Estimating the boll development and boll yield from single-leaf photosynthesis is difficult as the source-sink relationship of cotton (Gossypium hirsutum L.) is complicated. As the boll-leaf system (BLS), which includes the main-stem leaf, sympodial leaf, and non-leaf organs, is the basic unit of the cotton source-sink relationship and yield formation, the concept of "BLS photosynthesis" is introduced in this study. We speculate that the characteristics of BLS gas exchange can more accurately reflect the photosynthetic function of the system, thus revealing the law of photosynthesis in the process of boll development. The results showed that the photosynthetic rate of single leaves measured by a BLS chamber was consistent with that measured by a standard single-leaf chamber. BLSs exhibited typical light response curves, and the shape of the curves was similar to those of single leaves. The light compensation point and respiration rate of BLSs were higher than those of single leaves, while the apparent quantum efficiency of BLSs was lower. Compared with single leaves, the duration of the photosynthetic function of BLSs was longer. Increasing plant density decreased the gas exchange rate per unit BLS more significantly under field conditions. There was a better linear correlation between the net CO₂ assimilation rate, respiration rate of BLSs and boll biomass. Therefore, we think that the gas exchange of BLSs can better reveal the changes in photosynthetic function of BLSs and boll development. This provides a new basis for analyzing the mechanism and regulation of cotton yield formation.

由于棉花的源库关系（ Gossypium hirsutum），单叶光合作用的棉铃发育和产量难以估算L.) 很复杂。由于棉铃叶系统（BLS）包括主茎叶、合叶和非叶器官，是棉花源库关系和产量形成的基本单位，“BLS光合作用”的概念是本研究中介绍。我们推测BLS气体交换的特性可以更准确地反映系统的光合功能，从而揭示棉铃发育过程中的光合作用规律。结果表明，BLS室测得的单叶光合速率与标准单叶室测得的光合速率一致。BLSs表现出典型的光响应曲线，曲线形状与单叶相似。BLSs的光补偿点和呼吸速率均高于单叶，而 BLS 的表观量子效率较低。与单叶相比，BLSs的光合功能持续时间更长。在田间条件下，增加植物密度会更显着地降低每单位 BLS 的气体交换率。净 CO 之间存在更好的线性相关性₂同化速率、BLSs 的呼吸速率和棉铃生物量。因此，我们认为BLSs的气体交换能更好地揭示BLSs光合功能的变化和铃的发育。这为分析棉花产量形成的机制和调控提供了新的依据。