Grain Capability Of Photosynthates And Its Relationship With Hull In Rice(Oryza Sativa L.)

The degree of grain filling has close relation with yield and quality in rice. Thorough and broad studies on growth of hull, differentiation and growth of endosperm cell, process of grain filling, source of grain filling substance, distribution of photosynthates and inside or outside factors affecting grain capacity were carried out and led to many achievements, which accelerated the production of rice hugely. But up to now, we are still short of thorough and systemic studies on whether rice grains have the ability of actively accepting photosynthates, and on function of panicle axis, branches and pedicle during grain filling, and on the function of hull to grain capacity of photosynthates. By feeding the whole plants with 14CO2 and by covering different paper when cutting part of a hull 2 days after flowering and other ways, 14C-labeled photosynthates and soluble carbohydrates in organs, weights of brown-rice and hull were analyzed to make above problems clear. The main results were as follows:1. At initial grain filling, concentration of 14C-labeled photosynthates in grain was 3.7, 11.4, 5.9 times of that in green leaf, leaf sheet and stem, branches (including panicle axis, branches and pedicle) respectively; concentration of l4C-labeled soluble carbohydrates in grain was 1.0, 3.3, 1.6 times of that in green leaf, leaf sheet and stem, branches respectively; the ratios of 14C-labeled soluble carbohydrates in green leaf, leaf sheet and stem, branches and grain were 89.1, 80.4, 85.9, 23.4 percentage respectively; which indicated that grains not only had the ability of actively accumulating photosynthates, and also had strong ability of synthesizing starch at this stage.2. At the initial, middle or end of grain filling, concentration of 14C-labeledphotosynthates and soluble carbohydrates in leaf were significantly higher than those in leaf sheet and stem, which showed that translocation of I4C-labeled photosynthates from leaf to leaf sheet and stem was according to concentration difference, belong to passive transportation; At the beginning or end of grain filling, concentration of 14C-labeled photosynthates and soluble carbohydrates in leaf sheet and stem were significantly lower than those in branches, which showed that translocation of 14C-labeled photosynthates from leaf sheet and stem to branches was not depended on concentration difference, belong to active transportation; At the beginning of grain filling, concentration of I4C-labeled photosynthates and soluble carbohydrates in branches were significantly lower than those in grains, which showed that translocation of 14C-labeled photosynthates from branches to grains belonged to active transportation.3.At the initial and middle of grain filling, leaf had strong ability of translocating photosynthates out, whereas that decreased at the end of grain filling; The trend of percentage of l4C-labeled photosynthates in root or leaf sheet and stem took on a curve, which reached the peak 20th day after heading followed by 35th, 5th day after heading in turn; At the early stage of grain filling, almost all of photosynthates assimilated was translocated to grains, as grains grew the percentage decreased rapidly; Grain capacity of photosynthates had close relation with its water content, and with starch synthesis rate as well.4. 1000 brown rice weight in cutting hull treatment was significantly lower than that of non-cutting treatment and the difference between them became larger as grain grew, the same trend showed in two indica and japonica cultivars, which testified that hull had deep effect on grain capacity of photosynthates. and grain filling, and that the effect became deeper as grain grew.5. 1000 brown rice weight in covering Sulfuric acid paper treatment was higher obviously than that in cutting hull treatment, and the difference became larger as grain grew, the same trend showed in two indica and japonica cultivars, which indicated thatmaintaining relative humidity inside the hull had great effect on grain capacity of photosynthates and grain f...