Q. No.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
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
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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.
| 1. Only A | 2. Only B |
| 3. Both A and B | 4. Neither A nor B |
Plants came on land before animals. All the following were evolutionary adaptations for terrestrial life except:
1. guard cells
2. photosynthesis
3. rhizoids
4. vascular bundles
Trace the correct path of water from the soil through the plant to the atmosphere:
| 1. | endodermis- cortex - epidermis - vessel elements - intercellular spaces in mesophyll - stomata. |
| 2. | epidermis - cortex - Casparian strip - endodermis - sieve cells - intercellular spaces in the mesophyll - stomata. |
| 3. | Casparian strip - root hairs - epidermis - cortex - xylem - endodermis - intercellular spaces in mesophyll - stomata. |
| 4. | root hairs - cortex - endodermis - vessel elements - intercellular spaces in mesophyll - stomata. |
Closure of stomata occurs as the guard cells:
1. lose water.
2. begin photosynthesis reducing internal concentration.
3. pick up chloride ions.
4. gain potassium ions.
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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.
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A column of water in the xylem even in a tall tree normally does not sink because of its weight due to:
| 1. | the exceptionally large diameter of vessels. |
| 2. | bubbles too large to be transported even through the pits. |
| 3. | the presence of strong ion concentrations near the top of the tree. |
| 4. | the tensile strength of a column of water. |
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The type of phyllotaxy seen in most angiosperms is:
1. Alternate
2. Opposite
3. Whorled
4. Random
A plant treated with a fungicide may develop:
1. Loss of root hair
2. Inhibition of transport proteins in root cells
3. Deficiency of mineral
4. Formation of root knots
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