Physiological studies on pea tendrils. XIII. Respiration is necessary for contact coiling

When 9 day old light grown pea ( Pisum sativum L. cv. Alaska 2B) plants are irrigated for 4–6 days with 50 μ M 4-chloro-5-(dimethylamino)-2-(α, α, α-trifluoro- m -totyl)-3(2H)-pyridazinone, designated San-6706, the new leaves and tendrils grow morphologically normal, but with neither chlorophyll nor the ability to carry out photosynthesis. Excised tendrils from these plants coil in response to rubbing as well as those from water irrigated controls. Tendrils from San-6706 irrigated plants, which have been dark adapted for 2 or 3 days, proceed to coil when illuminated, just as do those from water irrigated plants. Rubbing of dark adapted tendrils results in an increased respiration rate over the first hour or two, when most of the coiling response occurs. Inhibitor studies indicate that blockage of oxidative phosphorylation, but not of the alternative, cyanide-insensitive, path of respiration, results in a failure of tendrils to coil in response to mechanical perturbation. It is concluded that the normal path of respiration, perhaps via ATP production, may be necessary for thigmosensory perception leading to contact coiling in pea tendrils.