الفهرس 
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Abstract
The history of man has always been marked by a special relationship
with water. Biological function and the properties of life are often directly
a result of the properties of water. It is the most abundant molecule in
living organisms and it is, therefore, possible to learn a great deal about life
by learning about water.
On a global basis, water is a paramount factor in determining the
distribution of species, and the responses and adaptation of ’species to
water-stress are critical for their success in any environmental niche
(Bazzaz and Fajer, 1992). Cell enlargement results from an increasing
water content of the tissues. Water is absorbed by osmosis, and turgor
pressure builds as the water enters. The lack of full turgor pressure keeps
the water potential lower inside the cells than outside (Maruyoma and
Boyer, 1994).
Drought is probably the most important climatic factor limiting crop
productivity world-wide and particularly in temperate regions (Jones and
Corlett, 1992).
Generally, water deficit reduces the growth of drought-sensitive
glycophytes. Reduction in plant growth by water deficit may result from
the disturbance of water balance, reduction of leaf expansion and
elongation, mitotic division of cells, fresh and dry weights, changes in
various physiological and metabolic processes such as decline in solute and
antioxidant accumulation and expression of stress-specific genes (Hughes
et aI., 1989; Munns and Sharp, 1993; Sangwan et al., 1994; Nonami et al.,
1997; Schuppler et al., 1998).