Effects of Varied Carbon and Nitrogen Supply on Starch and Protein Accumulation in Grain during Early Filling of Wheat

In vitro ear culture experiments were conducted to determine how the concentrations and combinations of sucrose and glutamine in medium were suitable for the accumulation of grain starch and protein in winter wheat (cv. Ningmai 9). The results showed that with the same level of glutamine supply, the grain weight and starch yield were increased but the protein formation was inhibited with increasing sucrose supply significantly. While with the same sucrose supply, both starch and protein accumulation in grains were increased with glutamine supply increase. Higher sucrose supply led to higher sucrose and starch content in grains, but lower activities of Sucrose Synthase (SS), Soluble Starch Synthase (SSS) and Granule Bound Starch Synthase (GBSS), whereas higher glutamine supply led to the higher starch yield and enzyme activities. In conclusion, starch accumulation in wheat grains was controlled not only by sucrose supply, but also by nitrogen supply. Protein accumulation in grains was positively associated with the ratio of glutamine/sucrose in the culture media. It suggested that controlling substrate composition during grain filling was one of the effective approaches for regulation of protein and starch formation in grains.