Transport in Plants · Question 14

Which of the following facilitates opening of stomatal aperture?

1. Decrease in turgidity of guard cells
2. Radial orientation of cellulose microfibrils in the cell wall of guard cells
3. Longitudinal orientation of cellulose microfibrils in the cell wall of guard cells
4. Contraction of outer wall of guard cells

Water vapour comes out from the plant leaf through the stomatal opening. Through the same stomatal opening carbon dioxide diffuses into the plant during photosynthesis. Reason out the above statements using one of following options.

1. The above processes happen only during night time.
2. One process occurs during day time and the other at night.
3. Both processes cannot happen simultaneously.
4. Both processes can happen together because the diffusion coefficient of water and CO2 is different.

A few drops of sap were collected by cutting across a plant stem by a suitable method. The sap was tested chemically. Which one of the following test results indicates that it is phloem sap?

1. Acidic
2. Alkaline
3. Low refractive index
4. Absence of sugar

Root pressure develops due to

1. passive absorption
2. active absorption
3. increase in transpiration
4. low osmotic potential in soil.

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

1. lignification of xylem vessels
2. positive root pressure
3. dissolved sugars in water
4. tensile strength of water.

In a ring girdled plant

1. the shoot and root die together
2. neither root nor shoot will die
3. the shoot dies first
4. the root dies first.

Transpiration and root pressure cause water to rise in plants by

1. pushing it upward
2. pushing and pulling it, respectively
3. pulling it upward
4. pulling and pushing it, respectively.

Which one gives the most valid and recent explanation for stomatal movement?

1. Starch hydrolysis
2. Guard cell photosynthesis
3. Transpiration
4. Potassium influx and efflux

Which of the following criteria does not pertain to facilitated transport?

1. Transport saturation
2. Uphill transport
3. Requirement of special membrane proteins
4. High selectivity

Function of companion cells is :

1. Providing water to phloem
2. Loading of sucrose into sieve elements
3. Loading of sucrose into sieve elements by passive transport
4. Providing energy to sieve elements for active transport