ISOLATION OF SUBSTANCE FROM SWEET-POTATO (IPOMOEA-BATATAS) PERIDERM TISSUE THAT INHIBITS SEED-GERMINATION

Chromatographic procedures were used to isolate inhibitors of seed germination from sweet potato root periderm tissue. The inhibitory activity of all fractions was monitored using a proso millet seed germination bioassay. A single HPLC peak, representing approximately 1.2% of the periderm dry weight, accounted for most of the inhibitory activity. The active fraction was labile in methanolic solution. Further fractionation of this peak by HPLC methods was not successful. In vitro seed germination dose-response relationships were established for the peak. The various seed species exhibited an extremely wide range of sensitivity. The I50 values were 0.16, 0.013 and 0.011 mg/ml for redroot pigweed, velvetleaf, and proso millet, respectively. Tall morning glory was not inhibited by any concentration tested.