Abstract:
Objective Responses of azalea (Rhododendron simsii) seedlings cultivated under the applications of fungi and NPK fertilizer were studied.
Method Various fungal additions and NPK fertilizations were applied in cultivating 2-year-old azalea seedlings. The fungal treatments included Rhododendron mycorrhizae (J1), mixture of R. mycorrhizae and exophytic Pinus massoniana (J2), and blank control (J3). The fertilization was varied on the rate of application. Physiology and biochemistry of the azalea seedlings grown under the treatments were determined. Seedling biomass, chlorophyll (Chl) content, and activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as contents of malondialdehyde (MDA), soluble protein (SP), soluble sugar (SS), auxin (IAA), cytokinin (ZR), gibberellic acid (GA3), and abscisic acid (ABA) of the plants were measured and subjected to a principal component analysis.
Results The fungal additions increased the contents of Chla, Chlb, total Chl, SP, IAA, ZR, and GA3 as well as the activities of SOD, POD, and CAT, but reduced the MDA content in the seedlings. The addition, especially J2 treatment, allowed the seedlings to performed well physiologically with merely 1/4 to 1/2 of the normally applied amount of NPK fertilizer. It was speculated that the mycorrhizal symbiosis as observed might be the result of the improved nutrient absorption, photosynthesis, hormone synthesis, protective enzyme activity, stress resistance, and growth of, as well as the reduced membrane lipid peroxidation in the plants. It appeared that all indicators selected for this study were correlated.
Conclusion The overall physiological and biochemical indicators on the azalea seedlings cultivated with the fungal applications were better than those of control. In particular, the treatment of J2 not only reduced the NPK fertilization by half (i.e., urea 1.1 g ·plant−1, CaMgP 1 g·plant−1, and KCl 0.7 g KCl·pllant−1) but also elevated the levels of Chl, SOD, SP, IAA, and GA3 on the azalea seedlings.