Question

A farmer made an observation in a backwater paddy field of coastal Kerala that the paddy plants wilt during noon onwards everyday but appear normal next morning. What would be the possible reason for wilting?
A) The rate of water absorption is less than the rate of transpiration in the afternoon
B) The rate of water absorption is more than the rate of transpiration in the afternoon
C) The changes in the rate of water absorption and transpiration are not associated with wilting
D) The rate of water absorption is not related to the rate of transpiration

Answer 1

Wilting is the term used in plants who lose water from them due some uncertain conditions. Those uncertain conditions can be due to drought, high salinity, saturated soil conditions, bacteria or fungi that clog the plants and also can cause temperature falls. As we discussed Plants tend to lose rigidity in their non-woody parts due to above mentioned conditions. In non-lignified plants, this happens as the turgor pressure of the plant begins to fall towards zero.

Complete answer:
Option A) The rate of water absorption is less than the rate of transpiration in the afternoon- water absorption in higher plants is done through root hairs which are under contact with soil water and root hair zone. As we know, during the morning the paddy field seems fine but in the afternoon it wilts. The possible reason behind this is the loss of water in the afternoon. We discussed above the conditions that affect the crop wilting. Hence, the rate of water absorption is less than the rate of transpiration in the afternoon.
So, option A is correct.
Option B) The rate of water absorption is more than the rate of transpiration in the afternoon. Transpiration is the process of exhalation of water through evaporation from aerial parts of plants such as leaves, stems, flowers. Water is necessary for the growth of plants and its metabolism too. Roots take up water in plants but most water is lost by guttation and transpiration. Factors affecting the water absorption are due to temperature rise in the afternoon and the uptake of water is less than the transpiration. It is harder for the plant to withstand the heat.
So, option B is not correct.
Option C) The changes in the rate of water absorption and transpiration are not associated with wilting- Wilting is the process of loss of water from plant parts. Rates of transpiration are affected by environmental factors such as temperature, wind speed, humidity, light intensity as transpiration occurs in stomata and stomata open wider to allow more carbon dioxide into the leaf for photosynthesis. The plant staying in hot or dry environments is adapted to reduced transpiration. But plants like paddy are not used to living in dry conditions. They require water but due to unfavorable conditions they lack the water absorption.
So, option C is not correct.
Option D) The rate of water absorption is not related to the rate of transpiration – both the systems are related to each other as we discussed above the factors which affect the rate of absorption and transpiration as well. The relation between these two indicates the growing conditions.
So, option D is not correct.

So the correct answer is option A.

Note:
Transpiration decreases the pressure called hydrostatic pressure in plants due to which water easily moves upward due to this capillary action. Water eventually released to the atmosphere as vapor via plant stomata. Water is released in the medium of water vapor by evaporation and they are released from leaves of the plant.