Differences And Physiological Basis Of Nitrogen Upteke And Utilization Efficiency In Rice Cultivars

The sustainable agriculture of regarding saving energy and protecting agriculture as the aim has become the topic of the social development. It is an ideal approach for increasing nitrogen uptake and utilization efficiency in rice and reducing environmental pollution to explore and utilize crop's natural potential. A field experiment was carried out to study difference of nitrogen uptake and utilization efficiency in rice, genotypic differences of accumulation and partition of different nitrogen forms in rice at heading stage, and relationships between nitrogen uptake and utilization efficiency and partition of different nitrogen forms in rice at heading stage by using 30 representative rice genotypes as materials.1. There were significant or highly significant differences in nitrogen uptake and utilization efficiency in rice. It was exactly possible to select higher nitrogen utilization efficiency of rice from existent rice varieties. At different growth stages, dry matter accumulation, nitrogen content, nitrogen accumulation were significant or highly significant in different rice varieties of early and late season rice. Dry matter accumulation and nitrogen accumulation gradually increased as development progress and were the highest at ripening, but nitrogen content of stem and leaf decreased and nitrogen content of panicle increased.2. The cluster analysis indicated that the tested varieties could be classified into three categories with different nitrogen uptake and utilization efficiency, including high efficiency type, middle efficiency type and low efficiency type. High efficiency type exhibited superior nitrogen uptake and utilization efficiency. Synthesizing the result of clustering analysis, we can find out some rice varieties, which have characters of high nitrogen uptake and utilization efficiency in early and late season, such as Guizhao 2, Xinyangruanmi, Teyou 2035, 7019.3. Accumulation of different nitrogen forms in rice was highly significant different at heading stage. There were highly different in plant protein N, plant amino N, chlorophyll N, Soluble protein N and Rubisco N, while maximum nitrogen content of Rubisco to minimum nitrogen content of Rubisco at heading in early and late season was 4.23 and 4.65, respectively. The differences of nitrogen distribution from plant nitrogen to free amino acid, soluble protein, Rubisco and chlorophyll was highly significant, but that of protein nitrogen was not significant. The ration of protein nitrogen to plant nitrogen was the highest and was more than 78%. The nitrogen distribution ration of different nitrogen forms in different organs was highly significant. Plant nitrogen and protein nitrogen accumulation were highest in leaf at early season but were highest in stem at late season. The highest amino nitrogen content was found in stem and range of amino nitrogen content was bigger than other organs.4. The ration of different nitrogen forms in rice plant was different and relationships among their contents were different at heading stage. Plant nitrogen accumulation showed close relationship with plant protein nitrogen. Plant amino nitrogen accumulation was the second form with close relationship with plant nitrogen accumulation. Soluble protein nitrogen and Rubisco nitrogen were not significantly related to plant nitrogen accumulation. Plant protein nitrogen relative contents showed close relationship with chlorophyll nitrogen relative contents, soluble protein nitrogen relative contents, plant amino nitrogen relative contents and Rubisco nitrogen relative contents. Nitrogen uptake and utilization efficiency was related not only to absolute contents of various nitrogen forms, but to their relative contents. Nitrogen dry matter production efficiency and nitrogen grain production efficiency was positively related to plant amino nitrogen content and was significantly negative related to plant protein nitrogen content. Nitrogen grain production efficiency was negatively related to chlorophyll nitrogen content and soluble protein nitrogen content, positively related to soluble protein nitrogen relative contents and negatively related to chlorophyll nitrogen relative contents. Nitrogen harvest index was negatively related to Rubisco nitrogen relative contents.