糯玉米淀粉品质响应籽粒建成期高温干旱胁迫的生理机制与外源BR调控效应

气候变暖不可逆转，干热气候下干旱经常伴随高温，严重影响玉米生长发育。籽粒建成期是玉米胚乳细胞分化、淀粉体发育与淀粉形成的关键时期，对高温和/或干旱极为敏感。课题组前期阐明了结实期高温或干旱胁迫显著影响糯玉米淀粉结构和品质，但高温干旱双重胁迫的影响是叠加效应还是触发新的胁迫机制尚不可知。本项目进一步探究籽粒建成期高温干旱胁迫对糯玉米籽粒产量和淀粉品质的影响。通过分析籽粒发育过程中淀粉合成关键基因表达和酶活性变化，胚乳细胞生长、发育、衰老和凋亡过程，淀粉体发育和增殖动态与内源激素含量，阐明高温干旱胁迫影响胚乳发育和淀粉形成的生理机制。解析外源油菜素内酯(BR)喷施对高温胁迫下干旱持续期处理后淀粉品质形成的调控作用，结合大田播期灌溉试验，明晰糯玉米淀粉品质对籽粒建成期高温干旱胁迫的响应与BR调控效应。结果可为温度升高条件下糯玉米抗旱栽培和品质调优提供理论支持，缓解干热气候对糯玉米生产的不利影响。

Global warming is irreversible. Under dry-hot climate, drought often accompany with high temperature and severely affect the growth and development of maize. Grain formation stage (1-15 d after pollination) is the key stage that affect the endosperm cell differentiation, amyloplast development, and starch formation. Grain development at formation stage is very sensitive to adversities such as high temperature and/or drought. In our former studies, we demonstrated that the effects of post-silking high temperature or water deficit on waxy maize starch structural and functional properties. However, underlying injury mechanism (new mechanism or only the superimposed effect) of high temperature and water deficit on starch quality formation still remain unknown. In the present project, we will continue to study the effects of heat and/or drought stress during grain formation period on waxy maize grain yield and starch physicochemical properties. The activities of enzymes and expressions of genes involved in starch biosynthesis were analyzed. The growth, development, senescence, and apoptosis processes of endosperm cells, development and multiplication of amyloplasts, and contents phytohormones were measured. By which, the physiological and biochemical mechanisms that affect grain endosperm development and starch formation in response to heat and/or drought stresses at grain formation stage were clarified. On this basis, the regulation effects of spraying exogenous brassinolide (BR) on the grain quality and related parameters under the high temperature combined with different water deficit durations were elucidated. In field production, by adopt different sowing dates and restrict irrigation treatments, we expound the waxy maize starch quality response mechanism to heat and drought stress combinations during grain formation and adjust effects of exogenous BR. The generated results could afford theoretical support for anti-drought and water-saving cultivation, and quality improvement of waxy maize under the increased temperature conditions. Those observations can relieve the negative impacts of predicted global dry-hot climate on waxy maize production.