SWEET-POTATO ALLELOPATHIC SUBSTANCE INHIBITS GROWTH OF PURPLE NUTSEDGE (CYPERUS-ROTUNDUS)

The allelopathic influence of sweet potato cultivar 'Regal' on purple nutsedge was compared to the influence on yellow nutsedge under contro lled conditions. Purple nutsedge shoot dry weight, total shoot length and tuber numbers were significantly lower than the controls (47, 36, and 19% inhibition, respectively). The influence on the same parameter s for yellow nutsedge (35, 21, and 43% inhibition, respectively) were not significantly different from purple nutsedge. Sweet potato shoot d ry weight was inhibited by purple and yellow nutsedge by 42% and 45%, respectively, The major allelopathic substance from 'Regal' root perid erm tissue was isolated and tested in vitro on the two sedges, The I-5 0's for shoot growth, root number, and root length were 118, 62, and 4 4 mu g/ml, respectively, for yellow nutsedge, The I-50's for root numb er and root length were 91 and 85 mu g/ml, respectively, for purple nu tsedge and the I-50 for shoot growth could not be calculated, Nomencla ture: Purple nutsedge, Cyperus rotundus L. #(3) CYPRO, yellow nutsedge , Cyperus esculentus L. # CYPES, sweet potato, Ipomoea batatas (Lam.), 'Regal.'