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The exogenous application of melatonin by the root drenching method is an effective way to improve crop drought resistance. However, the optimal concentration of melatonin by root drenching and the physiological mechanisms underlying melatonin-induced drought tolerance in cotton (Gossypium hirsutumL.) roots remain elusive. This study determined the optimal concentration of melatonin by root drenching and explored the protective effects of melatonin on cotton roots. The results showed that 50 μmol L−1melatonin was optimal and significantly mitigated the inhibitory effect of drought on cotton seedling growth. Exogenous melatonin promoted root development in drought-stressed cotton plants by remarkably increasing the root length, projected area, surface area, volume, diameter, and biomass. Melatonin also mitigated the drought-weakened photosynthetic capacity of cotton and regulated the endogenous hormone contents by regulating the relative expression levels of hormone-synthesis genes under drought stress. Melatonin-treated cotton seedlings maintained optimal enzymatic and non-enzymatic antioxidant capacities, and produced relatively lower levels of reactive oxygen species and malondialdehyde, thus reducing the drought stress damage to cotton roots (such as mitochondrial damage). Moreover, melatonin alleviated the yield and fiber length declines caused by drought stress. Taken together, these findings show that root drenching with exogenous melatonin increases the cotton yield by enhancing root development and reducing the root damage induced by drought stress. In summary, these results provide a foundation for the application of melatonin in the field by the root drenching method.

Nitrogen (N) serves as an essential nutrient for yield formation across diverse crop types. However, agricultural production encounters numerous challenges, notably high N fertilizer rates coupled with low N use efficiency and serious environmental pollution. Deep placement of nitrogen fertilizer (DPNF) is an agronomic measure that shows promise in addressing these issues. This review aims to offer a comprehensive understanding of DPNF, beginning with a succinct overview of its development and methodologies for implementation. Subsequently, the optimal fertilization depth and influencing factors for different crops are analyzed and discussed. Additionally, it investigates the regulation and mechanism underlying the DPNF on crop development, yield, N use efficiency and greenhouse gas emissions. Finally, the review delineates the limitations and challenges of this technology and provides suggestions for its improvement and application. This review provides valuable insight and reference for the promotion and adoption of DPNF in agricultural practice.

Cotton (Gossypium hirsutumL.) is characterized by an indeterminate growth habit, and removal of early fruiting forms often elicits compensatory growth. However, no consensus has been reached on the response of cotton to removal of fruiting forms. We conducted field experiments in 2010 and 2011 with four different early fruiting branch removal treatments (CK, untreated control; R1, removal of one basal fruiting branch; R2, removal of two basal fruiting branches; and R3, removal of three basal fruiting branches) to explore the effects of removing early fruiting branches on premature senescence, yield, and fiber quality of cotton planted on two planting dates. Our results showed that removing early fruiting branches delayed premature senescence of cotton in terms of chlorophyll content, malondialdehyde content, and peroxidase and superoxide dismutase activities at the mid‐late growth stage, especially with R1 and R2 treatments for early‐planted cotton. Removing early fruiting branches increased the leaf area index, leaf area duration, and net assimilation rate compared with untreated plants, which further increased the dry matter accumulation, yield, and some yield components, and significant differences were observed for the R1 and R2 treatments, especially for early‐planted cotton. However, no significant beneficial effects were observed on fiber quality after removing early fruiting branches. In conclusion, removing one or two early fruiting branches delayed premature senescence and improved yield in early‐planted cotton but did not affect fiber quality. Therefore, it could be an effective practice to incorporate into cotton production.

This study evaluated the therapeutic efficacy of Schisandrin A on systemic colibacillosis of chickens. One hundred and eighty, 1-day-old Hailan Brown chickens were divided into 6 groups of 30 chickens each and assigned to the following treatments: 1) uninfected/untreated control; 2) infected Escherichia coli; 3) infected-plus low dose of Schisandrin A therapy (50 mg/kg); 4) infected-plus medium dose of Schisandrin A therapy (100 mg/kg); 5) infected-plus high dose of Schisandrin A therapy (200 mg/kg) and 6) infected-plus antimicrobial therapy (florfenicol). Each group of chickens was placed in cages with a photoperiod of 12 h of light and 12 h of dark. Feed and water for all groups were provided ad libitum for the duration of the study. On d 14, all the chickens except the uninfected control group were intraperitoneally inoculated with a fresh culture of E. colicontaining 1 × 108CFU/mL. The parameters measured included: average daily weight gain (ADG), percent survivability, liver index, serum activity of enzymes (ALT and AST), hepatic and intestinal concentrations of TNF-α, IL-1β, IL-6, IL-8, and LPS, expression of tight junction proteins (occludin, ZO-1, and claudin-1), relative abundance of bacterial species and histopathological changes in hepatic and intestinal tissue. The results showed that the medium and high doses of Schisandrin A ameliorated the detrimental effects of colibacillosis on weight gain. Regarding organ indexes, E. coliinfection induced a significant increase in liver index, all the doses of Schisandrin A produced a significant reduction of liver index in comparison to the E. coliinfected control. Serum activity of ALT and AST enzymes significantly increased due to E. coliinfection, with the exception of the low dose of Schisandrin A for AST enzyme activity, all the Schisandrin A treatments significantly lowered enzyme activity in comparison to the E. coliinfected control. Regarding concentrations of inflammatory markers in hepatic and intestinal, E. coliinfection caused a significant increase in TNF-α, IL-1β, IL-6, and IL-8, except the lowest dose of Schisandrin A for IL-1β, the rest of the doses tested were able to significantly reduced the concentrations of inflammatory markers. Concentrations of LPS in hepatic and intestinal tissues were significantly increased by E. coliinfection, all doses of Schisandrin A significantly reduced the concentration of LPS in hepatic and intestinal tissue. E. coliinfection significantly reduced the expression of 2 tight junction proteins (ZO-1 and Claudin-1), the higher doses of Schisandrin A were effective in significantly increasing the expression of these tight junction proteins when compared with the E. coliinfected control. Taken together, these results show that Schisandrin A has potential as an alternative therapy for the treatment of colibacillosis in chickens.