We investigated the effects of exogenous abscisic acid (ABA) on grain filling, starch accumulation, and endogenous hormones in maize (both the heat-tolerant maize variety Zhengdan 958 (ZD958) and the heat-sensitive variety Xianyu 335 (XY335)) under early post-anthesis high temperature stress by simulating high temperature stress for a period of 6 to 12 days post-anthesis in 2022 and 2023. There were three treatments: spraying water at ambient temperature as the control, spraying water at high temperature, and spraying ABA at high temperature. The results showed that early post-anthesis high temperature stress resulted in a significant reduction in grain weight and yield in maize, with XY335 showing a greater reduction than ZD958. The application of ABA mitigated the effects of high temperature stress on grain weight and yield, with the mean yield of ZD958 and XY335 over the two years being increased by 9.6% and 12.3%, respectively. High temperature stress inhibited the activities of enzymes involved in starch synthesis in the grain, resulting in reduced starch content. In contrast, ABA application after high temperature stress increased the activities of sucrose synthase, ADP-glucose pyrophosphorylase, granule-bound starch synthases, soluble starch synthase, and starch branching enzyme, thereby promoting starch accumulation. High temperature stress disturbed the balance of endogenous hormones in the grain, resulting in inhibition of grain filling, whereas ABA application mitigated the adverse effects of high temperature stress on endogenous hormone levels by increasing zeatin riboside, indole-3-acetic acid, and ABA levels and decreasing gibberellin level, which increased grain filling rate, prolonged filling duration, and improved filling characteristics. The grain filling characteristics, starch accumulation, endogenous hormone levels, and grain yield were more sensitive to exogenous ABA regulation in XY335 than in ZD958 under early post-anthesis high temperature stress. In conclusion, exogenous ABA could improve maize grain filling characteristics, promote starch accumulation, and regulate endogenous hormone levels, and ultimately increase grain weight and yield under early post-anthesis high temperature stress.
为探究外源脱落酸(ABA)对花后早期高温胁迫下玉米籽粒灌浆、淀粉积累及内源激素的影响,以耐热型玉米品种‘郑单958’(ZD958)和热敏感型品种‘先玉335’(XY335)为材料,于2022—2023年在花后6~12 d模拟高温胁迫,设置常温下喷水对照、高温下喷水及高温下喷施ABA 3个处理。结果表明: 花后早期高温胁迫显著降低了玉米粒重和产量,其中XY335的降幅高于ZD958,施用ABA可缓解高温胁迫对粒重和产量的影响,其中ZD958和XY335的产量两年平均分别提高9.6%和12.3%。高温胁迫抑制了籽粒中淀粉合成相关酶活性,降低了淀粉含量;施用ABA提高了高温胁迫后蔗糖合成酶、ADP-葡萄糖焦磷酸化酶、颗粒结合淀粉合成酶、可溶性淀粉合成酶和淀粉分支酶的活性,促进了淀粉积累。高温胁迫扰乱了籽粒中内源激素的平衡,抑制了籽粒灌浆;施用ABA通过提高籽粒中玉米素核苷、生长素和ABA的含量,降低赤霉素含量,有效缓解了高温胁迫对内源激素水平的不利影响,增加了籽粒灌浆速率,延长灌浆时间,改善了灌浆特性。此外,与ZD958相比,花后早期高温胁迫下XY335籽粒的灌浆特性、淀粉积累、内源激素水平及籽粒产量更易受到外源ABA的调控。综上,花后早期高温胁迫下外源ABA可改善玉米籽粒灌浆特性、促进淀粉积累、调节内源激素水平,最终增加粒重及产量。.
Keywords: abscisic acid; filling characteristic; high temperature; hormone; maize; starch.