Antidote action of humic substances on atrazine inhibition of sulfate uptake in barley roots

Atrazine 10-4 M rapidly inhibits sulfate uptake by excised barley roots. When humic substances are present in the uptake solution the inhibition is reduced. This effect is enhanced by 10 to 16 hr incubation of the roots in the presence of humus. Humus action is accompanied by the stimulation of leucine incorporation into protein, which, on the contrary, is unaffected by atrazine. The same experiments carried out with barley seedlings, in nutrient solution containing either atrazine or humus, or both, confirm the inhibitory action of atrazine on SO42- absorption by the whole plant and the inhibition reduction by humic substances. © 1981.