The Preliminarily Study On The Leaf Photosynthetic Rate And Material Accumulation In The Formative Period Of Economic Yield For Different Primary Seedling Population Of Rice

This study was made based on indica hybrid rice II you 838 and Xinong 10 as the test materials in the field. The rowspacing was fixed and seedling number was 1,2,3,4 plant/hill as the four different treatments. The experiment was designed to be 24 plots and repeated 3 times. The accumulation of dry matter, NAR, LAI, CGR and the change of photosynthetic rate were investigated during the formative period of economic yield, when the relevance between photosynthetic rate and accumulation of dry matter was studied as well.1. Accumulation of dry matterThe accumulation of population dry matter in the rice corresponded to the Logistic Curve. The ecomomic yield was primarily formed by the accumulated dry matter and the dry matter transfered from stem sheath after flowering, and the accumulation of dry matter was accounted the main part.The law of dry matter accumulation of the population and individuals showed that the accumulation of population dry matter changed as a parabola with the seedling number per hill (SNH) increased. The field reached the highest at two seedlings per hill in response to the highest economic field, while the individual dry matter sustained decreasing in the whole period. The amount of dry matter transformed from stem sheath went up as the SNH increased. The results above indicated that the population SNH made an effect on the accumulation and transformation of dry matter, thereby affecting the economic yield. More or less than the appropriate SNH would both go against the accumulation of population dry matter and the increase of ecnomic yield after the flowering as well as overdependence on transformation of dry matter in the stem sheath.The population dry matter in flowering period was positively correlated with the leaf area index (LAI), and both of them increased as the SNH with the correlation like a parabola, which showed control the increase of SNH may help to enhance the LAI and dry matter. On contrary, much higher LAI and dry matter may urge the ecnomic yield decline.2. NAR, LAI, CGR in the period of yield formationThe relation among NAR, LAI, and CGR can be showed as CGR=NARXLAI. In this study, the rice population LAI declined constantly from the beginning of yield formation period to the end. The values of NAR and CGR changed as a parabola, and reached the maximizing in the final stage of flowering-milkyripe. With the increase of SNH, LAI increased. NAR decreased, CGR changed as a parabola and maximize in two seedling per hill instead. The two varieties had the same performance. Therefore, for a higher CGR, NAR and LAI should be coordinated growth.Population luminousness and leaf area distribution are also affected by SNH. The larger the SNH is. the further away from the ground to reach the same luminousness and the smaller the photic leaf area (PLA) is. The leaf area tends to scatter on the top of the plants. Thus, the SNH can influence both LAI and leaf area distribution.3. the photosynthetic rate, the accumulation of dry matter and the yield in formative period of economic yieldThis article defined four types of photosynthetic rate:maximum apparent photosynthesis rate of leaves on one stem(MAPLS); average maximum apparent photosynthesis rate of leaves on one stem of two adjacent period(AMAPLS); maximum apparent photosynthesis rate of canopy leaves(MAPCL) and average maximum apparent photosynthesis rate of canopy leaves of two adjacent period (AMAPCL). The computing method of them was detailedly described in chapter of Material and Method.MAPCL is positively correlated to the accumulation of dry matter in formative period of economic yield. The accumulation amount and rate both arrived at the maximum from flowering to milkyripe, when relatively high MAPLS and MAPCL become the guarantee of high dry matter accumulation and economic yield. Through the correlation analysis of MAPCL and population yield, the sink-source ratio had a positive correlation with MAPCL. which means the increase of sink-source ratio(Kernel weight/leaf) and the enhancement of its pull compel photosynthetic organs to improve the rate so as to produce more dry matter to meet the require of the sink. In addition, the effects of SNH on the photosynthetic rate and accumulation of dry matter were made by the external environment such as population stucture. plant morphology, MAPCL, luminousness distribution, etc.The way to get MAPCL was by calculation, although this method is different from the one used assimilation box, it could discribe the correlation among the colony apparent photosynthesis, accumulation of dry matte and yield, which means this measure has its value and significance in studing the population photosynthesis to some extent.