Effects of nitrogen and tiller type on grain yield and physiological responses in rice

Tillering is an important agronomic trait for rice population quality and grain production. Nitrogen fertilizer application increased the number of rice tillers, but not every tiller contributes equally to the overall yield. Heterogeneity in tiller yield of rice increased with increasing nitrogen levels. Typically, late emerging tillers contributed less to the grain yield. Under high nitrogen conditions, most of the nutrients were retained in the straw of late emerging tillers; these tillers have high transport efficiency in vascular bundles, but there is less time for nutrients to transport into the grain. Despite the high light intensity, less than half of the light is used for photosynthesis in late emerging tillers. The low activity of enzymes related to grain filling in late emerging tillers is another reason for low yield.