Flax (Linum usitatissimun) is a promising candidate for copper (Cu) phytoextraction from agricultural soils. However, the effects of nitrogen (N) fertilizer driving the efficiency of Cu phytoextraction remain poorly understood. This study aimed to evaluate the dynamics of different levels of N (0, 125, 250, 375 mg kg-1 soil) on flax growth and Cu uptake with Cu-contaminated soil (2137 mg kg-1Cu) and in mixtures of Cu-contaminated soil and natural soil (1189 mg kg-1 Cu). Our results demonstrated that the application of N (250 mg kg-1 soil) alleviated Cu toxicity by increasing plant growth and biomass, including dry weight, plant height, stem length, number of pods and number of branches per plant by 153.7 %, 43.1 %, 52.2 %, and 220.8 %, respectively, compared to control. N application at Cu0.5N2 significantly reduced malondialdehyde, proline, and peroxidase activity by 26 %, 66.8 %, and 60.1 %, respectively, while superoxide dismutase activity was maximally enhanced by 365.6 % under Cu0.5N3 treatment. N application progressively modulated antioxidants response, indicating that N plays a protective role against Cu-induced oxidative stress. Furthermore, transcriptome analysis identified differentially expressed genes (DEGs) associated with signal transduction and the phenylpropanoid biosynthesis pathway, which play key roles in N-mediated Cu detoxification. The involvement of phytohormones, including auxin (Aux1, LAX, and SAUR), gibberellic acid (DELLA), and salicylic acid (PR1, TGA), suggests that N improves heavy metals (HMs) tolerance via hormone signal transduction. Notably, N fertilization activated the expression of genes encoding peroxidase (E1.11.1.7) and respiratory burst oxidase homolog (RBOH) in the phenylpropanoid biosynthesis and MAPK signaling pathways, respectively, thereby alleviating Cu-induced damage. These findings indicate that varying N levels enhance Cu accumulation while maintaining ionic balance, facilitated by the activity of key transporters such as ZIP, CTR1, and AMT. These findings provide deeper insights into the mechanisms through which N alleviates Cu phytotoxicity, laying the foundation for optimizing phytoremediation strategies.

The partial substitution of chemical fertilizer with organic fertilizer is a crucial practice for enhancing crop production and quality, although its impact on natural rubber has rarely been explored. In this study, a two-year field experiment was conducted to investigate the impact of different nitrogen application rates and varying proportions of organic nitrogen substitution on dry rubber yield, nitrogen nutrition, and natural rubber properties. Regarding nitrogen application, the control treatment received no nitrogen amendment, while the low-nitrogen treatment was amended with 138 gtree-1year-1 of nitrogen. The medium-nitrogen treatment received 276 gtree-1year-1 of nitrogen, and the high-nitrogen treatment received 552 gtree-1year-1 of nitrogen. In addition, the low-organic-nitrogen substitution treatment and medium-organic-nitrogen substitution treatment were amended with 276 gtree-1year-1 of nitrogen each. The results demonstrated that the 50% organic nitrogen substitution treatment resulted in the highest dry rubber yield across all sampling periods, ranging from 46.43 to 94.65 gtree-1. Additionally, this treatment exhibited superior soil total nitrogen (1067.69 mgkg-1), available nitrogen (84.06 mgkg-1), and nitrogen content in roots (1.08%), leaves (3.25%), fresh rubber latex (0.27%), and raw natural rubber (0.44%) compared with other treatments. In terms of the physical properties of natural rubber, the 50% organic nitrogen substitution treatment resulted in advantages in the weight-average molecular weight (1.57 x 106 gmol-1), number-average molecular weight (0.36 x 106 gmol-1), plasticity retention index (97.35%), Wallace plasticity (40.25), and Mooney viscosity (81.40). For mechanical properties, natural rubber from the substitution treatment exhibited higher tensile strength (19.84 MPa), greater elongation at break (834.75%), and increased tear strength (31.07 Nmm-1). Overall, the substitution of 50% chemical nitrogen fertilizer with organic nitrogen fertilizer improved nitrogen nutrition in rubber trees by introducing organic nitrogen input, resulting in remarkable enhancements in natural rubber properties. Therefore, the incorporation of organic fertilizer as a substitution for 50% of chemical fertilizer is demonstrated as an effective strategy for improving both the yield and properties of natural rubber.

The soil water and nitrogen (N) levels are the important factors affecting turfgrass growth. However, the impact of the water-N interaction on tall fescue (Festuca arundinacea Schreb) in terms of the N metabolism and plant morphology remains uncertain. Therefore, the objective of this study was to investigate the impacts of different N and water levels on the physiological and morphological responses of tall fescue. The experiment was designed with N (N-0, N-2, and N-4 representing N application rates of 0, 2, and 4 g m(-2), respectively) and irrigation [W-1, W-2, W-3, W-4, and W-5 representing field water capacities (FWCs) of 90 similar to 100%, 75 similar to 85%, 60 similar to 70%, 45 similar to 55%, and 30 similar to 40%, respectively] treatments, and the relevant indexes of the soil water content and soil NH4+-N and NO3--N levels as well as the physiology and morphology of the tall fescue were determined. The results demonstrated significant changes in the contents of soil water (SWC) and N and the physiological and morphological indexes, except for the enzymes related to N metabolism, including nitrite reductase (NiR), glutamate dehydrogenase (GDH), and glutamate synthetase (GOGAT). The water stress significantly enhanced the water and N use efficiencies (WUE and NUE), except the NUE in the W-5 treatment. The N stress significantly influenced the SWC, soil NO3--N content, and physiological and morphological indexes, excluding malondialdehyde, NiR, GOGAT, and above- (AGB) and below-ground biomass, resulting in the increased WUE and NUE. The application of a low N rate effectively alleviated the detrimental impacts of water stress on the SWC and glutamine synthetase activity. In conclusion, W-2 and N-2 are deemed more appropriate treatments for the low-maintenance measures of tall fescue turf. Among all the treatments, N2W2 is recommended as the optimal water-N interaction treatment due to its ability to conserve resources while still ensuring high turf quality.

Rubber can improve the mechanical properties of the coated nitrogen fertilizers (CNFs), but the biomass components cause holes in the urea release process, thus accelerating the release of urea. In this study, a self-healing rubber (SHR) shell/hydrogel core based on a supramolecular network was fabricated as a coating material for CNFs to improve the above problems. The core of CNFs consists of vanillin(Van)-cross-linked poly(vinyl alcohol) (PVA)/carboxymethyl chitosan (CMCS) hydrogel, prepared by a freeze-thaw cycle. The shell of CNFs was prepared by soaking Van-cross-linked natural rubber (NR)/chitosan (CS)/PVA material in Zn2+ solution. A green core-shell structured CNF with hydrogen bonding and metal coordination was finally prepared, which has improved the mechanical properties, slow-release effect, and soil water retention capacity of the CNF. The effects of CS and PVA contents and the impregnation of Zn2+ on the physical and chemical properties of the SHR supramolecular composite and its self-healing ability were investigated, and the urea release kinetics were analyzed. The CNFs could reach release equilibrium in water for 10 days, with a slow-release rate of 62.7%, and the urea release kinetics were in accordance with the Korsmeyer-Peppas model (R-2 >= 0.90), with a possible release mechanism of Fickian diffusion.