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

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.

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.

A column of water in the xylem even in a tall tree normally does not sink because of its weight due to:

The apoplast pathway in plants includes all the following except:
1. the lumen of a xylem vessel
2. the lumen of a sieve tube
3. the lumen of tracheids
4. the cell wall of a root hair

Osmosis in plants would not be affected by:
1. water potential gradient
2. a difference in solute concentrations
3. type of cell membrane receptor proteins
4. number of aquaporins

Active transport of substances does not involve:
1. transport of solute along the concentration gradient.
2. use of a specific membrane transport protein.
3. hydrolysis of ATP.
4. transport of solute against a concentration gradient.

The direction of water movement in plants can always be predicted by measuring:
1. pressure potential
2. number of aquaporins
3. proton gradients
4. water potential (ψ)