Physiological Effects of Fluometuron on Some Unicellular Algae

Abstract

Unicellular green algae were used as test organisms in experiments designed to provide an insight into the mode of action of 3-(m-trifluoromethylphenyl)-1,1-dimethylurea (fluometuron). Fluometuron suppressed the autotrophic growth of Chorella pyrenoidosa Chick (hereafter referred to as C. pyrenoidosa) and Euglena gracilis Klebs-strain ‘Z’ (hereafter referred to as Euglena) and the extent of inhibition was a function of herbicidal concentration. Euglena was less sensitive than C. pyrenoidosa. Treated cells contained less protein and chlorophyll than untreated cells, but the inhibitory effect of the herbicide on the algal growth was overcome when the organisms were grown heterotrophically. Fluometuron did not adversely influence respiration or the light-independent reactions that lead to the formation of chlorophyll or chloroplast precursors. It did interfere with the light-dependent or the greening process of chlorophyll synthesis and with photosynthetic oxygen evolution. Fluometuron appears to be selectively toxic to one or more light-mediated biochemical reactions required for the formation and function of photosynthetic pigments and organelles.