Comparative study of allelopathy and allelochemicals of some common weeds in Cyperaceae

Three serious and common weeds, Cyperus rotundus L., Kyllinga nemoralis Rottb) and K. brevifolius Rottb, were chosen for the study of their allelopathy. Root exudates were collected from K. nemoralis, K. brevifolius and C. rotundus of different chemotypes using a continuous root exudate trapping system. The allelopathic activity of root exudates was compared between species (K. nemoralis versus K. brevifolius) and between chemotypes of C. rotundus (H-type versus K- and O-type). Root exudates collected from all three species showed inhibitory activity against lettuce seed germination and seedling growth. Root exudates from K. nemoralis were more inhibitory than those from K. brevifolius. Root exudates from H-type were more inhibitory than those from K-type and O-type.; The inhibitory activity of extracts of roots and/or tubers was compared between genus and species (C. rotundus, K. nemoralis and K. brevifolius) and between chemotypes (H-type versus K- and O-type) using the lettuce seed germination bioassay. Tuber extract of C. rotundus was more inhibitory than root extracts of K. nemoralis and K. brevifolius. Seedling growth bioassay showed that root extract of K. nemoralis was more inhibitory than that of K. brevifolius and that tuber extract of H-type was more inhibitory than that of K-type. Water deficit stress enhanced allelopathic activity of root exudates from K. nemoralis and K. brevifolius. Inhibitory activity of tuber extracts of C. rotundus was also enhanced under water deficit stress and the tuber extract of H-type was more inhibitory than that of K-type under both water status.; Inhibitory activities of MeOH and {dollar}rm CHsb2Clsb2{dollar} fractions of root exudates and of MeOH and hexane fractions of extracts were compared for the three weeds. The MeOH fraction of root exudates was more inhibitory than the {dollar}rm CHsb2Clsb2{dollar} fraction. MeOH fraction of root/tuber extract was more inhibitory than the hexane fraction. Inhibitory palmitic acid and aristolone were identified by GC-MS in the MeOH extract of C. rotundus tubers. Three other fatty acids (lauric, myristic, pentadecanoic acids) were identified by GC-MS in the {dollar}rm CHsb2Clsb2{dollar} fraction of the hydrolyzed MeOH tuber extract.