Abstract
Drought influences cereal crop yield and quality. However, little is known about changes in the structural and functional properties of wheat starch under soil drought conditions. In this study, two wheat cultivars were subjected to well-watered (WW), moderate soil-drought (MD), and severe soil-drought (SD) from 7 tillers in the main stem to maturity. The structural and functional properties of the resultant endosperm starch were investigated. In comparison with WW soil, the MD increased starch accumulation in grains, the proportion of large starch granules, amylose and amylopectin long branch chain contents, and average amylopectin branch chain length, which were accompanied by the increase in activities of granule bound starch synthase and soluble starch synthase. MD treated-starch had a lower gelatinization enthalpy, and swelling power, but a higher gelatinization temperature, retrogradation enthalpy, and retrogradation percentage when compared to WW conditions. The MD also increased starch resistance to acid hydrolysis, amylase hydrolysis, and in vitro digestion. The SD had the opposite effects to the MD in all cases. The results suggest that soil drought more severely affects amylose synthesis than amylopectin synthesis in wheat grains, and moderate soil-drought improves molecular structure and functional properties of the starch.
Highlights
Stages[12,13]
For plants grown under the well-watered (WW) treatment, midday (11:30) leaf water potential (LWP) ranged from −0.46 MPa at the beginning of measurements to −1.19 MPa at the late grain filling stage
The results suggest that the higher proportion of large granules and total starch accumulation in moderate soil-drought (MD)-treated grains is mainly due to the enhancement of granule bound starch synthase (GBSS) activity, while SD treatment had the opposite effect (Fig. 3), which contributes to a greater grain filling rate under the MD and a smaller grain filling rate under the SD treatment (Fig. 2)
Summary
Stages[12,13]. Water stress can affect starch synthesis and grain weight and can change the components and accumulation rate of grain starch[14,15]. Previous studies have mainly focused on the effects of drought on grain development[18,19,20,21,22], starch biosynthesis[12,23] and physicochemical properties[11,24,25] in cereal crops. In this study, fine structures and functional properties of wheat starch were determined and carefully compared in two wheat cultivars under different degrees of soil drought. The objectives of this study were (1) to investigate how soil drought affects physicochemical properties of starches in wheat kernels, (2) to elucidate the relationship between functional properties and fine structures of starch, and (3) to test the hypothesis that moderate soil drought increases grain quality by improving structural and functional properties of starch in the kernel
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