| The relationship between source-sink structure and grain quality is one of the most important aspects should be considered in rice breeding and cultivation. Expanding the sink and enhancing the source of rice is the only way to achieve high yield. How to increase yield and keep good grain quality at the same time became one of the hot and difficulty point in rice study. In this study, a field experiment was carried out with27early rice and30late rice cultivars. The cultivars of early rice and late rice were classified into3types respectively based on their sink potential level using the system clustering method. Then we analyzed the differences of source, nitrogen uptake and utilization and rice quality among the large, medium and small sink-potential types of early and late rice, investigated the effects of panicle nitrogen fertilizer on source-sink structure and rice quality. And moreover, we discussed the relationship between source-sink structure and rice quality, in order to provide a reference for the genetic improvement of rice quality and optimized cultivate. The main results of the study were as follows:(1)Sink potential and its components of early and late rice cultivars were studied, and sink-potential of different cultivars were classified. The sink-potential of the cultivars used in study showed a huge difference. The coefficient of variation of early rice and late rice were40.5%and35.0%respectively. The same as late rice, contribution of components to sink potential of early rice was manifested as panicles>grains per panicle>1000-grain weight.And Cluster analysis results showed that27early rice and30late rice cultivars could both be divided into three types:large, medium, and small. The averages of sink potential of the3tyes were1211.9,1073.2,921.6gm-2of early rice and1424.7,1201.8,1007.1g m-2of late rice. These results will lay a foundation for the further research on the source, nitrogen uptake and utilization and rice quality characteristics.(2) The difference of leaf photosynthesis characteristics, dry matter production and transportation, grain filling and source-sink ratio among the large, medium and small sink-potential types of early and late rice were studied. The results showed that leaf mass and photosynthetic capacity of large and medium sink-potential types were higher than that of small sink-potential type. Large sink-potential type rice had larger LAI and leaf weight at heading and maturing stage, lower extinction rate of leaf area and higher net assimilation rate photosynthetic rate and chlorophyll content, smaller leaf angle and leaf drop angle of the top three leaves during grain filling period. Dry matter accumulation and reuse capacity of large sink-potential type rice was better than that of small sink-potential type. Large sink-potential type rice had higher dry matter accumulation especially at heading and maturing stage, dry matter of stem and sheath translocation and translocation rate than those of small sink-potential type. Sink potential obviously influented the grain filling, while with its increasing, the grain filling days significantly increased and the grain filling rate decreased, which was due to the less leaf area/sink potential, stem and sheath weight/sink potential and net assimilation rate/sink potential of large sink-potential type rice.(3) The difference of nitrogen accumulation and translocation among different sink-potential types of early and late rice were analyzed. The relationship between sink potential and nitrogen uptake and utilization was also studied. The results showed that the large sink-potential type had higher nitrogen accumulation at heading and maturity stage, nitrogen translocation and contribution than that of the small sink-potential type rice. Nitrogen utilization efficiency was significantly influenced by sink potential. With the increasing of sink potential, nitrogen use efficiency of the plant of the early rice cultivars was slightly decreased, while nitrogen use efficiency for grain output and nitrogen use efficiency were increased or significantly increased. But nitrogen use efficiency for the plant, nitrogen use efficiency for grain output and nitrogen use efficiency of the late rice cultivars were significantly increased.(4) The difference of processing quality, appearance quality, cooking and eating quality and nutrient quality among large, medium and small sink-potential types of early and late rice were analyzed. The relationship between sink potential and grain quality were studied. The results showed that there is a great difference in head rice rate and grain chalky whereas brown rice rate, milled rice rate and grain type was relatively small in term of different sink potential types. The head rice rate of early rice manifested as medium>small>large sink-potential type, and late rice manifested as small>medium>large sink-potential type, while the grain chalky was opposite with head rice rate. The effects of sink potential on physical and chemical characteristics were obvious. With the sink potential increases, the gel consistency and amylose content were decreased, protein content and its components was increased. (5) The differences of response to panicle nitrogen in rice cultivars with different sink-potential were studied. The results showed that with nitrogen fertilizer increased to a proper extent, sink potential increased, the photosynthetic capacity of leaves and dry matter accumulation were enhanced, dry matter transport from stem and sheath to panicle was promoted and source-sink ratio decreased. Top dressing nitrogen fertilizer had great impact on the chalky, which showed some differences because of sink potential. Chalky grain rate and chalkiness degree of early rice with small sink-potential were decreased and then increased with the nitrogen increasing, but that of early rice with large and medium sink-potential and all three sink-potential types of late rice were increased. The effects of panicle nitrogen fertilizer on physical and chemical characteristics were significant. With the nitrogen level increased, protein and its components content were increased and amylose content and gel consistency were decreased. The responses of source-sink structure and rice quality to top dressing nitrogen fertilizer was manifested as large> medium> small sink-potential type. In this experiment,135kg hm-2N (early rice) and180kg hm"2N (late rice) were optimum level for large sink-potential type cultivars to gain higher yield and better quality;90kg hm-2N (early rice) and120kg hm-2N (late rice) were optimum level for small sink-potential type cultivars.(6) The relationship between source-sink structure and rice quality were studied by the canonical analysis. The results showed that the rice quality factor group was significantly correlated with the sink component, leaf photosynthetic, material production, nitrogen accumulation and source-sink ratio factor group. But the quality factor group was not significantly correlated with the plant type factor group. The number of grains per panicle, LAI at heading, extinction rate of leaf area, dry matter translocation, dry matter production during grain filling, nitrogen uptake during grain filling, nitrogen translocation, leaf area/sink potential and stem and sheath weight/sink potential played an important role in each group. These indexes had great effect on chalky grain rate, chalkiness degree and protein content. |
PDF Full Text Request