Abstract
Nitrogen topdressing at anthesis increases protein content of grain in bread wheat. Nitrogen content of plant at anthesis may also influence this increase in protein content of grain. We conducted experiments to demonstrate the effect of nitrogen content of plant at anthesis on protein content of grain and its increase in response to nitrogen topdressing at anthesis. First, we compared plants grown in a drained paddy-field and an upland field. Plants grown in the upland field accumulated larger amounts of nitrogen in their aboveground parts at anthesis than those in the drained paddy field. The larger amounts of nitrogen accumulated were translocated to the spikes, and the grain protein content was higher in the upland plants than in the paddy plants. However, the increase in grain protein content by nitrogen topdressing at anthesis was smaller in the plants grown in the upland field than in the paddy field. We then examined grain protein content, and the effect of nitrogen topdressing at anthesis on the increase in grain protein content, in the upland field treated with different levels of nitrogen basal dressing and topdressing at jointing-stage. The grain protein content was higher, but the increase in grain protein content in response to nitrogen topdressing at anthesis was smaller, in plants that had accumulated a larger amount of nitrogen through high-dose fertilization before anthesis. These results suggested that the nitrogen content of plants at anthesis would affect the grain protein content and its increase in response to nitrogen topdressing at anthesis, which would depend on the amount of remobilized nitrogen from culms and leaves to ears during the grain filling period.
