Effects of simulated acid rain on the allelopathic potential of invasive weed Wedelia trilobata

Authors: WANG, RUILONG - South China Agricultural University; REHMAN, SHAFIQ - South China Agricultural University; LIANG, XIAOTING - South China Agricultural University; SONG, YUANYUAN - South China Agricultural University; SU, YIJUAN - South China Agricultural University; Baerson, Scott; ZENG, RENSEN - South China Agricultural University

Submitted to: Allelopathy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2012
Publication Date: 7/20/2012
Citation: Wang, R., Rehman, S.U., Liang, X., Song, Y., Su, Y., Baerson, S.R., Zeng, R. 2012. Effects of simulated acid rain on the allelopathic potential of invasive weed Wedelia trilobata. Allelopathy Journal. 30: 23-32.

Interpretive Summary: Certain plant species produce compounds referred to as allelochemicals, which inhibit the growth of neighboring susceptible plant species, thus reducing competition for available nutrients and other resources. The production of allelochemicals is thought to have profound effects on natural ecosystems, as non-native plant species producing allelochemicals may have an enhanced ability to compete with native species for limited resources, ultimately leading to their displacement. At the same time, environmental stresses have been shown to increase the toxicity of allelochemical mixtures released by plants in some instances, which may in turn increase their ability to invade and disrupt ecosystems. In this study, the toxicity of allelochemicals released from the highly destructive weed Wedelia trilobata were shown to significantly increase in response to simulated acid rain exposure. Acid rain deposition currently poses a major threat to agriculture and natural ecosystems in rapidly developing nations, some of which are also experiencing significant Wedelia trilobata infestations. Thus the possibility exists that acid rain and other phenomena which adversely impact the environment could also accelerate the loss of native species by enhancing the competitiveness of non-native allelopathic weeds.

Technical Abstract: Acid rain continues to pose a major threat to natural ecosystems in rapidly-developing industrialized regions such as southern China. Despite the significant environmental impact of this phenomenon, relatively little is known concerning its effects on important aspects of ecosystem dynamics such as plant-plant allelopathic interactions, which prior studies suggest could be enhanced by various abiotic stresses. The invasive allelopathic weed Wedelia trilobata has caused significant disruption to native plant communities in southern China, and is used in the present work to examine possible effects of acid rain exposure on the allelopathic potential of invasive plant species. The phytotoxicity of aqueous leachates and dried leaf litter derived from field-grown W. trilobata plants treated with control and foliar applications of simulated acid rain (SAR) of pH 2.5, 4.0, and 5.6 were examined in in vitro assays using two different target species. Substantial increases in the phytotoxicity of the leachates as well as leaf litter were observed as a function of decreasing SAR treatment pH. Additionally, glasshouse experiments were performed to determine the effects of various SAR-treatments on W. trilobata biomass accumulation and shoot height, and both parameters showed modest increases at pH 4.0, and decreases at pH 2.5 relative to control (pH 7.0) -treated plants. Collectively, these data indicate an increase in the allelopathic potential of W. trilobata under acidic conditions, suggesting that acid rain exposure could increase the invasiveness of this plant.