TOXICITY OF SOME HERBICIDES TO INVITRO GROWING TOBACCO POLLEN TUBES (THE POLLEN TEST)

Commercial formulations of seven herbicides, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3-methoxy-carbonylamino-phenylmethyl-carbamate (phenmedipham), 6-(sec-butyl)-2,4-dinitrophenol (DNBP), 4,6-dinitro-ortho-cresol (DNOC), N,N-diisopropyl-2,3-dichloroallyl-thiocarbamate (DDTC), N-3-chlorophenyl-isopropyl-carbamate (CIPC) and N-(phosphonomethyl)-glycine (glyphosate), were used to test the suitability of a new pollen tube growth system for toxicological screening of phytoeffectors. The technique is based upon photometric measurement of in vitro pollen tube production by using the binding capacity of the tube walls to Alcian blue. Five different ranges of toxicity were distinguished in relation to five different types of action represented by the herbicides used. The sequence of herbicides with increasing toxicity was glyphosate, CIPC, DCMU, phenmedipham, DDTC, DNOC and DNBP; the sequence correlated well with the toxicity sequence expressed by LD50 values for rats. This relation indicates that the pollen test can be used as a pre-screening assay in toxicology and can probably help to reduce animal testing of herbicides, although it is based on a plant system.