Grain Filling Mechanisms in Spring Wheat. V. Evaluation of varietal differences in plant growth and assimilate accumulation with grain filling phases.

A regression analysis was conducted on four grain filling phases to evaluate differences in plant growth and assimilate accumulation in spring wheat varieties. Three varieties, early semi-dwarf Haruyutaka bred in Hokkaido Japan, early semi-dwarf Norin 61 bred in Kyushu Japan and late tall Selpek bred in Germany were selected in the present experiments. Plants were sampled everyday throughout the grain filling period to measure total dry weight, ear dry weight, water soluble carbohydrate (WSC) in culm and the weight of the culm structure. According to the growth and accumulation pattern, four grain filling phases were determined and a regression equation was fitted to each phase. The characteristics of these varieties are described. Haruyutaka had an intensive growth of culm structure during the initial phase. WSC was kept high until cessation of photosynthesis, then translocated into grain rapidly during the long final phase. Norin 61 had a long early phase with a moderate rate of WSC accumulation in culm. The grain growth rate was kept high even during the final phase. Selpek had the longest duration of the initial phase but the lowest rate of culm structure growth during this phase. The rates of grain growth and WSC accumulation in culm were higher during the early phase. This analysis seemded to be helpful to assess the regional grain yield with physiological characteristics of genotype.