玉米籽粒淀粉粒结构形成与直、支链籽粒淀粉合成的关系机制与调节

In maize (Zea mays L.), starch is a major component of grain yield, accounting for 70% of the final dry weight of the grain, and an important factor affecting quality of maize. Starch serves as a multifunctional ingredient for the food or nonfood industries. During grain development, starch is deposited in the endosperm as discrete semi-crystalline aggregates known as starch granules. Granule size distribution of maize starch is an important characteristic that can affect its chemical composition and functionality. .The shape and distribution of starch granules vary significantly with grain developmental stage. Studies have revealed that starch synthesis in maize grain are determined developmentally and influenced evidently with planting environment. Environmental factors have a noticeable impact on the starch granules distribution. However, this aspect has not been studied in detail. This study was conducted to investigate the effect of cultivated and environmental factors on starch granule size distribution and starch component content in maize grain. .In order to investigate starch granule size distribution during endosperm development, the relationship between starch component and granule distribution, the relationship between starch component and activities of enzymes in starch synthesis and its physiological and enzymatic mechanism, and the effects of cultivated and environmental factors on grain starch formation of maize cultivars differing quality, three typical maze cultivars, normal, waxy and sweet maize., were chosen in this study. Effects of cultivated and environmental factors on starch granule size distribution, starch synthesis and related enzymes activities were roundly investigated. The results elucidated the relationship between starch component and granule distribution, the relationship between starch component and related enzymes activities, and the physiological and enzymatic mechanism, and effects of environmental factors on grain starch formation of maize cultivars differing quality..This information will help to provide a theoretical basis for obtaining higher grain yield and superior grain starch quality in maize.

籽粒直、支链淀粉含量和淀粉粒分布是决定玉米淀粉品质的关键因素之一。研究选用不同品质类型玉米品种，设计不同栽培与环境因子试验，从基因型和环境因素两方面，通过研究籽粒发育不同阶段淀粉合成关键酶活性变化、淀粉合成及淀粉粒形成等，把籽粒发育不同阶段籽粒淀粉质体的形成与增殖——淀粉合成关键酶活性——直、支链淀粉合成——淀粉粒形成、结构等联系起来。探讨籽粒直、支链淀粉合成及其调节的关键时期与关键酶；探明决定籽粒淀粉粒生长、结构形成的酶学机制，及调节的关键时期；阐明栽培环境对淀粉合成和淀粉粒形成影响的酶学机制与调节效应。研究结果将为提高玉米籽粒的淀粉品质提供理论依据和技术途径。

本研究明确了不同品质玉米籽粒淀粉积累与粒度分布特性；明确了籽粒淀粉粒的形成与淀粉组分、淀粉黏度参数之间的关系；明确了决定玉米果穗内不同籽粒淀粉粒形成的生理与酶学机制，及调节的关键途径与栽培措施。研究结果表明，（1）不同品质类型玉米比较，糯玉米淀粉峰值黏度、低谷黏度和稀懈值最高，普通玉米次之，甜玉米最低。普通玉米大淀粉粒体积百分比最高，甜玉米最低。表明与小型淀粉粒相比，大淀粉粒有更高的淀粉峰值黏度、最终黏度和反弹值。（2）玉米强势籽粒淀粉积累量显著高于弱势籽粒，强势粒较高的籽粒淀粉积累量由其籽粒淀粉积累启动时间较早和积累速率较高造成的。籽粒生长过程中弱势粒蔗糖含量明显高于强势粒。强势粒中SS、AGPase活性显著高于弱势粒。与弱势籽粒相比，强势粒＜18 μm淀粉粒的体积百分比较高，＞18 μm淀粉粒的体积百分比较低。而粒位对<3、3-18、>18 μm淀粉粒数目百分比无显著影响。说明与弱势粒相比，强势粒更有利于中、小淀粉粒个体体积的增大。适宜氮肥可以提高玉米蔗糖的降解利用率和淀粉合成水平，进而有利于玉米籽粒胚乳小淀粉粒的形成，同时适宜氮肥施用可降低玉米果穗内不同粒位籽粒淀粉积累和大淀粉粒体积百分比的差异。（3）适宜氮、磷、钾水平显著增加中小型淀粉粒比例、降低大型淀粉粒比例，进而改变淀粉糊化特性，即降低了淀粉峰值黏度、保持黏度与最终黏度。种植密度增大后，籽粒AGPase活性下降，玉米胚乳中型淀粉粒的体积和表面积下降，可见高密度处理玉米籽粒中小型淀粉粒比例较低的原因是较低的ADPG焦磷酸化酶活性。（4）与对照相比，高温使籽粒淀粉峰值黏度、低谷黏度、最终黏度与糊化温度显著升高，灌浆期高温处理的升幅较开花期高温处理大。开花期高温影响玉米果穗结实率较灌浆期高温处理大，而灌浆期高温影响籽粒品质较开花期高温大，不同玉米品种耐高温存在显著差异。研究结果可为玉米高产优质栽培过程中采用适宜的技术措施以提高籽粒淀粉品质提供理论依据。