Impact of soil drought stress on photochemical efficiency of photosystem II and antioxidant enzyme activities of Phaseolus vulgaris cultivars

Common bean (Phaseolus vulgaris L.) cultivars (cvs) (Goynuk 98, Karaca.ehir 90, .ehirali 90, ES 855, and Yunus 90) were subjected to drought stress in order to assess the levels of drought tolerance through the analysis ofgrowth parameters, leaf water potential (Ψleaf), stomatal conductance (gs), chlorophyll (chl) content, and lipidperoxidation. Significant differences were recorded among cultivars in most traits. Yunus 90 was identified as the mosttolerant, and Karaca.ehir 90 was the most sensitive. Furthermore, the changes in antioxidant enzyme activities, H2O2 content, and Photosystem II were investigated under drought stress, where Antioxidant enzyme activities increased while H2O2 contents decreased. In Yunus 90, increases in catalase (CAT) and ascorbate peroxidase (APX) activities were higher than those of the other cvs. Increase in GPX activity was higher in Karaca.ehir 90 compared to Yunus 90. Drought stress reduced quantum yield of PS II photochemistry („UPSII) and photochemical quenching (qP) in all cultivars. The reduction was more pronounced in Karaca.ehir 90. These results showed that different common bean cvs had different photochemical efficiencies and used different antioxidant enzymes in order to scavenge reactive oxygen species.