Abstract:Using ferricyanide as the membrane impermeable electron acceptor, the effects of extracellular calmodulin on transplasma membrane redox reaction of the root protoplasts in Zea mays L. were studied. The calmodulin antagonists (calmidazolium, W7-agarose) and anti-calmodulin serum had inhibitory effect on the extracellular reduction of ferricyanide with their concentration that yielded 50% inhibition were 1.5 μmoL/L, 10 μmol/L and 10 mg/L respectively. Inhibition of calmidazolimn could be restored by calmodulin completely. And the reduction of ferricyanide could be specifically stimulated by the exogerous purified calmodulin. These results suggested that transplasma membrane redox system of root protoplasts in Zea mays L. could be modulated by calmodulin outside the plasma membrane.