| Fully exploring yield potential has been the main way of developing rice production and meeting food shortage problems in the present. Hybrid rice usually shows a strong superiority in larger spike, higher photosynthetic rate and bigger assimilation capability, but a low efficiency in carbohydrate translocation from stem and sheath to spike, which has become a major obstacle in reaching yield target In this paper, Hybrid rice that showed similar life-span but different sink size were selected as plant material, the effect of spike-fertilizer, leaf-cutting (source-sink regulation) and dry matter distribution and translocation were studied. The main purpose of the experiments is to identify the dry matter translocation characteristics during maturation, this may contribute to high yield cultivation technology. The accumulation and distribution of Na~+ and K~+ under salt stress were also studied in this experiment. The main results are summarized as follows:1. There were significant differences in dry matter translocation of stem, sheath and leaf among different hybrid rice, high yield varieties showed a higher efficiency in translocation rate of dry matter than low yield varieties after flowering stage. It was positively correlated between dry matter translocation prencentage and grain yield, indicating that stronger translocation capability of stored assimilation after flowering stage was needed to obtain a high yield target. The results in this experiment also indicated that there was a peak regarding dry matter translocation from stem and sheath to spike after flowering had a peak, occurred mainly during 5-15 days after flowering, which was synchronized the filling peak of panicle. Grain weight lied on grain filling rate and lasting period.Result from this experiment showed that varieties with heavy 1000-grain weight usually showed a higher grain filling rate, greater peak value and more day matter translocation from stem to spike than varieties with light 1000-grain weight.2. The dry matter translocation characteristic of stem, sheath and leaf under different spike-fertilizer treatments after flowering stage were conducted. The results showed that the stem weight and dry matter accumulation obviously increased during the early stage after heading. The dry matter from different stem nodes was mainly ship out 5-15 days after flowering stage. When compared with Liangyoupeijiu, stem weight increase of Guodao 6 was slower before early heading and faster during 0-5 days after flowering. There was obvious difference in dry matter translocation among different stem nodes. Top stem node showed a low translocation rate. Dry matter translocation rate of the top first and the second stem node showed negative value. Dry matter translocation rate among stem nodes was increased from top to bottom. Dynamic variance of stem dry matter had close related with spike weight and grain filling. The results indicated the dry matter translocation from stem in early filling stage was important to the grain filling. With N-fertilizer level increasing, dry matter translocation rate from the stem, sheath and leaf declined.3. With spike-fertilizer level increasing, the length and area of the flag leaf and the top second leaf increased, however, less effects of spike-fertilizer on growth of stem, sheath and other leaves was observed. There were positive correlations between nitrogen level and SPAD values of leaves,drooping angle of flag leaf at flowering stage. Photosynthetic rate of the flag leaf could improve by increasing nitrogen application. While the SPAD values of the top second and third leaf sharply decreased under high nitrogen condition at late stage. In order to keep good plant type.4. Differentiation and degeneration of the secondary branches showed a high positive correlation with the spike-fertilizer level. Nitrogen could increase differentiation of the secondary branches, also resulting a big degeneration. The degeneration of the secondary branches mainly occurred in the primary branches of basal panicle. With a increasing in spike-fertilizer level, degenerate percentage of the secondary branches on the top panicle increased. Under low spike-fertilizercondition, the aborted florets on primary branches were fewer. The higher of a spike-fertilizer level, the more of the aborted florets of top panicle.5. Under the condition of leaf-cut, the translocation rate of rice stem and sheath were increased. The results showed that with the leaf area decreased, the photosynthesis capacity also descend. In order to guarantee the grain-filling, the plant could improve the translocation capability of stem and sheath. But after the branch-cutting, the dry matter translocation rate of stem and sheath decreased, which indicated that the sink size had the feedback function to the source production, regulating the dry matter translocation from stem and sheath to grain. Under the leaf-cut condition, the seed setting rate fell, which proved the leaf photosynthesis is very important to grain filling, and the flag leaf-cut is top important, next are the top second and the top third leaf. 6. Under salt stress, rice seedling absorbed sodium ionic from roots and discharged potassiumionic. There was a regular range distribution of Na~+ and K~+ in rice seedlings. The Na~+ concentration ofdifferent organs ranged from low to high were green leaves, roots, stems, sheathes and dead leaves.Generally, younger green leaves contained less Na~+ than that of dead leaves, and kept low Na~+ level andhigh K~+ concentration under salt stress. It seems a major characteristic of salt tolerance mechanism inrice seedling that the confine distribution area of Na~+ in shoots maintaining green leaves a homeostasisof Na~+, K~+ with the higher K~+/Na~+ ratio by selective transportation K~+ from stems and sheathes to greenleaves and roots, and interception Na~+ in stems and sheathes. The results suggest that it could cause lessNa~+ concentration and maintain higher K~+/Na~+ ratio in green leaves.
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