Allelopathic effects of Wedelia trilobata residues on lettuce germination and seedling growth

The invasive plant Wedelia trilobata has allelopathic effects on germination and growth of native plants due to the allelochemicals released from its leaves and roots, however, little is known about the allelopathic potential of its residues. We studied the effects of residues of W. trilobata on lettuce germination and seedling growth in sterilized and non-sterilized soils. The residue leachates inhibited the germination of lettuce, and the inhibition increased with the increment of residue content in the soil. Seedling growth was relatively less affected, hence the biomass, ameliorated in both sterilized and non-sterilized soil's. The chlorophyll content of lettuce leaves increased in the non-sterilized soil but decreased in sterilized soil. The decreased activity of CAT and the increased MDA indicated an oxidative stress in non-sterilized treatment. However, germination rate, biomass and chlorophyll content were higher than sterilized treatment. These results indicated that the residues of invasive W. trilobata may facilitate its invasion through inhibiting the germination of native plants. Soil microbes could alleviate the adverse effects of W. trilobata residues.