To explore the beneficial effect of melatonin on photosynthesis of wheat seedlings under Cr6+ stress, Yumai 51(Cr-sensitive) and Yangmai 16(Cr-resistant) were used as the experimental materials in this study. The effects of exogenous melatonin pretreatment(100 μmmol·L-1 melatonin) on the changes of photosynthetic characteristics and nutrient absorption of wheat seedlings under Cr6+ stress were studied through hydroponic method. The results showed that Cr6+ stress significantly reduced chlorophyll content, stomatal conductance(Gs) photosystem Ⅱ activity, ultimately resulting significant reduction of net photosynthetic rate(Pn). Besides, Cr6+ stress significantly reduced the uptake and transport of nutrient elements(N, P, K, Mg, Fe, and Mn) in roots. However, exogenous melatonin pretreatment significantly increased the Pn, Gs, chlorophyll content, actual photochemical efficiency(ΦPSⅡ), maximum photochemical efficiency(Fv/Fm), photochemical quenching(qL), electron transport rate(ETR), and nutrient element contents in roots and leaves of wheat seedlings under Cr6+ stress. Therefore, exogenous melatonin pretreatment can improve the nutrient absorption and transport capacity, stomatal opening and CO2 conduction capacity, light energy absorption and electron transport capacity of wheat seedlings under Cr6+ stress, and thus alleviate the inhibition of photosynthesis of wheat seedlings under Cr6+ stress. |