Rongshao Huang

Drought stress severely constrains yield and quality stability in longan (Dimocarpus longan Lour.), an important medicine and food homology fruit in China. Melatonin (MT) shows potential for alleviating abiotic stress, but its mechanisms in drought-stressed longan remain unclear. Here, we investigated two cultivars (Shixia and Chuliang) under drought and exogenous MT treatments (CW, well-watered control; CM, exogenous MT application under well-watered control; DW, drought stress; DM, exogenous MT application under drought stress), revealing the following findings: (i) Drought treatment significantly reduced endogenous MT levels in both studied cultivars, and the reduction was reversed by exogenous foliar MT application. Specifically, under drought conditions, exogenous MT treatment increased endogenous MT content by 272.7% in Shixia and 53.6% in Chuliang, respectively. (ii) Drought and exogenous MT treatments modulated the activities of plant defense enzymes (superoxide dismutase, SOD; peroxidase, POD; phenylalanine ammonia lyase, PAL; and catalase, CAT) and the levels of related metabolites (malondialdehyde, MDA; proline, Pro). Across both cultivars, drought stress increased the activities of SOD, POD, and PAL, as well as the Pro content. Exogenous MT treatment, however, reduced the activities of SOD, POD, and PAL while increasing CAT activity and MDA content to some extent in both cultivars. Notably, the Pro content was significantly reduced in Shixia but significantly increased in Chuliang following exogenous MT application under drought stress. (iii) Drought and exogenous MT treatments regulated gene expression in longan cultivars. Relative to CW, 848, 3356, and 2447 differentially expressed genes (DEGs) were detected in CM, DW, and DM in Shixia, respectively. Relative to CW, 1349, 5260, and 5116 DEGs were identified in CM, DW, and DM in Chuliang. A gene ontology analysis indicated significant enrichment for abiotic stress defense and hormone-responsive processes. The KEGG pathway analysis showed significant enrichment in protein processing in the endoplasmic reticulum (ko04141), amino sugar and nucleotide sugar metabolism (ko00520), ascorbate and aldarate metabolism (ko00053), plant–pathogen interaction (ko04626), and starch and sucrose metabolism (ko00500). These findings provide physiological and transcriptomic insights into MT-regulated drought responses in longan, highlighting its potential for improving productivity in drought-prone regions.

Illicium verum Hook. f. (star anise) is a highly important plant in terms of both its edible and medicinal properties and its economic value. The suitable habitat for star anise may undergo alterations in response to climate changes and human activities, which in turn might impact its quality. To ensure the future introduction and protection of star anise, it is crucial to analyze the impacts of climate change on the potential distribution of the species. The approach presented in this study integrates the MaxEnt model and chemical composition analysis to assess the potential distribution patterns of star anise in response to climate change and evaluate the impact of environmental variables on its quality. The results revealed that the soil pH, mean temperature of the coldest quarter, mean diurnal range, precipitation of the warmest quarter and annual precipitation were the main factors affecting the current distribution of I. verum. The current area of suitable habitat is approximately 17.6 × 10⁴ km², accounting for 74% of the total area of Guangxi Province. Under the future climate scenarios, the overall pattern of the potential distribution range shifted northwards, and the SSP3126 scenario showed the most significant increase in the area. By utilizing comprehensive 2D chromatography technologies, 111 volatile compounds present in the 61 batches of star anise were identified. Further analysis via chemometric methods revealed that the components β-bisabolene, caryophyllene, 4-methoxyphenylacetone, cis-β-farnesene, anethole and linalool could serve as potential markers for distinguishing the quality of star anise from different geographical origins. Finally, a stepwise regression model between chemical compositions and environmental variables was established, and based on this, a quality zoning map was subsequently plotted. This study provides valuable scientific insights for resource conservation, planting site selection and quality control for star anise.