Straw retention could reduce phosphorus (P) application without decreasing seedcotton yield but related physiological mechanisms were unclear. Cotton root is the first organ to sense the changes in soil environment, and its growth and development, especially carbohydrate metabolism, significantly affected the formation of seedcotton yield. Therefore, it is necessary to explore the responses of cotton root carbohydrate metabolism to straw retention combined with P application. This study was to investigate the effects of straw retention combined with P application on root carbohydrate metabolism and its relationship with seedcotton yield. A field experiment (2020–2022) was conducted to evaluate the changes in seedcotton yield, cotton canopy apparent photosynthesis rate (CAP), biomass, root productivity, root carbohydrate contents and related enzyme activities under different straw management [removal (S), retention (S)] and P rates (0, 100, 200 kg PO ha). Straw retention and P application both increased seedcotton yield and had a significant interaction effect on it. In the 5th-7th year of straw retention, straw retention reduced 24 %-26 % P application to reach a similar yield of S with 100 kg PO ha. Analyzing the reasons: (1) Straw retention combined with P application increased cotton CAP, providing adequate assimilates for cotton development; (2) Straw retention combined with P application promoted the utilization of root carbohydrates, thereby increasing root productivity and seedcotton yield. Specifically, compared with S without P, S combined with P application increased the enzyme activities related to carbohydrate metabolism, especially sucrose synthase (7.6 %-59.4 %) and acid invertase (3.9 %-58.6 %), which reduced sucrose (3.3 %-32.2 %) and starch (4.3 %-28.7 %) contents at the peak boll setting stage. Efficient utilization of sucrose and starch enhanced root productivity, the ratio of root to shoot (R/S) reduced by 2.7 %-21.6 %, while the boll loading of root system (BLR) and boll capacity of root system (BCR) increased by 0.6 %-39.2 % and 3.1 %-50.6 % at the boll opening stage, respectively, favoring the formation of seedcotton yield. Furthermore, when the R/S, BLR, and BCR reached 0.12, 0.81 boll g, and 4.33 g g, cotton harvested the maximum theoretical yield of 3780, 3774, and 4069 kg ha, respectively. Straw retention combined with P application increased root productivity and seedcotton yield by promoting the utilization of root carbohydrates. This study revealed the internal mechanism for straw retention combined with P application to affect seedcotton yield from the angle of root carbohydrate metabolism and provided a theoretical basis for rationally reducing P fertilizer under straw retention.

中文翻译：

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麦棉秸秆连续滞留施磷通过改善根系碳水化合物代谢提高棉花根系生产力和籽棉产量


秸秆滞留可以减少磷（P）施用而不降低籽棉产量，但相关生理机制尚不清楚。棉花根系是最早感受土壤环境变化的器官，其生长发育特别是碳水化合物代谢显着影响籽棉产量的形成。因此，有必要探讨棉花根系碳水化合物代谢对秸秆滞留与施磷的响应。本研究旨在探讨秸秆滞留结合施磷对根系碳水化合物代谢的影响及其与籽棉产量的关系。通过田间试验（2020-2022年），评价不同秸秆管理[去除量（S）、保留量]下籽棉产量、棉花冠层表观光合速率（CAP）、生物量、根系生产力、根系碳水化合物含量及相关酶活性的变化。 (S)] 和施磷量（0、100、200 千克 PO 公顷）。秸秆保留和施磷均能提高籽棉产量，且交互作用显着。在秸秆保留的第 5-7 年，秸秆保留减少了 24%-26% 的施磷量，以达到与 100 kg PO ha 相似的硫产量。分析其原因：(1)秸秆滞留结合施磷提高了棉花CAP，为棉花发育提供了充足的同化物； （2）秸秆滞留与施磷结合，促进根系碳水化合物的利用，从而提高根系生产力和籽棉产量。具体而言，与不施磷相比，施磷与施磷相比，增加了与碳水化合物代谢相关的酶活性，特别是蔗糖合酶（7.6%-59.4%）和酸性转化酶（3.9%-58.6%），使蔗糖减少（3.3%- 32.2%）和淀粉（4.3%-28.7%）在结铃高峰期的含量。蔗糖和淀粉的高效利用提高了根系生产力，根冠比（R/S）降低了2.7%-21.6%，而根系铃负荷（BLR）和根系铃容量（BCR）提高了吐絮期分别增产0.6%-39.2%和3.1%-50.6%，有利于籽棉产量的形成。此外，当R/S、BLR和BCR达到0.12、0.81铃g和4.33 gg时，棉花收获的最大理论产量分别为3780、3774和4069 kg ha。秸秆保留与施磷相结合，通过促进根部碳水化合物的利用，提高了根部生产力和籽棉产量。本研究从根系碳水化合物代谢的角度揭示了秸秆滞留结合施磷影响籽棉产量的内在机制，为秸秆滞留下合理减施磷肥提供理论依据。