Physiological performance of sunflower genotypes under combined salt and drought stress environment

The physiological performance of some sunflower genotypes (S.28111, SF0049, Hysun-33, Hysun-39) under salt, drought stress separately and in combination was examined. Salt, drought and a combination of these stresses were applied to plants by gradual increments. The plants were exposed to stress for two weeks. Relative water content, osmotic potential, stomatal conductance, performance index, dark adapted quantum yield and chlorophyll contents were reduced upon salinity and drought stresses. However, when plants were subjected to a combination of these stresses, a greater reduction in all tested attributes was observed. Proline and carotenoid contents in drought stress were elevated compared to salt stress. Superoxide dismutase (SOD) and catalase (CAT) showed the highest activity in individual salt and drought stress with less accumulation of H2O2. Combined stress reduced the activity of antioxidant enzymes which ultimately decreased the physiological performance of sunflower plants. However, among the tested genotypes, S.28111 and SF0049 were found to be more tolerant to drought, salt and combined stress than both Hysun genotypes. The physiological performance of genotypes against salinity and drought individually and in combination is discussed in detail