GROWTH, PHOTOSYNTHETIC AND BIOCHEMICAL RESPONSES OF RHODODENDRON DELAVAYI FRANCH SEEDLINGS IRRIGATED WITH DIFFERENT pH SOLUTIONS

Rhododendron delavayi Franch, an evergreen ornamental shrub, has a special preference for acidic soils, however, the exact pH value of the matrix suitable for R. delavayi growth is still unknown. In this study, three --year--old R. delavayi seedlings were irrigated with different pH solutions (4, 4.5, 5, 5.5, 6, 6.5, 7, and groundwater) to observe their growth, photosynthetic, and biochemical responses. Results showed that R. delavayi seedlings maintained well--growth and leaf development under pH 5.5 solution irrigation, without a remarkable difference in the branch numbers per plant. Meanwhile, the maximum values of the chlorophyll content, photosynthesis ability, and antioxidant enzyme activities were observed. Redundancy analysis indicated that the higher net photosynthesis rate and total chlorophyll content of R. delavayi seedlings were contributed to the rapid growth and improvement resistance of individuals. Our study suggested that the irrigation under pH 5.5 solution was the optimal treatment for the cultivation of R. delavayi seedling. The study provides a reliable scientific basis for exploring efficient cultivation and adaptation of R. delavayi seedlings under different pH matrixes.