宽幅播种对适度密植小麦冠层结构和冠层光合效率的调控及其生理机制

Properly increasing the plant density of winter wheat was beneficial for the radiation interception and utilization and consequently improve the grain yield, and also for the increment of root length density and consequently enhance the absorption of nutrient and moisture. Therefore, the wheat sowing at relatively high plant density presents extended application prospect, owing to its high-yield potential under decreased nitrogen and moisture available. However, the unreasonable canopy architecture and its limitation to the canopy photosynthetic efficiency restricts a further improvement of grain yield and nitrogen utilization of wheat sowing at relatively high plant density. In present study, with the intention to analyze the canopy architecture characteristics change of wheat sowing at relatively high plant density and its limitation to the canopy photosynthetic efficiency, we would compare the differences of canopy architecture characteristics, the radiation and leaf lamina nitrogen mass per unit leaf area (SLN) vertical distribution and its dynamics, the single leaf photosynthesis capacity at each leaf layer, and canopy photosynthesis efficiency, between the wheat sowing at relatively high and low plant density. The optimization and its physiological mechanisms of wide-precision sowing pattern to the canopy architecture of wheat sowing at relatively high plant density would be elucidated through comparing the above indices between wide-precision and conventional drilling sowing pattern. Finally, we would define the canopy architecture characteristics of the wheat which is able to obtain further improvement in grain yield when sowing at a relatively high plant density. The clearing of the above questions would be beneficial not only to investigate the matching of canopy architecture and canopy photosynthetic efficiency, but also to guide the regulating direction of canopy architecture. This would provide theoretical basis for the sustainable improvement of crop yield.

适当增加种植密度可以促进光能截获和利用并提高小麦产量，亦可提高小麦根长密度，促进养分和水分吸收，在小麦节水、减氮的生产条件下表现出较高的产量潜力，应用前景广泛。然而，不合理的冠层结构及其对冠层光合效率的限制，制约了密植小麦的进一步增产增效。本项目以适度密植小麦为研究对象，以小麦宽幅播种的群体调节和承载能力为切入点，通过研究适度密植与稀植小麦在冠层结构特征、光氮垂直分布及其动态变化、各叶位叶片光合性能、冠层光合速率间的差异，系统解析密植小麦的冠层结构特征变化及其限制冠层光合效率进一步提升的关键因素；通过分析上述指标在宽幅播种与常规条播两播种方式间的差异，探索密植小麦冠层结构的优化途径及其生理机制，揭示高产密植小麦的冠层特征。明确上述问题，不仅可深入研究作物冠层结构与冠层光合效率的匹配关系，而且还可明晰作物高产冠层的调控方向，为粮食持续增产提供理论依据。

适当增加种植密度可以促进光能截获与利用并提高小麦产量，亦可提高小麦根长密度，促进养分和水分吸收，在小麦节水、减氮方面表现出较高的产量潜力，应用前景广泛。然而，不合理的冠层结构及其对冠层光合效率的限制，制约了密植小麦的进一步增产增效。本项目以适度密植小麦为研究对象，以小麦宽幅播种的群体调节和承载能力为切入点，研究了宽幅播种对适度密植小麦冠层结构和冠层光合效率的调控效应及其生理机制。研究发现：（1）常规条播下密植小麦旗叶层光合有效辐射透射率低和冠层总截获量低是其冠层光合效率和产量低的主要原因，宽幅播种下光合有效辐射利用率及群体光合速率最优的种植密度以及合理密植对光合有效辐射利用率、群体光合速率的增加效应均高于常规条播，宽幅播种与合理密植互作通过增加对入射和截获光合有效辐射的利用效率，进一步提高了冠层光合速率和产量。（2）相较于常规条播，宽幅播种下适度密植小麦旗叶叶长、单叶叶面积下降，但单位面积穗数较高进而旗叶叶面积指数维持不变，较小的旗叶叶倾角优化了冠层结构，打破了冠层郁闭，降低了旗叶层的光合有效辐射截获率，增强了旗叶层的透光性，促进了光合有效辐射向倒二叶的透射，改善了倒二叶光环境，提高了倒二叶的净光合速率，在倒二叶叶面积指数增加的条件下显著提高了开花期、灌浆期冠层的群体光合速率，提高了干物质积累量和产量；相关结论亦通过13C标记的同化物示踪进行了验证，适度密植条件下改常规条播为宽幅播种，旗叶层光合产物对产量贡献量未发生明显变化，而倒二叶层光合产物对产量贡献量显著提高。（3）基于大田试验，在≥10t ha-1产量水平上，研究揭示适当较小的旗叶长、旗叶面积和叶倾角是密植小麦在足量群体条件下冠层光合效率和产量协同提高的冠层结构特征，提出优化旗叶面积和旗叶叶倾角是小麦高产高效耐密株型的调控方向和遗传改良的重要目标性状。研究结果可为小麦高产高效栽培理论与技术创新和高产品种株型选择提供依据和支撑。