糯玉米籽粒产量和淀粉品质形成对高温胁迫的响应及水氮调控机制

Heat stress during grain filling is one of the most important environmental factors that affect the formation of grain yield and starch quality for waxy maize. Our former studies clarified that the cell division stage (about 15 days after pollination) was the key stage that affected the grain yield and starch quality. In the present research, we will study the effects of different high temperature stress durations (1-5, 6-10, 11-15, 1-10, 6-15 and 1-15 days after pollination) at the cell division stage on the formation of grain yield and starch quality, and clarify the mechanism which results in those changes based on the grain proximate composition and structure. The effects of heat stress on the dynamics of grain filling rate and durations, grain endosperm amyloplast development, starch granule morphology, size and distribution, starch crystalline structure, amylopectin chain-length distribution and the activities of enzymes (ADGP, SSS, SBE, SS, SPS) that involved in starch and sugar metabolism, and other parameters that may be influence the grain yield and starch quality were studied. The effects of water management and nitrogen application on grain yield and starch quality under high temperature conditions were studied to seek for the reasonable cultivation measures under heat stress by pot treatments and sown date treatments. The research could generate new knowledge of the development of starch under heat stress that affect the formation of grain yield and starch quality, which could afforded theoretical basis of high-yield and better-quality cultivation under higher temperature environment.

灌浆结实期高温胁迫是影响糯玉米籽粒产量与淀粉品质形成的关键环境因子。前期已明确糯玉米籽粒产量和淀粉品质对高温胁迫响应的关键时期为籽粒建成期（花后1-15天）。本项目研究籽粒建成期不同阶段高温胁迫和持续时间(花后1-5、6-10、11-15、1-10、6-15和1-15天)对糯玉米籽粒产量和淀粉品质形成的作用，分析高温胁迫处理下籽粒灌浆动态，淀粉形成过程中胚乳淀粉体发育，淀粉粒形态、大小和分布，淀粉晶体结构，链长分布，淀粉和糖代谢相关酶（ADPG、SSS、SBE、SS和SPS）活性等的变化动态，并明确这些参数变化动态与籽粒产量及淀粉品质形成的关系。利用盆栽处理和播期处理研究高温胁迫条件下水分和氮素运筹对籽粒产量和淀粉品质形成的调控机制。从淀粉发育过程中相关参数的变化动态上获得高温胁迫影响籽粒产量与品质形成的新认识，为未来温度升高条件下糯玉米高产优质栽培提供理论与技术支撑。

籽粒建成期是玉米籽粒产量和品质形成的关键时期，亦是对高温胁迫最敏感时期。高温胁迫显著降低籽粒产量，影响以1-5 DAP最大，且影响随着胁迫时间延长逐渐加剧。淀粉含量高温胁迫下显著降低，降幅以1-5DAP最大。淀粉粒径高温胁迫下增大，升幅苏玉糯5号1-5DAP高温胁迫下最大，渝糯7号1-10 DAP高温胁迫下最大。高温胁迫显著增加淀粉中长链比例。两品种高温胁迫下峰值黏度显著升高，且升幅1-15DAP处理下最高。回生值苏玉糯5号受11-15DAP高温胁迫处理影响较小，渝糯7号受1-5DAP高温胁迫影响较小，其它高温胁迫处理下均显著升高。.结实期高温胁迫显著影响籽粒灌浆，高温胁迫下7-15DAP胚乳细胞中淀粉体数量多，体积大，22DAP后高温胁迫下灌浆终止，常温处理下籽粒干重继续增加。与常温相比，高温胁迫显著降低ADPG焦磷酸羧化酶、可溶性淀粉合成酶和淀粉分支酶酶活性和下调相关基因表达量，进而降低籽粒淀粉含量。.高温和常温下糯玉米籽粒产量和淀粉中长链比例随施氮量增加先升后降，淀粉粒径常温下随追氮量增加先升后降，而高温下逐渐降低。随着追氮量增加，淀粉峰值黏度常温下逐渐降低，高温下先升后降。不同温度条件下回生值随追氮量增加先降后升。表明温度升高条件下适量追氮有利于高产优质。.结实期高温与水分（干旱或涝渍）互作胁迫下淀粉粒径和短链比例降低，淀粉回生值增加。结实期高温与水分单因素和互作均显著降低淀粉峰值黏度，且降幅高温胁迫大于干旱胁迫或渍水胁迫，高温渍水胁迫下降幅最大。.籽粒产量春玉米和夏玉米推迟播种时较低。春玉米随播期推迟，两品种的平均粒径先升后降，峰值黏度两品种早播处理下较高，回生值苏玉糯5号先升后降，渝糯7号先降后升。夏玉米播期处理下早播可以提高黏度，迟播可以降低回生。.在糯玉米生产中应通过调整播期（春玉米提早、夏玉米适当推迟）避开高温胁迫，尤其是籽粒建成初期。适量施氮、合理排灌可减轻高温胁迫危害，亦可根据淀粉品质变化趋势选择合理用途。