Effects of foliar application of magnesium sulfate on photosynthetic characteristics, dry matter accumulation and its translocation, and carbohydrate metabolism in grain during wheat grain filling

Our previous studies showed that foliar applied magnesium sulfate during the booting stage can effectively increase wheat grain weight. To explore the effects of foliar application of magnesium sulfate during wheat grain filling on photosynthetic characteristics of flag leaf and grain filling, an experiment was conducted using winter wheat cultivars to assess the effects of foliar application of magnesium sulphate on photosynthetic characteristics of flag leaves, carbohydrate metabolism in grains, and dry matter translocation in different organs in the Zhoumai 27 and Aikang 58 cultivars at different growth stages. The results indicated throughout the different stages of growth, the flag leaves exhibited a high net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration (Tr), and a decrease in the concentration of intercellular CO2 (Ci). Therefore, foliar application of magnesium sulfate during the booting stage maintained high canopy photosynthesis after anthesis. Simultaneously, exogenous supply of magnesium sulphate enhanced the sucrose synthase (SUS) and invertase (INV) enzyme activities in detached wheat grains, meanwhile reinforced the activities of most starch synthesis enzyme such as ADP-glucose pyrophosphorylase and soluble starch synthase, and consequently lead to a higher content of grain starch. Furthermore, field experiment also confirmed foliar application of magnesium sulphate can improve superior dry matter accumulation and translocation in grain.