Author(s): M. AMEENA, V. L. GEETHAKUMARI AND S. GEORGE

Abstract: Purple nutsedge, (Cyperus rotundus L.), a native of India is a pernicious perennial weed in many crops in more than 90 tropical and subtropical countries and is ranked as one of world\'s worst weeds. It asserts allelopathic effects on crop plants through inhibition of germination, growth or metabolism. Under field conditions, the deleterious effect of weeds may be facilitated by exudates, leachates from decomposing residues and residues incorporated to the growing medium. In the present study, laboratory experiments were carried out to investigate the allelopathic influence of nutsedge root exudates collected at different growth stages of the weed viz. sprouting, tuberisation, flowering and dormant tuber formation on seedling growth of rice, cowpea, sesamum, okra and brinjal. Exudates were collected at different growth stages of the weed and their effect on germination percentage, radicle length, plumule length and dry matter production and the vigour index (VI) of important field crops were observed to assess the effect of exudates. The nutsedge root exudates collected at sprouting stage inhibited the germination and growth of all the crop seeds tested which would be due to the release of some inhibitory chemicals from nutsedge tubers into the medium during the process of sprouting. However, the exudates collected at later stages did not elicit any response on growth characters of crop seeds. Significant reduction in vigour index was observed in sesamum and okra indicating that nutsedge inhibits the growth of associated crops by the production of inhibitory substances as root exudates. However, such an inhibitory effect on the development of plumule and radicle was not observed in rice, cowpea and brinjal. The tuber extracts of nutsedge as identified by HPLC technique revealed the presence of phenolic compounds viz.p-hydroxy benzoic acid, gentisic acid, caffeic acid, o-coumaric acid and ferulic acid. The results from our study suggest that compounds from Cyperusrotundus especially after flowering can serve as lead molecules for the synthesis of bioherbicides.

Download Full Article: Click Here