Acetylcholine causes rooting in leaf explants of in vitro raised tomato (Lycopersicon esculentum Miller) seedlings

The animal neurotransmitter acetylcholine (ACh) induces rooting and promotes secondary root formation in leaf explants of tomato (Lycopersicon esculentum Miller var. Pusa Ruby), cultured in vitro on Murashige and Skoog's medium. The roots originate from the midrib of leaf explants and resemble taproot. ACh at 10− 5 M was found to be the optimum over a wide range of effective concentrations between 10− 7 and 10− 3 M. The breakdown products, choline and acetate were ineffective even at 10− 3 M concentration. ACh appears to have a natural role in tomato rhizogenesis because exogenous application of neostigmine, an inhibitor of ACh hydrolysis, could mimic the effect of ACh. Neostigmine, if applied in combination with ACh, potentiated the ACh effect.