Germplasm Identification And Phsiological Bases For High Nitrogn Nutrition Efficencies In Rice

Application of chemical nitrogen fertilizers has been an important technique to stabilize and increase rice yield for a long time, but excess nitrogen supply has also resulted in rapid decreasing nitrogen use efficiency and serious environmental contamination while facing increased population and production demand in rice. Thus, it is of urgent importance to clarify the genotypic differences of nitrogen nutrition efficiencies in rice germplasms, determine the possibilities and methods in identifying and evaluating nitrogen nutrition efficiencies in rice germplasms and elucidate the physiological basis on high nitrogen nutrition efficiencies in different rice genotypes. In this study, rice germplasms with different nitrogen nutrition efficiencies including nitrogen absorption efficiency (NAE), nitrogen utilization efficiency (NUE) and nitrogen harvest index (NHI) were evaluated in pot and field experiments to determine the genotypic differences of rice germplasms, and to explore some effective methods for identifying nitrogen nutrition efficiencies in rice germplasms . Futher. different rice genotypes with variable nitrogen nutrition efficiencies were selected to investigate the effects of nitrogen rates on accumulation and translocation of dry matter and nitrogen in relation to nitrogen nutrition efficiency, and to elucidate the physiological basis of high nitrogen nutrition efficiencies. The main results were summarized as follows:1. The genotypic differences of NAE and NUE in 88 rice germplasms were investigated under low (20mg/kgN), medium (40mg/kgN) and high nitrogen (60mg/kgN) levels in pot experiment. The results showed that NAE and NUE in 88 rice germplasms at seedling stage had notable genotypic discrepancy,with the difference of NAE was greater than that of NUE. The genotypic distributions of NUE and NAE in rice germplasms at seedling stage basically resembled normal curve. Rice germplasms in the experiment could be classified into 8 types according to normal deviation of nitrogen nutrition efficiencies, and the distribution patterns showed that that very few types possessed NAE and NUE of both low or both high nitrogen nutrition efficiencies simultaneously. The correlation between NUE...