To clarify maturity-associated metabolic differences in flue-cured tobacco grown in distinct ecological regions of Guizhou and their relationships with post-curing style characteristics, middle leaves of Yunyan 87 were collected from Dafang County (DF) and Weining County (WN), representing honey-sweet and fresh-sweet regions, respectively, at 16 (T1), 18 (T2), 20 (T3), 22 (T4), and 24 (T5) days after topping. Leaf phenotypes, color parameters, SPAD values, key enzyme activities, and sensory style scores were assessed across the five stages, whereas widely targeted metabolomics was performed on cured leaves from T1 and T5, resulting in four metabolomic groups: DF_T1, DF_T5, WN_T1, and WN_T5. Local environmental and soil variables and RT-qPCR validation of selected pathway genes were incorporated to strengthen ecological and transcriptional interpretation. With delayed harvest, leaves from both regions changed from green to yellow-green and pale yellow, the midrib gradually lost greenness and turned whitish, and trichome shedding increased; these phenotypes appeared earlier in DF. SPAD values generally declined in both regions and remained higher in WN than in DF. POD, LOX, PPO, and SPS activities increased with maturity, with generally higher activities in DF. Sensory evaluation indicated that the target style characteristics of cured leaves from both regions were enhanced with increasing maturity. Widely targeted metabolomics of cured leaves identified 72 differential metabolites in DF between T5 and T1, including 44 upregulated and 28 downregulated metabolites, with high proportions of flavonoids, alkaloids, terpenoids, and other phenolic-related metabolites. In WN cured leaves, 51 differential metabolites were identified, including 19 upregulated and 32 downregulated metabolites, mainly associated with sugar metabolism, glutathione metabolism, flavonoid biosynthesis, and ABC transporters. Environmental correlation analysis suggested that radiation-, temperature-, precipitation-, and soil-related variables were associated with region-specific flavonoid and antioxidant-related metabolic patterns. RT-qPCR of selected flavonoid biosynthesis and sugar metabolism/transport genes in fresh leaves supported pathway-level transcriptional divergence, although partial transcription–metabolite decoupling was also observed. Collectively, these results reveal regional differences in physiological and metabolic remodeling at key maturity stages and provide preliminary metabolomics-based evidence for optimizing harvest timing and style-oriented quality regulation of flue-cured tobacco in Guizhou.

Green manure is a biological fertilizer source with complete nutrients, which provides reference for the selection of green manure resistant to low temperature germination. Six green manure crops including Brassica napus L., Orychophragmus violaceus (L.) O. E. Schulz, Medicago sativa L., Lolium perenne L., Melilotus officinalis (Linn.) Pall. and Vicia villosaRoth were selected as experimental materials to study the effects of low temperature stress on germination and seedling growth of different green manure through low temperature germination experiments. The results showed that there were significant differences in cold tolerance of the seeds of 6 medium green manure crops during germination. The germination potential, germination rate, germination index, vitality index, seedling height, root length, seedling fresh weight, soluble protein content and chlorophyll content of Brassica napus L. and Vicia villosaRoth seeds were all better than those of other green manure crops, which provided theoretical basis for the actual production of green manure.

In order to explore the response mechanism of heavy metal content in Oryza sativa L. fields under winter green manure. In this study, through field experiments, the changes of soil chemical properties and heavy metal content in Brassica napus L. and Oryza sativa L. at different growth stages were analyzed. The results are as follows: the pH value in Brassica napus L. harvest stage is higher than that before sowing, while the pH value in Oryza sativa L. harvest stage is lower than that before sowing. Eh of Brassica napus L. soil is positive during the whole growth period, showing a fluctuating upward trend. Eh of soil decreased to negative value during the whole growth period of Oryza sativa L. The contents of As, Hg, Pb, Cd and Cr in the soil decreased gradually in the whole growth period of Brassica napus L., and decreased to the lowest level in the harvest period. During the whole growth period of Oryza sativa L., the content of Hg and Cd decreased, while the content of Pb and Cr increased in the harvest period compared with before sowing. Therefore, planting green manure Brassica napus L. in winter is beneficial to alleviate heavy metal pollution in soil.

Harvest maturity is associated with the biochemical status of leaf-harvested crops before postharvest processing, but the extent to which maturity-established metabolic differences are retained or transformed during flue-curing remains unclear in Nicotiana tabacum . Here, middle leaves of Yunyan 87 grown at a single experimental site were harvested at five harvest-maturity treatments (16, 18, 20, 22, and 24 days after topping). T1 and T5 were selected as contrasting harvest-maturity endpoints for paired metabolomic analyses of fresh leaves (F_T5 vs. F_T1), flue-cured leaves (FC_T5 vs. FC_T1), and direct fresh-to-flue-cured metabolite abundance changes at the same harvest-maturity treatment (FC_T1 vs. F_T1 and FC_T5 vs. F_T5). Phenotype, SPAD values, color traits, enzyme activities, conventional chemical constituents, auxiliary flue-cured leaf traits, and untargeted UPLC-HRMS metabolomics were integrated. Increasing maturity was accompanied by progressive yellowing, decreased SPAD and H° values, and increased L*, a*, b*, and C*. Fresh T5 leaves showed metabolic changes linked to carbon allocation, secondary metabolism, hormone/terpenoid-related pathways, phenylpropanoid-related metabolism, and redox adjustment. After flue-curing, maturity-associated differences were mainly reflected in aromatic amino acid metabolism, especially tryptophan and phenylalanine metabolism, together with secondary metabolism, metabolites assigned to transporter-associated KEGG categories, carbohydrate-related substrates, amino acid-related compounds, and lipid-associated remodeling. Direct fresh-to-flue-cured comparisons identified 84 and 85 differential metabolites at T1 and T5, respectively, including 70 shared metabolites and harvest-maturity-associated, comparison-specific components. These results identify a continuous physiological and conventional chemical maturity gradient across T1–T5 and endpoint metabolomic differences between the contrasting T1 and T5 treatments. Together, the findings suggest that harvest maturity is associated with both the fresh-leaf biochemical starting point and the metabolite abundance profile observed after flue-curing, although intermediate metabolomic states and causal mechanisms underlying individual metabolite changes remain to be determined.

Soil salinization is one of the major abiotic stresses that influences agricultural production and the environment. Auxin response factors (ARFs) are key components of the auxin signal transduction pathway, while their role in wheat salt stress responses remains unclear. In this study, we identified TaARF18 as a negative regulator of salt tolerance in wheat. The coding sequences of TaARF18-A, TaARF18-B, and TaARF18-D were 2106, 2088, and 2088 bp, respectively. TaARF18 is a hydrophilic protein featuring typical Auxin-resp and B3 DNA-binding domains and exhibits relatively high evolutionary conservation among Poaceae species. The expression of TaARF18 was upregulated under salt stress. TaARF18 predominantly accumulated in the nucleus. Silencing of TaARF18 via the BSMV-VIGS approach enhanced salt tolerance in wheat seedlings. In addition, haplotype analysis based on resequencing data from 355 wheat accessions identified 25, 31, and 16 haplotypes for TaARF18-A, TaARF18-B, and TaARF18-D, respectively. Fourteen wheat accessions carrying different haplotypes were evaluated under salt stress, and HapIII of TaARF18-A exhibited the highest level of salt tolerance, which can act as a strong selection locus in global wheat breeding. Our findings provide insight into the function of ARFs in salt stress responses and offer a potential target for CRISPR/Cas-mediated salt-tolerant wheat breeding programs.