Effect of nitrogen on yield and some physiological characteristics of sorghum (Sorghum sp.) genotypes under drought stress

In order to investigate the effect of drought stress and nitrogen application on growth and some physiological characteristics of sorghum genotypes, an experiment was conducted in a split-split plot with randomized complete block design in three replications at Research farm of collage of agriculture, Isfahan University of Technology. Experimental treatments consisted of two irrigation regimes (50% and 85% depletion of available soil water), two levels of nitrogen fertilizer (available rate, 121.5 kg ha-1, nitrogen from Urea fertilizer, N= 45%) and 15 sorghum genotypes (Pegah, Sepideh, GS4, GS5 , GS24, GS25, GS26, GS28, KGS29, KGS33, MGS1, MGS5, SF001, SF002, SF003). The results showed that drought stress significantly decreased biological yield by decreasing plant leaf area, plant height, quantum efficiency of photosystem II and chlorophyll content. In contrast, the activity of antioxidant enzymes including catalase, ascorbate peroxidase and peroxidase was significantly increased under drought stress conditions. Application of nitrogen under normal irrigation and drought stress increased all the above traits except chlorophyll a/b ratio and ascorbate peroxidase activity, however, this increase was less in drought condition. Therefore, application of nitrogen fertilizer under drought stress can modulate the effect of stress and increase yield. Among the studied genotypes, SF001, SF002 and MGS5 genotypes had the highest response to nitrogen and the least sensitivity to drought stress. Therefore, they can be used in areas of water scarcity.