Studies On The Characters Of Calcium Accumulation And Distribution Of Rice And Its Regulation

Calcium has been playing an important physiological function for animals andplants growth．Most of Chinese people are in state of taking low amount of calciumfor a long time．Most population of our country regard rice as the staple food,butcalcium content of rice is relatively low．The unreasonable supply of calcium notonly reduces the yield and quality of the rice,but also reduces content of rice calcium．Genotypic differences of calcium contents in brown rice,physiological responses ofrice to calcium at seedling stage,dynamic of calcium accumulation and distributionin rice and sub-cell,the function of different kinds of soil and calcium fertilization onenhancing calcium content in brown rice are systematically studied in thisexperiment,by means of pot experiment,water culture experiment and field test．Theresults are as follows:1 Genotypic differences of calcium content in brown riceA pot experiment was conducted to investigate calcium(Ca)content in brownrice of 89 rice cultivars belonging to 5 genotypes．Results show that the tested ricecultivars differed sharply between genotypes and vary from 44．5²45．5mg·kg^-1 in Caaccumulation．In terms of Ca content in brown rice,the 5 genotypes of rice are in theorder of conventional late Japonica rice>hybrid late Indica rice>conventional lateIndica rice>conventional early Indica rice>conventional medium Japonica rice．Thebrown rice calcium content of japonica rice is higher than that of Indica rice,late rice>medium rice>early rice,the differences of calcium content among early rice,medium rice and late rice were not significant．2 Physiological responses of different rice genotypes to calcium in seedling stageand their genotypie differencesResults of water culture experiment indicated that low concentation Ca²⁺(0．5-1．0mmol·L^-1) application Can promote the growth and development of rice in seedlingstage．The dry weight and the ratio of Root／Canopy were higher than that of CK．Theratio of R／C increased as the concentration of Ca²⁺ increased．The rational applicationof Ca²⁺ can enhance the content of chlorophyll and root system vigor．The netphotosynthesis rate was ascended when Ca²⁺ concentation was increased in seedling stage．Compared with the cultivar with low calcium content in brown rice,the cultivarwith high Ca²⁺content in brown rice had higher photosynthesis and stronger toleranceto Ca²⁺．The high concentration of Ca²⁺ (10．0 mmol·L^-1) bring poisonous effect to rice．3 The accumulation and distribution of calcium in rice plant and its genotypicdifferencesTwo typical rice varieties were used to study the absorption,accumulation anddistribution of rice to calcium under different calcium fertilizer level．The resultshowed that the level of calcium fertilizer had significant influence on rice absorbingand accumulating the calcium．At the fertilizing level of450 kg Ca(OH)2·hm^-2,thebleeding amount and the calcium content in bleeding liquid and different organs wereall highest．Hybrid rice Yanliangyou498 had the better ability to absorb calcium thanconventional rice Aihua5hao,under the same fertilizer level．4 Subcellular distribution of calcium in rice and its genotypic differenceThe cultivars with high--calcium in grain and cultivars with low-calcium in grainwere used for test．Rice plants were grown in hydroponic system to study the effectsof 0．0,0．5,1．0,5．0,10．0 mg·L^-1 Ca on Ca subcellular distribution in two type'scultivars．The results showed that the calcium concentration in leaves was higher thanin roots．Ca was distributed as cell wall>ribosome and the fractions of solublecomponent>plastid (or chloroplast in leaf)>the fractions ofnucleolus>mitochondrion．Ca was mostly distributed in cell wall and less in nucleolusand mitochondrion．Ca contents were increased with Ca concentration increasing．Because the Ca content in the important organelles increased with Ca concentration incultivars with high-calcium in grain,SO their ability to absorb Ca may be stronger thanthat of the cultivars with low-calcium in grain．5 Effects Of different kinds of soil on the accumulation of calcium in brown ricePot experiment was conducted to investigate the effects of 5 different kinds soil oncalcium accumulation in brown rice of 3 rice varieties．The results showed that theaverage content calcium of brown rice was in accordance with the content ofexchangeable calcium in the soil．The order was Neutral purple mud>Purple tide mud>Grayish yellow mud>Red earth of Quaternary Period>Yellow mud．Correlationanalysis indicated that the exchangeable calcium content of soil and the calcium content in the brown rice presented extremely significant positive correlation,thecoeffcient of correlation is 0．9927．The content of CaCO₃ and total calcium in soil hadlittle effect on calcium content in brown rice．The grain yield was lower and rice qualitywas poor in the soil of Red earth of Quaternary Period and Yellow mud．The yield washigher and rice quality was better in the soil of Purple tide mud and Grayish yellowmud．6 Effects of calcium fertilizer on the content of calcium in brown riceField experiment showed that topdressing 450-600 kg·hm^-2 lime at booting stagehad the best effects on increasing calcium content in brown rice and white rice,significant superior to orther treatments．There were big differences in calciumabsorption amount and grain calcium content among different cultivars．Under thecalcium fertilizing level of 0-450 kg·hm^-2,rice yield increased with calcium fertilizerincrease,however, excess calcium fertilizer (kg·hm^-2)resulted in yield decrease．Calcium fertilizing had significant effects on rice quality, under calcium fertilizingrate of 450 kg·hm^-2,the white rice rate,intact white rice rate and amylase contentwere all highest．...