1Key Laboratory of Tropical Agro-environment, Ministry of Agriculture, South China Agricultural University, Guangzhou510642, China
2USDA-ARS, Natural Products Utilization Research Unit, P. O. Box 8048, University, MS- 38677, USA.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, South China Agricultural University, Guangzhou510642, China
*Correspondence author: E.Mail: rszeng@scau.edu.cn
**E.Mail: rlw2009@scau.edu.cn
Online published on 7 November, 2012.
Acid rain poses a major threat to natural ecosystems in rapidly-developing industrialized regions like southern China. Despite the significant environmental impact of acid rain, little is known about its effects on important aspects of ecosystem dynamics such as plant-plant allelopathic interactions. The major invasive weed Wedelia trilobata in southern China, was used in this study to examine the possible effects of acid rain on the allelopathic potential of invasive plant species. The phytotoxicities of aqueous leachates and dried leaf litter of field-grown W. trilobata plants exposed to simulated acid rain [(SAR) of pH 2.5, 4.0, 5.6, 7.0 water control] were determined in in-vitro assays on two receptor species: Brassica campestris and Raphanus sativus. Substantial increases in the phytotoxicity of the leachates as well as leaf litter were observed as a function of decreasing SAR pH. Additionally, glasshouse experiments were done to determine the effects of various SAR-treatments on W. trilobata biomass accumulation and shoot height, both parameters showed modest increases at SAR pH 4.0 and decreases at SAR pH 2.5 than control (pH 7.0) plants. These data indicated that acidic conditions increased the allelopathic potential of W. trilobata, suggesting that acid rain exposure may increase the invasiveness of this weed.
Allelopathy, biological invasion, Brassica campestris, phytotoxicity, Raphanus sativus, simulated acid rain, Wedelia trilobata
