Growth Phases of Spring Wheat in Terms of Dry Matter Partitioning and its Relation with Some Characteristics of Varieties

Changes with time in dry weight of each part and dry matter partitioning were investigated for three wheat varieties, tall Haruhikari, semi-dwarf Haruyutaka and tall late Selpek. The seasonal pattern of dry matter partitioning was quite similar among the varieties, and the growth was divided into five main phases based on the pattern of partitionings as reported in the previous paper. The dry matter partitionings to each part (Y) were simply presented by the regressions against the days after emergence (X) as follows (Fig. 3). In growth phase I (emergence to flag leaf initiation) and growth phase II (flag leaf initiation to flag leaf emergence), the partitioning to leaf blade was represented by a linear regression, Yl1 = b1X+c1 and Yl2=-b2X+c2. In growth phase III (flag leaf emergence to anthesis), the partitioning to ear (chaff plus rachis) was represented by a quadratic equation, Ye=-a3(X-b3)2+c3. In growth phase IV (anthesis to milk ripe stage), the partitioning to grain was represented by a linear regression, Yg=b4X-c4. The varietal differences in partitionings were explained by using these regressions (Table 2). In growth phase II, tall Selpek had a smaller coefficient b2 than the other two varieties, because Selpek had a longer term in this phase. In the growth phase III, semi-dwarf Haruyutaka had the highest value of constant c3 than others, but that of coefficient a3 did not differ among the varieties, indicating that the rate of partitioning to ear was higher in Haruyutaka than in others.