Effects Of Sulfur Nutrition On Physiology Anti-drought Parameters Of Crops

Drought is one of severe constraints on farming and one of the important pathway in theresolution to drought is to increase the tolerance of crops. Sulfur is an essential element incrops nutrition, which plays a vital role in crop growth and metabolism. It has been reportedthat sulfur can stimulate the metabolism of sulfur-containing compounds in crops and also beof importance in photosynthetic pigments synthesis, enzymic activities, protein anabolism andcatabolism in plant. Sulfur nutrition regulates the functions of some channel proteins and hasa crucial role in the transmembrane transport of water and inorganic nutrient elements.Therefore, to study the effects of sulfur on the physiological indices of drought tolerance incrops has the theoretic meaning in the elucidation of the physiological mechanism of plantnutrition and the practical importance in guiding the appropriate water and fertilizermanagement in dryland farming. In this study, maize and two different cultivars of wheat were grown under water deficitin hydroponic culture and pot tests with different sulfur supply and the chlorophyll content,MDA, soluble protein, GSH and GSH-PX in tested crops were measured to elucidate the roleof sulfur in the drought tolerance in crops and to provide some scientific data in theunderstanding of the physiological mechanism of drought tolerance in crops. Our conclusion were as followed: 1. Sulfur nutrition significantly affects the photosynthetic pigments content in leaves ofcrop seedlings and the increased S supply resulted in the increase of chlorophyll andcaroteniod. With the concentration of S in the nutrient solution, the chlorophyll content infunctional leaves apparently increased and it seemed there was a threshold of S concentrationin this case. Drought resulted in the decrease of chlorophyll in crops' functional leaves, butwhich was inhibited with the concentrated S supply in solution. when water was resupplied tocrops, sulfur addition showed a positive role in the restore of chlorophyll in leaves. 2. In the hydroponic cultures and pot tests we found that the water-sensitive anddrought-tolerant cultivars responded differently not only to drought stress but also to S supply.Both Chla and chlb in maize and higher water and fertilizer required wheat cultivars wereresponded sensitively to S supply. The chlorophyll content in S supply treatment weresignificantly higher than that in the low S supply. 3. When the drought continued, MDA and soluble protein content were increased andthey showed a decline in the response to the removal of drought stress. MDA and solubleprotein content in all the S supply treatments were lower than those in no S supply suggestingthat the supply of S could alleviate the injury of membrane-related lipid peroxidation causedby drought stress. 4. GSH content closely correlated to drought tolerance in crops. In wheat, the GSH wereincreased under drought and decreased when the drought stress was removed. In the responseof GSH to drought, there were different performance between the two wheat cultivars and thehigher GSH in ShanHe Ⅺ was a kind of marker of drought-tolerant cultivars. Theaccumulation of GSH in crops were related to S supply, a higher GSH levels in S supply andan induced increase of GSH in some cases of S deprivation. Without S supply, although GSHkept a higher level in ShanHeⅪ, its response to drought stress were obviously different,45.45% higher of GSH in –SD treatment than in –SH showing a responsibility to stresses ofdrought-tolerant cultivars which differed from the performances in S supply. Similar GSHcontents were observed in –SH and –SD of the water-sensitive wheat cultivars, ZhengYinⅠsuggesting S limit affected the responsibility to drought stress in water-sensitive cultivars tosome extent. 5. GSH-PX activities in crops also notably changed in the response to drought. In theinitial 24h of drought stress, GSH-PX activities increased sharply. Wh...