Physiological Screening Against Abiotic Stress

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 thesestresses were applied to plants by gradual increments. The plants were exposed to stress for two weeks. Relative watercontent, osmotic potential, stomatal conductance, performance index, dark adapted quantum yield and chlorophyllcontents were reduced upon salinity and drought stresses. However, when plants were subjected to a combination ofthese stresses, a greater reduction in all tested attributes was observed. Proline and carotenoid contents in droughtstress were elevated compared to salt stress. Superoxide dismutase (SOD) and catalase (CAT) showed the highest activityin individual salt and drought stress with less accumulation of H2O2. Combined stress reduced the activity ofantioxidant enzymes which ultimately decreased the physiological performance of sunflower plants. However, amongthe tested genotypes, S.28111 and SF0049 were found to be more tolerant to drought, salt and combined stress thanboth Hysun genotypes.The physiological performance of genotypes against salinity.