Effects of phenolic acids on seed germination and seedling growth and physiological characteristics of Pinus koraiensis

Through the relevant indoor simulation experiments, this research aims to clarify the effects of three phenolic acids(benzoic acid, syringic acid, and vanillic acid) with high content in broad-leaved Pinus koraiensis forest on the seed germination and seedling growth of Pinus koraiensis, so as to provide scientific basis for exploring the allelopathy mechanism of broad-leaved Pinus koraiensis forest and solving the problem of regeneration obstacle of Pinus koraiensis. The experiment adopts petri dish culture method and the indoor potted culture method. The Pinus koraiensis seeds and triennial Pinus koraiensis seedlings as experimental object were treated with different concentrations(2, 20, and 200 mg/L) of benzoic acid, syringic acid, vanillic acid solution, and distilled water was used as control. The germination experiment of Pinus koraiensis seed and the Pinus koraiensis seedling growth test were carried out to study the effects of three phenolic acids on germination, seedling growth, photosynthetic pigment, antioxidant enzyme activity, membrane lipid peroxidation, and osmoregulation substances of Pinus koraiensis seeds. The results show that:(1) all the three phenolic acids with different concentrations had the effects of inhibiting germination of Pinus koraiensis seeds, but the change of phenolic acid concentration only had a significant difference in the germination rate of Pinus koraiensis seeds.(2) The three phenolic acids had significant inhibitory effects on the growth and substance accumulation of Pinus koraiensis seedlings. Phenolic acid concentration had no significant effect on plant height and root length, but had significant effect on biomass, root weight and stem weight.(3) The changes in the contents of chlorophyll a, chlorophyll b, and carotenoids in needles had same reaction to the phenolic acid treatment. All the three phenolic acids of 20 mg/L had significant inhibition on the production of photosynthetic pigments, while the syringic acid solution of 200 mg/L and the vanillic acid solution of 2 mg/L had significant effects on promoting the accumulation of chlorophyll a and carotenoids.(4) Phenolic acid treatment reduced the activity of peroxidase and catalase and increased the activity of superoxide dismutase. The content of malondialdehyde in needles was significantly increased, while the content of MDA in needles treated with 200 mg/L syringic acid group was 70.51% higher than that in control group.(5) Benzoic acid solutions of dif