THIOCARBAMATE HERBICIDES INHIBIT FATTY-ACID ELONGATION IN A VARIETY OF MONOCOTYLEDONS

The action of the thiocarbamate herbicide, diallate [S-(2,3 dichloroallyl-)diisopropylthiocarbamate], on lipid metabolism in several monocotyledonous plants was investigated. In all systems tested, diallate reduced very long chain (20-24 carbons) fatty acid labelling from [1-C-14]acetate without altering de novo synthesis. Young leaf blades from barley and oats were particularly active at labelling very long chain fatty acids (up to 40% of total [C-14]-fatty acids) and these tissues were thought to be potentially useful in investigating further the action of diallate. The data confirmed conclusions from experiments with germinating peas and aged potato slices that thiocarbamates such as diallate, which alter the production of plant surface layers (waxes, cutin, suberin), may do so by inhibiting synthesis of their precursor very long chain fatty acids.