Answer to Question #54139 in Biology for C.E. Munasinghe

Inadequate oxygen supply to root system results in plant wilting under warm conditions and high light levels.
Insufficient oxygen reduces the permeability of the roots to water. It results in accumulation of toxins. As a result, water and minerals are not absorbed in the needed amount to support plant growth.
In the continuous conditions of lack of oxygen plant roots produce stress hormone – ethylene. It accumulates in the root system and causes collapse of the whole plant.