Variation in nonstructural carbohydrates and antioxidant metabolism in wheat leaf and spike under changing CO2 and nitrogen supply

Nonstructural carbohydrates and antioxidants affect the yield of any plant. In this study, changes in nonstructural carbohydrates and antioxidant metabolism in leaf and spike, as well as their effects on grain yield, were examined in relation to elevated CO₂ and nitrogen supply. For this, a wheat (Triticum aestivum) was grown at two levels of CO₂, i.e., ambient 400 ppm (T1) and elevated 800 ppm (T2), with two levels of nitrogen supply, i.e., 0 gN (N1) and 1 gN (N2). In the sink, elevated CO₂ and nitrogen caused a several-fold increase in glucose content. Fructose showed an increase of 53% and 60% in N₂ treatment under both carbon levels. At the same time, sucrose content decreased by 112% and 100% with an increase in nitrogen doses under 400 ppm and 800 ppm. Higher N decreased the superoxide dismutase activity at ambient CO₂, while higher N at elevated carbon levels increased the superoxide dismutase activity. Elevated CO₂ decreased the catalase activity, while the peroxidases activity increased. In the spike, catalase activity increased at a higher N level. Grain yield was significantly enhanced at elevated CO₂. The correlation analysis showed that catalase has a strong positive correlation with grain yield. The changes in nonstructural carbohydrates and antioxidant enzyme activities are associated with the altered leaf-spike relationship under N availability at high CO₂ levels, which could be a key factor contributing to variable yield. Differential response of nonstructural carbohydrates and antioxidant enzymes in leaf and spike is responsible for changes in grain yield.