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Egyptian Journal of Agronomy http://agro.journals.ekb.eg/ Review 20T HE WATER stress harshly influences the plant growth and development with considerable reductions in plant growth and biomass accumulates. It declines the number of bolls per plant, bolls weight, and seed cotton (Gossypium spp.) yield. Fiber length, fiber strength, seed index and boll weight are reduced dynamically. The relative leaf water contents, transpiration rate and leaf water potential are decreased while leaf and canopy temperature is increased under water stress conditions. Limited water availability restricts the total uptake of nutrients, thus deprecating their concentration in the plant tissues. The major effects of water stress on the plants are lowered photosynthesis stimulated by reduced leaf expansion, early leaf senescence, deteriorated photosynthetic machinery and reduction in food production.The Plant accomplishes escape from moisture stress by shortening its growing season which results in a reduction in yield. The plants cut down their water spending under water stress conditions by dercreasing the number and area of leaves to minimize the yield losses. The growth and development of tolerant genotypes are relatively fast because of retention of more moisture from soil earlier. Genes are induced by water stress, categorized into regulatory and functional genes; from them, functional genes produce functional proteins, whereas regulatory genes product regulatory proteins like transcriptional factors, they control a cluster of genes by regulating the expression of different targeted genes in their promoter region through specific binding of it with cis-acting elements. The development of stress-tolerant cotton varieties based on the stability of yield and yield components under water stress conditions should be the prime focus of breeders.