Cotton root systems sustain photosynthesis by nutrient uptake and coordinate with above-ground growth to influence yield. This study explored the effects of fulvic acid (FA) and phosphorus (P) fertilizers on the relationships between cotton photosynthetic capacity (CAP) and root carbohydrate metabolism. A field experiment was conducted including five treatments: no P fertilizer (CK), 105 kg P₂O₅ ha⁻¹ (P1), 150 kg P₂O₅ ha⁻¹ (P2), 105 kg P₂O₅ ha⁻¹ + FA (FP1), and 150 kg P₂O₅ ha⁻¹ + FA (FP2). Results found that FP2 showed the most significant advantage, ensuring a suitable leaf area index (LAI) and cotton fractional interception of photosynthetically active radiation (IPAR) and consequently maintaining a high CAP. Compared with FP2, FP1 resulted in an increase in the boll loading of the root system (BLR) by 8.1% and the boll capacity of the root system (BCR) by 9.3%. From the peak flowering stage to the peak boll setting stage, sucrose and starch contents in FP1 were 6.2–19.2% and 26.5–27.9% lower than those in FP2, respectively. Conversely, fructose and glucose contents in FP1 were 6.4–10.8% and 7.2–8.8% higher than in FP2. The cotton reproductive organ biomass was increased by 11.1% and 14.7% relative to FP2. Moreover, FP1 achieved the highest yield, with an increase of 8.5% and 11.0% compared with P2 and FP2, respectively. Taken together, our study suggests that application of FP1 (105 kg P₂O₅ ha⁻¹ + FA) could be a proper P fertilization method in cotton production of saline-alkali and arid regions.

Plant specialized metabolites sit at the boundary between plant genetics, environmental response, and useful natural products. Their accumulation is rarely constitutive; instead, it changes with tissue type, developmental stage, stress exposure, hormone signaling, and cellular storage capacity. In this review, we revisit basic helix-loop-helix (bHLH) transcription factors as regulatory switch points in plant specialized metabolism, with particular attention to the jasmonate-JAZ-MYC module. In resting tissues, JAZ repressors dampen MYC/bHLH activity. After wounding, herbivory, pathogen challenge, or elicitation, jasmonoyl-isoleucine promotes COI1-dependent JAZ turnover, freeing MYC factors to bind E-box/G-box motifs, recruit co-regulators such as MED25, and activate biosynthetic genes or downstream transcription-factor cascades. This logic has been repeatedly adapted in different plant lineages to regulate terpenoids, alkaloids, phenylpropanoids, flavonoids, glucosinolates, phytoalexins, and related metabolites. Examples discussed include Arabidopsis sesquiterpenes and glucosinolates, Taxus taxanes, Artemisia artemisinin, Catharanthus terpenoid indole alkaloids, Salvia phenolic acids and tanshinones, Ginkgo terpene trilactones, rice diterpenoid phytoalexins, and cotton gossypol. Rather than treating bHLHs as stand-alone master regulators, we frame them as context-dependent nodes whose outputs depend on dimer choice, promoter grammar, chromatin accessibility, hormone crosstalk, partner transcription factors, and cell-type competence. We also outline evidence standards and engineering principles for using bHLH switches in crop defense, food-quality improvement, medicinal-plant production, and synthetic biology.

Background: Dry matter accumulation and distribution constitute the essential material basis for crop yield formation, directly impacting both yield and quality development. Nonetheless, the effects of planting density on dry matter accumulation, distribution, and nutrient uptake in cotton across various row spacing configurations remain ambiguous. Methods: This study conducted a two-year field experiment utilizing the cotton cultivar “Tahe 2”. In 2024, a single-factor trial was adopted with three row spacing treatments: same row spacing (S3), wide-ultra-narrow row spacing (S4), and wide-narrow row planting (S6). In 2025, a two-factor split-plot design was used: main plots were the three row spacing patterns (S3, S4, S6), and subplots were three planting densities: 135 000 plants ha ^-1 (D1), 180 000 plants ha ^-1 (D2), 225 000 plants ha ^- ¹ (D3). We investigated leaf area index (LAI), dry matter accumulation and distribution, nutrient content, and yield. Results: In 2024, S6 showed the highest leaf area index (LAI) and dry matter accumulation ( p < 0.05). In 2025, LAI and dry matter accumulation increased significantly with increasing plant density ( p < 0.05). The dry matter partitioning ratio to reproductive organs increased with growth. Row spacing and planting density significantly affected leaf nutrient contents; upper-leaf nitrogen (N) and potassium (K) first increased then decreased, while middle- and lower-leaf N and leaf phosphorus (P) at all positions declined gradually. Boll number per plant decreased with increasing density, whereas yield was significantly affected by their interaction ( p < 0.05). The highest yield was found in S6 in 2024 and S6D2 in 2025. Two-year experiments indicated that S6 combined with 180,000 plants ha ^- ¹ optimized population structure, improved resource use efficiency, and increased cotton yield. Conclusion: Among the three row spacing configurations tested, the medium planting density of 180,000 plants ha ^-1 under the wide-narrow row planting pattern (S6) optimized the leaf area index, enhanced population dry matter accumulation, and improved distribution to reproductive organs, thereby maximizing seed cotton yield, which reached up to 6420.47 kg·ha ^-1 .

Background: Saline-alkali soils commonly face the dual challenges of low stock and activity in soil organic carbon (SOC), and long-term excessive nitrogen (N) fertilizer application further exacerbates soil quality degradation. Acid-modified biochar offers a promising approach for improving the fertility of saline-alkali soils, yet the effects of its combined application with N fertilizer on SOC fractions and soil quality remain insufficiently studies. Methods: Therefore, we conducted a two-year field experiment to comprehensively assess the effects of acid-modified biochar combined with N fertilizer application on soil quality index (SQI), microbial nutrient limitation and microbial carbon use efficiency (CUE), SOC fractions and yield. A randomized complete block experiment with five treatments was established: no chemical N fertilizer and no acid-modified biochar (CK), 300 kg N ha ⁻¹ (N1), 450 kg N ha ⁻¹ (Recommended N application rate, N2), 300 kg N ha ⁻¹ + acid-modified biochar (BN1), and 450 kg N ha ⁻¹ + acid-modified biochar (BN2). Results: The BN1 and BN2 treatments effectively lowered soil pH by 3.7%–5.6% and increased the contents of available phosphorus (Av-P), available potassium (Av-K), nitrate nitrogen (NO ₃ ⁻ -N), ammonium nitrogen (NH ₄ ⁺ -N), and microbial biomass nitrogen (MBN). These improvements collectively resulted in a SQI that was 4.0–5.1 times higher than that in the N1 and N2 treatments. Furthermore, the BN1 and BN2 treatments reversed the suppression of soil enzyme activities induced by sole N application, enhanced microbial CUE by 71.7%–105.2%, and mitigated microbial C limitation. Compared with N2, BN1 and BN2 treatments increased SOC by 35.5%–51.2%, easily oxidizable carbon (EOC) by 1.2–2.7 folds, and microbial biomass carbon (MBC) by 34.4%–46.1%. The cotton yield under BN treatments exceeded that of N2 by 10.1%–15.5% in two years. No significant differences were observed between BN1 and BN2 in terms of SQI, microbial CUE, and yield. Path analysis confirmed that fertilization-induced alterations in soil properties indirectly promoted soil enzyme activities and microbial CUE, which not only facilitated SOC accumulation but also directly boosted yield. Conclusion: Overall, 20% reduction of conventional N fertilizer combined with acid-modified biochar was more effective at improving soil quality and reducing microbial C limitation, enhance microbial CUE, and foster the accumulation of SOC, providing guidance for sustainable development in saline-alkali soil.

Background: Although chemical topping agents are now widely used in cotton production, there is a lack of research on screening specialized formulations tailored to the unique ecological conditions of cotton region south of the Tianshan Mountains in Xinjiang. Current reliance on a single-agent application regime often leads to suboptimal efficacy. Given that the root-shoot system is a core determinant of high cotton yields, the underlying mechanism by which chemical topping agents modulate root-shoot coordination remains largely elusive. Methods: A two-year field trial was conducted during 2024 and 2025, involving three different chemical topping agents (X1: zifengding agent, X2: paclobutrazol-copper complex, X3: paclobutrazol-zinc complex), manual topping (CK) was conducted as a control. A total of four treatments were included. Results: Different chemical topping treatments effectively controlled plant height (PH) and increased number of fruiting branches (NFB) compared to manual topping (CK). It significantly enhanced the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr), while reducing intercellular CO ₂ concentration (Ci). Compared with the CK treatment, the X1, X2, and X3 treatments increased the boll capacity of the root system(BCR) by 9.40%-9.60%, 15.60%-17.50%, and 20.00%-22.40%, and increased the boll loading of the root system (BLR) by 3.30%-3.80%, 9.80%-10.20%, and 12.40%-14.10%, respectively. Consequently, biomass accumulation peaked under X3 treatment, increasing seed cotton and lint yields by 10.44%-12.17% and 9.20%-11.00%, respectively, while also improving fiber strength. Conclusion: This study breaks the extensive “one-size-fits-all” application mode. Specifically, the X3 treatment enables precise and localized application of chemical topping technology, providing theoretical and technical support for high-yield, high-quality, efficient, and green cotton cultivation.

Salt stress is one of the environmental factors that limit the growth and development of cotton. Screening salt-tolerant varieties is of great significance for the utilization of salt-tolerant cotton germplasm resources and efficient production in saline land. This study used seven varieties, TH2 (Tahe 2), TH2311, XTM3 (Xintamian 3), XHM1 (Xinhuimian 1), QH18 (Qianhai 18), XLZ61 (Xinluzhong 61), and ZM63 (Zhongmian 63), to investigate the growth and physiological responses of different varieties to salt stress and to comprehensively evaluate their salt tolerance by setting three salt concentrations (0, 0.3, and 0.6%). The results showed that the K⁺ content of many varieties was significantly reduced under salt stress, such as ZM63, XHM1, XTM3, and TH2311. However, the K⁺ content in TH2 was significantly increased under salt stress; at 0.6% salinity, the K⁺ content in QH18 and XLZ61 did not change significantly compared with the control, which may mean that TH2 has a unique ability to regulate potassium homeostasis under salt stress, while QH18 and XLZ61 can maintain relatively normal potassium levels even in a high salt environment. Furthermore, this study found that salt stress significantly reduced the activity of some antioxidant enzymes in most varieties, but some varieties maintained high enzyme activity levels even at a salinity of 0.3%. Compared to the control, QH18 and TH2311 showed no significant change in SOD activity at 0.3% salinity; ZM63 showed no significant difference in POD activity; and XHM1 showed no significant difference in CAT activity. In addition, this study found that QH18, TH2311, and XHM1 exhibited relatively strong salt tolerance among the seven varieties. The research results provide a basis for the screening and utilization of salt-tolerant cotton varieties. Due to the fact that the research results were obtained based on seedling stage data, further research should be conducted in conjunction with multiple growth stages and field experiments to confirm.