Water Stress - Responses of Plants to Stress

Water stress in a plant can result from drought, excess salinity in the soil and very low or high temperatures. It has been found that during water stress certain organic compounds such as sucrose and amino acids particularly proline accumulate and thus lower the osmotic potential in the cells. But the metabolic activity of the cell is not much affected.

However, the activity of some enzymes such as nitrate reductase and phenylalanine ammonia lyase decreases while activity of degrading enzymes like α-amylase and ribonucleases increases. It is proposed that the enzymes break down starch and other molecules into their monomeric units which make osmotic potential of the cells more negative.