Abstract

Pepper is mostly produced in greenhouses and fields in spring up to the end of summer. The reproductive stage coincides with high temperature of summer, which causes flowers to drop, leading to reduction in the yield, Se as a beneficial element can improved some stress indices. Control randomized design experiment was conducted to investigate the effect(s) of Se on heat stresses of pepper in control environment. Se in three concentrations of  SeCl2 (4 (Se1), 6 (Se2) and 8 (Se3) mg  L−1) was used at 35 ± 2 °C for 4 h a day, matching the high afternoon temperature. Growth, photosynthesis traits (Photosynthesis rate, transpiration and stomatal conductance), flower dropping and antioxidant changes were all measured. Results showed that Se1 decreased deleterious effects of heat stresses on vegetative traits (fresh and dry weight of fruit). Including dry weight of shoot, fresh and dry weight of root, and reproductive growth, such as Fresh weight and dry weight of fruit, flowers and fruit number. Photosynthesis rate, fruit antioxidant and phenol improved with the application of Se to heat stresses. POD and SOD activity increased, and MDA content decreased with Se application at the high temperature. Se also improved the P and S uptake. Generally, using 4 and 6 mg L−1 of Se could improve growth and physiological and phytochemical parameters of pepper and decrease the flower dropping at high temperature.