Hormetic-like dose response relationships of allelochemicals of invasive Solidago canadensis L.

Understanding of the hormetic dose-response relationships of allelochemicals from invasive plants may reveal the role of allelopathy in plant invasion. Effects of Solidago canadensis L. rhizome extracts on the germination, seedling growth and physiological activities of lettuce (Lactuca tatarica Breitung) were studied. The hormetic dose-response relationships were tested with nonlinear curve fitting methods using the OriginLab software. Germination rate, biomass and physiological activities including superoxide dismutase (SOD), malondialdehyde (MDA) content, relative conductivity (cellular electrolyte leakage index) and chlorophyll a and b followed dose-dependent responses. The extracts were inhibitory when the concentrations were higher than 0.6% (for germination), 0.5% (for growth) and 0.067% (for physiological activities). Stimulation was observed at low concentrations followed by inhibition at higher concentrations, thus the model simulated all the data very well with high coefficient of determination (0.76561 and 0.98304).