Identify the incorrect statement regarding cohesion-tension theory that explains the process of water flow upwards through the xylem of the plants:

1. Transpiration in leaves creates tension (differential pressure) in the cell walls of mesophyll cells.

2. Because of this tension, water is being pulled up from the roots into the leaves.

3. The pull is helped by cohesion (the stickiness between water molecules and the hydrophilic cell walls of plants) and adhesion (the pull between individual water molecules, due to hydrogen bonds).

4. This mechanism of water flow works because of water potential (water flows from high to low potential), and the rules of simple diffusion.

Consider the following two statements:
I. The evolution of ${\mathrm{C}}_4$  photosynthesis is probably one of the strategies for maximizing the availability of ${\mathrm{CO}}_2$ while minimizing water loss.
II. Plants with ${\mathrm{C}}_4$ photosynthesis close their stomata during day and open them in night.
1. Both I and II are correct
2. I is correct and II is incorrect
3. I is incorrect and II is correct
4. Both I and II are incorrect

Which of the following will always be a “sink” in a plant?

Consider the following events occurring during mass flow [pressure flow] of phloem sap at the source. The initial events are given in correct chronological sequence. But some of the statements carry mistakes regarding the principles of the process. Identify them:
I. The sucrose is passively transported to the companion cells of the smallest veins in the leaves.
II. The sucrose is actively transported from the companion cells to the sieve tube elements.
III. Water moves by osmosis from the nearby xylem in the same leaf vein.
IV. Hydrostatic pressure moves the sucrose and other substances through the sieve tube cells, towards a sink.
1. I and II only
2. III and IV only
3. I, II and III only
4. I, II, III and IV

With respect to the mass flow translocation of phloem sap, the following events are given in the correct chronological sequence. Identify the statements that do not carry any mistake regarding the principles of the process:
I. In the storage sinks sucrose is removed into apoplast prior to entering the symplast of the sink.
II. Water moves out of the sieve tube cells by osmosis.
III. The phloem sugar is removed by the cortex of both stem and root, and is consumed by cellular respiration or else converted into starch.
IV. Finally relatively pure water is left in the phloem and this is thought to leave by osmosis or be drawn back into nearby xylem vessels by suction of the transpiration pull.
1. I, II and III only
2. I, II and IV only
3. II, III and IV only
4. I, II, III and IV

In classic experiments on the translocation of organic solutes performed by the Italian anatomist Marcello Malpighi in 1686, the bark of a tree was removed in a ring around the trunk. This experiment, called girdling, was also done by T. G. Mason and E. J. Maskell in 1928. The following were the observations:
I. It has no immediate effect on transpiration.
II. Sugars accumulate above the girdle—that is, on the side toward the leaves—and are depleted below the treated region.
What conclusion/s can be drawn from the above observations?
A: Water moves in the xylem, interior to the bark.
B: Sugar is transported in the bark of the tree and that the sieve elements are the cellular channels of sugar transport.

Plants came on land before animals. All the following were evolutionary adaptations for terrestrial life except:
1. guard cells
2. ${\mathrm{C}}_3$ photosynthesis
3. rhizoids
4. vascular bundles

Trace the correct path of water from the soil through the plant to the atmosphere:

Closure of stomata occurs as the guard cells:
1. lose water.
2. begin photosynthesis reducing internal ${\mathrm{CO}}_2$ concentration.
3. pick up chloride ions.
4. gain potassium ions.

Guttation is:
1. deposition of dew drops on the leaves in the morning.
2. shrinking of protoplast away from the cell wall.
3. evidence of root pressure.
4. cavitation in the water column.