Allelopathic and autotoxic effects of aqueous extracts of Codonopsis pilosula root secretions.

Abstract

Abstract Aims Water-soluble components in root exudates of C. pilosula are auto-toxic and allelopathic, severely limiting its growth. To effectively alleviate limitations to continuous cropping of C. pilosula. Methods C. pilosula seedlings were cultured by hydroponics and aqueous leachate were collected. The growth indexs and enzyme activity of C. pilosula seedlings were measured under the treatment of aqueous extracts of C. pilosula root exudates. Gas chromatography-mass spectrometry (GC-MS) analysis was used to qualitatively identify the chemical constituents in an aqueous solution of root secretion of C. pilosula at a concentration of 125 mg/mL. Results The inhibitory effects on seed germination, seedling growth, and antioxidant enzyme activity, gradually increased with the increase in concentration of the aqueous extracts of C. pilosula root exudates. The auto-toxic comprehensive effect of the aqueous extracts of root exudates of C. pilosula were strongest at 50 mL concentration and during the reproductive period, reducing SOD and POD activity, and MDA content of C. pilosula seedlings by 72.3, 71.7, and 83.3% (P < 0.05) compared to the control. Three major allelopathic components, acetic acid, hexamethyl cyclotrisiloxane, and methoxybenzene oxime were isolated and identified in the aqueous extract of root exudates of C. pilosula. Acetic acid had the highest relative content, accounting for 44.1% of all chemical components. Conclusions The aqueous extracts of root exudates of C. pilosula had a significant auto-toxic effect on seed germination and seedling growth of C. pilosula, with the strongest such effect during the reproductive period of C. pilosula, and low molecular weight organic acids were the main allelopathic components.