Climate models predict greater increases in temperature in the future. The impacts of high temperature on wheat (Triticum aestivum L.) are not well understood. The aim of this study was to quantify the effects of high temperature on photosynthetic performance, pigment content, relative water content, lipid peroxidation, proline accumulation as well as antioxidative enzymes on wheat seedlings. Surface sterile seeds were soaked in water for 6 hours and were put on filter paper moisture with water to germinate. Germinated seeds then transferred to pots of vermiculite and fed with Hoagland solution. Wheat seedlings were exposed to increasing day/night temperature (25/20°C, 30/25°C and 35/30°C). Chlorophylls and carotenoids contents decreased significantly at high temperature stress. The reduction of chlorophyll a and b contents of leaves was detected after 35/30°C day/night temperature treatment in leaves. The maximum quantum yield of PSII (FV/FM), photon yield of PSII (ΦPSII), non-photochemical quenching (QNP) in the stressed seedlings were inhibited, while photochemical quenching (QP) was increased. The positive correlations between chlorophyll a content and FV/FM, total chlorophyll content and ΦPSII, QNP were found. Antioxidative responses of rice seedlings were also explored. A significant increase in superoxide dismutase, catalase, glutathione reductase and asscorbate peroxidase activities under high temperature stress.
