Liquid-liquid extraction and solid phase extraction followed by high-performance liquid chromatography (HPLC) connected with ultraviolet (UV) detection were used for the determination of phytohormones. The parameters influencing the performance of the HPLC-UV method, including composition of the mobile phase for gradient elution, column temperature, flow rate, and detection wavelength, were optimized. This method can simultaneously determine 11 phytohormones, including nine cytokinins, indole-3-acetic acid, and abscisic acid. The limit of detection of this method is 0.22 to 1.1 µg L⁻¹, and the coefficient factors of linear regression are >0.998. The recoveries of the target phytohormones ranged between 62.1~109.4%, and the relative standard deviations were <10%. This method is suitable for determining phytohormones, especially cytokinins, in young panicles, roots, and xylem sap of rice plants.

Currently, vegetation restoration is being implemented in the ecologically fragile karst areas in southwest China; however, the stoichiometry of the dominant shrubs and their relationship with the environmental factors in the degraded habitats is still unclear. In this study, we investigated the stoichiometry of C, N, and P, their internal correlations, and influencing factors in 23 shrub species in the Huanjiang County in northwest Guangxi Province, China. We found that the mean contents of C, N and P in leaves were higher than those in roots. In addition, the N:P ratio in the leaves was significantly higher than that in the roots, but the opposite was observed for the C:N and C:P ratios. Except for Leaf C and Root C, significant positive or negative correlations were observed across the stoichiometry of the shrub leaves and roots. A factor analysis of variance demonstrated that the differences across species had higher explanatory power than the topography and soil nutrients in terms of the shrub leaf and root stoichiometry. Hence, our results can improve the understanding of the distribution patterns of these vital elements, as well as of the interactions and influencing factors in the different organs of the karst shrubs.

Climate-change-induced temperature fluctuations pose significant threats to global rice production, particularly through their impact on photosynthetic efficiency. The differential mechanisms by which low and high temperatures affect leaf photosynthetic processes in rice remain poorly understood. Here, we investigate the effects of temperature stress (15 °C, 30 °C, 45 °C) on rice photosynthetic performance across a gradient of nitrogen supply levels: low nitrogen (LN), medium nitrogen (MN), and high nitrogen (HN). The low temperature exhibited stronger negative impacts on photosynthesis than the high temperature, primarily through increased mesophyll limitation and disrupted cellular CO₂ diffusion, while the high temperature showed less pronounced effects, particularly under HN and MN conditions. While photosynthetic nitrogen use efficiency (PNUE) decreased with increasing nitrogen under the optimal temperature, moderate nitrogen supply maintained optimal PNUE under temperature stress, suggesting that a balanced nitrogen level is crucial for maximizing both photosynthetic capacity and nitrogen use efficiency. Plants with adequate nitrogen maintained higher intrinsic water use efficiency (_iWUE) under both temperature extremes through improved coordination between CO₂ uptake and water loss. Our findings reveal distinct mechanisms underlying low- and high-temperature stress effects on photosynthesis and highlight the importance of optimizing nitrogen management for enhancing crop resilience to temperature extremes under climate change.

Although many land-use patterns have been established to restore vegetation and eliminate poverty in the karst area in southwest China, the ecosystem services (ESs) of these patterns are still not fully understood. To compare the differences in seven typical monoculture patterns and three agroforestry patterns, their ESs and tradeoffs were analyzed within the Millennium Ecosystem Assessment Framework. Compared with the local traditional corn pattern, the marigold pattern improved provisioning, regulating, and cultural services by >100%. The pomegranate pattern provided far more provisioning services than the other patterns. The apple + soybean intercropping pattern reduced regulating services, and eventually, its Total ESs (TES) and ecosystem multifunctionality index (EMF) also decreased. Cultural services will be enhanced by the introduction of fruit trees, as well as intercropping. Orange + peach had the greatest negative tradeoffs between provisioning and regulating services (P-R), provisioning and supporting services (P-S), and provisioning and cultural services (P-C), which indicates that the provisioning services urgently require improvement. Peach + pumpkin intercropping decreased the negative tradeoffs of P-R, P-S, and P-C (all > 10%), while pomegranate + grass intercropping increased the negative tradeoffs of R-S and R-C (all > 100%). Our results suggest that all six of these patterns are worthy of promotion but the pomegranate pattern should be given priority. Among the three intercropping patterns studied herein, the apple + soybean pattern should be redesigned to improve performance.

Illicium difengpi Kib and Kim, an endangered plant unique to karst areas in China, has evolved an extremely high tolerance to arid environments. To elucidate the molecular mechanisms of the response to drought stress in I. difengpi, physiological index determination and transcriptome sequencing experiments were conducted in biennial seedlings grown under different soil moisture conditions (70~80%, 40~50% and 10~20%). With increasing drought stress, the leaf chlorophyll content decreased, while the proline (Pro), soluble sugar (SS) and malondialdehyde (MDA) contents increased; superoxide dismutase (SOD) and peroxidase (POD) activities also increased. Transcriptome sequencing and pairwise comparisons of the treatments revealed 2489, 4451 and 753 differentially expressed genes (DEGs) in CK70~80 vs. XP40~50, CK70~80 vs. XP10~20 and XP40~50 vs. XP10~20, respectively. These DEGs were divided into seven clusters according to their expression trends, and the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment results of different clusters indicated that genes in the hormone signal transduction and osmotic regulation pathways were greatly activated under mild drought stress. When drought stress increased, the DEGs related to membrane system and protein modification and folding were all upregulated; simultaneously, chitin catabolism- and glycolysis/gluconeogenesis-related genes were continuously upregulated throughout drought stress, while the genes involved in photosynthesis were downregulated. Here, 244 transcription factors derived from 10 families were also identified. These results lay a foundation for further research on the adaptation of I. difengpi to arid environments in karst areas and the establishment of a core regulatory relationship in its drought resistance mechanism.

Polygala fallax Hemsl. (Polygalaceae), a traditional Chinese medicinal species, requires optimal growth conditions for artificial cultivation. Irradiance is one of the primary environmental factors that affects the growth and survival of P. fallax Hemsl. plants, which seemingly grow better under weak irradiance conditions. However, the optimum light intensity for growing P. fallax Hemsl. is not clear. To determine the optimum light intensity for cultivating this medicinal plant species, P. fallax Hemsl. plants from two different habitats were grown and exposed to three shade treatments (50% shade, 70% shade and 90% shade, which resulted in photosynthetically active radiation amounts equal to 662 μmol m⁻² s⁻¹, 401 μmol m⁻² s⁻¹, and 131 μmol m⁻² s⁻¹, respectively) to evaluate survival, growth, leaf photosynthesis, and the main pharmacological active ingredients (saponins) in response to shade. Our results revealed that the P. fallax Hemsl. plants in the different habitats consistently exhibited relatively high photosynthesis rates, biomass, survival rates and saponins under 662 μmol m⁻² s⁻¹ created by the 50% shade treatment. We concluded that photosynthetically active radiation of approximately 662 μmol m⁻² s⁻¹ is suitable for the cultivation of P. fallax Hemsl. plants.