Studies Of Differences In Nitrogen Metabolism Between Different Genotype Rice Cultivars

To provide scientific basis for the selection and cultivation of high -protein rice, water culture and field plot experiments were conducted to study the rice root characters, accumulation and transport regularity of total nitrogen (N) and protein N in rice functional leaves, stem-sheathes and seeds, differences of key enzyme activities in rice functional leaves between two genotype conventional early rice cultivars and two genotype hybrids at different growth stages and under different cultivation conditions, and differences of rice grain yield and protein yield between the two genotype conventional early rice cultivars and the two genotype hybrids at the yellow ripe stage and under different cultivation conditions. The main results are as fellows:1. The dry weight, a -NA oxidation ability, active absorption area of rice roots, bleeding sap amounts and absolute contents of metal nutrients in the bleeding sap from the basic stem of both conventional and hybrid high-protein rice cultivars were all significantly higher than those of the checks, and the above indexes in 'three-strong and three-high' (strong seedling, stem and grain, and high yield, protein and yielding brown rice ratio) cultivation were also higher than those of conventional cultivation in field plot experiments, and the above indexes of the normal N treatment were higher than those of the low N treatment in water culture experiments, too. It demonstrated that the root absorption ability of the high-protein rice cultivars was better than that of the checks, and characters of rice roots could be improved by 'three-strong and three-high' cultivation and rational application of nitrogen fertilizer.2. The accumulation and transport of total N and protein N in the functional leaves and stem-sheathes of both conventional and hybrids high-protein rice were obviously superior to those of the checks. The above indexes in 'three-strong and three-high' cultivation were also higher than those of die conventional cultivation in field plot experiments, and the above indexes of the normal N treatment were also higher than those of the low N treatment in water culture experiments. It showed that there were evident differences in N uptake between the rice varieties. Rational cultivation could also raise the N absorption of rice.3. The activities of key nitrogen metabolism enzymes in the functional leaves of high-protein cultivars such as nitrate reductase, glutamine synthetase, glutamine transersase, and protease were all higher than those of the checks. The activities of these enzymes in the rice functional leaves under 'three-strong and three-high' cultivation in field plot experiments and the normal N treatment in water culture experiments were all superior to those of the checks, which further showed that the nitrogen metabolism of high-protein conventional or hybrid rice cultivar was superior to that of the checks based on biochemistry mechanisms; and rational cultivation could improve the activities of key enzymes of nitrogen metabolism.4. Contents of total N and protein N in rice grain, and protein yield of high-protein rice were obviously higher than those of the checks. The water culture experiments showed that contents of protein N in rice grain of Xiangzaoxian 24 (an early conventional rice variety ) were higher than those of the check (Zhongyouzao 81) by 3.92-5.02 g/kg at the yellow ripe stage. The field plot experiments showed that contents of protein N in rice grain of Xiangzaoxian 24 were higher than those of the check (Zhongyouzao 81) by 1.38-2.17 g/kg and contents of protein N in rice grain of Weiyou 56 were higher than those of the check (Jingyou 974) by 0.32-0.56 g/kg. Contents of protein N and total N in rice grain under 'three-strong and three-high' cultivation were obviously higher than those of the conventional cultivation in field plot experiments, and contents of those in rice grain under the normal N treatment were also higher than those of the low N treatment in water culture experiments. It indicated that the accumulation of p...