Effects of different nitrogen forms and concentrations on seedling growth traits and physiological characteristics of Populus simonii ×  P. nigra

Abstract

Numerous growth and physiological variables of 3-week-old Populus simonii ×  P. nigra seedlings were assessed after treatment with either nitrate nitrogen (NO₃ ⁻–N) (0.1, 0.5, 1, 5, or 10 mmol·L⁻¹) or ammonium nitrogen (NH₄ ⁺–N) (0.1, 0.5, 1, 5, or 10 mmol·L⁻¹) to determine the best nitrogen form and concentration to optimize growth, biomass allocation, pigment content, and photosynthetic capacity. The results of combining membership function and an evaluation index suggested that, 5 mmol·L⁻¹ nitrogen, regardless of the form, yielded the highest comprehensive evaluation index and good growth. In addition, a Pearson correlation analysis and network visualization revealed that the total mass, shoot mass, root mass, leaf dry mass, plant height, leaf area, chlorophyll a and total chlorophyll had a physiological index connectivity degree ≥ 15 for both nitrogen forms. Net photosynthetic rate, stomatal conductance, transpiration rate, maximum photochemical efficiency of PSII, total nitrogen content, ground diameter, chlorophyll b, and carotenoid were unique indices for evaluating NH₄ ⁺–N-based nutrition, which could provide a theoretical basis for evaluating the effects of nitrogen fertilizer on seedlings, cultivation periods, and stress tolerance in P. simonii ×  P. nigra.

Keywords

Nitrogen form / Nitrogen concentration / Growth traits / Physiological characteristics