Fine pruning, or the artificial removal of vegetative branches (VB) and main stem tips (plant topping), is a traditional cotton (Gossypium hirsutum L.) cultivation practice. Pruning can be simplified without reducing yield by retaining the vegetative branches and adopting chemical topping; however, cotton yield formation under different plant pruning modes remains unclear. We aimed to determine if and how simplified pruning results in comparable yields to fine pruning in terms of canopy photosynthesis and photoassimilate partitioning. A two-year field experiment was thus conducted to determine the effects and interactions of vegetative branch management (retaining and removing of vegetative branches) and plant topping pattern (non-topping, manual topping, and chemical topping) on yield, canopy photosynthesis, and photoassimilate partitioning. Seed cotton yield, canopy photosynthesis, and photoassimilate partitioning were significantly affected by VB removal or retention and plant topping modes, but not by their interaction. Boll weight and harvest index under VB retention were reduced compared to VB removal, while boll density and biological yield increased. Compared with non-topping, the biological and seed cotton yield increased and the harvest index decreased under chemical topping, whereas these all increased under manual topping. Seed cotton yield was comparable between chemical and manual topping. The leaf area index (LAI) under VB retention was higher than under VB removal at peak squaring, peak flowering, and peak boll-setting, and comparable at boll-opening. The carbon assimilation rate (CAR) under VB retention increased compared with that under VB removal at peak flowering, peak boll-setting, and boll-opening. Meanwhile, VB retention partitioned more photoassimilates to the vegetative organs, and less to the reproductive organs, than VB removal at peak flowering and peak boll-setting. Compared with no topping, LAI and CAR under chemical and manual topping increased at peak-boll setting and boll-opening. Furthermore, the partitioning of photoassimilates to the reproductive organs under chemical topping was similar to that of non-topping at the peak boll-setting and boll opening stages, whereas this increased under manual topping. Cotton yield did not vary between VB managements due to the coordination between canopy carbon assimilation and assimilate partitioning. Manual topping improved both CAR and photoassimilate partitioning to the bolls, and thus increased the seed cotton yield compared with non-topping. By contrast, chemical topping reduced the photoassimilate partitioning to the reproductive organs, and the increased yield was attributed to the improved carbon assimilation rate. In summary, chemical topping achieved the same yield as manual topping, but the mechanism of yield increase differed from the perspective of photosynthetic production and assimilate partitioning.

精细修剪，或人工去除营养枝 (VB) 和主茎尖（植物打顶），是一种传统的棉花 ( Gossypium hirsutumL.) 栽培实践。保留营养枝条，采用化学打顶，可在不降低产量的情况下简化修剪；然而，不同植物修剪模式下棉花产量的形成尚不清楚。我们旨在确定在冠层光合作用和光同化物分配方面，简化修剪是否以及如何产生与精细修剪相当的产量。因此进行了为期两年的田间试验，以确定营养枝管理（保留和去除营养枝）和植物打顶模式（不打顶、人工打顶和化学打顶）对产量、树冠光合作用和光同化分配。籽棉产量、冠层光合作用、和光同化物分配受 VB 去除或保留和植物打顶模式的显着影响，但不受它们的相互作用影响。与去除 VB 相比，保留 VB 的棉铃重量和收获指数降低，而棉铃密度和生物产量增加。与不打顶相比，化学打顶下生物棉和籽棉产量增加，收获指数降低，而人工打顶下均有所增加。化学打顶和人工打顶之间的籽棉产量相当。VB保留下的叶面积指数（LAI）在平方峰、开花峰和坐铃峰时高于VB去除，在吐铃时具有可比性。与VB去除相比，VB保留下的碳同化率（CAR）在开花高峰期、坐铃高峰期和吐絮期增加。同时，与在开花高峰期和坐铃高峰期去除 VB 相比，VB 保留将更多的光同化物分配到营养器官，而较少分配到生殖器官。与不打顶相比，化学打顶和人工打顶下的LAI和CAR在坐铃和开铃时均有所增加。此外，化学打顶下光同化物分配到生殖器官的分配与不打顶在坐铃高峰期和开棉期相似，而在人工打顶下增加。由于冠层碳同化和同化分配之间的协调，棉花产量在 VB 管理之间没有变化。手动打顶改善了 CAR 和光同化物分配给棉铃，从而与未打顶相比提高了籽棉产量。相比之下，化学打顶减少了光同化物分配到生殖器官，产量增加归因于碳同化率的提高。综上所述，化学打顶与人工打顶的产量相同，但从光合生产和同化物分配的角度来看，其增产机制不同。