a common basis, e.g., per unit initial parameter. This is called the relative growth rate.
Types of plants depending upon photoperiodism :
1. Short day plants : These plants produce flowers in winter. They are also called long night plants e.g. Chrysanthemum, tabacco etc.
2. Long day plants : These plants produce flowers in summer, when the days are long and duration of light is above critical point e.g. Melon, Momordica, Water-melon, Lady's finger plant etc.
3. Short long day plants : These plants need short photoperiod for initiation and long photoperiod for blossoming of flowers e.g. Rye, Campanula etc.
4. Long short day plants : These plants need long photoperiod for initiation and short photoperiod for opening of floral buds. They give flowers between summer and winter e.g. Cestrum, Bryophyllum etc.
5. Intermediate plants : These plants need definite photoperiod for flowering e.g. wild kidney bean.
6. Day neutral plants : These plants produce flowers in both winter and summer seasons. They do not need any specific photoperiod e.g. Sunflower Tomato etc.
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1. These are plants which require less exposure to light for a period less than the critical duration.
2. If night is interrupted by light then there is no flowering.
3. These need light of short wave lengths whose value is below critical point.
4. These produce flowering in winter.
7. If days are interrupted by darkness then no effect.
Long day plants :
1. These are plants which require the exposure to light for a period exceeding a well defined critical duration.
2. If night is interrupted by light then no such effect on flowering.
3. These need light whose value is above critical point.
5. These produce flowers in summer.
6. If days are interrupted by darkness then no flowers.
Positive role of ethylene are as follows:
1. Breaking of dormancy : It breaks dormancy of storage organs.
3. Root initiation : In low concentration ethylene helps in root initiation, growth of lateral roots and root hairs.
4. Fruit ripening : It aids in ripening of fruits. C Ethylene is used to induce artificial ripening of these fruits e.g. Citrus, Apple, Mango, Banana etc.
5. Flowering : It stimulates flowering in pineapple and related plants though in other cases the gaseous hormone causes fading of flowers.
Negative role of Ethylene :
1. Growth : It inhibits longitudinal growth and stimulates transverse growth.
2. Senescence : It hastens the senescence of leaves and flowers.
3. Abscission : Abscission of various parts is stimulated by ethylene which induces the formation of hydrolases.
4. Apical dominance : Ethylene promotes apical domiance and prolongs dormancy of lateral buds.
Explain different phases of growth.
Plant growth has following three phases
(i) Meristematic Phase - This phase is characterised by constantly dividing cells. The cells are rich in protoplasm, possess large conspicuous nuclei. Their cell walls are primary in nature, thin and cellulosic with abundant plasmodesmatal connections.
(ii) Elongation Phase - The cells of this phase elongate. Increased vacuolation, cell enlargement and new cell wall deposition are the characteristics of the cells in this phase.
(iii) Maturation Phase - The cells in this phase stop dividing and undergo differentiation and maturation.The cells of this zone, attain their maximal size in terms of wall thickening and protoplasmic modifications.
Synthetic auxins are used to get rid of dicot, such as Dandlions and thistles in areas reserved for monocots such as grain fields. A dicot responds to unnaturally high concentrations of auxins by growing rapidly and then die; whereas monocot, remains unaffected by the treatment.
Apparatus : Few pea seeds, raw sand, marking pencil, blotting paper, petridish, scale, etc.
Procedure :
1. A few pea seeds are taken and placed on moist sand for 24-28 hours. The radicles are seen to come out of the seeds after some time.
2. The seedling with a radicle measuring more than 3cm in leghth is chosen.
3. The radicle is divided and marked into 15 equal parts from the tip to top.
4. The seedling is placed on a moist blotting paper and kept in a petridish undisturbed for 3-4 days.
The figure shows.
A. Youngroot marked into 1 mm zones.
B. The same after 24 hours.
Observation : After 3-4 days it is observed that the size of the radicle increases. The distance between the marks near the tip remains almost the same. But in the middle, distance between the marks increased and at the upper end again the distance remained the same.
Result : The distance between marks in upper and lower regions remains the same. Thus, no growth has taken place. But the middle part where the growth has taken place is called phase of elongation.
Growth curve is the graphical representation of growth against time, thus it is also called sigmoid curve.
A typical S-shaped grand period of growth curve
It has three phases :
(1) Lag phase: It is in the beginning of the growth and represents the time in which minimum growth occurs. The growth is very slow in this phase.
(2) Log/Exponential phase : It represents the phase of maximum growth. If log phase persists for longer time then growth is linear. Both the progeny cells following mitotic cell division retain the ability to divide and continue to do so.
(3) Stationary phase : It is the phase in which no growth occurs. The limited nutrient supply, the growth slows down leading to a stationary phase.
Plant growth regulators are small, simple molecules having different compositions. Chemically they may be indole compounds (indole-3-acetic acid, IAA), adenine derivatives like N6- furfrylamino purine, kinetin), derivative of carotenoids (abscisssic acid, ABA), terpenes (giberellic acid, GA3) , gases (ethylene, C2H4).
They can be divided into two main groups on the basis of the function they perform.
i. One group is involved in growth promoting activities like cell division, cell enlargement, pattern formation, tropic growth, flowering, fruiting and seed formation etc. For example Auxin, cytokinin, gibberelins etc.
ii. Hormones in the other group play an important role in plant responses to wounds and stresses of biotic and abiotic origin. They are also involved in various growth inhibiting activities such as dormancy and abscission. For example abscissic acid and ethylene.
The conditions necessary for growth are
i. Water - Water is required for the enlargement of the cells and various metabolic processes. Water also provides the medium for the enzymatic reactions necessary for the growth. Water imparts turgidity which helps in extension growth of the cells.
ii. Oxygen - Oxygen helps in releasing the metabolic energy that is needed for growth activities. It is needed for the respiration of the cells.
iii. Nutrients - are required by plants for the synthesis of protoplasm and act as source of energy.
iv Temperature - Optimum temperature is required the growth
v. Environmental signals - Light and gravity also affect certain phases/stages of growth
Yes growth is measureable.
Parameters for growth :
Growth is measured by a variety of parameters some of which are increase in fresh weight, dry weight, length, area, volume cell and growth in number of cells. For example
Growth by increase in the number of the cells : Maize root apical meristem can give rise to more than 17, 500 new cells per hour.
Growth in size : Cells of watermelon may increase in size by upto 3,50,000 times.
Growth in length : Growth of pollen tube is measured in terms of its length.
Growth in surface area : An increase in surface area denotes the growth in a dorsiventral leaf.
Auxins and cytokinins together cause cell division in callus tissue culture. More auxin and less cytokinin causes root initiation whereas less auxin and more cytokinin cause bud differentiation. This is an example of synergetic action.
Abscisic acid is known as the stress hormone because of the following reasons :
1. It helps plant to cope with adverse environmental conditions or stresses.
2. It causes temporary closure of stomata due to which there is reduction in the rate of transpiration. Therefore, it acts as antitranspirant and reduces water loss.
3. It acts as a general growth inhibtor and inhibitor of plant metabolism
4. It inhibits seed germination.
5. It induces dormancy to escape the unfavourable conditions.
The main five groups of plant growth regulators (PGRs) are :
1. Auxins
2. Cytokinins
3. Gibberellins
4. Ethylene
5. Abscisic acid.
Auxin -
Physiological functions of auxins are:
1. They help to initiate and enhance rootings in the stem cuttings.
2. They promote flowering in certain plants like pineapple.
3. They prevent the leaf and fruit drop at early stages. They promote abscission of older or mature leaf and fruit.
4. They induce apical dominance.
5. They are responsible for tropic movements.
Horticultural/Agricultural importance:
1. They induce parthenocarpy in plants like tomatoes..
2. They are used as weedicides that kill dicotyledenous weeds.
Growth : Growth may be defined as permanent or irreversible change in the size of a cell, organ or whole organism usually accompanied by an increase in dry weight.
Differentiation : Differentiation is the process whereby cells undergo few to major structural changes that lead to the maturation. The cells mature to perform specialized functions.
Development: Development includes all the series of changes which an organism goes through during its life cycle.
Dedifferentiation : It is the process by which the living differentiated cells which had lost the capacity to divide regain the capacity to divide under certain conditions.
Redifferentiation : Redifferentiation is defined as maturation or differentiation of dedifferentiated tissues.
Determination growth . The ability of a cell, tissue or the organism to grow for a limited period is called determinate growth.
Meristem : Meristem is a group of cells which have power of division and add new cells to the body.
Growth rate : It is the increased growth per unit time.
The flowering in plants is in response to duration period of light or relative length of light. The long day plants need a longer duration of light whereas the short day plants need short duration of light.
If the long day plant and the short day plants gets the required duration of the light necessary for their flowering they may produce flower simultaneosly in a given plave. If the long day plants is planted before the short day one such that the long day plants gets a longer duration of light , both the short day plant and a long day plant can produce flower simultaneously in a given place
Which one of the plant growth regulators would you use if you are asked to :
(a) Induce rooting in a twig
(b) quickly ripen a fruit
(c) delay leaf senescence
(d) induce growth in axilliary buds
(e) ‘bolt’ a rosestte plant.
(f) induce immediate stomatal closure in leaves.
(a) GA3 is applied to rice seedlings.
(b) Dividing cells stop differentiating.
(c) A rotten fruit gets mixed with urripe fruits.
(d) You forget to add cytokinin to the culture medium
(a) The elongation of stem will occur at fast rate.
(b) An undifferentiated mass of cells is formed.
(c) The unripe fruits will ripen quickly.
(d) There will be no differentiation of shoot buds.
(A) Photoperiodism . It is the response of plants to periods of day/night. The flowering in some plants depends not only on a combination of light and dark exposures but also their relative durations. The plants that need a longer duration for a period exceeding a well defined critical duration, while the short day plants must be exposed to light for a period less than this critical duration before the flowering is initiated in them.
Significance : Photoperiodism helps in studying the response of flowering in various crop plants with respect to the duration of exposure to light. It is the phenomenon which helps in flowering out of season.
(B) Vernalization : Vernalisation refers specially to the promotion of flowering by a
period of low temperature. It is the treatment of cold (3-15°C) to arrest vegetative growth and initiate flowering.
Significance of vernalization :
1. It shortens the vegetative phase.
2. It makes the plant resistant to cold and fungal pathogens.
3. It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.
Example : Elongation of root at a constant rate. When a graph is drawn of length against time ; linear curve is obtained.
Mathematically its expression is given below :
Lt = L0+rt
Here, Lt is length at time ‘t’, L0 is length at time 0 and r is the rate per unit time.
(b) Geometric growth : In this type of growth the initial growth is slow and is called the lag phase. After this, the growth is quite rapid and at an exponential rate. This phase is called the log or exponential phase. In this phase, both the daughter cells (formed after mitosis) continue to divide. The last phase marks a slowed down growth. This happens because of limited nutrient supply. This phase is called the stationary phase. The graph of the geometric growth gives a sigmoid curve.
The exponential growth can be mathematically represented as follows:
W1 = W0ert
Here, W1 = final size (weight, height, number etc.), W0 = initial size at the beginning of the period, r = growth rate, t = time of growth and e = base of natural logarithms
(c) Sigmoid growth curve : The S-shaped curve on graph; to show geometric growth is called the sigmoid growth curve. It is S shaped curve which is characteristic feature of living organism in natural environment. It consists of lag phase, log phase or exponential phase and stationary phase.
(d) Absolute and relative growth rates
Absolute growth rate : It is the measurement and comparison of total growth per unit time. When growth is measured in absolute terms, e.g. in terms of length or weight, it is called absolute growth.
Relative growth rate : It is the growth of given system per unit time expressed on common basis eg per unit initial parameter is relative growth rate. When growth is measure in terms of comparative terms; like percentage growth; it is called relative growth.
Open growth : It is a type of growth where in new cells are always being added to the plant body by the activity of the meristem.
Growth is considered to be open. Plant growth is unique because plants retain the capacity for unlimited growth throughout their life. The meristems present in different locations have the capacity to divide and self-perpetuate. The daughter cells may lose the capacity to divide and such cells make up the plant body. ns in which they are formed.
Diagrammatic representation of locations of root apical meristem, shoot apical meristem and vascular cambium. Arrows exhibit the direction of growth of cells and organ
Differentiation in plants is open, because cells/tissues arising out of the same meristem have different structures at maturity. The location also decides the final
structure of a cell/tissue at maturity. For example, cells positioned away from root apical
meristems differentiate as root-cap cells, while those pushed to the periphery mature as epidermis.
During seed germination its stored food is mobilised by
ethylene
cytokinin
ABA
gibberellin
D.
gibberellin
Gibberellin induces aleurone cells to secrete an enzyme to break stored food in the seed. Cytokinines promote nutrient mobilisation, which helps in the delay of leaf senescence.
ABA plays an important role in seed development, maturation and dormancy. Ethylene induces fruit ripening, breaks seed dormancy.
Match the following and select the correct answer.
|
Column I |
Column II |
||
|
A. |
Centriole |
1. |
Infolding in mitochondria |
|
B. |
Chlorophyll |
2. |
Thylakoids |
|
C. |
Cristae |
3. |
Nucleic acid |
|
D. |
Ribozymes |
4. |
Basal body cilia of flagella |
|
A |
B |
C |
D |
|
4 |
3 |
1 |
2 |
|
A |
B |
C |
D |
|
1 |
2 |
4 |
3 |
|
A |
B |
C |
D |
|
1 |
3 |
2 |
4 |
|
A |
B |
C |
D |
|
4 |
3 |
1 |
2 |
A.
|
A |
B |
C |
D |
|
4 |
3 |
1 |
2 |
a) Centriole: In an organism with flagella and cilia, the position of these organelles is determined by the mother centriole which becomes the basal body.
b) Chlorophyll: Chlorophyll molecules are specially arranged in and around photosystem that is embedded in the thylakoid membrane of the chloroplast.
c) Cristae: These are folded in the inner membrane of mitochondria, which provides a large amount of surface area for chemical reaction.
d) Ribozymes (Ribonucleic acid enzymes) is an RNA molecule that is capable of catalysing the specific biochemical reaction of nucleic acids.
A few normal seedlings of tomato were kept in a dark room. After a few days they were found to have become white - coloured like albinos. Which of the following terms will you use to describe them?
Mutated
Embolised
Etiolated
Defoliated
C.
Etiolated
Etiolation is a process in which flowering plants are grown in the parital or complete absence of light. Etiolation is mainly characterised by long and weak steam and smaller, sparse pale yellow colour (chlorosis) leaves due to longer internodes.
Which one of the following growth regulators is known as stress hormone?
abscsic acid
Ethylene
GA3
Indole acetic acid
A.
abscsic acid
Abscisic Acid (ABA) is also known as stress hormone or dormin because it is produced in much higher amounts, when plants are subjected to various kinds of stresses. It often gives plants organs a signal that they are undergoing physiological stresses such as lack of water, saline soil, cold temperature and frost. ABA often cause responses that help plants and protect against these stresses.
Auxin can be bioassayed by
Avena coleoptile curvature
Hydroponics
Potometer
Lettuce hypocotyl elongation
A.
Avena coleoptile curvature
Auxin is a phytohormone that is often bioassayed by Avena coleoptile curvature test. The angle of curvature of a decapitated oat coleoptile is measured after placing an agar block containing auxin on one side. The ability of auxin to stimulate shoot growth is then measured.
Through their effect on plant growth regulators, what do the temperature and light control in the plants?
Apical dominance
Flowering
Closure of stomata
Fruit elongation
B.
Flowering
There are three factors which govern the flowering in angiosperms. These factors are completion of juvenile phase and attaintment of mature or adult phase, suitable light and proper temperature.
Which one of the following generally acts as an antagonist to gibberellins?
Zeatin
Ethylene
ABA
IAA
C.
ABA
Abscisic acid (ABA) is also called stress hormone. It is a mildly acidic growth hormone which functions as a general growth inhibitor by counteracting other hormones (auxin, gibberellin, cytokinin) or reactions mediated by them. It causes stomatal closure, abscission of flower and fruits while gibberellin helps in opening of stomata and promote development of fruits.
Vernalisation stimulates flowering in
Zamikand
Turmeric
Carrot
Ginger
C.
Carrot
Vernalization is a process of shortening of juvenile or vegetative phase and hastening flowering by a previous cold treatment. Example - henbane, carrot, cabbage.
What causes a green plant exposed to the light on only one side, to bend toward the source of light as it grows?
Green plants need light to perform photosynthesis.
Green plants seek light because they are phototropic
Light stimulates plant cells on the lighted side to grow faster
Auxin accumulates on the shaded side, stimulating greater cell elongation there
D.
Auxin accumulates on the shaded side, stimulating greater cell elongation there
When a green plant exposed to light (phototropism) on one side, which make it bend towards the source of light is due to the effect of auxins. Auxin accumulates on the shaded side due to which it stimulates cell elongation and enlargement. Its movement is polar and passes from shoot tip to region of elongation. It helps in elongation of both roots and shoots. Auxin(indole 3-acetic acid) also produces tropical responses like phototropism and geotropism.
Typical growth curve in plants is
sigmoid
linear
Stair-steps shaped
parabolic
A.
sigmoid
Sigmoid curve shows the growth in plants. It contains three phases
(i) Lag phase(initial phase)
(ii) Log phase(initial phase)
(iii) Steady phase (stationary phase).
Typical growth curve in plants is
sigmoid
linear
stair-steps shaped
parabolic
A.
sigmoid
Sigmoid curve shows the growth in plants. It contains three phases:
(i) Lag phase (initial phase)
(ii) Log phase (exponential phase)
(iii) Steady phase (stationary phase)
A drupe develop in
Wheat
pea
tomato
Mango
D.
Mango
In mango, coconut, plum, etc., the fruit is known as drupe (stony fruit).They develop from monocarpellary, superior ovaries and are one seeded. In mango, the pericarp is well differentiated into an outer thin epicarp, a middle fleshy edible mesocarp and an inner stony hard endocarp.
Phototropic curvature is the result of uneven distribution of
gibberellin
phytochrome
cytokinins
auxin
D.
auxin
Darwin and his son Francis used germinating oat (Avena sativa) and canary grass (phalaris canaries) seeding in their experiments and hypothesised that when shoots were illuminated from one side, they bent forward the light in response to an influence, that was the tip of the shoot. Paal concluded that the tip secretes a substance, which promotes the growth of part below it. In 1926, Frits Went discovered that some unidentified compound probably caused curvature of oat coleoptile towards the light, i.e, phototropism. The compound (auxin) found by Went is relatively abundant in coleoptile tips.
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The technical term used for the androecium in a flower of China rose (Hibiscus rosa siensis( is
monadelphous
diadelphous
polyandrous
polyadelphous
A.
monadelphous
In Monadelphous condition, all filaments become fused and form a group, while other remain free, eg, China rose Achyranthes, etc. In diadelphous, more than two separate bundles of filaments are formed, eg, Ricinus.
One of the commonly used plant growth hormone in tea plantations is
ethylene
abscisic acid
Zeatin
indole-3- acetic acid
D.
indole-3- acetic acid
Tea plants are grown by stem cuttings. If we dip the lower cut end of a cutting in a dilute solution of auxins (IAA, IBA etc) , large number large number of roots are developed on the cut ends, due to which these cutting develop into successful plants.
Root development is promoted by
abscisic acid
auxin
gibberellin
ethylene
B.
auxin
The higher concentration of auxin causes inhibition of root elongation, but the number of lateral branches in the root is considerably increased. In plant tissue cultures, relatively amounts of auxin and cytokinin induce the development of root, shoot or undifferentiated mass of tissues. High auxin to cytokinin ratio favours the root development high cytokinin to auxin ratio favours shoot development, while intermediate concentration results in the formation of undifferentiated cell mass.
Stroma in the chloroplasts of higher plants contains
light -independent reaction enzymes
Light -dependent reaction enzymes
ribosomes
chlorophyll
A.
light -independent reaction enzymes
In higher plants, enzymes for light-independent reactions (dark reactions) are present in the stroma of chloroplasts.
The light-dependent reaction occurs in grana of the chloroplast.
Ribosomes are necessary for protein synthesis.
Chlorophyll is green photosynthetic pigment found in chloroplasts.
One of the synthetic auxins is
NAA
IAA
GA
IBA
A.
NAA
The term auxin is applied to the indole -3-acetic acid (IAA) and to other natural and synthetic compounds having certain growth regulating properties.
NAA (Naphthalene Acetic Acid) and 2-4-D (2-4 dichlorophenoxy acetic acid) are synthetic auxins.
IAA and IBA (Indole Butyric acid) have been isolated from plants. All these auxins have been used extensively in agricultural and horticultural practices.
In which one of the following, the male and female gametophytes don't have free -living independent existence ?
Pteris
Funaria
Polytrichum
Cedrus
A.
Pteris
In Pteris (also Dryopteris) the spore germinates to produce the prothallus. The prothallus is small, green, flat, surface loving, thallus - like object. It is monoecious and bears sex organs on the ventral side. The antheridia (male sex organs) arise among the rhizoids towards the posterior side of the prothallus and are emergent. The archegonia develop in central cushion behind the apical notch. In these plants, male and female gametophytes do not have free living independent existence.
All species of polytrichum are dioecious. The antheridia and archegonia are borne on different gametophore. The plant body is an erect leafy shoot but is not the entire gametophyte. The leafy shoot arises from protonema (the juvenile stage).
The leafy gametophore of Funaria reproduces sexually by the formation of antheridia and archegonia. The antheridia are formed at the summit of relatively small, thin leafy shoot which develops first. The female branch arises later as a lateral outgrowth from the base of parent male shoot.
Senescence as an active development cellular process in the growth and functioning of a flowering plant is indicated in
vessel and tracheid differentiation
leaf abscission
annual plants
floral parts
B.
leaf abscission
Senescence can be defined as ' the sum of deteriorative processes, which naturally terminate the functional life of an organism'. Senescence is not confined only to the whole plant, it may be limited to a particular plant organ such as leaf and flower or cells such as phloem and xylem. Abscission is the natural shedding of leaves, foliage branches, fruits, floral parts etc. According to Leopold (1967) abscission is a Senescence phenomenon. Senescence as an active development cellular process in growth and functioning of a flowering plant is indicted in leaf abscission.
Whole plant senescence also known as overall senescence occur in annulas (eg, rice, wheat, gramme, mustard) biennials (eg, henbane or perennials.)
The length of different internodes in a culm of sugarcane is variable because of
shoot apical meristem
position of axillary buds
size of leaf lamina at the node below each internode
intercalary meristem
D.
intercalary meristem
Intercalary meristem is prsent away from apical meristem in primary permanent tissue. It is present at the base of internodes, eg, in family-Gramineae or at the base of leaves, eg, Pinus or at the base of the node, eg, Mentha. Intercalary meristem is responsible for the increase in length.
The shoot apical meristem present at the apices of the shoot is self-determining and autonomous organising centre. The primary growth and differentiation of primary tissue are entirely due to this meristem as it continuously divides giving rise to new cells. These are the apical meristems that increase the length of the plant but not internodes variability.
In leaves of C4 -plants malic acid synthesis during CO2 -fixation occurs in
epidermal cells
mesophyll cells
bundle sheath
guard cells
B.
mesophyll cells
C4- plants show Kranz anatomy. In the leaves of C4- Plants the vascular bundles are surrounded by bundle sheath of parenchymatous cells, which in turn are surrounded by mesophyll cells. In C4 -plants and Hatch and Stack pathway involve two carboxylation reaction one taking place in the chloroplast of mesophyll cells and other in the chloroplast of bundle sheath cells.
In germinating seeds fatty acids are degraded exclusively in the
proplastid
glyoxisomes
peroxisomes
mitochondria
B.
glyoxisomes
Glyoxysomes are found to occur in the cells of yeast, Neurospora and oil-rich seeds of many higher plants. During germination of oily seeds, the stored lipid molecules of spherosomes are hydrolyzed by the enzyme lipase to glycerol and fatty acids. The long chain fatty acids are then broken down by successive removal of two carbon fragments in the process of beta -oxidation.
Peroxisomes are present in all photosynthetic cells of higher plants in etiolated leaf tissue. It is the site of hydrogen peroxide metabolism and glycolate cycle.
Mitochondria is the site of aerobic respiration in a eukaryotic cell. It is called powerhouse of the cell.
During the development of chloroplast, the first structure to appear is so called proplastid, which has a double membrane.
The wavelength of light absorbed by Pr form of phytochrome is
640 nm
680 nm
720 nm
620 nm
B.
680 nm
When Pr absorbs red light (660- 665 nm) it is converted into Pfr form and when Pfr absorbs far red light (730-735 nm) it is converted into Pr form
'Foolish seedling' disease of rice led to the discovery of
GA
ABA
2, 4-D
IAA
A.
GA
Gibberellins (GA) were first isolated from the fungus Gibberella fujikuroi the causal organism of foolish seedling disease of rice plants in Japan by kurasawa in 1926.
Which one of the following pairs, is not correctly matched?
Abscisic acid - Stomatal closure
Gibberellic acid - Leaf fall
Cytokinin - Cell division
IAA - Cell wall elongation
B.
Gibberellic acid - Leaf fall
Gibberellins help in cell growth of stem, leaves and other aerial parts.
Pineapple (ananas) fruit develops from
a unilocular polycarpellary flower
a multipistillate syncarpous flower
a cluster of compactly borne flowers on a common axis
a multilocular monocarpellary flower
C.
a cluster of compactly borne flowers on a common axis
The fruit of Ananas comosus (pineapple or ananas) is sorosis, (a type of multiple fruits), developing from spike, spadix or catkin. In this type, the flowers associate by their succulent tepals, the axis bearing them grows and becomes fleshy or woody, thus, the whole inflorescence turns into a compact fruit.
Fruit and leaf drop at early stages can be prevented by the application of
Cytokinins
Ethylene
Auxins
Gibberellic acid
C.
Auxins
Auxins prevent premature leaf and fruit fall.
NAA prevents fruit drop in tomato; 2,4-D prevents fruit
drop in Citrus
The Golgi complex participates in
Fatty acid breakdown
Formation of secretory vesicles
Activation of amino acid
Respiration in bacteria
B.
Formation of secretory vesicles
Golgi complex, after processing releases secretory vesicles from their trans-face. It is also the organelle that builds lysosomes (Cell digestion machines).
Pneumatophores occur in
Halophytes
Free-floating hydrophytes
Submerged hydrophytes
Carnivorous plants
A.
Halophytes
Plants having little or no secondary growth are
Grasses
Deciduous angiosperms
Cycads
Conifers
A.
Grasses
Grasses are monocots and monocots usually do not have secondary growth.
Sweet potato is a modified
Stem
Adventitious root
Rhizome
Tap root
B.
Adventitious root
Sweet potato is a modified adventitious root for storage of food.
Rhizomes are underground modified stem.
Tap root is primary root directly elongated from the redicle.
Which one of the following generally acts as an antagonist to gibberellins?
Zeatin
Ethylene
ABA
IAA
C.
ABA
Gibberellins and abscisic Acid (ABA) are antagonistic to each other. Gibberellins promote seed germination whereas ABA promotes seed dormancy.
Phellogen and phellem respectively denote
Cork and cork cambium
Cork cambium and cork
Secondary cortex and cork
Cork and secondary cortex
A.
Cork and cork cambium
In the dicot stem, the cortical cells get differentiated to give rise to another meristematic tissue, which is called cork cambium or phellogen. On the other side, it forms phellem (cork) and in the inner region, it forms secondary cortical cells (phelloderm).
Which one correctly describe reproduction and life cycle of fern?
Spore → Gamete → Prothallus → Sporophyte
Gamete → Spore → Prothallus → Plant
Prothallus → Sporophyte → Gamete → Fern
Sporangia → Spore → Prothallus → Sporophyte → Plant
C.
Prothallus → Sporophyte → Gamete → Fern
During favourable month sporangia are produced on the underside of the margin of leaves in ferns. After development, it becomes dry and bursts so release spores. These spores germinate on the suitable substrate. Each spore absorbs water, then ruptures and produce gree filament which grows into prothallus (heart-shaped) prothallus develops into young sporophyte which in turn grows into an adult plant.
Which of the following is not an auxin?
IM
IBA
Zeatin
NM
C.
Zeatin
Zeatin is a cytokinin. IAA or indole acetic acid is a natural auxin. IBA or indole butyric acid and NAA or naphthalene acetic acid are synthetic auxins.
Which of the following properties is shown by cytokinins?
Delay leaf senescence
Cause leaf abscission
Promote seed dormancy
Promote stornatal closing
B.
Cause leaf abscission
Cytokinin is a plant growth hormone, which is mostly synthesised in the roots. Cytokinin delays leaf senescence.
Genetic dwarfism can be overcome by
Gibberellin
Ethylene
Auxin
ABA
A.
Gibberellin
Genetic dwarfism is overcome by the usage of gibberellins. Ethylene is a gaseous hormone, which induces ripening in unripe fruits. ABA cause ageing and abscission of leaves.
Hormone inducing fruit ripening is
Cytokinin
Ethylene
Aabscissic acid
Gibberellic acid
B.
Ethylene
Ethylene is a natural gaseous hormone, which is predominantly known for inducing fruit ripening.
The year 1900 AD is highly significant for geneticists due to
Discovery of genes
Principle of linkage
Chromosome theory of heredity
Rediscovery of Mendelism
D.
Rediscovery of Mendelism
In the year 1900 Hugo de Vries, Karl Correns and Erich Tschermark independently rediscovered the research carried out by Mendel, his experiment on heredity and variations and laid the basis of modern genetics.
F1-generation means
First filial generation
First seed generation
First flowering generation
First fertile generation
A.
First filial generation
The 1st generation obtained from crossing two parents is called as a first filial generation or F1- generation.
Which of the following cross will produce terminal flower in garden pea?
AA x Aa
AA x aa
Aa x Aa
Aa x AA
C.
Aa x Aa
Axillary position (A) is dominant over terminal (a) position. When Aa x Aa is crossed we get 3:1 ratio of axillary and terminal flowers.
Which one of the following pairs of plants are not seed producers?
Funaria and Ficus
Fern and Funaria
Funada and Pinus
Ficus and Chlamydomonas
B.
Fern and Funaria
Seed producing plants belong to Spermatophyta. It includes gymnosperms and angiosperms. Seed originated in gymnosperms. Fern and Funaria belong to pteridophytes and bryophytes respectively. So, they do not reproduce by producing seeds.
Study the following statements and select the correct option.
I. Tapetum nourishes the developing pollen grains.
II. Hilum represents the junction between ovule and funicle.
III. In aquatic plants such as water hyacinth and water lily, pollination is by water.
IV. The primary endosperm nucleus is triploid.
I, II, and IV are correct, but III is incorrect
I and II are correct, but III and IV are incorrect
I and IV are correct, but II and III are incorrect
I, Ill and IV are correct, but I is incorrect
A.
I, II, and IV are correct, but III is incorrect
In a majority of water plants like water hyacinth and flowers, water lily emergy above the water level and are pollinated by insects.
Masses of pollen grains, i.e., pollinia is found in
Gramineae
Solanaceae
Orchidaceae
Malvaceae
C.
Orchidaceae
Pollinia is a coherent mass of pollen grains. They are the product of only one anther lobe but are transferred during pollination as a single unit.
Morphine, which is used as an analgesic is obtained from
Taxusbrevifolia
Berberisnilghiriensis
Cinchona officinalis
Pa paver somniferum
D.
Pa paver somniferum
Morphine is the principle opium alkaloid. It is a strong analgesic. Opium is dried latex of unripe capsular fruits of poppy plant, Papaver somniferum. It is eaten or smoked.
Darwin’s finches are an excellent example of
Adaptive Radiation
Seasonal migration
Brood parasitism
Connecting links
A.
Adaptive Radiation
Vascular tissues in flowering plants develop from
Phellogen
Plerome
Periblem
Dermatogen
B.
Plerome
C.
Periblem
Histogen theory for shoot apical meristem has been proposed by Hanstein (1870). It advocates that there are three distinct meristematic zones (layers) called dermatogen periblem and plerome.
The dermatogen is the outermost histogen giving rise to the epidermis, periblem is the middle on producing the cortex and plerome is the innermost resulting in central cylinder (i.e., vascular tissue).
Cork cambium (phellogen) is the secondary lateral meristem found in the outer cortical region. Its cells divide periclinally cutting off cells towards the outside (forming cork or phellem) and inside (forming secondary cortex or Phelloderm).
A mature pollen grain of Pinus has
2 cells
3 cells
4 cells
5 cells
C.
4 cells
In Pinus, the microspore nucleus divides by a periclinal wall and forms a very small prothallial cell and large central cell. The central cell cuts off a second prothallial cell and antheridial cell. The nucleus of the antheridial cell divides to form generative cell and tube cell. Thus, the pollen grain of Pinus is shed at four cell stage when it consists of two vegetative prothallial cells, a generative cell and a tube cell.
Green potatoes are toxic due to
Phytoalexins
Solanin
Triazine
Hormones
B.
Solanin
Solanin is a glycoalkaloid poison or natural nerve toxin produced in the green part of the potato. It is a bitter poisonous crystalline alkaloid, which helps the plant to defend against predators,insects, diseases, etc Ingestion of it may cause vomiting, diarrhoea, headache and even paralysis of central nervous system.
Which is a useful product of epidermal origin?
Saffron
Cotton Fibres
Clove
Jute
B.
Cotton Fibres
Cotton is obtained from the epidermal hair present on the surface of seeds of Gossypium sp. These are made up of cellulose only and may be of two types, i.e., extractable lint and non-extractable fluffy fuzz. Cotton fibres are mainly used for textiles, celluloid, cellophane, rayon and paper pulp.
A monocarpic plant is one, which
has only one carpel
Flowers once in a life-time
Produces only one seed
Produces only one fruit
B.
Flowers once in a life-time
On the basis of the frequency of flowering or fruiting in the lifetime, plants may be either monocarpic or polycarpic. Monocarpic plants are those, in which flowering and fruiting occur only once in their life, e.g., all annual and biennial plants and some perennial plants like bamboo and Agave. In contrast, polycarpic plants bear flowers and fruits repeatedly after attaining maturity, e.g., mango, Acacia, Eucalyptus, etc.
The rupture and fractionation do not usually occur in water column in vessel/tracheids during the ascent of sap because of
Lignified thick walls
Cohesion and adhesion
Weak gravitational pull
Transpiration pull
B.
Cohesion and adhesion
The vertical conduction of water from root to arial part of a plant is called ascent of sap. The water molecules remain joined to each other due to a force of attraction called cohesion force. The attraction between water molecules and the walls of xylem is due to adhesion forces. These forces help to ensure the continuity of the water column in xylem.
Viscum album grown on trees. This is an example of
Symbiosis
Parasitism
Commensalism
Predation
B.
Parasitism
Viscum album is a partial stem parasite that grows on poplar, apple, walnut, oats, etc. The parasite sends primary haustorium into the host for deriving food from them.
In some organisms, karyokinesis is not followed by cytokinesis as a result of which, the multinucleate condition arises leading to the formation of the syncytium. The perfect example of this is
The appearance of a furrow in the cell membrane
Liquid endosperm in coconut
Sexual reproduction
Fertilization
B.
Liquid endosperm in coconut
Coconut endosperm is unique because of its early liquid syntactical stages which form the hard matured kernel at later stages of fruit development.
Which one of the following pair is not correctly matched?
Almond-Drupe
Brinjal-Berry
Guava-Pepo
Loquat-Pome
C.
Guava-Pepo
Guava (Psidium guajava) fruit is a pseudoscopic berry. in which pericarp and placenta are edible.
Compare the statements I and II and choose the correct option.
Statement (I) Auxin promotes apical dominance by suppressing the activity of lateral buds.
Statement (II) In moriculture, periodic pruning of shoot tips is done to make mulberry plants bushy.
Choose the correct options
I is false, but II is true
II is false, but I is true
Both I and II are true
Both I and II are false
C.
Both I and II are true
Periodic pruning of lateral buds always makes a plant bushy.
The quiescent centre in root meristem serves as a
Site for storage of food, which is utilised during maturation
Reservoir of growth hormones
Reserve for replenishment of damaged cells of the meristem
Region for absorption of water
C.
Reserve for replenishment of damaged cells of the meristem
The quiescent centre is found in the centre of the root apex. Cells of this region have a lower content of RNA and smaller nuclei. This represents an inactive region of root apex (Clowers; 1958) and serves as a reserve for replenishment of damaged cells.
Which one of the following pairs, is not correctly matched?
Abscisic acid - Stomatal closure
Gibberellic acid - Leaf fall
Cytokinin - Cell division
IAA - Cell wall elongation
B.
Gibberellic acid - Leaf fall
Gibberellin helps in cell growth of stem, leaves and other aerial parts.
The bioassay of auxin is
avena curvature test
callus formation
culture of fungus
seed dormancy
A.
avena curvature test
Bioassay is the testing of biological activity of a substance by employing living material. Went used Avena sativa (oat) coleoptiles in a technique called Avena coleoptile curvature test.
ABA or abscisic acid induces dormancy in buds, seeds and underground storage organs. In callus culture, shoot and root regenration is generally controlled by auxin and cytokinin ratio.
Induction of flowering by low temperature treatment is
vernalization
cryobiology
photoperiodism
prunning
A.
vernalization
Vernalization is chilling or cold treatment of the young plants in order to induce flowering. It is a process for shortening the juvenile or vegetative phase of the plants in order to fasten the flowering process. Common examples includes winter rye, winter wheat, winter barley, pea etc.
Cryobiology is the study of life at low temperature, ie, at liquid nitrogen and preservation of organisms by chemical methods.
Photoperiodism is the effect of photoperiods or daily duration of light hours on the growth and development of flowering in plants.
The bioassay of auxin is
avena curvature test
callus formation
culture of fungus
seed dormancy
A.
avena curvature test
A bioassay is a measurement of the effect of a known or suspected biologically active substance on living material. Went used Avena sativa (oat) coleoptiles in a technique called that Avena coleoptile curvature test for auxin.
Which one of the following is a natural growth inhibitor?
NAA
ABA
IAA
GA
B.
ABA
ABA (Abscisic acid) is a naturally occuring growth inhibitor in plants.
Apical dominance is caused by
auxin
gibberellin
kinetin
ABA
A.
auxin
In most of the plants, as the apical bud grows, the growth of lower axillary buds is suppressed. Removal of apical bud results in the growth of lower buds. The auxin (IAA) of the terminal bud inhibits the growth of lateral buds. This phenomenon is known as apical dominance.
Which of the following is not caused by deficiency of mineral?
Chlorosis
Etiolation
Shortening of internodes
Necrosis
B.
Etiolation
Etiolation is a process in flowering plants when grown in partial or complete absence of light. Symptoms include- pale yellow or white colour due to lack of chlorophyll, long internodes, small and rudimentary leaves, poor development of lignified tissue.
Chlorosis is the yellowing of leaves due to lack of chlorophyll. It occurs due to lack of Manganese (Mn), Zinc (Zn) or Iron (Fe) deficiency.
Shortening of internodes ocuurs in rosette plants such as lettuce. It occurs due to deficinecy of Zinc (Zn).
Necrosis in plants is a disease in which tissues of the plants starts degenerating. It causes leaves, stem and other parts of the plants to darken and wilt. It is caused by the deficiency of Nitrogen (N), Potassium (K), Magnesium (Mg), Sulphur (S), Iron (Fe), Manganese (Mn), Zinc (Zn) and Molybdenum (Mo).
Which of the following plant is LDP?
Xanthium
Soybean
Wheat
Tobacco
C.
Wheat
Long Day Plants (LDP) require a photoperiod of more than a critical length, ie, 4 to 18 hours. The best flowering of long day plants usually occurs in continuous light. For flowering, they require either no dark period or a very short dark period. Example of long day plants are wheat, maize, oats, spinach etc.
In which one pair both the plants can be vegetatively propagated by leaf pieces?
Bryophyllum and Kalanchoe
Chrysanthemum and Agave
Agave and Kalanchoe
Asparagus and Bryophyllum
A.
Bryophyllum and Kalanchoe
Marginal notches in Kalanchoe and Bryophyllum possess adventitious buds in their leaves for vegetative propagation.
Gibberellin was first extracted from
Gibberella fujikuro
algae
bacteria
roots of higher plants
A.
Gibberella fujikuro
Yabuta and Hayashi (1939) isolated an active substance from a fungus, Gibberella fujikuroi and called it gibberellin-A. It causes backane disease in rice seedlings.
Auxin in plant means for
cell elongation
fruit ripening
cell division
inhibit the root growth
A.
cell elongation
Auxins induce cell elongation. IAA is true auxin hormone. Auxins are generally acidic in nature.
Ethylene is responsible for ripening of fruits.
Cytokinin is the hormone responsible for cell division as it stimulates the metabolism and the formation of flowers on side shoots.
Pencils are prepared from the wood of
Pinus vinaster
Juniperus virginiana
Chamaecyparis piscifera
Abies pindrow
B.
Juniperus virginiana
Juniperus virginiana wood is used for making pencils.
Pinus vinaster wood is used for carpentry items such as furniture, window frames, floors, roofing etc.
Chamaecyparis piscifera is used as a material for builiding palaces,temples, shrines and baths.
Abies pindrow is used for curing Respiratory ailments like Asthma.
Ageing is retarded by
ABA
CKN
GA
C2H4
B.
CKN
Cytokinins are a class of plant growth substances (phytohormones) that promote cell division or cytokinesis, in plant roots and shoots. They are also involved in cell growth and differentiation but also affect apical dominance, axillary bud growth and leaf senescence.
Eg, degradation of protein and chlorophyll was delayed in the detached leaves of Xanthium, if cytokinin was used in a medium.
Agricultural chemicals include
growth regulators
fertilizers
pesticides
all of these
D.
all of these
As growth regulators control the growth of plants, pesticides control the pests and fertilizers enhance productivity of the soil, hence all of these are regarded as agricultural chemicals.
The dormancy of seed is regulated by
ABA
Ethylene
GA- 3
Dihydrozeatin
A.
ABA
Dormancy is a mechanism to prevent germination during unsuitable ecological conditions, when the probability of seedling survival is low. It is mainly regulated by ABA (Absicsic acid).
Which of the following is a day neutral plant
Helianthus annuus
Euphorbia pulcherrima
Avena sativa
Beta vulgaris
A.
Helianthus annuus
Day neutral plants do not need a specific photoperiod to produce flowers. They are also called intermediates or photoneutrals. Their photoperiod varies from a few hours to 24 hours of uninterrupted light e.g. tomato, cucumber, sunflower, Helianthus annuus, maize and cotton etc.
Which of the following is an antigibberellin
Auxin
Ethylene
ABA
Cytokinin
C.
ABA
The ABA inhibits gibberellin induced growth activities on account of this antagonistic behaviour, it is also called antigibberellin.
Identify the incorrect statement about ABA growth regulator
It increases the tolerance of plants against different stresses.
It acts as general plant growth inhibitor and inhibitor of metabolism.
It helps in seed maturation and dormancy.
It promotes morphogenesis and differentiation of shoots.
D.
It promotes morphogenesis and differentiation of shoots.
Abscisic acid (ABA) is a growth inhibitor. Both auxins and cytokinins are essential for morphogenesis or differentiation of tissues and organs. Auxins stimulate root formation however when cytokinins are in excess stem buds develop.
2,4- D is an effective
fungicide
weedicide
rodenticide
wormicide
B.
weedicide
2, 4-D is a selective weed killer. It kills broad-leaved plants (dicots) but do not affect mature monocot plants.
Assertion: Secondary metabolites are produced in small quantities and their extraction from the plant is difficult and expensive.
Reason: Secondary metabolites can be commercially produced by using tissue culture technique.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
B.
If both assertion and reason are true but reason is not the correct explanation of assertion.
Secondary metabolites are biosynthetically derived from primary metabolites but more limited in distribution in plant kingdom, being restricted to a particular taxonomic group. Secondary metabolites are accumulated by plants in smaller quantities as compared to primary metabolites. Also, they are synthesised in specialised cell types at distinct developmental stages, making their extraction and purification difficult and expensive. By the culture media using tissue culture techniques, secondary metabolites can be produced on a large scale
Assertion: Yeasts are unicellular fungi that are used in bakery and brewery industries.
Reason: Potato spindle tuber disease is caused by viroids
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
B.
If both assertion and reason are true but reason is not the correct explanation of assertion.
Saccharomyces cerevisiae (commonly known as baker's yeast) is a single-celled eukaryote that is frequently used in scientific research. The Potato spindle tuber viroid was the first viroid to be identified. PSTVd is a small, circular RNA molecule closely related to the chrysanthemum stunt viroid.
One hormone hastens maturity period in juvenile conifers, a second hormone controls xylem differentiation, while the third hormone increases the tolerance of plants to various stresses. They are respectively
Gibberellin, Auxin, Ethylene
Auxin, Gibberellin, Cytokinin
Gibberellin, Auxin, ABA
Auxin, Gibberellin, ABA
C.
Gibberellin, Auxin, ABA
Spraying juvenile conifers with gibberellins hastens their maturity period, thus leading to early seed production. Auxin controls xylem differentiation. Abscisic acid (ABA) increases the tolerance ofplants to various kinds ofstresses therefore, is also known as stress hormone.
Gibberellins can promote seed germination because of their influence on
rate of cell division
production of hydrolysing enzymes
synthesis of abscisic acid
absorption of water through hard seed coat.
B.
production of hydrolysing enzymes
Gibberellins induce the production of hydrolysing enzymes in the endosperm of germinating seeds. It stimulates the production of digestive enzymes like proteases, amylase and lipase which help to mobilise stored nutrients.
Assertion: Plant growth regulators (PGRs) are very important for plant growth and development.
Reason: Auxins do not induce flowering in gymnosperms
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
B.
If both assertion and reason are true but reason is not the correct explanation of assertion.
Plant growth regulators (PGRs) are small, simple molecules of diverse chemical composition, which in low concentration regulate growth, differentiation and development by promoting or inhibiting the same. One type of plant growth regulators are plant hormones or phytohormones. Auxins are the phytohormones. They do not induce flowering in gymnosperms.
Assertion: A correct concentration of auxin and cytokinin is required for the development of root and shoot in a callus.
Reason: When the ratio of kinetin to auxin is high, then only shoots develop. But when the ratio is low then only roots develop.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
A.
If both assertion and reason are true and reason is the correct explanation of assertion.
The ratio of cytokinin (kinetin) to auxin (IAA) is important in determining the nature of organogenesis in tissue culture. High level of kinetin results in bud initiation, while high concentration of auxin favours rooting.
Assertion: No secondary growth takes place in monocots.
Reason: Secondary growth is not related with cambium.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
C.
If assertion is true but reason is false.
Secondary growth is the growth in thickness due to the formation of secondary tissues by lateral meristems. With the exception of some annuals, most of the dicots and gymnosperms show secondary growth in their stems and roots. It takes place by the production of two types of secondary tissues: secondary vascular tissues and periderm. These tissues are formed by meristems, vascular cambium and cork cambium respectively.
Secondary growth does not occur in monocots because monocots do not possess vascular cambium in between the vascular bundles.
Vernalisation is subjected to plants growing in
tropical areas
sub tropical areas
temperate areas
hot areas/arctic region.
C.
temperate areas
Vernalization is the induction of a plant's flowering process by exposure to the prolonged cold of winter, or by an artificial equivalent. After vernalization, plants have acquired the ability to flower, but they may require additional seasonal cues or weeks of growth before they will actually flower.
Many temperate plants have vernalisation requirement and must experience a period of low temperature in winter, to initiate or accelerate flowering process, or in many fruit tree species, to induce dormancy and then break dormancy prior to flowering.
The phenomenon that operates in the formation of root or shoot in a callus culture is
differentiation
re-differentiation
de-differentiation
re-juvenation
A.
differentiation
The cells derived from root apical and shoot apical meristems and cambium differentiate and mature to perform special functions. This act leading to maturation is termed as differentiation.
Differentiation is the process by which a less specialized cell becomes a more specialized cell type. It is part of developmental biology. Different tissues have different kinds of organisms inside the cells. Differentiation occurs many times during the development of a multicellular organism.
Which of the following genes do not occur naturally in living organisms
Bt genes
RNAi genes
Cry genes
Endogeneous cytoplasmic defence genes
D.
Endogeneous cytoplasmic defence genes
Bt genes, RNAi genes and Cry genes occur naturally in living organisms.
Bt toxic gene of bacterium Bacillus thuringiensis has been cloned from bacteria, and expressed in plants, to provide resistance to insects without the need of insecticides. The choice of genes depends upon the crop and the targeted pest as most Bt toxins are insect group specific. The toxin is coded by a gene named Cry.
RNAi takes place in all eukaryotic organisms as a method of cellular defence. This method involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA (silencing).
DNA and RNA comprise of
sugar, phosphate, base
sugar, phosphate
base, phosphate
sugar, base
A.
sugar, phosphate, base
DNA and RNA are nucleic acids which are found in living systems. DNA is a long polymer of deoxyribonucleotides and RNA is a long polymer of ribonucleotides. A nucleotide has 3 components- a nitrogenous base, a pentose sugar and a phosphate group.
Most animals are tree dwellers in a
coniferous forest
thorn woodland
temperature deciduous forest
tropical rain forest
D.
tropical rain forest
Tropical rain forest biome his in equatorial or sub equatorial regions with abundant rainfall and warmth.
The vegetation is stratified, i.e. each stratum has different fauna contributing to the diversity, because of this most animals in this biome are tree dwellers.
Assertion: Cytokinins increases shelf life of fruits and vegetables.
Reason : Cytokinins induce cell division.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
B.
If both assertion and reason are true but reason is not the correct explanation of assertion
Shelf life of cut shoots and flowers is prolonged by using the hormone cytokinin. The main reason is that the cytokinin increases retention of chlorophyll and delayed senescence in leaves. Cytokinin is essential for cell division or cytokinesis. It promotes cell division along with auxin by controlling the activity of cyclin dependent kinases.
Which one of the following methods is commonly used to maintain the genetic traits of a given plant
By propagating through seed germination
By propagating through vegetative multiplication
By generating hybrids through intergeneric pollination
By treating the seeds with gamma radiations
B.
By propagating through vegetative multiplication
The propagation through vegetative multiplication is used to maintain the genetic traits of a given plant. It gives rise to genetically uniform population or clone. In case of plants propagated through seeds, variations creep in due to chance segregation of genes during meiosis and their chance combination during fertilization.
Phytohormones are
hormones regulating growth from seed to adulthood
growth regulators synthesised by plants and influencing physiological process
hormones regulating flowering
hormones regulating secondary growth.
B.
growth regulators synthesised by plants and influencing physiological process
Growth regulators are organic substances, other than nutrients, which in low concentration regulate growth, differentiation and development by promoting or inhibiting the same. Phytohormones are growth regulators produced naturally in plants and translocated to another region for regulating one or more physiological reactions when present in low concentration. Phytohormone can have a promoting or inhibiting effect on a process
The cells of the quiescent centre are characterised by
having dense cytoplasm and prominent nuclei
having light cytoplasm and small nuclei
dividing regularly to add to the corpus
dividing regularly to add to tunica
B.
having light cytoplasm and small nuclei
In the apices ofsome roots, (e.g., Zea mays, maize), there is a central region of cells which normally does not divide. This central inactive region was called quiescent centre by FE.A.L. Clowes (1959, 1961).
The cells of this region have lesser amounts of RNA and DNA so they have small nuclei. These cells also have a lower rate of protein synthesis. Mitochondria and endoplasmic reticulum arc less developed. The cells of the quiescent centre arc usually inactive. However, if already existing meristematic cells are injured or become inactive due to any other reason, the cells ofquiescent centre become active.
Assertion : Vernalization is acceleration of subsquent flowering by low temperature treatment.
Reason : Site of vernalization is apical meristem.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
B.
If both assertion and reason are true but reason is not the correct explanation of assertion
Vernalization is coolong of seed during germination in order to accelerate flowering when it is planted.
In colder countries, there are cereals of 2 physiological types, i.e., winter cereals and spring
cereals. Winter cereals are sown in winter and flower in following summer whereas spring cereals are sown in spring and flower in summer.
If winter cereal are sown in spring, it shows vegetative growth but does not flower unless it receives low temperature of winter. However, they can be converted into spring cereal by providing artificial low temperature treatment, (i.e., springification.)
Some plants requiring low temperature requirement (vernalization) for flowering are Secale cereale (European rye), Triticum vulgare, Brassica oleracea, Beta vulgaris, Apium and Lolium perenne, etc.
Site of vernalization is apical meristem or all the meristematic cells. As a result of vernalization, a flowering hormone called 'vernalin' is formed (reported by Melchers), but venalin has never been isolated. Once a plant is vernalized, it can be devernalized by exposing the plant to temperature of 30C or above. For establishing vernalization, plant should be kept at 20°Cfor 4-5 days.
Avena curvature test is a bioassay for examining the activity of
auxins
cytokinins
gibberellins
ethylene.
A.
auxins
Bioassay is a testing of biological activity like growth response of a substance by employing plant part. Avena curvature test is a bioassay for examining the activity of auxins. It is based upon experiments of Went. 10° curvature is produced by auxin concentration of150 g/lit at 250C and 90% relative humidity. It can measure auxin upto 300g/litre. Auxin from shoot tip or any other plant organ is allowed to diffuse in a standard size agar block. 15- 30 mm long oat coleoptile grown in dark is held vertically over water. 1 mm tip of colcoptile is removed without injuring the primary leaf. After 3 hours a second decapitation is carried out for 4mm distance. Primary leaf is now pulled loose and agar block supported against it at the tip of decapitated coleoptile. After 90- 100 mm the coleoptile is found to have bent. The curvature is measured
Gibberellins can promote seed germination because of their influence on
rate of cell division
production of hydrolyzing enzymes
synthesis of abscisic acid
absorption of water through hard seed coat
B.
production of hydrolyzing enzymes
Gibberellins induces the hydrolyzing enzymes in the endosperm of germinating seeds. It stimulates the production of digestive enzymes like proteases, amylase, lipase which help to mobilise stored nutrients.
Pruning of plants promotes branching because the axillary buds get sensitized to
ethylene
gibberellin
cytokinin
indole acetic acid.
D.
indole acetic acid.
“It has been known since the 1930s that the plant hormone auxin is released by the plant’s actively growing tip and is transported down the main stem where it has an indirect effect on buds to inhibit branching. There are a number of ways in which the hormone exerts this effect and we have discovered a new path by which it works.”
The research suggests that for a shoot tip to be active, it must be able to export auxin into the main stem. But if substantial amounts of auxin already exist in the main stem, export from an additional shoot tip cannot be established
In a plant organ which is covered by periderm and in which the stomata are absent, some gaseous exchange still takes place through
aerenchyma
trichornes
pneumatophores
lenticels.
D.
lenticels.
Due to continued formation of secondary tissues in the older stem and roots however the epidermis gets stressed and ultimately tends to rupture and followed by death of epidermal cells and outer tissues, and a new protective layer is developed called periderm.
Structurally it consists of three parts Phellogen or Cork cambium, phellem or cork and phelloderm. Usually in the periderm of most plants, certain areas with loosely arranged cells have been found, which possess more or less raised and corky spots where the underneath tissues break through the epidermis. Such areas are universally found in the stems of woody plants. These broken areas are called lenticels, which perform the function of exchange of gases in the absence of stomata.
Cork cambium results in the formation of cork which becomes impermeable to water due to the accumulation of
resins
lignins
suberin
tannins.
B.
lignins
Cork is impervious to water because it has deposition of suberin. The thin walls of those cells are saturated with fatty waxy substance, called suberin which makes cork almost impervious to water and air.
'Climacteric' is
a phenomenon related to fruit ripening
the condition of a plant when all its fruits are almost ripe
the condition of a plant when most of its leaves have turned yellow
none of the above
A.
a phenomenon related to fruit ripening
The development of multi-cellular organisms begins from a single-celled zygote, which undergoes rapid cell division to form the blastula. The rapid, multiple rounds of cell division are termed cleavage. After the cleavage has produced over 100 cells, the embryo is called a blastula.
Ethylene is a
gaseous hormone
gaseous enzyme
liquid-gas mixture
solid hormone
A.
gaseous hormone
Ethylene is thought of as the aging hormone in plants. In addition to causing fruit to ripen, it can cause plants to die. It can be produced when plants are injured, either mechanically or by disease. Ethylene gas is used commercially to ripen tomatoes, bananas, pears, and a few other fruits postharvest
The plants respond to photoperiods due to the presence of :
enzymes
stomata
phytochromes
phytohormones
C.
phytochromes
Photoperiodism is the response of an organism to seasonal changes in day length.
It is regulated by the photoreversible pigment called phytochrome. Phytochrome is a photoreceptor chromoprotein.
Which chemical is used for induction of polyploidy?
Cytokinin
Nitrous acid
Colchicine
IAA
C.
Colchicine
Colchicine is an alkaloid obtained from the plant. Colchicum autumnale and is found to prevent the formation and organization of spindle fibres. It induces polyploidy in many plant and animal cells.
Tendrils exhibit/twining of tendrils is due to
thigmotropism
seismonasty
heliotropism
diageotropism
A.
thigmotropism
Thigmotropism is a directional growth movementwhich occurs as a mechanosensory response to a touch stimulus. Thigmotropism is typically found in twining plants and tendrils, however plant biologists have also found thigmotropic responses in flowering plants and fungi.
Flowering dependent on cold treatment is
cryotherapy
cryogenics
cryoscopy
vernalisation
D.
vernalisation
Many plants have a vernalization requirement, that is, they actively repress flowering until after a period of prolonged cold, in order to align seed production with the favourable environmental conditions of spring. Vernalization occurs during the cold, but flowering only occurs many weeks or even months later when other specific conditions, including the presence of certain photoperiods and ambient temperatures, are also met.
A substance that induces dormancy of seed is
ABA
GA
thio-urea
cytokinin
A.
ABA
ABA or Abscisic Acid induces dormancy in buds and seeds. The buds as well as seeds sprout only when abscisic acid is overcome by gibberellins.
Which of the following is called stress hormone?
Abscisic acid
Auxin
Cytokinin
Gibberellic acid
A.
Abscisic acid
Abscisic acid is also called stress hormone because the production of this hormone is stimulated by drought, water logging and other adverse environmental conditions.
Vascular tissue in higher plants develop from which of the following
Procambium
Protoderm
Periblem
Cortex
A.
Procambium
The procambium is a meristematic tissue concerned with providing the primary tissues of thevascular system; the cambium proper is the continuous cylinder of meristematic cells responsible for producing the new vascular tissues in mature stems and roots.
The discovery of gibberellins is related with one of the following
blast disease of rice
rust disease of wheat
bakane disease of rice
early blight disease of potato
C.
bakane disease of rice
Kurosawa, a Japanese botanist, discovered gibberellin while investigating the rice foolish seedling disease in which spindly seedlings are formed due to GA like compounds produced by the fungus ( Gibberella fujikuroi) infecting the plant.( see text for more information).
Cellular totipotency was first demonstrated by
F C Steward
Robert Hooke
T Schwann
A v Leeuwenhoek
A.
F C Steward
Concept of cellular totipotency was first given by Haberlandt (1902) but was proved by Steward (1965). Cellular totipotency is the ability of a somatic cell to produce the entire organism
Choose the minor carp from the following
Cyprinus carpio
Anguilla sp
Labeo bata
cetanophyrngodon idella
C.
Labeo bata
Labeo bata is a minor carp, its size is smaller and growth rate is slower
Name of a gaseous plant hormone is
IAA
gibberellin
ethylenes
abscisic acid
C.
ethylenes
Ethylene is a gaseous plant hormone that regulates many aspects of plant growth and development ranging from seed germination to organ senescence.
During seed germination its stored food is mobilised by
ethylene
cytokinin
ABA
gibberellin
D.
gibberellin
Gibberellin induces aleurone cells to secrete enzyme to break stored food in seed. Cytokinines promote nutrient mobilisation, which helps in the delay of leaf senescence. ABA plays an important role in seed development, maturation and dormancy. Ethylene induces fruit ripening, breaks seed dormancy.
Which one of the following is a growth regulator produced by plants?
Naphthalene acetic acid
Zeatin
2,4-dichlorophenoxy acetic acid
Benzyl aminopurine
B.
Zeatin
Zeatin is a naturally occurring cytokinin (type of plant growth regulator) isolated from the endosperm of a corn. It is remarkably known to be more active than any other cytokinin, while others growth regulators given in the, potions such as 2, 4 dichlorophenoxy acetic acid (2, 4-D), Naphthalene Acetic Acid (NAA) and benzylaminopurine are all synthetic plant growth regulators.
Match the items in column I with those in column II and choose the correct answer
| Column I | Column II |
| A. Control of weeds | 1. Gibberellin |
| B. Induction of germination | 2. Cytokinin |
| C. Ripening of fruit | 3. 2, 4- D |
| D. Delaying of senescence | 4. Ethylene |
A- 2; B- 4; C- 3; D- 1
A- 3; B- 1; C- 4; D- 2
A- 1; B- 2; C- 4; D- 3
A- 2; B- 3; C- 1; D- 4
B.
A- 3; B- 1; C- 4; D- 2
| Column I | Column II |
| A. Control of weeds | 3. 2, 4-D |
| B. Induction of germination | 1. Gibberelin |
| C. Ripening of fruit | 4. Ethylene |
| D. Delaying of senescence | 2. Cytokinin |
The aleurone synthesises and secretes digestive enzymes that hydrolyse nutrients stored in the endosperm, in the presence of
auxin
gibberellin
cytokinin
ethylene
B.
gibberellin
The aleurone layer is the outermost layer of the endosperm. It synthesizes and secretes digestive enzymes that hydrolyze nutrients stored in the endosperm in presence of enzyme gibberellin. Gibberellin is released by the embryo. The digestive enzymes hydrolyze the components stored in the endosperm to support the early growth of the embryo.
Vernalisation promotes flowering by
low temperature
high temperature
prolonged photoperiod
short photoperiod
A.
low temperature
Vernalization promotes flowering by low temperature. It prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.
Elongation of internode is caused by
ethylene
gibberellin
abscisic acid
cytokinin
B.
gibberellin
Gibberellin helps in internodal elongation. It helps in elongation of fruits and improve its shape. If sprayed on sugarcanes, it increases its length of stem.
Which one of the following is correct for blooming of 'short day' plants?
The long dark period is not critical
It is affected by interruption of long dark period by brief exposure of light
It is not affected by interruption of long dark period by brief exposure of light
It is affected if the continuous light period is interrupted
B.
It is affected by interruption of long dark period by brief exposure of light
Short day plants flower when exposed to day lengths shorter than a certain critical duration. Interruption by dark during long light period does not stimulate flowering. It means they do not flower if dark period is interrupted by a flash of light. They are also called long night plants. Whereas interruption by dark during long light period does not inhibit flowering in long-day plants (short-night plants).
The hormone involved in the regulation of florigen synthesis is
ethylene
zeatin
cytokinin
gibberrellin
D.
gibberrellin
Florigen or flowering hormone is the hypothesized hormone like molecule responsible for controlling or triggering flowering in plants.
Gibberrellins (GA) are plant hormones that regulate growth and influence various developmental process like flowering, elongation, germination, etc.
Statement I : Sugar beet, cabbage, carrot like plants are monocarpic.
Statement II : Both vernalisation and photoperiodism are related to flowering.
Statement I is correct, but Statement II is incorrect
Statement II is correct, but Statement I is incorrect.
Both statements are correct.
Both statements are incorrect.
C.
Both statements are correct.
Monocarpic plants flower only once in their life. These plants are generally annual biennial. They dies after flowering and fruiting e.g., sugar beet, cabbage, carrot, etc.
Veralisation is the process of inducing flowering by cold treatment and photoperiodism is the time period required for flowering. Thus, both the terms are related the flowering, but do not explain the assertion.
Fruit ripening is promoted by the hormone that also
promotes thinning of fruits in cherry and walnut
induce parthenocarpy in tomato
promote flowering in lemma
induce dormancy
A.
promotes thinning of fruits in cherry and walnut
Ethylene is the hormone that promotes fruit ripening. It also promoted thinning of fruits in cherry, cotton and walnut. It is a gaseous hormones, i.e. a gas that forms through the breakdown of methionine, which is in all cells. It is produced at a faster rate in rapidly growing and dividing cells, especially in darkness.
The correct sequence of cellular growth stages is
division differentiation elongation
differentiation division elongation
division elongation differentiation
elongation differentiation division
C.
division elongation differentiation
During cellular growth of any plant organ, the cells firstly divide and then elongation takes place. After sufficient elongation (vegetative growth) they cells got specialised after differentiation. This led to the final development.
Auxin was first named by
C Darwin
FW Went
Alexopolus
KV Thimann
B.
FW Went
FW Went (1928) was the first person to name auxins. Thimann (1936) isolated IAA from Rhizopus sinus and Avena coleoptiles.
Phototropic curvature in Avena coleoptile is the result of uneven distribution of
auxin
starch
gibberellins
phytochrome
A.
auxin
The Cholodny-Went theory, states that plant tropisms in roots and shoots are due to the unequal distribution of the growth regulator auxin in reponse to light or gravity, presented a simple and direct explanation of these phenomena.
Study of bakanae disease of rice led to discovery of
auxins
bakery rice
Both (a) and (b)
gibberellins
D.
gibberellins
In Japan, 'bakanae disease' or 'foolish seedling disease' in rice was known. It was found that there is some connection between bakanae disease and fungus Gibberella fujikuroi or Fusarium moniliformae. The active substance present in fungus was separated and named gibberellin by Yabuta.
Equipment used for the measurement of growth in plants is known as
respirometer
auxanometer
atmometer
potometer
B.
auxanometer
An auxanometer is an apparatus for measuring increase or rate of growth in plants. It is in shape of an arc or lever. In case of an arc-auxanometer there is a wire fixed with the plant apex on one end and a dead-weight on the other.
The hormone, which prevents abscission is
IBA
ABA
NAA
Cytokinin
A.
IBA
Auxins like IAA, IBA, etc., prevents the formation of abscission layer in fruits and leaves.
When an ovary develops into a fruit without fertilization it is called
porogamy
apospory
apogamy
parthenocarpy
D.
parthenocarpy
Parthenocarpicfruits are seedless and develop from ovary without fertilization.
Porogamy is the fertilization of a seed plant involving passage of the pollen tube into the ovule by the micropyle.
Apospory is the development of 2n gametophytes, without meiosis and spores, from vegetative, or non- reproductive, cells of the sporophyte.
Apogamy is the development of 1n sporophytes without gametes and syngamy from vegetative cells of the gametophyte.
GA usually promotes
sterility in flowers
maleness in flowers
femaleness in flowers
Both (b) and (c)
B.
maleness in flowers
It was observed in flowers of Geranium and Balsamea that GA induces male flowers.
Ethylene is
gaseous hormone
largest hormone
liquid hormone
solid hormone
A.
gaseous hormone
Ethylene is the smallest gaseous phytohormone.
Induction of cell division and delay in senescence is done by
cytokinins
auxins
GA
Co-A
A.
cytokinins
Cytokinins stimulate cell division and delay senescence by moblising food from other leaf parts.
Which of the following induces and promotes cell division?
ABA
Auxin
Cytokinin
Gibberellin
C.
Cytokinin
Cytokinin is a plant cell division hormone, i.e. it induces and promotes cell division in plants. It is primarily involved in cell growth and its differentiation. It also affects apical dominance, axillary bud growth and leaf senescence.
Artificial application of auxins like IAA, IBA and NAA to unpollinated pistils can form
fruits with much flash
larger fruits
sweet fruits
seedless fruits
D.
seedless fruits
The auxin's application on unpollinated pistils develops into seedless fruits and parthenocarps, which carry a better market price than normal fruits.
Internodal elongation is stimulated by
auxin
cytokinin
gibberellin
phenol
C.
gibberellin
The gibberellins induce internodal elongation. When the lettuce plants are treated with gibberellin, they become wine like.
Flash of light in dark inhibits flnwering in
SDP
LDP
LSDP
DNP
A.
SDP
Short day plant needs short-light period and uninterrupted long night period and a flash of light in dark inhibits flowering in short day plant (SDP).
LDP or Long Day Plants flower when the days are longer. Light period is very critical in these plants.
LSDP are Lond Day Short Plants.
DNP stands for 2, 4- Dinitrophenol.
Plant length is increased by
apical meristem
lateral meristem
dermarogen
periblem
A.
apical meristem
Apical meristem are present at the apices of shoots and root of the plants and possess actively dividing cells. These meristems are virus free and are responsible for increase in length and all primary tissues of the plant body originate from them.
The mutagenic agent among following is
ethyl methane
ethylene
2, 4-D
IAA
A.
ethyl methane
A mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level. Ethyl methane is a mutagenic agent causing gene mutations.
Which one of the following is a natural growth inhibitor?
NAA
ABA
IAA
GA
B.
ABA
ABA (Abscisic Acid) is a naturally occurring growth inhibitor in plants.
Which one is a short day plant?
Brassica campestris
Raphanus sativus
Glycine max
Papaver somniferum
C.
Glycine max
Short day plants initiate flowering when the day length (photoperiod) become shorter than a certain critical period. Most of winter flowering plants belong to this category, eg, cocklebur (Xanthimum), sugarcane, soybean (Glycine max), Chrysanthemum etc.
Leaf abscission is caused by
ABA
cytokinin
auxin
gibberellin
A.
ABA
Abscission is the fall of leaves and fruits. Abscisic acid (ABA). a stress hormone, accelerated leaf abscission in cotton plants. Since, then it is believed that cause of abscission is the presence of growth inhibiting hormone (ABA), but its universal role for abscission is yet to be established.
The synthetic hormone used as a weedicide is
Indole 3-acetic acid
gibberellic acid
2, 4- D
Indole butyric acid
C.
2, 4- D
High concentration of synthetic auxins such as 2, 4- D or 2, 4- Dichlorophenoxyacetic acid and 2, 4- T or 2, 4- Trichlorophenoxy acetic acid helps in destroying the dicot seeds.
Natural auxins are IAA or Indole 3-acetic acid and IBA or Indole butyric acid.
First natural cytokinin was discovered by :
Skoog and Miller
Letham
Benson and Calvin
Thimann and Went
B.
Letham
First natural cytokinin was obtained from unripe maize grains or Kernels. It is known as zeatin or 6- hydroxy 3- methyl trans butenyl amino purine.
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