Dynamic root exudation of phenolic allelochemicals from Johnson grass (Sorghum halepense)

Hongjuan Huang, Chun Liu, Shouhui Wei, Jinxin Wang, Chaoxian Zhang*

Abstract：The phenolic allelochemicals from the root exudates of Johnson grass (Sorghum halepense) were collected at different developmental stages and analyzed using high performance liquid chromatography-ultraviolet/photo-diode array. The results revealed that three simple phenolic components, p-hydroxybenzoic acid, p-hydroxybenzaldehyde and ethyl p-hydroxybenzoate, along with two flavonoids, diosmetin (3′,5,7-trihydroxy-4′- methoxyflavone) and tricin (5,7,4′-trihydroxy-3′,5′-dimethoxyflavone), were found in the root exudates of Johnson grass. However, the major phenolic compounds varied and the quality of each compound was dynamic at different developmental stages: the only phenolic compound that was detected in the seedling stage was p-hydroxybenzoic acid; three simple phenolic allelochemicals, p-hydroxybenzoic acid, p-hydroxybenzaldehyde and ethyl p-hydroxybenzoate, were found in the jointing stage; and five compounds, including the two flavonoids, tricin and diosmetin, appeared in the reproductive stage along with the other three simple phenolic allelochemicals. The highest diversity in phenolic constituents was in the reproductive stage, with five allelochemicals. Only p-hydroxybenzoic acid was found in the whole life cycle of Johnson grass, with a range of 2.9 nmol to 6.8 nmol per plant per day. P-Hydroxybenzaldehyde had the highest quality among all the compounds, with the highest releasing rate of 26.8 nmol per plant per day. The lowest-content compounds were the two flavonoids, with the highest quality of 1.8 nmol per plant per day. The results suggest that the temporal dynamic of phenolic allelochemicals in the root exudates of Johnson grass corresponds with the dynamic of development.

Key Words：allelochemicals, dynamic, root exudation, Sorghum halepense

Weed Biology and Management，2015, 15()：133-137

DOI: 10.1111/wbm.12076