Nitrogen fertiliser changes the soil environment, regulates the water balance of plants, and directly affects nitrogen and water use efficiency. In order to identify the adaptation mechanism and water regulation strategy of Notopterygium franchetii to the soil nitrogen environment, this study was conducted. Two-year-old Notopterygium franchetii plants grown in farmland were used as the test material. The hydraulic characteristics, natural dehydration, water capacitance and biomass allocation were investigated at three nitrogen application levels (0, 40, 80 kg/ha) and four growth periods (seedling, jointing, flowering and harvesting period). Nitrogen content in roots, stems and leaves increased with different levels of nitrogen treatments at each growth stage, and the change of nitrogen content in stems was the most significant. The overall water capacitance of all tissues was root > stem > leaf. After medium nitrogen treatment and high nitrogen treatments, the average water capacitance of leaves was 122.00% and 129.26% of low nitrogen treatment, and the average water capacitance of stems was 125.78% and 134.59% of low nitrogen treatment, the average water capacitance of leaves was 112.28% and 116.37% of low nitrogen treatment. Nitrogen treatment can improve the water use efficiency of plant roots, stems and leaves, and the relative content of stable carbon isotope (δ13C) in the whole growing season increased by 0.77%, 1.96% and 5.27% of the control group after medium nitrogen treatment, and 1.60%, 2.18% and 1.61% of the control group after high nitrogen treatment. The ratio of root to canopy decreased significantly in each growth stage after nitrogen treatment, and the change was most significant at seedling period (from 1.25 to 0.66), and the change was the most least at jointing period (from 0.77 to 0.63). Our study thus indicates that nitrogen addition could regulate water balance in plants, which is beneficial to water storage and utilisation, but excessive nitrogen fertiliser supply will also affect the distribution of plant biomass.
This study evaluated the effects of cluster thinning on yield and quality of 12-year-old Merlot/41B grapevines over the 2019-2020 and 2020-2021 growing seasons. Six phenological stages-before flowering, setting, bunch closure, veraison, half maturity, and before maturity-and three thinning levels (0%, 25%, and 50%) were assessed. Key parameters included total soluble solids (TSS), total acidity (TA), pH, sugar accumulation, maturity indices (TSS/TA, pH2 × °Brix), secondary metabolites (total anthocyanins, total tannins, total phenolic content, total polyphenol index), and yield. Cluster thinning significantly enhanced most quality traits, with veraison emerging as the optimal stage for improving phytochemical composition. The highest TSS was observed at setting, while maximum total anthocyanins, tannins, total polyphenol index (TPI), and maturity indices occurred at veraison under 50% thinning. Sugar accumulation was optimised at 25% thinning. Yield decreased proportionally with thinning intensity, with Control vines producing the highest yield and 50% thinning the lowest. Overall, 25% cluster thinning at veraison achieved a balance between improved grape quality and commercial yield, providing a practical management strategy for Merlot production.
The objective of this research was to investigate the effects of different concentrations of salicylic acid (SA) on seed germination and seedling growth physiology of sweet melon under NaCl stress. Under salt stress, low concentrations of 0.25-0.5 mmol/L SA treatment can effectively alleviate plant salt damage and promote the germination rate of sweet melon seeds. Simultaneously, high concentrations of SA had a significant inhibitory effect on the root length, root fresh weight, and root : shoot ratio of sweet melon, but using medium concentrations (1.0 mmol/L) of SA can increase the root length and root : shoot ratio of seedlings. In addition, low concentration SA treatment can reduce the malondialdehyde (MDA) content of plants and increase the activity of peroxidase (POD). High concentrations will reduce POD activity and increase MDA content. Adding exogenous salicylic acid at different concentrations without NaCl stress can, to some extent, inhibit seedling growth, reduce plant root length, root fresh weight and other growth indicators, but can reduce MDA content, increase POD activity, and enhance plant defence ability against the outside world. Under NaCl stress, treatment with 0.25 mmol/L SA can reduce MDA content, increase POD activity, enhance plant salt resistance, and improve seed germination rate. Treatment with 1.0 mmol/L SA promoted seedling root elongation and increased root : shoot ratio. In the absence of NaCl stress, treated plants with different concentrations of SA can inhibit seedling growth to some extent.
