Soil Available Phosphorus Deficiency Reduces Boll Biomass and Lint Yield by Affecting Sucrose Metabolism in Cotton-Boll Subtending Leaves

Soil available phosphorus (AP) deficiency and shortage of phosphate rocks limit cotton production in China. Therefore, pool-culture experiments were conducted 2019 2020 using two cultivars (CCRI-79, low-P tolerant; SCRC-28, sensitive) under three soil AP levels (P0: 3 ± 0.5, P1: 6 P2 (control): 15 0.5 mg kg−1) to ascertain the effect on boll biomass lint yield. P0 P1 decreased P concentration net photosynthetic rate (Pn) subtending leaves, thus, reducing Additionally, wall:boll, lint:boll, lint:seed, increased seed:boll ratio. Upper fruiting branch positions (FB9–12) had higher lint:seed ratio proportion total yield low AP. Moreover, also reduced sucrose transformation (Tr) activities sucrose-metabolizing enzymes, such as ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), synthase (SPS), (SuSy), while carbohydrate (soluble sugar, sucrose, starch) activity cytosolic fructose-1,6-bisphosphatase (cy-FBPase) leaves. The starch contents, cy-FBPase, SPS SCRC-28 more sensitive than CCRI-79. Higher Tr initial Rubisco SuSy leaves improved