Relationship Between Nitrogen Uptake & Utilization And Important Agronomic Characters In Rice (Oryza Sativa L.)

A F2 asexual population including 138 lines, derived from TeqingxLemont, and a population with 33 Indica varieties from both domestic and abroad was hydroponically cultured in 2002 and 2003, respectively, to investigate the relationship between nitrogen nutritional traits and other important agronomic characters in rice. The experiment was carried out in rice research center of Yangzhou University. We sampled rice plants at different rice growth stages and measured nitrogen nutrition related traits including nitrogen concentration (NC), nitrogen accumulation (NA), nitrogen absorbing rate (NAR), nitrogen use efficiency for biomass production (NUEp), nitrogen use efficiency for grain output (NUEg), nitrogen harvest index (NHI) and important agronomic characters including grain yield, plant height, sink potential, growth duration and the morphological and physiological indexes of rice root system. The relation between nitrogen nutritional traits and the important agronomic characters in tested rice population was systematically analyzed in this study with the purpose of providing valuable bases for selection and genetic improvements of rice varieties with higher nitrogen use efficiency which is of economic and environmental importance in current rice production. Result showed as follows:(1) Grain yield had no influence on NC in rice plant at heading but significantly affected NC at maturity, and NC decreased at maturity, as grain yield increased. Close relationship between NA & NAR and yield was found in this study, higher yield significantly enhanced the NA and NAR. The effect of yield on NA in panicle was the main cause of the difference of NA in rice plant. The NUEp of rice at heading andmaturity were not closely related to yield, while the NUEg increased significantly as yield increased.(2) NC of different organs in dwarf rice was higher than that of long-stalked rice lines or varieties. Excepting the root at heading, NA of different organs at heading and maturity significantly increased as the plant height enhanced. Before heading, NA of rice plant significantly increased as the plant height enhanced, while after heading, NA in middle-stalked rice ranked the highest, followed by long-stalked rice, dwarf rice. Rice materials with higher plant height had higher NAR. NUEp of dwarf rice was the lowest, while difference between middle-stalked and long-stalked rice was not significant. Close relationship between NUEg and plant height was found in this study, NUEg in middle-stalked rice ranked the highest, followed by long-stalked rice, dwarf rice. NHI in rice plant was not significantly affected by plant height.(3) Close relationship was found between NC in rice plant and growth duration at heading and maturity. NC at heading in shorter-growth duration rice was the highest, followed by longer-growth duration rice, middle-growth duration rice, while NC at maturity in rice plant increased significantly as the growth duration prolonged. After heading, the shorter growth duration rice absorbed lowest nitrogen but NA in panicle was the most, while the longer growth duration rice was reversed. NUEp in rice plant was closely related to growth duration, NUEp in rice with shorter growth duration was the lowest at heading, but it was higher than that in rice with longer growth duration rice at maturity. The biomass production rate in shorter growth duration was highest at heading and maturity. The influence of growth period on NUEg and NHI were significant, the NUEg, nitrogen transportation efficiency (NTE), distribution percentages of nitrogen in spike, NHI decreased as the growth duration prolonged after heading.(4) Close relationship between NC in rice plant and sink potentials was found at maturity, NC in rice plant decreased as sink potentials increased, while effect of sink potential on NC in rice plant at heading was not significant. NA was positively correlated to sink potentials at heading and maturity, except NA at heading in 2002. NA increased as sink potentials increased. Average NA in vegetative organs such as root, st...