ECTO-ATPASE (NUCLEOTIDASE) ACTIVITY IN AXENIC CULTURES OF EXCISED ROOTS

Axenic cultures of excised roots of clover (Trifolium repens L,.), cucumber (Cucumber sativus L.), and marshmallow (Althaea officinalis L.) were used to study the dependence of phosphohydrolase activity on pH, the presence of mono- and divalent cations and inhibitors of acid phosphatase and ion-transporting ATPases in the incubation medium. Glycerophosphate (GP), ATP and other nucleoside triphosphates, ADP, and AMP were used as substrates. Activities of acid phosphatase and ATPase (nucleotidase) were distinguished from the total phosphohydrolase activity of the root surface. ATPase activity of the surface of the excised roots cultivated in axenic culture and the ecto-ATPase activity found earlier on nonaseptically grown roots of barley seedlings had the same properties (substrate specificity, stimulation by cations, pH optimum, and insensitivity to inhibitors of transporting ATPases). It is concluded that ecto-ATPase activity is attributed not (or not only) to rhizospheric microorganisms, but to the root cells of higher plants.