Plant and Human Physiology NDA Questions

NDA BIOLOGY

Plant and Human Physiology MCQ Questions


7.
Turgor pressure (TP) is the pressure exerted by the cell contents against the cell wall. A fully turgid cell has:
A.
Zero turgor pressure
B.
Maximum turgor pressure and zero osmotic potential difference with outside
C.
Equal TP and OP causing no net water movement but TP is zero
D.
Negative turgor pressure
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ANSWER :
B. Maximum turgor pressure and zero osmotic potential difference with outside
8.
The upward movement of water in tall trees against gravity is best explained by the:
A.
Capillary action alone
B.
Active transport of water by xylem cells
C.
Cohesion-tension (transpiration pull) theory
D.
Root pressure theory alone
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ANSWER :
C. Cohesion-tension (transpiration pull) theory
9.
Guttation is the exudation of water droplets from hydathodes at leaf margins. It occurs when:
A.
Transpiration rate is very high
B.
Soil water potential is very low
C.
Stomata are fully open
D.
Root pressure is high and transpiration is very low (usually at night/early morning)
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ANSWER :
D. Root pressure is high and transpiration is very low (usually at night/early morning)
10.
Transpiration is the loss of water in the form of vapour from aerial parts of plants. The major pathway of transpiration in plants is through:
A.
Lenticels
B.
Stomata (stomatal transpiration)
C.
Cuticle
D.
Root surface
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ANSWER :
B. Stomata (stomatal transpiration)
11.
The opening and closing of stomata is regulated by:
A.
Changes in turgor pressure of guard cells
B.
Pressure from neighbouring mesophyll cells
C.
Hormone signalling from phloem only
D.
Changes in root pressure
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ANSWER :
A. Changes in turgor pressure of guard cells
12.
The pressure-flow hypothesis (Munch's hypothesis) explains translocation in phloem. According to this hypothesis, sugar moves from source to sink due to:
A.
Transpiration pull acting on phloem
B.
A turgor pressure gradient — high pressure at source (loading area) to low pressure at sink (unloading area)
C.
Active transport using ATP pumps in sieve tubes
D.
Electrical potential gradient along sieve tubes
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ANSWER :
B. A turgor pressure gradient — high pressure at source (loading area) to low pressure at sink (unloading area)