IAA has been reported to mediate the ATPase activity inducing photosynthate transportation and distribution, thereby improving grain filling [26]. IAA is also associated with the regulation of starch

synthase activity and involved in promoting starch synthesis [27]. Previous studies have indicated that endogenous ABA increased starch content by regulating the activity of starch synthase and sucrose synthase. ABA promoted the accumulation of storage materials such as starch [27] and [28] and induced stress-related material production [29], via inducing gene expression [30]. More recently, Cui et al. [31] found that exogenous ABA enhanced xylem sap at the neck–panicle node, increasing the transport of photosynthetic products from buy Doramapimod leaves to growing kernels. ABA-treated plants showed increased numbers of vascular bundles and more phloem area in vascular bundles, suggesting that they had greater structural capacity for the conduction of assimilates to kernels [32]. In the present study, ABA application markedly increased the grain filling rate of two

types of cultivars, extended the active grain filling period and grain filling duration of Jimai 20, but did not significantly affect the active grain filling period of Wennong 6. The two varieties showed similar behavior, with starch content and accumulation both increased by exogenous ABA. Application of ABA strongly affected dry matter MG132 accumulation and remobilization. Exogenous ABA decreased carbohydrate amounts in the photosynthetic tissue and stem sheath and increased dry matter assimilation of kernels. Consequently, the dry matter distribution and remobilization ratios of different organs were changed. We referred to a previously described method to calculate dry matter translocation amounts and ratios, so that the resulting numbers represent apparent and not actual translocation amounts and ratios. Further research on exogenous ABA regulation of dry matter translocation is desirable. Based on our results and previous studies, we may summarize the relationship between

ABA treatment and grain yield as follows: exogenous ABA (i) accelerated grain carbohydrate accumulation by enhancing Dynein starch accumulation and accelerating grain filling and (ii) affected the dry matter distribution and remobilization of different organs, accelerating the transportation and partition of photo assimilates from stem and sheath into the grain sink. Grain filling duration, active grain filling period, and mean and maximum grain filling rate in kernels of Wennong 6 were higher than in those of Jimai 20. Final grain weight differed significantly between Wennong 6 and Jimai 20. ABA increased the grain filling rate and shortened the grain filling period of Wennong 6 but prolonged that of Jimai 20. Starch content and starch accumulation were increased in both cultivars by ABA treatment.