Drought is a severe abiotic stress affecting the plant's antioxidant system and interrupting compatible solute translocation processes, which leads to low productivity.Melatonin acts as a common growth regulator enhancing the plants defense system and regulates sugar metabolism in challenging environments. Melatonin treatments enable plants to be tolerant to abiotic stresses via enhancing their recovery potential, but its impact using various concentrations has not yet been studied in leaf physiological aspects when applied to cotton foliage during their peak flowering and boll loading stage. The overall objective of this research was to facilitate cotton boll distribution characteristics by modifying cotton leaf sugar metabolism and antioxidant activity by applying foliar melatonin (0, 25, 50, and 100 μmol l À1 ) under drought levels with a relative soil water content of 75%, 60%, and 45% ± 5 (FC1, FC2, and FC3, respectively). Higher rates of melatonin application (100 μmol l À1 ) enhanced boll distribution characteristics and controlled the boll shedding rate during drought conditions. An increase in melatonin rates proved to be more helpful in stimulating cotton sympodial leaf physiological attributes, including leaf gas exchange parameters, sugar metabolism, proline content, and antioxidants defense system as compared with less or no melatonin application during all FC conditions and showed the most significant effect at a higher melatonin concentration (M100) at 7-21 DAF. The total proline content and antioxidant activity were enhanced in the M100 treatment during all FC levels, which caused a reduction in the total malondialdehyde (MDA) contents and hydrogen peroxide (H 2 O 2 ) concentrations in cotton leaves. Moreover, sugar metabolism responsible genes GhSusA and SPS2 showed an upsurge in expression levels and enhanced sucrose degradation in M100 treatments during all FC levels. Furthermore, cotton boll attributes showed also a positive relation with leaf physiological and gas exchange attributes. The results suggested that foliar melatonin application during the flowering initiation stage improved the overall performance and is helpful for cotton crops productivity against drought stress.

Phosphorus (P) plays a pivotal role in cotton by enhancing the reproductive growth and yield formation. Cotton cultivars vary greatly in response to P availability, especially under P-deficient conditions. So, we hypothesized that the increasing P level promotes the reproductive growth in cotton cultivars varying with P sensitivity. For this, two cotton cultivars, Lu-54 (sensitive to low P) and Yuzaomian-9110 (tolerant to low P), in response to three different P levels (P0: 0 (control), P1: 100, and P2: 200 kg P2O5 ha−1) were studied at 39, 52, 69, 83, and 99 days after transplanting during 2017 and 2018. The results revealed that the seed cotton yield was improved in P1 and P2 treatments by 23.9%–34.5% and 30.8%–52.3% in Lu-54, and 16.6%–25.6% and 20.6%–38.5% in Yuzaomian-9110 during 2017 and 2018, respectively. The accumulation of reproductive organ biomass was 21.0%–52.1% and 28.5%–56.8% higher in Lu-54 and 24.2%–56.8% and 34.8%–69.1% higher in Yuzaomian-9110 in P1 and P2 over the control, respectively. During the fast accumulation period, the average accumulation of N, P, K, and biomass across the years in P2 were recorded as 0.75, 0.6, 0.5, and 120.5 kg ha−1 d−1 in Lu-54, while they were 0.65, 0.5, 0.8, and 98.5 kg ha−1 d−1 in Yuzaomian-9110. Overall, a longer period, in terms of reproductive biomass accumulation, was recorded for Yuzaomian-9110 compared with Lu-54 in 2017 and vice versa across the 2018 growing season. The results suggested that increasing P rate improved yield, reproductive organ biomass, as well as nutrient accumulation in both cotton cultivars. However, low P-sensitive cultivar (Lu-54) was more responsive to P application compared with low P-tolerant cultivar.

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BACKGROUND: Stimulating maize ear development is an effective way of improving yield. However, limited information is available regarding the regulation of sink strength change from weak to strong at the same position of maize plants. Here, a novel method for stimulating development combined with physiological assays and proteomics was applied to explore the regulation of ear strengthened development.RESULTS: By blocking pollination of the upper ear of maize hybrid Suyu 41, the adjacent lower ear was dramatically stimulated at 4 days after pollination (DAP). Tandem mass tag (TMT)-based proteomics identified 173 differentially expressed proteins (fold change >1.2 or <0.83, P < 0.05) from 7793 total proteins. Gene ontology annotations indicated that several pathways showed noticeable changes, with a preferential distribution to cell wall remodeling, hormone signals and lipid metabolism in the stimulated kernels. Cell wall remodeling was highly mediated by chitinase, exhydrolase II and xyloglucan enotransglucosylase/hydrolase, and accompanied by increased sucrose and glucose content. A series of lipoxygenase proteins were significantly upregulated, causing a significant alteration in lipid metabolism. Hormone signals were influenced by the expression of the proteins involved in indole-3-acetic acid (IAA) transport, zeatin (ZT) biosynthesis and abscisic acid (ABA) signal response, and increased IAA, ZT and ABA content.CONCLUSION: The critical time for understanding the mechanism by which ear growth is stimulated is 4 DAP. Comparative proteomics and physiological analysis revealed that lipid metabolism enhancement, cell wall remodeling and changes in hormone signaling (IAA, ZT and ABA) were all important in stimulating early ear development. Proper regulation of these pathways may improve ear development, resulting in increased maize yield.

Summary Research on aggregate‐associated organic carbon (AOC) stability has increased, but its response to nitrogen (N) and straw (S) application after nitrogen reduction in alkaline sandy loam soil remains unclear. A 2‐year field study and a short‐term incubation experiment were performed to investigate the combined effect of the N + S application on aggregate distribution and stability, and AOC content and mineralization in eastern China. The study involved three N amounts (75, 150 and 300 kg N ha−1) with or without straw amendments under continuous cotton–barley rotation. The N + S application promoted the formation of larger macroaggregates (8–2 mm), with larger mean weight diameter and geometric mean diameter than with N application alone. Aggregate stability increased significantly with increasing rate of N application. The amount of N had less effect on AOC content in the 0–20‐cm layer and cumulative mineralization of AOC in both layers compared with the N + S application. The addition of straw in promoting AOC, however, was more evident in the 20–40‐cm layer. Compared with N fertilizer alone, applying N + S increased the cumulative mineralization of AOC by 27.7% in the 0–20‐cm layer and by 80.9% in the 20–40‐cm layer for different rates of N and aggregate sizes. In addition, at 0–20‐cm depth, there was less C mineralization in macroaggregates than in microaggregates, indicating that macroaggregates showed better protection of AOC in that layer. Our study suggests that N application alone had a large effect on aggregate stability, whereas combined N + S application had a large effect on AOC content and its mineralization in the soil studied. Highlights We studied aggregate and aggregate‐associated organic carbon stability under N and straw application in alkaline sandy loam soil. Nitrogen and straw treatment carried out with prior application of a gradient of excessively large N inputs. Macroaggregates showed better protection of AOC in the 0–20‐cm soil layer. N and N + S applications had large effects on aggregate stability, AOC content and its mineralization.