Lipid synthesis by isolated duckweed (Lemna minor) chloroplasts in the presence of a sublethal concentration of atrazine
We have examined the effects of a sublethal concentration of atrazine on the incorporation of sodium-[U-14C] acetate into isolated chloroplast lipids of Lemna minor. A high level of [14C]-acetate was incorporated into diacylgalactosylglycerol (DGG) and diacylglycerol (DAG). Consequently, the conversion of phosphatide acid to DAG and that of DAG to DGG seems to be as active in L. minor (an "18:3-plant") as in "16:3-plants." Chloroplast lipids from atrazine-treated plants were more extensively labelled with [14C]-acetate than the control plants. These results are in agreement with our previous in vivo studies which suggest that sublethal concentrations of atrazine stimulate the lipid metabolism of L. minor to form more thylakoid membranes. Furthermore, the specific radioactivity of linolenic acid was the highest in DAG and the lowest in DGG. These data suggest that desaturation of linoleic acid to linolenic acid mainly occurs before the galactosylation of DAG to form DGG in L. minor.