Effects of allelochemicals from Ageratina adenophora (Spreng.) on its own autotoxicity

We investigated the autotoxic effects of 4-allelopathic compounds [dis2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), amorpha-4,7(11)-dien-8-one (DTD), 6-hydroxy-5-isopropyl-3,8- dimethyl-4a, 5,6,7,8,8a- hexahydraphthalen-2(1H)- one (HHO)] from the invasive Weed species Ageratina adenophora and their biochemical mechanisms. The allelochemicals DEHP and DBP were extracted from the roots, while, DTD and HHO (the main allelopathic compounds) were isolated from the leachates of A. adenophora. In bioassay, the allelochemical DBP from the root exudates was inhibitory to seed germination and seedling growth of A. adenophora, but the DEHP was not autotoxic. Both allelochemicals i.e. DTD and HHO from leachates of A. adenophora also inhibted either germination or seedling growth of A. adenophora at different concentrations. The application of DEHP and DBP increased the activities of superoxide dismutase (SOD) enzyme. Whereas DTD had no significant effects on SOD activities and HHO inhibited the SOD activities. All these four allelochemicals did not influence the activity of peroxidase (POD). Thus two allelochemicals (DEHP and DBP) from the root exudates of A. adenophora caused the lipid peroxidation and damage to cell membrane of A. adenophora leaves.