Study On Allelopathy Of White Clover (Trifolium Repense L.) Root Exduates

White clover （Trifolium repens L.）, as a vivacious and perennial creeping type herb, isused to be common lawn plant in China with its strong fecundity and prolonged period to staygreen. In recent years, it was hypothesized that white clover would dominate the turf grass ifintercropped with it. It is well established that as an important biological interactionmechanism, allelopathy is widespread in nature. Some researchers have demonstrated thatwhite clover has an allelopathic effect. However, the effect of root exduates which is one ofimportant way by which plants release allelochemicals during encroaching process, has notbeen reported yet. The allelopathy effects of different root exudate levels of white clover onryegrass （Lolium perenne L.）, red fescue （Festuca rubra L.）, tall fescue （Festuca arundinaceaSchreb.）, kentucky （Poa pratensis L.）, creeping bentgrass （Agrostis stolonifera L.） werestudied. The objective of this work was to work out the real occupation and replacementmechanism of white clover and to reasonably arrange the plants in garden construction.According to the results:1. The root exudates were obtained with hydroponics system. Bioassay results indicatedthat the root exudates improved the seed germination and plant height of all tested turf grassesat low concentration (0.002g mL^-1), whereas inhibited these indexes at high concentration(0.05g mL^-1)（P<0.05）. The root length of all acceptors was inhibited by root exudates andthis inhibitory effect increased with the concentration change. The effect of root exduates onfresh and dry weight of turf grass varied with the acceptor types. The sequence of intensity ofroot exudates from white clover on all the acceptors was ranked as red fescue> tall fescue>kentucky> ryegrass> creeping bent grass. Among them, white clover always had an increaseeffect on tall fescue and perennial ryegrass while it had the same effect on other threeacceptors at low concentration and inhibited the three acceptors at high concentration. Itindicates that root exduates is not the main mechanism of the invasion by white clover ofperennial ryegrass and tall fescue and the root exduates at high concentration play a role in theprocess of which white clover invade kentucky and red fescue and creeping bent grass.2. Root activity, leaf superoxide dismutase, peroxidase, catalase activity and the contentof malondialdehyde of acceptors which had grew seven days were tested. The result showed that root exudates of white clover had concentration effect on the tested indexes of all theacceptors. That was the root exudates improved the activities of superoxide dismutase andcatalase of all tested turf grasses at low concentration (0.002g mL^-1), whereas inhibited thetwo indexes at high concentration (0.05g mL^-1)（P<0.05）. The activities of peroxidase andcontent of malondialdehyde of all acceptors were enhanced along with the increase of theconcentration of root exudates while root activities of all turf grasses declined with theincrease of concentration.3. Root exudates contained hydrophilic phenolics which may have caused change of seedgermination, seedling growth and antioxidant enzymes activities with the function of rootexudates.