Question

which of the following environmental stimuli would most likely cause stomatal opening?

a. Excessive watering

b. a prolonged drought

c. decrease in sunlight

d. a very hot day

Answer 1

Answer: a. Excessive watering

Explanation:

The opening and closing of stomata depends on the need of the plant to regulate transpiration in order to lose water and heat when required. When the plant has excessive water in it, the guard cells around the stomata become turgid due to the presence of excess water. This causes the guard cells to expand and thereby causes the stomata to open.

A prolonged drought will cause the plant to lose water. As a result, when the water poteintial of the leaf drops below a particular threshold, the guard cells become flaccid and close.

When the sunlight intensity drops, the prospects of photosynthesis also lower. Thus, the stomata get closed because the gaseous diffusion (intake of carbondioxide and expelling of oxygen) is not required. Since stomatal opening also causes water loss by transpiration, the plant closes its stomata to prevent water loss when no photosynthesis is occuring simultaneously.

On a very hot day, the plant happens to lose its water content. This causes the guard cells to become flaccid and thus causes stomatal closure.

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