Question

In waterlogged soil, plants generally are killed because of
(a) Deficiency of minerals
(b) Excessive absorption of water
(c) Absence of air in the soil
(d) Starvation

Answer 1

Hint: When the amount of water in the soil reaches its saturation point then it will lower the amount of oxygen in the soil resulting in less aeration and thus leads to the death of the plants.

Complete answer:
The condition where the amount of water in the soil is in maximum and no more extra amount of water can be absorbed by the soil. This results in a lower amount of oxygen in the soil resulting in waterlogging. This results in the air being restricted and the condition that occurs will be anaerobic respiration. When the plants are unable to acquire the required amount of oxygen then it will result in the plants being shredded off and killed.
-When the soil present is aerated then it has a required amount of air in the soil which helps the soil to respire and breathe.
-When the amount of oxygen is decreased in the soil then it will lower the rate of respiration in plants.
-The lower respiration rate in plants will result in lower permeability of the plasma membrane that leads to lower absorption of water which eventually will lead to the death of the plants.
-The waterlogging may later result in soil salinity as it will prevent the soil from leaching out the salts by irrigation.

So, the correct answer is ‘Absence of air in the soil’.

Note:
The other reasons why plants die are the excessive use of fertilizers, less or excessive amount of water and minerals, insects that attack plants, sunlight is too less, plant diseases, etc. To keep a check on plants one should spray insecticides regularly and provide the required amount of water and minerals to the plants with good and fertile soil.