夏玉米花期弱光逆境对籽粒及产量形成的影响机理

Maize is the highest yield grain crop and plays an important role in ensuring food security in China. Henan is the most important grain production province. And maize is the largest cultivated autumn grain crop with the highest total grain yield. Insufficient solar radiation is one of the most important meteorological disasters for maize production due to the prolonged overcast/rainy days. Previous studies showed that insufficient solar radiation happened during flowering has the most detrimental effects on kernel set and yield formation. However, quantitative relationship between solar radiation during flower and yield is unclear, and mechanism of failure of kernel set lead by insufficient solar radiation is unknown. This project is aimed to determine the quantitative relationship between solar radiation during flowering and yield, and elucidate the mechanism of the failure of kernel set lead by solar radiation limitation. So a light control experiment during flowering by shading lasts different days will be conducted. Leaf photosynthesis, dry matter accumulation and distribution, assimilation transport related key metabolism components and enzymes, pollen daily shedding quantity, pollen activity, ear development character, fertilization rate and seed setting rate will be investigated. Then the function of kernel number in response to solar radiation during flowering will be set. And key physiology factor for failure of kernel set due to light limitation during flowering will be selected. Results of this project will provide a basis for maize yield forecast, maize cultivation management and government decision-making.

玉米是我国第一大粮食作物，在保障国家粮食安全上有举足轻重的地位。河南省是我国第一粮食生产大省，玉米是河南省种植面积最大、总产最高的秋粮作物，阴雨寡照是该省玉米生长季常见的气象灾害之一。国内外同类研究认为花期光辐射不足是限制玉米籽粒和产量形成的主要障碍因子，但有关花期弱光逆境影响玉米产量形成的机理及两者间的定量关系至今尚不明确。本项目拟开展花期遮光控制试验，通过设置不同的处理天数来模拟花期弱光逆境持续时间对玉米籽粒形成及与之密切有关的生理生态过程（如叶片光合作用、干物质积累与分配、同化物转运关键物质含量及关键酶活性、雄花逐日散粉量、花粉活力、雌穗动态发育特征、受精结实率等）的影响，并建立穗粒数和产量对花期太阳辐射的响应函数，筛选出花期弱光逆境下影响玉米籽粒形成的关键生理指标，以期明确花期弱光逆境影响夏玉米籽粒和产量形成的动态规律和生理机制，为玉米产量预报、玉米生产管理和政府决策提供科学依据。

河南省是我国的粮食生产大省，玉米是河南省种植面积最大、总产最高的秋粮作物，阴雨寡照是该省玉米生长季常见的气象灾害之一。其中花期光辐射不足是限制玉米籽粒和产量形成的主要障碍因子。本项目通过开展花期遮光控制试验，并设置不同的处理天数，探索了花期弱光逆境持续时间对玉米籽粒形成及与密切有关的生理生态过程（如叶片光合作用、干物质积累与分配、同化物转运关键物质含量及关键酶活性、雄花逐日散粉量、花粉活力、雌穗动态发育特征、受精结实率等）的影响，建立了穗粒数和产量与花期太阳辐射的响应函数。主要研究结果如下：.花期弱光胁迫导致玉米光合速率降低，9天及以上的弱光胁迫还造成光饱和点的显著下降，提示时间过长的弱光胁迫将造成叶片光合生产能力不可逆的下降。在生物量方面，花期弱光胁迫造成植株生物量增长速率显著降低，且对雌穗生物量的影响大于对整株生物量的影响，雌穗物质供应不足造成花丝伸长速率显著降低，吐丝日期显著推迟，这一影响随着遮阴处理时间的增加而增加，从而造成吐丝散粉不协调，受精结实率显著降低。花期弱光还扰乱了玉米叶片和籽粒生理代谢的平衡，造成叶片Rubp、PEPc和SPS酶活性下降，叶片和籽粒（子房）可溶性糖含量降低，籽粒参与淀粉合成的酶活性和籽粒淀粉含量降低，尤其是对上部籽粒。相关和回归分析发现，穗粒数和籽粒产量与弱光胁迫持续时间及抽雄后累积太阳辐射量间存在显著的相关关系。自抽雄至抽雄后15d单位面积累积太阳辐射量每减少10MJ，穗粒数和单株籽粒产量分别减少22粒和6克。研究结果可为玉米产量预报、玉米生产管理和政府决策提供科学依据。