Response Of Rice Carbon-nitrogen Metabolism Key Enzyme Gene Expression And The Yield And Quality To Nitrogen At Filling Stage

The rice quality and yield were closely related with application amount and application method of nitrogen. Reasonable application of nitrogen fertilizer can increase rice yield and nitrogen utilization efficiency, and improve rice quality. Understand the changes of carbon-nitrogen metabolism key enzyme gene expression and activity in rice leaves and grain under different nitrogen treatment may be better coordinated the relationship of yield, quality and utilization efficiency of fertilizer. In this pot experiment, multi-panicle type and high yield cultivar Songjing 6 and heavy panicle type and super japonica cultivar Songjing 9 in cold region were used, and we investigated the effect of different ratio of tillering and panicle fertilizers on yield traits and key enzyme encoding gene expression involved in carbon and nitrogen metabolism in flag leaf and grain at filling stage. The results showed that when the application of nitrogen fertilizer increased at tillering stage, the highest tillering number gradual ly increased, but the panicle amount gradually declined, resulting in slight difference in panicle amount per plant among different nitrogen treatments. Reducing nitrogen fertilizer at tillering stage and increasing nitrogen fertilizer at panicle stage were conductive to enhancement of the yield and milled rice rate of multi-panicle type, on the contrast, increasing nitrogen fertilizer at tillering stage and reducing nitrogen fertilizer at panicle stage were beneficial for the enhancement of the yield and m illed rice rate of heavy panicle type. The yield and milled rice rate of multi-panicle type rice were highest in T2(20%N + 30%N) treatment, and heavy panicle rice were highest in T4(40%N + 10%N) treatment.Additionally, the nitrogen forms absorbed and utilized in leaf and grain were different at different filling stages, the application of nitrogen fertilizer at panicle stage significantly promoted to increase the content of total nitrogen, NO3--N and NH4+-N.The expression level of Rubisco subunit genes showed similarly among different cultivars and nitrogen fertilizations at filling stage, moreover, nitrogen nutrition can affect the arrival of highest expression level and its duration time, especially the expression level of Os RBCSL, Os RBCS2 and Os RBCS4 were significantly up-regulated responsive to nitrogen application, while the expression level of Os RBCS3 and Os RBCS5 were up-regulated to some extent. Nitrogen nutrition affected the arrival of duration time of Os RBCSL, Os RBCS2 and Os RBCS4.The activity of Sucrose Synthase, Sucrose Phosphate Synthase, and Sucrose Acid Invertase showed similarly trend among different cultivars and nitrogen fertilizations at filling stage. Nitrogen treatment can affect the activity of Sucrose Synthase, Sucrose Phosphate Synthase, and Sucrose Acid Invertase. The activity of Sucrose Synthase and Sucrose Phosphate Synthase were significantly increased when tillering nitrogen fertilizer were reducing and panicle nitrogen fertilizer were increasing in leaves and grains of rice, but the activity of Sucrose Acid Invertase were up-regulated to some extent.Nitrogen treatment can affect the expression levels of cytoplasmic glutamine synthetase and Chloroplastic glutamine synthetase. With the application of nitrogen fertilizer, Os GS1; 1 expression level in leaf and grain will be enhanced at middle and late filling stage, while Os GS2 gene only showed high expression level in leaf at middle and late filling stage and Os GS1;3 gene exhibited high expression in leaf and grain during the whole filling stage. While the high panicle nitrogen fertilizer significantly delayed the arrival of p eak time of Os GS1 gene expression level in leaves and grains at filling stage.The content of protein were increased and the content of starch were reduced in grains of rice with tillering nitrogen fertilizer reduced and panicle nitrogen fertilizer increas ed. The quality of multi-panicle type rice were best in T2(20%N+30%N) treatment, and heavy panicle rice were best in T4(40%N+10%N) treatment.