High temperature effects on photosynthesis, PSII functionality and antioxidant activity of two Festuca arundinacea cultivars with different heat susceptibility

High temperature stress is a major limiting factor in the growth and development of tall fescue (Festuca arundinacea) in transitional and warm climatic regions. In this study, we evaluated the photosynthesis, PSII functionality, and antioxidant activity of two tall fescue cultivars, Jaguar 3 brand (heat-tolerant) and TF 66 (heat-sensitive) in response to high temperature stress. High temperature stress caused a net photosynthetic rate reduction in the two plants due to stomatal and non-stomatal limitations, photoinhibition increase, and Rubisco activity reduction. High temperature stress modified PSII functionality in leaves of the two plants, manifested by lower variable chlorophyll fluorescence yield (Fv), maximum photochemical efficiency of photosystem ІІ in dark adapted leaves (Fv/Fm), and efficiency of the open reaction centre in light (ΦPSIIopen) in the two heat shocked cultivars. Heat stress led to reductions in the chlorophyll a+b and chlorophyll/carotenoid ratios and to an increase in the chlorophyll a/b ratio for the two stressed cultivars. Moreover, high temperature stress significantly increased lipid peroxidation, decreased cell membrane thermostability, and changed the activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD) in the leaves of both plants. All the above effects induced by high temperature were more expressed in the TF 66 than in Jaguar 3 brand. Our results contain some insights which may prove useful in the selection and breeding of heat-tolerant tall fescue turfgrass cultivars.