Abstract:Crop plants could rarely attain their genetic potential yield because of environmental, limitations especially lack of water. About 28 % of the world‘s arable land is subiected to drought stress. The worldwide losses in yield by water stress probably exceed the losses by all other causes combined. Plant water deficits affect every aspect of plant life including photosynthesis, respiration, absorption of water and mineral elements, growth, develop- ment, reproduction and so on. The present review mainly intr...