THE EFFECTS OF HERBICIDES ON DEVELOPMENT OF MYRIOPHYLLUM-SPICATUM L CULTURED INVITRO

Tissue cultures of the aquatic plant, Myriophyllum spicatum L., were used to evaluate the effects of four different herbicides and a leaf defoliant on development. The developmental parameters used were the production of new axillary buds, leaves, roots and branches. Production of new branches was the most sensitive measure. The order of developmental inhibition was: 2,4-dichlorophenoxyacetic acid > atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) > glyphosate [N-(phosphonomethyl)glycine] > thidiazuron (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea). The herbicide linuron [8-(3,4-dichlorophenyl)-1-methoxy-1-methyl urea] showed no statistically significant toxic effects below 100 mg L-1. This bioassay system provided a quick, sensitive measure of herbicide effects on aquatic plant development. The short time period of only 5 d permits more rapid bioassays than conventional whole plant bioassays.