ATP production after pH shift in membrane vesicles from maize coleoptiles

Microsomal membrane vesicles and purified plasma membrane vesicles obtained from coleoptiles of maize (Zea mays L.) were subjected to pH shifts from p H 7.8 to 4.7. In the presence of ATPase inhibitors such as vanadate, net ac cumulation of radiolabelled butyric and indole-3-acetic acid (IAA) remained higher than in controls. When 2 min after the pH shift, at 4 degreesC, the microsomal vesicles were denatured the amount of ATP could be determined u sing the luciferin/luciferase assay. Significantly increased ATP production over control values - no pH-shift or ionophore treatment - was found. Ther efore, such vesicles might produce ATP for in vitro transport processes suc h as auxin efflux.