Localization and properties of ATPase activity in pea stems and wheat coleoptiles

Microsomal fractions from wheat coleoptiles and pea stems contain a microsomal ATPase activity that requires divalent cations (Ca2+ is more effective than Mg2+) and shows further stimulation by KCl. The effects of added indoleacetic acid were inconclusive. Cytochemical studies on both species showed most pronounced staining for ATPase in the plasmalemma at pH 7.0. However, at pH 5.5, the coleoptile cells showed heaviest staining for ATPase in the endoplasmic reticulum and dictyosomes. The results are discussed with regard to the postulated role of ATPase activity in relation to proton pumping and plant cell elongation.