Triacontanol Stimulates Nadh Oxidase Of Soybean Hypocotyl Plasma-Membrane

NADH oxidase activity of plasma membranes purified from etiolated hypocotyls of soybean (Glycine max Merr. cv. Williams) was stimulated by about 50% by triacontanol over the concentration range of 10(-7)-10(-5) M. Small but statistically significant stimulations of elongation of hypocotyl segments also were observed. Octacosanol, a triacontanol antagonist, was without effect on control growth or NADH oxidase activity but inhibited 2,4-dichlorophenoxyacetic acid(2,4-D)-induced growth. We suggest that growth promotions by triacontanol may be mediated by a direct action of triacontanol on the NADH oxidase of the plasma membrane, an enzyme the activity of which previously has been suggested to be rate-limiting to growth.