Effects of Pyridazinone Herbicides during Chloroplast Development in Detached Barley Leaves II. Effects on Lipid Content, Fatty Acid Composition and Ultrastructure of Chloroplasts

The effects o f three differently substituted pyridazinone herbicides were studied on the lipid content, fatty acid composition o f glycerolipids, fatty acid synthesizing capacity and ultrastruc­ ture of chloroplasts after 72 h o f greening o f etiolated barley leaves. SAN 9789 caused a nearly threefold increase in the total fatty acid content o f chloroplasts, and this increase was accom ­ panied by an increase in the D G D G and phospholipid-content as well. SAN 6706 and 9785 caused reduction in the linolenic to linoleic acid ratio in nearly all lipid classes, only PC was unaffected. Both herbicides reduced the saturated to unsaturated ratio in the PG, SAN 9789 had no effect on the fatty acid com position o f the PG. Fatty acid synthesis was inhibited in the SAN 6706and 9789-treated leaves as monitored by incorporation o f labelled acetate, but all o f the three pyridazinones stimulated the incorporation o f labelled galactose into chloroplast galactolipids. SAN 6706 and 9789 also caused abnormal organization o f chloroplast lamellar system.