Transport in Plants

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Question 1

A column of water within xylem vessels of tall trees does not break under its weight because of

  • Dissolved sugars in water

  • Tensile strength of water

  • Lignification of xylem vessels

  • Positive root pressure

Solution

B.

Tensile strength of water

A column of water within xylem vessels of tall tree does break under its weight because of high tensile strenght of water, i.e. an ability to resist a pulling force. This high tensile property depends on cohesion, adhesion and surface tension property of water. Due to these forces only transpiration drive ascent of xylem sap occurs.

Question 2

A protoplast is a cell

  • without plasma membrane

  • without nucleus

  • undergoing division

  • without cell wall

Solution

D.

without cell wall

A protoplast is a cell without cell wall. It is a plant, bacterial or fungal cell that had its cell wall completely or partially removed using either mechanical or enzymatic means. 

Question 3

Approximately seventy percent of carbon dioxide absorbed by the blood will be transported to the lungs

  • as bicarbonate ion

  • in the form of dissolved gas molecules

  • by binding to RBC

  • as carbamino - haemoglobin

Solution

A.

as bicarbonate ion

Because of its high solubility, about 7% of carbon  dioxide gets dissolved in the blood plasma and is carried to the wings in the same way. The largest fraction of carbon dioxide, i.e., (about 70% ) is converted  to bicarbonates (HCO3-) and transported in the plasma.

CO subscript 2 space plus space straight H subscript 2 straight O space rightwards harpoon over leftwards harpoon from anhydrase to carbonic of space straight H subscript 2 CO subscript 3 space rightwards harpoon over leftwards harpoon from anhydrase to Carbonic space of space HCO subscript 3 superscript minus space plus straight H to the power of plus

About space left parenthesis negative 23 percent sign space of space CO subscript 2 right parenthesis space is space carried space by space haemoglobin space as space carbominohaemglobin

CO subscript 2 space plus Hb space left parenthesis haemoglobin right parenthesis space rightwards harpoon over leftwards harpoon stack space HbCO subscript 3 with carboamino space haemoglobin below

Question 4

Carrier ions like Na+ facilitate the absorption of substance like

  • amino acids and glucose

  • glucose and fatty acids

  • fatty acids and glycerol

  • fructose and some amino acids

Solution

A.

amino acids and glucose

Active transport occurs with the help of energy, usually against a concentration gradient. For this, cell membrane possess carriers and gated channels. Active transports of one substance are often accompanied by permeation of other substances. The phenomenon is called secondary active transport. It is of two main types- Co-transport (eg, glucose and some amino acid along with inward pushing of excess Na+) and counters transport (Ca2+ and H+ movement outwardly as excess Na+ passes inwardly).

Question 5

Guard cell help in

  • protection against grazing

  • transpiration

  • guttation

  • fighting against infection

Solution

B.

transpiration

Guard cells help in transpiration. Each stomatal opening is surrounded by two specialized epidermal cells, called guard cells. Because of their small size guard cells are rapidly influenced by turgor change and thus regulate the opening and closing of stomata.