The excessive accumulation of copper (Cu²⁺) has become a threat to worldwide crop production. Recently, it was revealed that melatonin (MT) could play a crucial role against heavy metal (HM) stresses in plants. However, the underlying mechanism of MT function acted upon by Cu²⁺ stress (CS) has not been substantiated in tomatoes. In the present work, we produced MT-rich tomato plants by foliar usage of MT, and MT-deficient tomato plants by employing a virus-induced gene silencing methodology and exogenous foliar application of MT synthesis inhibitor para-chlorophenylalanine (pCPA). The obtained results indicate that exogenous MT meaningfully alleviated the dwarf phenotype and impeded the reduction in plant growth caused by excess Cu²⁺. Furthermore, MT effectively restricted the generation of reactive oxygen species (ROS) and habilitated cellular integrity by triggering antioxidant enzyme activities, especially via CAT and APX, but not SOD and POD. In addition, MT increased nonenzymatic antioxidant activity, including FRAP and the GSH/GSSG and ASA/DHA ratios. MT usage improved the expression of several defense genes (CAT, APX, GR and MDHAR) and MT biosynthesis-related genes (TDC, SNAT and COMT). Taken together, our results preliminarily reveal that MT alleviates Cu²⁺ toxicity via ROS scavenging, enhancing antioxidant capacity when subjected to excessive Cu²⁺. These results build a solid foundation for developing new insights to solve problems related to CS.

To gain insights into the roles of beneficial PGPR in controlling soil-borne disease, we adopted a metabolomics approach to investigate the beneficial impacts of P. polymyxa NSY50 on cucumber seedling roots under the pathogen of Fusarium oxysporum f. sp. cucumerinum (FOC). We found that NSY50 pretreatment (NSY50 + FOC) obviously reduced the production of reactive oxygen species (ROS). Untargeted metabolomic analysis revealed that 106 metabolites responded to NSY50 and/or FOC inoculation. Under FOC stress, the contents of root osmotic adjustment substances, such as proline and betaine were significantly increased, and dehydroascorbic acid and oxidized glutathione (GSH) considerably accumulated. Furthermore, the contents of free amino acids such as tryptophan, phenylalanine, and glutamic acid were also significantly accumulated under FOC stress. Similarly, FOC stress adversely affected glycolysis and the tricarboxylic acid cycles and transferred to the pentose phosphate pathway. Conversely, NSY50 + FOC better promoted the accumulation of α-ketoglutaric acid, ribulose-5-phosphate, and 7-phosphosodiheptanone compared to FOC alone. Furthermore, NSY50 + FOC activated GSH metabolism and increased GSH synthesis and metabolism-related enzyme activity and their encoding gene expressions, which may have improved redox homoeostasis, energy flow, and defense ability. Our results provide a novel perspective to understanding the function of P. polymyxa NSY50, accelerating the application of this beneficial PGPR in sustainable agricultural practices.

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) is a common disease that affects tomatoes, which can cause the whole plant to wilt and seriously reduce the production of tomatoes in greenhouses. In this study, the morphological indexes, photosynthetic performance and incidence rate of NSY50 under Fol infection were evaluated. It was found that NSY50 could improve the growth of tomato seedlings and significantly reduce the incidence rate of Fusarium wilt. However, the molecular mechanism of NSY50 that induces resistance to Fusarium wilt is still unclear. We used transcriptomic methods to analyze NSY50-induced resistance to Fol in tomatoes. The results showed that plant defense related genes, such as PR and PAL, were highly expressed in tomato seedlings pretreated with NSY50. At the same time, photosynthetic efficiency, sucrose metabolism, alkaloid biosynthesis and terpene biosynthesis were significantly improved, which played a positive role in reducing the damage caused by Fol infection and enhancing the disease tolerance of seedlings. Through transgenic validation, we identified an important tomato NAC transcription factor, SlNAP1, which was preliminarily confirmed to be effective in relieving the detrimental symptoms induced by Fol. Our findings reveal that P. polymyxa NSY50 is an effective plant-growth-promoting rhizosphere bacterium and also a biocontrol agent of soil-borne diseases, which can significantly improve the resistance of tomato to Fusarium wilt.

The large-span insulated plastic greenhouse is a highly promising horticultural facility. The design parameters and configuration of structural components significantly impact their safety and load-bearing performance. However, current research in this field remains insufficient. In this study, the deformation, stress distribution, and stability of large-span insulated plastic greenhouses with different structural configurations were investigated using the finite element method. Subsequently, the ultimate bearing capacity of large-span insulated plastic greenhouses with varying ridge heights was examined. The research indicated that the greenhouse with a plane truss and double-layer tie rod exhibited the smallest deformation and stress in its members, as well as the highest ultimate load-bearing capacity. The analysis revealed that the installation of double-layer tie rods not only enhanced the collaborative effect of arch frames within the structural calculation unit but also reduced displacement along the Z direction, effectively mitigated the $\mathrm{P}-∆$ effect, reduced out-of-plane bending stress, and improved the ultimate load-bearing capacity. Ridge height affected the load-bearing capacity of the greenhouse structure. However, a higher ridge height did not necessarily result in a stronger ultimate load-bearing capacity. The greenhouse structure with a ridge height of 5 m demonstrated the maximum ultimate load-bearing capacity, capable of bearing 1.98 times the initial load. This study provides theoretical support for the configuration of structural components of large-span insulated plastic greenhouses and offers a scientific basis for the optimal design of ridge height.

Solar radiation is the foundation of efficient greenhouse production. Studying how structural parameters affect light transmission and solar energy utilization efficiency is crucial for optimizing greenhouse design and increasing crop yields. This study constructed a full-process solar radiation model using ray tracing technology. It examined the solar radiation energy intercepted, captured, and distributed by the greenhouse. The simulation yielded high prediction accuracy and rapid subsequent computation after pre-calculation of the shape factor matrix. The coefficient of determination R² was at least 0.95 for four observation points, with computations for 51 time points completed within 125 s. Subsequently, a comparative analysis of large-span insulated plastic greenhouses with different parameters was conducted during the cold and warm seasons based on eight representative solar terms. The results indicated that for a 20-m-span greenhouse at 35° N, an east-west orientation with a 15 m south roof and a 6 m ridge was better for the cold season. For comprehensive seasonal adaptability, a north-south orientation with a 5 m ridge was recommended. This study provides seasonal-oriented decision support for the structural parameter design of large-span insulated plastic greenhouses.

Although peanut shells represent an abundant agricultural waste, their high-value utilization potential as a horticultural substrate has not been fully recognized. Meanwhile, horticultural crops such as tomatoes are in urgent demand for high-quality and innovative cultivation substrates. This study investigated the effects of different ratios of peanut shell–substrate on tomato yield and rhizosphere bacterial community structure, aiming to provide a theoretical basis for the utilization of agricultural waste and the development of novel growth substrates for tomato cultivation. Results showed that peanut shell–substrate improved tomato yield and quality, and enhanced soil urease, sucrase, and catalase activities. High-throughput 16S rRNA gene sequencing revealed significant differences in rhizosphere bacterial alpha diversity between peanut shell substrates and the control. Proteobacteria, Acidobacteria, and Actinobacteriota were the dominant phyla, while unclassified genera, Devosia A_501803 and Bauldia, were identified as the core genera at the genus level. In conclusion, peanut shell substrates enriched dominant functional bacterial genera and enhanced the ecological functions of the substrate.