干旱胁迫下棉花过剩激发能清除的光保护机制研究

China is one of the countries in the world facing serious scarcity of water resources. The drought has restricted most areas of sustainable development of agriculture in China. Cotton is the pillar industry of Xinjiang agriculture, which consumes most of the agricultural water. The utilization of biological characteristics of drought resistance, breeding drought tolerance cultivar, and excavation of biological water saving potential is an effective way to reduce the irrigation amount in cotton. The photoprotection helps to weaken excess excitation energy on the damage of the photosynthetic apparatus under drought stress in cotton, which is closely related to drought resistance. Our previous studies have shown that cotton photosynthetic electron flow transport and distribution demonstrated a unique acclimation mechanism to drought. In this project, cultivars of drought-tolerant and drought-sensitive are selected. Drought stress experiments are conducted in the field and the laboratory. The photosynthetic electron flow and its role in photoprotection of different drought resistance cultivars are studied and the collaborative mechanisms with xanthophyll cycle and reactive oxygen scavenging system are analyzed. As a result, the eliminative way and capacity of excess excitation energy and its relationship to drought resistance are clarified. Finally, photoprotective mechanisms under drought stress in cotton are revealed. It is of great significance for the enrichment and development of cotton drought resistance biological mechanisms. Physiological indicators for biological water saving and drought-resistant breeding in cotton are provided.

我国是世界上水资源匮乏最严重的国家之一，干旱缺水制约了我国绝大部分地区农业的可持续发展。棉花是新疆最重要的经济作物,植棉业是新疆的支柱产业。利用棉花抗旱生物学特性，选育抗旱品种，挖掘其生物节水的潜力是降低灌溉量的有效途径。干旱胁迫条件下棉花光保护途径的运行有助于减弱过剩激发能对光合机构的伤害，与其抗旱性关系密切。我们前期研究表明，棉花光合电子流传递和分配表现出独特的适应干旱的机制。本项目选取棉花抗旱性不同品种为研究材料，在田间和室内设置干旱胁迫处理，研究干旱胁迫条件下不同抗旱性品种光合电子流分配在光保护中的作用及与叶黄素循环和活性氧清除系统的协同机制，阐明过剩激发能清除方式和能力与其抗旱性的关系，揭示干旱胁迫条件下棉花的光保护机制。本研究对于充实和发展棉花抗旱生物学理论具有重要意义，同时为棉花生物节水和抗旱育种提供生理指标。

为了揭示干旱胁迫对棉花叶片光合机构稳定性以及光破坏防御机制的影响，本项目以棉花为试验材料，研究了干旱胁迫对棉花叶片光系统II（PSII）和光系统I（PSI）活性的影响，并进一步利用气体交换和叶绿素荧光同步测定技术研究叶片光系统II激发能分配和光合电子流分配的影响，同时结合与电子流分配相应的生理代谢活性分析了不同光破坏防御途径在棉花适应干旱胁迫中的作用。研究结果表明：干旱胁迫导致棉花叶片碳同化能力下降，但光合系统较稳定，未导致长期光抑制的发生，这与干旱条件下棉花启动了多种光破坏防御措施有关。轻度干旱条件下，棉花叶片主要通过光呼吸等交替电子传递耗散过剩光能，并结合活性氧清除系统共同行使着对棉花的光保护作用；中度干旱条件下，棉花叶片主要通过除光呼吸外的其他交替电子传递（Mehler反应和环式电子传递）来耗散过剩光能，并结合热耗散、活性氧清除系统进行调节。总之，干旱条件下这些防御系统相互协调来保护棉花的光合机构，其中通过交替电子传递进行调节是棉花最为重要的光破坏防御机制。