Autotoxic compounds from rhizosphere soil of lanzhou lily extracts: Identification and biological activity

Abstract

We investigated the autotoxicity of Lanzhou lily rhizosphere soil with different cultivation years. The allelochemicals in such soils were isolated and identified by gas chromatography-mass spectrometry (GC-MS). Based on our earlier studies, the antioxidant 2246 and dioctyl terephthalate were found in lily sick soil were used in pot experiments determine to their autotoxic effects on the Lanzhou lily seedlings growth, photosynthetic parameters and antioxidant enzyme activities in seedling leaves. The content of antioxidant 2246 and dioctyl terephthalate was determined by GC-MS in rhizosphere soil of different cultivation years. The aqueous extracts of Lanzhou lily rhizosphere soil promoted the growth of its own seedlings at 0.2 mg·mL-1, however, the concentrations > 2 mg·mL-1 were inhibitory. The longer the cultivation period (1-yr, 2-yr and 4-yr), the stronger were the inhibitory effects. In rhizosphere soils of 1-yr, 2-yr and 4-yr ; 8,: 15 and 18 compounds were identified, respectively. The identified compounds were camphor, 3-hydroxy-4-methoxy-benzaldehyde, 2,4-bis(1,1- dimethylethyl)-phenol, tributyl phosphate, dibutyl phthalate, antioxidant 2246 and dioctyl terephthalater and these are reported as allelochemicals. The pot experiment results showed that low concentrations of antioxidant 2246 stimulated the seedling growth but high concentrations were inhibitory, while all concentrations of dioctyl terephthalater inhibited the seedling growth. At 100 mg·mL-1, the antioxidant 2246 and dioctyl terephthalate significantly inhibited the photosynthesis and antioxidant enzyme activity in leaves (P <0.05). Furthermore, the content of these two compounds in soils increased with the increase of cultivation years. These results suggested that allelochemicals accumulated in replanted soil contributed to the autotoxicity of Lanzhou lily in rhizosphere soil.