FIGURE 5
In Exp. 1, the decreased grain filling rate and duration mostly occurred in phases I for superior grain (Figure 3, Table 1). As the most important grain filling period (Phase II, fast-increase period for grain dry matter) (Figure 3), the duration of grain filling in stress treatment was decreased (Table 1). Compared with CK, the growth duration was decreased by 4.7 days in DS treatment, 4.6 days in HS and 2.2 days in DHS treatment. For inferior grains, the response of grain filling was observed in the early stage (Phase I). For Exp. 2, the decreased grain weight in stress treatments was mainly because of the low grain filling rate while the growth duration was even extended for superior grains. During the Phase II, grain filling rate was decreased by 31.1% in DS treatment, 43.4% in HS treatment and 42.3% in DHS treatment. For inferior grains, the decreased grain weight in stress treatments also resulted from the lower grain filling rate compared with CK.