Abstract:

The effects of different nutrient solution pH conditions on the absorption characteristics of different nitrogen forms in Rosa roxburghii were studied, aiming to provide guidance for rational fertilizer in the cultivation of R. roxburghii on soil with different pH conditions. Taking R. roxburghii ‘Guinong 5’ seedlings as materials, using the method of nutrient solution culture and ion depletion, six treatments with nutrient solution pH 4, 5, 6, 7, 8, 9 were set up under the application of nitrate and ammonium nitrogen respectively, the absorption kinetics parameters of NO₃ ^-, NH₄⁺ in R. roxburghii seedlings were determined, and the plant height, dry weight biomass, nitrogen content and nitrogen uptake of the R. roxburghii seedlings were measured, the correlation between nutrient solution pH change and absorption kinetic parameters of NO₃ ^-, NH₄ and the correlation between nutrient solution pH change and plant height, dry weight biomass, nitrogen content and nitrogen uptake of R. roxburghii seedlings were analyzed. The results showed that the absorption pattern of nitrate nitrogen, ammonium nitrogen and total nitrogen followed the Michaelis-Menten kinetics equation. The nutrient solution pH change affected the absorption of NO₃^- and NH₄⁺ in the roots of R. roxburghii. When the nutrient solution pH change increased from 4 to 9 and nitrate nitrogen was applied, the maximum absorption rate (I_max) of the root of NO₃ ^-, the root and NO₃^- affinities, the rate (α) in the roots of the NO₃^- flow into the roots, plant height, dry weight biomass, nitrogen content and nitrogen uptake of R. roxburghii seedling decreased with the increase of pH, there was a significant negative correlation between the nutrient solution pH change and the above indexes. The above indexes of R. roxburghii seedling of NH₄ ⁺ increased with the increase of pH under the condition of ammonium nitrogen application, and there was a significant positive correlation between nutrient solution pH change and the above indexes. Acidic condition is beneficial to the nitrate uptake of R. roxburghii seedlings, while the increase of the pH of the nutrient solution is not beneficial for R. roxburghii seedlings to absorb nitrate. Alkaline condition is beneficial to the ammonium uptake of R. roxburghii seedlings, while acidic condition is unfavorable for R. roxburghii seedlings to absorb ammonium nitrogen.

Key words: Rosa roxburghii, nitrate-N, ammonium-N, nitrogen absorption kinetic parameters, nitrogen uptake