Touch-sensitive NADH oxidase activity of pea and cucumber tendrils and soybean hypocotyl sections

The cell surface reduced nicotinamide adenine dinucleotide (NADH) oxidase a ctivity of soybean stems and of pea and cucumber tendrils responded to touc h with a several-fold increase in activity. The increase in NADH oxidase pe rsisted for 20 min or longer, and further touch stimulation during this per iod did not alter activity. With soybean sections, the specific activities in response to touch approximated those achieved maximally by auxin. Where the NADH oxidase was fully stimulated by 2,4-D, the NADH oxidase failed to respond further to touch. The findings indicate that the NADH oxidase of th e plant cell surface is involved in the growth response to touch and in ten dril coiling.