Shengrong Xu, Lili Pei, Honghong Zhou, Yijin Hu, Tong Li, Ruili Ma
Nitrogen fertiliser changes the soil environment, regulates the water balance ofplants, and directly affects nitrogen and water use efficiency. Inorder toidentify the adaptation mechanism and water regulation strategy ofNotopterygium franchetii tothe soil nitrogen environment, this study was conducted. Two-year-old Notopterygium franchetii plants grown infarmland were used asthe test material. The hydraulic characteristics, natural dehydration, water capacitance and biomass allocation were investigated atthree nitrogen application levels (0, 40, 80kg/ha) and four growth periods (seedling, jointing, flowering and harvesting period). Nitrogen content inroots, stems and leaves increased with different levels ofnitrogen treatments ateach growth stage, and the change ofnitrogen content instems was the most significant. The overall water capacitance ofall tissues was root > stem > leaf. After medium nitrogen treatment and high nitrogen treatments, the average water capacitance ofleaves was 122.00% and 129.26% oflow nitrogen treatment, and the average water capacitance ofstems was 125.78% and 134.59% oflow nitrogen treatment, the average water capacitance ofleaves was 112.28% and 116.37% oflow nitrogen treatment. Nitrogen treatment can improve the water use efficiency ofplant roots, stems and leaves, and the relative content ofstable 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.