Phenolic acids and terpenoids in the soils of different weed-suppressive circles of allelopathic rice

Abstract

Allelopathic rice ‘PI312777’ (PI) and non-allelopathic rice ‘Lemont’ (Le) were used to assess phenolic acids and terpenoids in the soils of different circles using inhibitory-circle method. The rhizosphere soils of rice (inner circle) and barnyard grass at a 12 cm distance from rice (outer circle) were collected for analyses. The results showed total content of phenolic acids in outer circle of PI was significantly higher than that of Le, while the outer soil of PI contained a higher total content of benzoic acid derivatives and a lower total content of cinnamic acid derivatives than the inner soil. Total terpenoid and monoterpene contents in inner and outer circle soils of PI were significantly higher than that of Le, and the ratio of oxygenated monoterpenes in outer soil of PI was higher than that of Le. Furthermore, phenolic acid mixtures showed a more obvious inhibitory effect on root length than on shoot length of the receptor, while oxygenated monoterpenes were opposite, and a low concentration of oxygenated monoterpenes enhanced inhibitory effect of phenolic acids mixtures on shoot length of the receptor. All results suggested oxygenated monoterpenes participated in the weed-suppressive effect together with phenolic acids of allelopathic rice.