ALLELOPATHIC POTENTIAL OF NUPHAR-LUTEA (L) SIBTH AND SM (NYMPHAEACEAE)

Aqueous extracts of Nuphar lutea (L.) Sibth. & Sm. leaves (blades plus petioles) and roots plus rhizomes were tested for allelopathic activity using lettuce seedling and Lemna minor L. assay systems. The 12.5, 25, 125, and 250 parts per thousand (ppt) treatments of both extracts killed the lettuce seedlings. At 2.5 ppt of extract, radicle growth of lettuce was 29% of the control for leaves and 31% of the control for roots plus rhizomes. Lemna minor frond number was reduced to 34% of the control by the 25 ppt leaf extract and to 43% of the control by the 25 ppt roots plus rhizomes extract. L. minor was killed by concentrations of 125 ppt and above of both plant part extracts. As expected, the frond number and total chlorophyll content measured by the L. minor assay were highly correlated. Osmotic potentials below 143 mOsmol/kg had no influence on L. minor growth. Neither the osmotic potential nor the pH of the undiluted extracts of N. lutea were in the range known to influence the growth of either lettuce seedlings or L. minor. Nuphar lutea extracts were many times more inhibitory than 16 other hydrophytes we previously examined.