Melatonin (N-acetyl-5-methoxytryptamine) has been demonstrated to play a significant role in plant stress responses. This study aimed to evaluate the effects of exogenous melatonin (50, 100 and 200 μmol/L) on growth parameters, antioxidant enzyme activity, photosynthetic performance, and aquaporin-related gene expression in licorice (Glycyrrhiza uralensis Fisch.) seedlings under PEG-induced drought stress. The results indicated that drought significantly reduced plant height, root length, leaf mass, and antioxidant enzyme activities of leaves and roots. It also inhibited photosynthesis rate, stomatal conductance (gs), and water use efficiency (WUE), disrupted the potential activity and function of PSII, and decreased water channel protein gene expression. Melatonin treatments were found to mitigate the adverse effects of drought by restoring plant growth attributes and photosynthetic efficiency, decreasing transpiration, increasing water utilization, stomatal conductance, and water channel protein gene expression. Additionally, melatonin treatments increased fluorescence parameters such as actual photochemical efficiency of PSII (ΦPSII), electron transfer rate (ETR) and photochemical quenching (qP), as well as antioxidant enzyme activities. Water conditions are positively correlated with most photosynthetic indicators and significantly associated with the expression of the majority of aquaporin (AQPs) genes. Additionally, melatonin concentration is significantly positively correlated with stomatal limitation (Ls), ΦPSII, ETR, and the expression of the GuTIP1;3 gene in roots. In conclusion, melatonin can protect photosynthetic organs under drought stress, reduce reactive oxygen species (ROS) accumulation, and thus improve the adaptability of seedlings to drought stress.

This study assessed the effect of Bacillus megaterium on seedling growth of Glycyrrhiza uralensis Fisch. under control and phosphorus (P) deficiency conditions. The results showed that P deficiency improved 1) G. uralensis root growth, 2) superoxide dismutase, catalase, and peroxidase activities, 3) inorganic P, starch, and soluble sugar contents in roots, 4) dissipated energy flux per reaction center, trapped energy flux per reaction center, and absorption flux per reaction center, and 5) net photosynthetic rate, stomatal conductance, transpiration rate, maximum fluorescence intensity after dark adaptation, and variable fluorescence. However, P deficiency significantly decreased chlorophyll and carotenoid contents in G. uralensis, but enhanced chlorophyll and carotenoid contents in B. megaterium. Our findings on the regulatory mechanisms of B. megaterium in response to P starvation hold promise for improving the success of G. uralensis cultivation.Keywords: Bacillus megaterium; Glycyrrhiza uralensis Fisch; Phosphorus deficiency; Chlorophyll fluorescence; Antioxidant enzymes superoxide; Non-structural carbohydrate

The mature flesh of Cornus officinalis exhibits a vibrant red color, attributed to its rich anthocyanin content, imparting significant edible and medicinal value. Vibrant colors not only enhance the visual allure of medicinal materials but also maintain a close association with their intrinsic quality. However, the intricate process of pigment formation governing the anthocyanin accumulation in the pericarp of Cornus officinalis remains poorly understood. In this study, we conducted the comprehensive sampling and analysis of pericarp tissues at three distinct developmental stages, employing morphological-structure observation and metabolomic and transcriptomic techniques. Our findings reveal a substantial increase in the anthocyanin accumulation during the transition to the red stage of Cornus officinalis fruit maturation. Metabolomic profiling identified the highest expression levels of Cyanidin-3-O-glucoside and Pelargonidin-3-O-rutinoside during the mature stage, suggesting their association with the red coloration of the fruit. Through RNA sequencing, we identified 25,740 differentially expressed genes (DEGs), including 41 DEGs associated with anthocyanin biosynthesis. The correlation between the DEG expression levels and anthocyanin content was explored, further elucidating the regulatory network. Additionally, we validated the pivotal role of the candidate gene BZ1 in the synthesis of Cyanidin-3-O-glucoside through qRT-PCR, confirming its crucial impact on anthocyanin accumulation. This study provides preliminary insights into anthocyanin accumulation in Cornus officinalis, laying the foundation for the future development of new cultivars with enhanced anthocyanin contents.

To examine the hypothesis that microbes can function as antitranspirants regulating stomatal behavior, we studied the effect of Saccharomyces cerevisiae strain BY4741 on gas exchange and water-use efficiency (WUE) in Vicia faba L. Stomatal aperture and photosynthetic parameters were analyzed every day for 7 days after treatment. In the present study, spraying yeast decreased the stomatal aperture. On the 4th, 5th, 6th, and 7th days after the foliar application of yeast, a decreased in net photosynthetic rate (P_n) was observed. This decrease was accompanied with decreases in stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and transpiration (T_r). The carboxylation efficiency (CE) was reduced by yeast on the 1st day after treatment. On the 1st, 2nd, and 3rd days of treatment, the yeast dramatically decreased the maximum photochemical efficiency of photosystem (PS) II (F_v/F_m) and increased non-photochemical quenching (NPQ); however, these parameters eventually recovered to their normal levels. The marked decrease of qP was observed on the 1st and 2nd days after yeast treatment. At the beginning of the treatment, the yeast decreased electron the transport rate (ETR), but later increased it. Both concentrations of yeast (1×10⁶ and 1×10¹⁰ CFU mL⁻¹) increased the WUE on the 4th, 5th, 6th, and 7th days of treatments. At the concentrations of 1×10⁶ CFU mL⁻¹, yeast acted as a more effective antitranspirant, showing higher WUE, than at the concentration of 1 × 10¹⁰ CFU mL⁻¹. P_n was positively correlated with T_r and g_s on the 7th day of the treatment. Moreover, T_r was much more sensitive to yeast than was P_n. In general, the foliar application of yeast resulted in decreased T_r and increased WUE. The yeast-induced decrease in photosynthesis is mainly caused by stomatal closure, suggesting that yeast can be used as an antitranspirant or a priming agent for improving drought tolerance in plants.

This study investigated the interactive effects of different light conditions and weed control methods on the medicinal compound composition and rhizosphere bacterial community structure of Epimedium sagittatum. A completely randomized block design was employed, incorporating four treatments: full light with manual weeding (LN), shade with manual weeding (SN), full light with weed-control fabric mulch (LG), and shade with mulch (SG). Active compound levels in two-year-old plants were quantified using HPLC, and rhizobacterial diversity was assessed via high-throughput sequencing. The results indicated that the SG treatment significantly enhanced the photosynthetic efficiency and yielded the highest levels of epimedin C and total active compounds. In contrast, the SN treatment fostered a beneficial rhizosphere environment—characterized by increased pH, ammonium nitrogen (NH₄⁺-N), bacterial diversity, and the abundance of Flavobacterium—which supported the highest production of epimedin B and icariin. Redundancy analysis confirmed that these microbial shifts were primarily driven by soil pH, nitrate nitrogen (NO₃⁻-N), and shading. Furthermore, while stochastic processes governed bacterial community assembly, deterministic selection intensified across the treatments from LN to SG. Collectively, our findings demonstrate that light and mulching can be strategically tailored to manipulate the plant–soil-microbe system, thereby enabling precise modulation of the medicinal quality of E. sagittatum.