Biology Chapter 6 Anatomy Of Flowering Plants

Meristems are specialised regions of active cell division in plants. The meristems represent the regions of growth. Growth is largely restricted to the meristem regions of the plant.  Depending on their location the meristems are of three types.
(i) Apical meristem:
These meristems are present at the tips of the roots and shoots. The shoot apical meristem is present at the tip of the shoots and its active division results in the elongation of the stem and formation of new leaves. The root apical meristem helps in the elongation or growth of roots. They are primary meristems as they appear early in the plant life. 

(ii) Intercalary meristem:
These are present between the masses of mature tissues present at the bases of the leaves of grasses. It helps in the regeneration of grasses after they have been grazed by herbivores. They are primary meristem.

(iii) Lateral meristem:
It appears in the mature tissues of roots and shoots. It is called the secondary meristem as it appears later in a plant's life. It helps in adding secondary tissues to the plant body and in increasing the girth of plants. Examples include fascicular cambium, inter-fascicular cambium, and cork cambium.

The secondary growth in plants:
i. Increases the girth of plants,
ii. Increases the amount of water and nutrients to support the growing number of leaves.
iii. Provides support to plants.

(a) Monocot root and dicot root:

(b) Monocot stem and dicot stem:

We would ascertain whether the given stem is a monocot stem or dicot stem by looking at some characteristics which are unique as to the particular type.
The dicots stem is characterised by the following unique characters:
i. vascular bundles are arranged in a
ii. Each vascular bundle is conjoint, collateral, and open.
iii. Medullary rays are present between the vascular bundles.
iv. Pith is present.
If these characters are observed in the given stem, then it a dicot stem

The monocot stem are characterised by the following unqiue characteristics:
1. Vascular bundles are scatttered.
2. Each vascular bundle is conjoint, collateral, and closed vascular bundles. 
3. Medullary rays are absent. 

The scattered vascular bundles surrounded by sclerenchymatous bundle sheaths and the absence of the phloem parenchyma is unqiue to the monocot stem. Thus, the specimen is of a monocot stem.

Both the xylem and the phloem are made up of more than one type of the cells which work as a unit. 
Xylem helps in conducting water and minerals. It is made up of the following components:

• Tracheids (xylem vessels and xylem tracheids)
• Xylem parenchyma
• Xylem fibres

• Sieve tube elements
• Companion cells
• Phloem parenchyma
• Phloem fibres

Stomata are small pores present in the epiderms of leaves. 
The stomatal aperture, guard cells and the subsidiary cells together are called the stomatal apparatus. 
Structure of stomata: Each stomata is composed of two bean-shaped structure called guard cells. In grasses the guard cell is dumbbell shaped. The inner walls of guard cells are thick, while the outer walls are thin. The guard cells are surrounded by subsidiary cells. These are the specialised epidermal cells present around the guard cells called the subsidiary cells.

The three basic tissue system in plants are:
(i) Epidermal tissue system: It forms the outermost covering of the whole plants body. It comprises of  epidermal cells, stomata and the epidermal appendages like trichomes and hairs.
(ii) The vascular tissue system: It consists of the phloem and the xylem
(iii) Ground tissue system: All the tissues except the vascular bundles and the epidermis constitute the ground tissue system. For example parenchyma, collenchyma and sclerenchyma and mesophyll cells. 

The study of plant anatomy helps us to understand the structural adaptations of plants with respect to diverse environmental conditions. It also helps us to distinguish between monocots, dicots, and gymnosperms. Such a study is linked to plant physiology. Hence, it helps in the improvement of food crops. The study of plant-structure allows us to predict the strength of wood. This is useful in utilising it to its potential. The study of various plant fibres such as jute, flax, etc, helps in their commercial exploitation.

Periderm is composed of the phellogen, phellem, and phelloderm.
During secondary growth, the outer epidermal layer and the cortical layer are broken because of the cambium. To replace them, the cells of the cortex turn meristematic, giving rise to cork cambium or phellogen. It is composed of thin-walled, narrow and rectangular cells.
Phellogen cuts off cells on its either side. The cells cut off toward the outside give rise to the phellem or cork. The suberin deposits in its cell wall make it impervious to water. The inner walls give rise to the secondary cortex or phelloderm. The secondary cortex is parenchymatous.

Dorsiventral leaves are found in dicots. The vertical section of a dorsiventral leaf contains three distinct parts. 
(i) Epiderms: Epiderms is present on both the upper surface (adaxial epiderms) and the lower surface (abaxial epiderms).
(ii) Mesophyll: Mesophyll is a tissue of the leaf present between the adaxial and abaxial epidermises. It is differentiated into the palisade parenchyma (composed of tall, compactly-placed cells) and the spongy parenchyma (comprising oval or round, loosely-arranged cells with inter cellular spaces). Mesophyll contains the chloroplasts which perform the function of photosynthesis.
(iii) Vascular system: The vascular bundles present in leaves are conjoint and closed. They are surrounded by thick layers of bundle-sheath cells.

Cork cambium is a meristematic tissue which develops in the cortex region of a mature stem. Cork cambium is formed to replace the broken epidermal layer of the stem. The cells cut off on the outer side by cork cambium become cork. Hence, it can be said that the cork cambium is a tissue which forms the cork.

C.

Orange and yellow

Red and green

C.

Epidermis

C.

Collenchyma

D.

Dicot stem

B.

b. A-iii, B-i, C-ii, D-v, E-iv

A.

 A-iii, B-iv, C-i, D-ii

C.

Epidermis

C.

Cell dedifferentiation

B.

Cork cambium and cork

A.

Root tip and shoot tip

C.

5

C.

Pine

A.

Collenchyma

B.

Secondary xylem

A.

It is retained in the centre of the axis

D.

Trochodendron

Food is stored in parenchyma.

Protoxylem refers to the xylem which is formed first. 
If the protoxylem lies next to phloem then the arrangement is called Exarch. 

Phloem parenchyma performs the function of storage of food. It also helps in the translocation of food. 

The cuticle is present on the surface of the leaves. It is a waxy layer which helps to prevent water loss.

a.  Coir is obtained from Cotton husk. 
b. Hemp - is obtained from the stem of Cannabis sativa
c. cotton is obtained from cotton seeds.
d. Jute is obtained from Corchorus capsularis. 

Meristematic tissue

The functions are :
a. Sieve tubes - Translocation of food.
b. Interfascicular cambium - Facilitate secondary growth
c. Collenchyma - Provides mechanical strength to young stem.
d. Aerenchyma - Provides buoyancy of floating plants

Palm shows an increase in girth because of the division and enlargement of the parenchymatous cells in the ground tissue. This type of growth is known as diffused secondary growth 

A.

medullary rays

In dicot stems, the cells of cambium present between primary xylem and primary phloem are the intrafasicular cambium. The cells of medullary rays, adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium. Xylem parenchyma is living and thin-walled and their cell walls are made up of cellulose. In dicot roots, the innermost layer of the cortex is called endodermis. Next to endodermis lies a few layers of thin-walled parenchymatous cells called as pericycle.

B.

Gaseous exchange

Plants have stomata and Lenticles involved in gaseous exchange. In stems, the living cells are organised in thin layers inside and beneath the bark. They have openings called Lenticles.

A.

sieve elements

Companion cells are characteristic elements of phloem tissue associated with the sieve tubes(sieve elements) in the angiosperms. The siever tubes and companion cells are related ontogenically as they develop from the same mother cell. The companion cells and sieve tubes maintain close cytoplasmic connections through plasmodesmata.

C.

cambium

In dicot system, cambium is present between phloem and xylem. Such vascular bundles, because of the presence of cambium, posses the ability to form secondary xylem and phloem tissues and hence, are called open vascular bundles. On the contrary, vascular bundles in monocots have no cambium. Hence, they do not form secondary tissues, and are referred to as closed. 

B.

maize

In monocot stem like Zea mays, vascular bundles are conjoint, collateral and closed. In vascular bundles, the lowermost protoxylem vessels and xylem parenchyma cells dissolve forming a water containing schizolysigenous cavity called protoxylem cavity or lacuna or lysigenous cavity. Protoxylem cavity and protophloem may be absent in the smaller vascular bundles in maize.

C.

Both apical and axillary meristems

Both apical and axillary meristems are free of virus for the healthy plant cultivation because of strong interferon activity in this region. These tissue form a protective impermeable covering around themselves, which s non-penetrable by any pathogen. Hence, these tissue are used in the production of disease-free plants by tissue culture.

B.

many xylem bundles

The vasculature is radial in dicot root i.e.,xylem bundles alternate with phloem bundles. Usually vascular bundles are 2-6 in number while in monocot root the vascular strand consists of several (8 or more) alternate radial xylem and phloem bundles. Secondary growth takes place in dicot root while absent in monocot roots and annual rings do not form. 

C.

Protoxylem

In dicot stem, the protoxylem is present towards the center (pith) and metaxylem is present towards the periphery of the organ. This type of xylem is known as endarch. In root, the protoxylem is present towards periphery and metaxylem present towards the centre that is called exarch.

B.

cambium is absent

The vascular bundles of monocots do not contain a layer of meristematic tissue (cambium). There is absence of meristematic tissue near vascular bundles, therefore vascular system is closed in monocot. Hence, the further secondary growth is not seen in them. 
So, option (b) goes with question. 

C.

Vasculature without cambium

The characteristic feature of monocot root is presence of vasculature without cambium. The vascular bundles are alternate and radial and arranged in the form of a ring around a central pith. Phloem and xylem bundles are separated by narrow strips called conjunctive tissue and it does not take part in cambium formation. So, the vascular bundles in monocots are closed and do not show any secondary growth.

C.

axillary buds

Tuber is oval or spherical swollen underground modified stem lacking adventitious roots. It possesses a number of spirally arranged depressions called eyes. Each eye represents node and consists of 1-3 axillary buds in the axils of small scally leaves.

C.

chloroplasts

The guard cells of stomata in land plants are specialised epidermal cells which contain chloroplasts. In rest of epidermal cells, chloroplasts are absent. But chloroplasts of guard cells are capable of poor photosynthesis as there is the absence of NADP reductase enzyme.

B.

Periderm

The periderm is a secondary protective structure and is made up of cork cambium (phellogen), cork (phellem) and secondary cortex (phelloderm)

D.

Loading of sucrose into sieve elements

The companion cells are specialised parenchyma cells, which are closely associated with sieve tube elements. The sieve tube elements and companion cells help in maintaining the pressure gradient in the sieve tubes. they also function in the loading of sucrose into sieve elements actively.

B.

are capable of producing secondary xylem and phloem

In open vascular bundle, cambium is present between xylem and phloem of the same vascular bundle, eg, dicot stems.Due to the presence of cambium, secondary growth in stem occurs and secondary permanent tissues (secondary xylem, secondary phloem and vascular rays) are formed.

D.

Intercalary meristem

Intercalary meristems are the portions of apical meristems, which are separated from the apex during the growth of axis and formation of permanent tissue. It is present mostly at the base of the node (eg, Mentha virridis), the base of internode (eg, the stem of many monocots viz, wheat, paddy, grasses; pteridophytes like Equisetum) or at teh base of the leaf (eg Pinus).

C.

having dead and non-conducting elements

As a result of continued secondary growth in subsequent years, the older part of secondary xylem or wood becomes non - functional as it loses the power of conduction. The cells of this wood are filled with resins or tennis produced by adjacent functional, secondary xylem becomes hard, durable and blackish in colour, called heartwood, Now, the function of secondary xylem( water and mineral conduction from roots) is performed by outer younger-rings of xylem, which is called sapwood.

D.

sieve elements

Sieve elements are the food conducting cells of phloem tissue. Sieve element in angiosperms are sieve tubes, while in gymnosperms and pteridophytes, these are sieve cells. 

C.

Puccinia graminis

Black (stem) rust of Wheat is caused by Puccinia graminis tritici, a fungus belonging to Sub-class-Teliomycetidae, Order-Uredinales. It is a heteroecious species which completes its life cycle on two plants, ie, barberry (Berberis) plant and wheat (Triticum aestivum).

C.

Petals in the flowers of cotton (Gossypium sp) china rose (Hibiscus rosa sinesis), etc, show twisted aestivation. In this type of aestivation, a regular overlapping of petals occurs where one margin of each petal overlaps with the next one petal.

C.

widening

Vessel or tracheae are made up of a row of cells, placed one above the other, with their intervening walls absent or variously pored. The walls of vessels are lignified and hard, but not very thick. The cell cavity or the lumen is wide. The thickening may be annuler, spiral, scalariform, reticulate and pitted. 

B.

closed and scattered

The vascular bundles in Hordeum vulgare (barley) plant are scattered in ground tissue, many in number and vary in size-smaller towards the periphery and bigger towards the centre of the ground tissue, oval or rounded in outline, conjoint, collateral and closed.

B.

plerome

Histogen theory for shoot apical meristem has been proposed by Hastein (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 one producing the cortex and plerome is the innermost resulting in the certain cylinder (ie, vascular tissue).
Cork cambium (phellogen) is the secondary lateral meristem found in the outer cortical region. Its cells divide periclinally cutting offf cells towards the outside (formingcork or phellem) and inside (forming secondary cortex or phelloderm).

B.

Teak and pine

The increase in diameter or thickness is due to the formation of secondary tissues as a result of the activities of vascular cambium and cork cambium. This secondary growth is characteristic of dicot stem and root.

B.

pores on lateral walls

The wall of both vessel and sieve tube elements are perforated by large opening. Due to this adaptation, the cell to cell contact is possible. The vessels are nucleated whereas the sieve tube elements are enucleated.

A.

Maturation

B.

Halophytes

C.

Secondary xylem

C.

It conducts water and minerals efficiently

Heartwood is physiologically inactive due to deposition of organic compounds and tyloses formation, so this will not conduct water and minerals

C.

Endodermis

1. Endodermis has Casparian strip on radial and inner tangential wall.
2. It is suberin rich.

B.

Vascular cambium

Vascular cambium is partially secondary.

Form secondary xylem towards its inside and secondary phloem towards outsides.

4 – 10 times more secondary xylem is produced than secondary phloem.

B.

Pteridophyta

Pteridophyte is called vascular cryptogams. They are a seedless vascular plant as they posses water-conducting xylem and food translocating phloem but do not produce seed (instead spare formation takes place).

D.

Cucurbita

Angular collenchyma occurs in Cucurbita. It has thickening at the angles and there are no intercellular spaces. It is generally found in leaf petioles.

A.

Sorghum

Kranz anatomy is found in C-plants, e.g., Sorghum, Zea mays, Saccharum officinarum. It is characterised by connective, undifferentiated mesophyll around vascular bundles with chloroplast containing bundle sheath.

D.

Phellogen, phellem, phelloderm and Secondary phloem

All the dead cells lying outside the phellogen constitute the bark of the plant. It may include epidermis, cork, hypodermis and even part of cortex depending upon the position of the origin of cork cambium or phellogen.

B.

Differentiation of palisade and spongy parenchyma

Main differences between dicot and monocot leaves are as follows:

A.

inner region of secondary wood

The xylem elements of the stems of a number of trees develop dark brown colour, especially in the central or innermost layers.

It comprises dead element with higly lignified walls and is called heart wood or duramen. It is present in inner region of secondary wood.

D.

fascicular cambium

The cambium present between the xylem and phloem of vascular bundle  is called vascular cambium. It is a lateral meristem that gives rise to secondary xylem and phloem and occurs in the form of a thin strip. Vascular cambium is also called fascicular cambium.

A.

least mitotic activity in the root apex

Quiescent centre is an area at the top of the root apical meristem where the cells have least mitotic activity i.e., the rate of cell division is lower than in surrounding tissue. But the cell retains the meristematic property ones the meristamatic cells sourrounding them are damaged.

B.

Osmunda and Equisetum

In the ectophloic siphonostele the xylem surrounds pith and this xylem is surrounded by phloem, pericycle and endoderm is respectively.

eg, Osmunda and Equisetum.

C.

Shoot tips and root tips

Primary tissues are those meristematic tissues, which are derived directly from embryonal tissues, e.g., shoot apex and root apex.

B.

Radial with exarch xylem

When xylem and phloem groups are located on different radii, the bundles are said to be radial e.g. root. The protoxylem element lie at the periphery and metaxylem in the centre, this condition is called exarch e.g. root.

D.

cork cambium, cork and secondary cortex

Periderm formation occurs in the root and stems of dicots and gymnosperm in extra stelar region with the help of cork cambium. Periderm is external secondary protective tissue and compreses of cork, cork cambium and secondary cortex.

B.

heartwood increases

In a woody stem, due to secondary growth, secondary xylem constitutes the bulk of the stem and is commonly called wood. Width of secondary xylem increases continuously with the age of the plant. 

Older stem have two regions- younger sapwood and older heartwood. Both sapwood and heartwood increase in size initially, but when a tree reaches a certain age, amount of heartwood increases and the amount of sapwood remains constant.

D.

periderm + cortex + pericycle + secondary phloem

Bark is a loose term and is used to define all the tissues outside vascular cambium. It is the outermost layer of stems and roots of woody plants. It is further differentiated into outer bark or rhytidome (consisting of dead cells) and inner bark (of living cells, i.e., periderm, cortex, pericycle and secondary phloem). The outer layer of the bark are being constantly peeled off on account of the formation of new secondary vascular tissues in the interior. Bark is insect repellent, decay proof, fire-proof and acts as a heat screen.

B.

lignin content is high

Lignin is a complex organic polymer that is deposited within the cellulose of plant cells. The lignin content is high in jute fibres which causes deterioration very quickly.

A.

If both assertion and reason are true and reason is the correct explanation of assertion

Heartwood formation occurs spontaneously because it is a genetically programmed process. As a result of continued secondary growth for several years, the older parts of the stem and its old branches have a part of its secondary xylem rendered non - functional. Therfore, heart wood is a modified or non- functional secondary xylem. It is also known as duramen. Sap wood is the functional outer younger rings of secondary xylem. It is also known as alburnum. With the passage of time and addition of new outer rings of secondary xylem due to cambial activity more rings ofthe sap wood are changed into heart wood. This leads to the increase in the thickness of heart wood, whereas the sap wood remains of about the same thickness.

A.

If both assertion and reason are true and reason is the correct explanation of assertion

Latex of some plants containing long chain hydrocarbons is considered to be a good substitute for liquid fuels or petroleum. Therefore, plants having large amount of latex with long chain hydrocarbons are known as petroplants. Cultivation of petroplants is also a part of energy-cropping.

The most common petroplants belong to families of Euphorbiaceae, Asclepiadaceae, Apocynaceae, Compositae, Labiatae, Sapotaceae, Urticaceae, etc., which have property of converting large amounts of their photosynthates into latex with hydrocarbons. Their hydrocarbon contents can be increased by genetic manipulations (genetic engineering). But commercial production of petroleum or liquid fuel alternative (through petroplants) is in early stage. The use of these petroplants may reduce the pressure on liquid fuel or petroleum.

C.

Sieve tube elements possess cytoplasm but no nuclei.

Sieve tubes in flowering plants consists of elongated living cells of the phloem. Their main function is to transport sugars and other important molecules necessary for plants. On maturity, these loose nucleus and other cellular organelles.

Mature cork cells are plant cells that form the protective water resistant tissue in the outer covering of stems and trunks. They are genetically programmed not to divide, but instead to remain as they are dead cells. They also possess lenticels. A lenticel is produced beneath a former stomata or stoma of the epidermis. They encloses intercellular space for gaseous exchange.

Passage cells help in transfer of water from cortex. Quiescent centre is present in root apical meristem.

D.

movement of substances between cells

A characteristic of most plant cells is the presence of cytoplasmic material that establish continuity between adjacent cells. These bridges are called plasmodesmata. These permit the free circulation of fluid, which is essential to the maintenance of plant cell toxicity.

C.

reserve for replenishment of damaged cells of the meristem

Quiescent centre is a region in the apical meristem of a root where cell division proceeds very slowly. It is a hemispherical region of inactive cells present in between the root cap and the active meristematic region of root apex. This zone contains several hundred cells which are characterized by having lower concentration of DNA, RNA and protein. The quiescent centre acts as reservoir of cells and becomes active whenever the previously active initials get damaged or during the establishment of the secondary roots.

B.

If both Assertion and Reason are true but the reason is not the correct explanation of the assertion

The apoplast is the system of adjacent cell walls which is continuous through the plant. As water evaporates from the mesophyll cell walls into the intercellular air spaces, tension develops in the continuous stream of water in the apoplast, and water is drawn through the walls in a mass flow by the cohesion of water molecules. When water moving through spaces in the cell wall reaches the endodermis, it's progress is stopped by a waterproof substance called suberin which is deposited in cell walls in the form of bands called casparian strips. Therefore water and solutes must pass through the cell surface membrane and into the cytoplasm of the cells of the endodermis.

C.

phellem - endodermis - pericycle - phloem

Phellem or cork is a tissue formed on the outer side of phellogen or cork cambium. It is protective in function.

Endodermis is the boundary between the cortex and the stele. It is a distinctly visible layer of cells immediately outside the vascular cylinder in roots and shoots.

Pericycle regulates the formation of lateral roots by rapidly dividing near the xylem elements of the root.

Phloem is the vascular tissue in plants which conducts sugars and other metabolic products downwards from the leaves.

C.

endodermis

The casparian strips are thick depositions of lignin or suberin on the walls of eridodermis. These are impervious to water and has discovered by Caspari.

B.

When xylem is blocked

Wilting is the loss of turgidity of leaves and other soft aerial parts of a plant causing their drooping, folding and rolling. It is caused by blocking of xylem.

C.

Sclerenchyma and trachea

The cells of sclerenchyma are long or short, narrow, thick walled and lignified. These are dead cells and do not perform any metabolic function. Tracheids (tracheary element) are elongated cells with tapering ends. The wall of tracheids is moderatly thick and usually lignified.

A.

it is a part of phloem

The phloem consists of sieve elements companion cells, phloem fibres and phloem parenchyma. Sieve tube members are long, slender, tube-like cells joined end to end to form long tubular channels, the sieve tubes.

A.

protostele

Protostele is simplest and most primitive type of stele, in which, vascular cylinder consists of solid core of xylem surrounded by phloem, pericycle and endodermis. There is no pith.

A.

root tip

Quiescent centre is a region in the apical meristem of a root where cell division proceeds very slowly or not at all. Although, the cells are capable of resuming meristematic activity should tissue surrounding them to be damaged.

D.

secondary meristematic tissue

The meristem that occurs in the mature regions of roots and shoots of many plants, particularly those that produce woody axis and appea later than primary meristem is called the secondary or lateral meristem. They are cylindrical meristems. Fascicular vascular cambium, interfascicular cambium and cork cambium are examples of lateral meristems. These are mainly responsible for producing secondary tissues.

B.

procambium

Procambiumis a tissue of narrow, elongated, prosenchymatous meristematic cells in vascular plants. It is grouped into strands differentiating just behind growing points of stems and roots and gives rise to vascular tissue.

A.

medullary rays

In dicot stems, the cells of cambium present between primary xylem and primary phloem is the intrafasicular cambium. The cells of medullary rays, adjoining these intrafascicular cambium become meristematic and form the interfascicular cambium. 

In dicot roots the innermost layer of the cortex is called endodermis. Next to endodermis lies a few layers of thick-walled parenchymatous cells called as pericycle.

B.

gaseous exchange

Plants have stomata and lenticles involved in gaseous exchange. In stems the living cells are organised in thin layers inside and beneath the bark. They have openings called lenticles.

Transpiration is the evaporative loss of water by plants. It occurs mainly through stomata in leaves.

Food transport occurs by the vascular tissue phloem from a source to a sink.

Photosynthesis is a physico-chemical process by which they use light energy to derive re- synthesis of organic compounds.

C.

number of annual rings

Age of a tree can be estimated by number of annual rings. The two kinds of woods that appear as alternate concentric rings, constitute an annual ring heartwood comprises dead elements with highly lignified walls that give mechanical support to the stem. The height and girth of a tree increases due to the activity of vascular cambium.

B.

xylem parenchyma

Medullary rays are the vertical plates of parenchyma cells running radially through the cylinder of vascular tissue in the stems and roots of plants. Each may be one to many cell in width.

Primary medullary rays occur in young plants and in those not showing secondary thickening. They pass from the cortex to the pith.

Secondary medullary rays are produced by the vascular cambium and terminate in xylem and phloem tissues. Medullary rays store and transport food materials.

C.

a specific part of DNA from the Ti-plasmid gets integrated with the plant chromosome

Agrobacterium tumifaciens causes Crown gall disease in dicotlyledonous plants. It infects the plant through its Ti- plasmid that integrates a segment of its DNA. Hence, it is known as T- DNA.

C.

A- 3; B- 2; C- 4; D- 1

B.

Only the outer layer will develop into epidermal cells

Even, if there is more than one tunica layer in stem apex, only the outer layer will develop into epidermal cells. The stem has three simple cell types, i.e. the parenchyma, collenchyma and sclerenchyma cells that are responsible for metabolic functions, repairing and healing wounds and storing starch.

C.

Region of elongation

Region of elongation is present just above to the meristematic region, it is about 2-5 mm in length. In this region the cells elongate resulting in increase in length. Root cap protects the root from injury at the time of growth.

B.

heart wood

Heart wood is also known as dead wood which is formed by the lignification or resin collection in sap wood. The wood is called secondary xylem. The cambium is in the ring of meristematic cell which produce secondary
xylem and phloem in dicots.

D.

sieve elements

An enucleated cell is a cell where the nucleus, and thus all genetic information, has been removed. Sieve elements are living enucleated structures.

A.

scattered in the ground tissue

Actactostele is a type of eustele, found in monocots, in which the vascular tissue in the stem exists as scattered bundles.

A.

Tylosis

Tyloses develop in tracheary elements as the balloon like enlargements due to protrusions axial and ray parenchyma cells. This clogs the cavity of the xylem vessels.

A.

monocot stem

The parenchyma when associated with the phloem is called phloem parenchyma. They are present in pteridophytes and most of dicotyledonous angiosperms. Phloem Parenchyma are absent in monocots and few dicots like Ranunculus.

A.

lack cambium

The monocots lack cambium and therefore, secondary growth also. Hence, the grafting is not possible in monocots.

C.

Tepals

Tepals are individual parianth segments. The parianth is collective name as undifferentiated sepals and petals. These are found in monocot flowers. The parianth segment of Gramineae are called lodicules.

D.

all of the above

In the root apex of angiosperm, cup shaped zone of inactive cells is known as quiescent centre. These cells do not divide. Instead, they become active, whenever the active initials are damaged. It also acts as a reservoir of cells relatively resistant to change.

C.

Intercalary meristem

Intercalary meristem lies between region of permanent tissue. It is a part of primary meristem attached by a permanent tissue. It is present in the intemodal regions of grasses and also sometimes in nodal region.

A.

xylem and phloem are seprated by cambium;

Collateral bundle, that is, phloem on outside and xylem on inner side. It is open when a strip of cambium is present between xylem and phloem. e.g., dicot and Gymnosperms stem.

C.

lateral meristems

Cork cambium and vascular cambium are lateral meristems and responsible for growth in thickness.