الفهرس 
ContentsOnly 14 pages are availabe for public view
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Abstract
The work planned in this research program aims to cultivate rice plants under low water supply due to rice is the most widely grown and affected crop by water shortage, therefore we need new technologies in order to face water shortage and some ways must be available to grow rice with lesser demands of water. Drought is an important limiting factor for crop production and it is considered a very serious problem in many regions of the world. To improve rice productivity under limited water supply, it is important to understand the mechanism of responses under drought condition and the effect of this stress on rice plant must be taken into consideration besides, how Co can nullify or reduce this stress on rice plants. Therefore using Co as a beneficial element for retardation of senescence of leaves, increasing drought resistance, regulations of alkaloids accumulation, production of vitamin B12 , inhibition of ethylene biosynthesis is important strategy to improve rice resistance to drought stress. The two used rice cultivars (Sakha 104 as a drought sensitive) and (Giza178 as a drought tolerant) pre-soaked in appropriate concentrations of CoSO4 solutions (10µM for Giza 178 and 44.5 µM for Sakha104) for 72 hours before cultivation then the seedlings of both cultivars transplanted in a mixture of clay-sandy soil (2:1 v/v) in pots (25 cm in diameter). The treatments were applied to all transplants of both cultivars (irrigated every 4 days; as control, irrigated every 6 days; as moderate drought stress and irrigated every 8 days; as severe drought stress) as alone or in combination with the appropriate concentrations of CoSO4 for each cultivars. The experimental results obtained in this study were recorded in the nursery stage (outside the drought stress) and the three growth stages (vegetative, reproductive and yield) exposed to drought stress. This study includes investigating the effects of Co treatment alone or in combination with the two levels of drought stress on plant growth, water relations and changes in the contents of different metabolic aspects such as photosynthetic pigment, carbohydrates, protein, proline, MDA, electrolyte leakage, vitamins, ionic content, hormonal levels (ABA), mineral nutrition, some antioxidant activities and protein banding pattern of rice grains.