POTENTIAL ALLELOPATHIC EFFECTS OF LUDWIGIA ADSCENDENS L. ON THE SEED GERMINATION AND SEEDLING GROWTH OF RICE

摘要

The allelopathic potential of Ludwigia adscendens L. was studied under laboratory conditions and pot experiments in field conditions. Different parts (viz. leaf, stem, and leaf+stem) of the weed exudates at 2.5, 5, and 10% (w/v) concentrations were applied to determine their effect on rice (Oryza sativa cv. Satabdi) seed germination and seedling growth under laboratory conditions. Increasing concentrations of leaf and stem of L. adscendens weed inhibited seed germination and seedling growth of rice.Further, leaf+stem extract of this weed synergistically also inhibited seed germination and seedling growth of rice. The plumules of rice seedlings were more sensitive to allelopathic effects than radicles. Increasing concentrations from leaf, stem, andleaf+stem of this weed significantly (P<0.05) inhibited water uptake by rice seeds. The decrease in germination was also correlated with increased electrolyte leakage. Dry weed residues (i.e., 2.5, 5, and 10 g per 2.5 kg soil) incorporation in soil or application on soil surface also inhibited seed germination and seedling growth of rice in pots under field conditions. The germination inhibition was higher under soil surface placement of dry weed residues, whereas root length and shoot length inhibitionwas higher under soil incorporated dry weed residues.