Simulation On Photosynthetic Production And Dry Matter Partitioning In Wheat

Submodels of phenological development stages, photosynthetic production and dry matter accumulation, mass partitioning to organs, organ growth, green area index, tiller dynamic and grain yield of wheat were developed on the basis of ecophysiological processes and concept of constant physiological development time. Test of the model with a number of field experiment data indicated that the WheatGrow had better performance than the present models. In the phenological development subrnodel, physiological development times of heading, anthesis and maturity stages were made constant by regulating the daily thermal effectiveness and basic tilling duration factor, thus unified physiological time scale for different varieties. Test of the model indicated that heading, anthesis and matLirity stages cati be predicted accurately by?the concept of physiological development time, that is kept constant for different varieties at a given stagc. Filling duration and temperature responses of different varieties were considered as genetic parameters in the model, ~vhieh showed more explicit than thermal time model. Gauss integration was used to calculate daily photosynthetic rate, by integrating instantaneous photosynthetic i-ate over daylength and leaf area index. The effects of physiological age, and temperature on maximum photosynthetic rate were quantified. The relationship of plant critical and minimum nitrogen content to physiological development time were established. Partitioning indexes of shoot and root ~vere defined as the proportion of their dry weights in plant biomass. and those of green leaf, stem and ear as the proportion of their dry weights in shoot mass. The functional relationships of partitioning indexes to physiological development time over entire growth period were established, in which harvest index (HI) affects mass partitioning to ear as a genetic parameter. The dry weights of individual organs were the products of the respective partitioning index and plant or shoot weight. Green area index (GAl) was calculated as the product of the green leaf and spike 97 weight by their respective partitioning indexes, and GAl model was established based on the partitioning index. Furthermore, this model didn抰 simulate the leaf dying rate, which avoid the difficult measurement of leaf area death. Harvest index was used to regulate the spike growth rate of different varieties as a genetic parameter, explaining different grain filling rates and periods among different varieties, and resulting in the different ear weights and yields. Tiller dynamic was simulated in two growth periods, from seedling to jointing and jointing to maturity. Fibaracci equation was used to quantify tiller dynamic before jointing under ideal condition, and variety tiller potential was used to characterize genetic impact. Leaf area index and assimilate supply factors were used to calculate the effect of population on the tiller generation. Water and nitrogen deficit factors were used to conclude the regulating effect of environment. From jointing to maturity, assimilate supply and daily thermal time were used to calculate the decrease of tillers, and the effective tillers number before jointing was established as the final minimal tiller number. Submodels in WheatGrow were tested using a number of datasets from different location, sowing years and dates, cultural t...