Potato Sprout Inhibition by Camptothecin, a Naturally Occurring Plant Growth Regulator1

Abstract

An isolate of camptothecin alkaloids was applied to the eyes or sprouts on potatoes (Solanum tuberosum L.) as lanolin suspensions at concentrations of 1.5, 3, 9, and 15 mM, or to the whole tubers as aqueous sprays or dips at various concentrations. Potato sprouting at 15°C was completely inhibited for 4 weeks by all the lanoline suspensions. Inhibition was greater than 95% when a solution of the alkaloids at 5 × 10−1 mM was applied to the tubers as a 3-spray or 3-dip treatment. The camptothecin treatments that inhibited sprouting also reduced weight loss of potato tubers; and even after 4 months at 15°, no symptoms of internal sprouting or other deleterious effects were evident. Electron micrographs of sprouts suggest that camptothecin inhibited sprouting by inducing structural changes in vascular tissues and interfering with cell division in the meristematic portions of the sprouts.