Abstract: 【Objective】To study the photosynthetic capacity of cotton leaves and the activation of photoprotection measures under the condition of sink limitation.【Methods】With Xinluzao 45 as the test variety, the phloem ring was stripped on the upper and lower parts of the main stem of the fruit branches of Top 2. And the changes of carbon assimilation ability, specific leaf weight, spectral characteristics, chlorophyll fluorescence parameters, NDH-mediated ring electron flow activity, P700 reoxidation state and leaf movement of the fruit branches and leaves were studied.【Results】After 5 days of treatment, the retaining cotton bolls and the treatment of removing cotton bolls, the specific leaf weight of leaves on fruit branches increased by 6.9% and 36.2%, the photosynthetic rate decreased by 28% and 92%, the chlorophyll content decreased, the anthocyanin content increased, the heat dissipation ability of leaves increased, and the NDH-mediated ring electron transfer rate increased.【Conclusion】Under the condition of sink limitation, the feedback of large accumulation of photosynthetic products in cotton leaves inhibits the carbon assimilation rate of leaves and leads to excess light energy, and leaves avoid light stress by a series of photoprotection measures such as weakening the lateral diurnal movement of cotton leaves, increasing heat dissipation, activating ring electron transfer and synthesizing anthocyanins.

Key words: cotton; sink limitation; photoprotection; leaf movement; circular electron transport

摘要： 【目的】研究库限制下，棉花叶片光合能力及启动的光保护机制。【方法】以新陆早45号为供试品种，对倒二果枝主茎上下部韧皮部进行环剥，研究留铃与剪铃的果枝叶碳同化能力、比叶重、光谱特征、叶绿素荧光参数、NDH介导的环式电子流活性、P700氧化还原态、叶片运动等叶片光合相关指标的变化。【结果】处理5天后，留铃和去库处理果枝叶比叶重分别增加6.9％、36.2％，光合速率分别下降28％、92％，叶绿素含量降低，花青素含量升高，叶片热耗散能力增强，NDH介导的环式电子传递速率增加。【结论】库限制下，棉花叶片光合产物大量积累，反馈抑制了叶片的碳同化速率，导致光能过剩，棉花叶片通过减弱横向日性运动、增加热耗散、启动环式电子传递、合成花青素等一系列光保护措施，避免叶片光胁迫。

关键词: 棉花, 库限制, 光保护, 叶片运动, 环式电子传递