| To study the effects of exogenous melatonin on grain-filling characteristics, starch composition and physicochemical properties of wheat, using two soft wheat varieties Zhengmai 825 and Yunong 901 as materials, different concentrations of exogenous melatonin (0, 50, and 100 μmol·L-1) were sprayed at the full ear stage. The results showed that exogenous melatonin spraying increased the peak rate of grain filling, prolonged the active filling period, promoted the accumulation of dry matter in the grain, and ultimately increased the 1 000-grain weight and yield. The total starch content, amylopectin content, the ratio of amylopectin to amylose, the percentage of the volume and surface area distribution of large starch granules in wheat grains showed a decreasing trend after melatonin spraying treatment, while amylose content showed an increasing trend. The crystal properties of starch were not affected by exogenous melatonin, showing typical A-type characteristics. With the increase of melatonin concentration, the relative crystallinity of starch increased first and then decreased. The peak viscosity, trough viscosity, final viscosity, breakdown value and setback value of starch decreased in Yunong 901, but decreased first and then increased in Zhengmai 825. Both 50 and 100 μmol·L-1 melatonin significantly improved grain filling and starch physicochemical properties of soft wheat, and the yield increase was more significant at 100 μmol·L-1 melatonin concentration. |
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