The properties of the Ca-ATPase prepared from roots of wheat seedlings treated with benzylaminopurine were studied. The affinity of the ATPase towards Ca2+, plant or erythrocyte calmodulin increased after the hormonal treatment. It seems that in the membrane calmodulin-bonding sites were induced by benzylaminopurine, contributing to an increased affinity of the ATPase. The lower Ca-content of the hormone-treated plants suggests that in vivo the Ca-ATPase is involved in a Ca-extrusion process.
