Journal of Soil and Plant Interactions

Selenium (Se) is an important microelement for plants and has been shown to improve growth under normal and stressed conditions. In this study, effect of Se and nano-selenium (N-Se) on hydroponically-grown tomato (Lycopersicum esculentum Mill. cv. ‘Halil’) on photosynthesis, antioxidant activity and total polyphenolic content was assessed. A factorial experiment with three temperature levels and Se and Nano Se level was designed. All plants were first exposed to Se or N-Se [Se at 0 µM (control), 2.5 µM (Se1), 5 µM (Se2) and 8 µM (Se3)], while N-Se was applied at four levels [1 µM (N-Se1), 4 µM (N-Se2), 8 µM (N-Se3) and 12 µM (N-Se4)]. Plants were exposed to three temperature levels [optimal temperature (25.17 ± 2 °C day/night = T1), high temperature (40 °C for 24 hr = T2) and low (chilling) temperature (10 °C for 24 hr = T3)]. They were then placed at normal temperature conditions for 7 days and photosynthetic and antioxidant factors were measured. Based on the results, both temperature-related stresses had negative effect on tomato growth. However, under high temperature stress, photosynthetic rate, mesophyll conductance and photosynthetic water use efficiency improved significantly. While, cold stress significantly enhanced transpiration. Most photosynthetic parameters could be improved in the presence of Se and N-Se. In Se1 treatment, under the temperature stress, the best photosynthetis rate, respiration and mesophyll conductance were obtained and plant resistance was enhanced. In N-Se treatments, N-Se1 had the best results of photosynthetis rate, antioxidant and phenol. However, in the absence of stress, the use of Se or N-Se, especially at higher concentrations (i.e., 5 and 8 µM), negatively impacted photosynthetic rate, internal CO2 of stomata, mesophyll conductance and photosynthetic water use efficiency. In general, under the low and high temperature stress, the physiological parameters of tomato were improved in N-Se1 treatment.