Effects of Early- and Late-Sowing on Starch Accumulation and Associated Enzyme Activities During Grain Filling Stage in Rice

The environmental temperature occurring during the grain filling stage is an important factor affecting starch synthesis and accumulation in rice. We investigated starch accumulation, amylase activity and starch granule size distribution in two low-amylose japonica rice varieties, Nanjing 9108 and Fujing 1606, grown in the field at different filling temperatures by manipulating sowing date. The two rice varieties exhibited similar performances between two sowing dates. Total starch, amylose and amylopectin contents were lower at the early-filling stage of T1 treatment (Early-sowing) compared with those at the same stage in T2 treatment (Late-sowing). In contrast, at the late-filling stage, when field temperatures were generally decreasing, total starch and amylopectin contents in T1 were higher compared to those in T2. The ideal temperature for strong activity of ADP-glucose pyrophosphorylase and soluble starch synthase was about 22 °C. A higher temperature from the heading to maturity stages in T1 increased the activities of starch branching enzyme and suppressed the activities of granule bound starch synthetase and starch debranching enzyme. We found that rice produced larger-sized starch granules under the T1 treatment. These results suggested that due to the early-sowing date, the high temperature (30 °C) occurring at the early-filling stage hindered starch synthesis and accumulation, however, the lower temperatures (22 °C) at the late-filling stage allowed starch synthesis and accumulation to return to normal levels.

Abstract licence: CC BY-NC-ND

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