Preparation of plasma membrane vesicles from black spruce and jack pine roots

A plasma membrane fraction was isolated from roots of jack pine (Pinus banksiand) and black spruce (Picea mariana) by sucrose density gradient fractionation of root microsomes. This fraction was distinct from endoplasmic reticulum, Golgi, mitochondrial and tonoplast membranes as determined from an analysis of marker enzymes. The identification as plasma membrane is supported by the characterization of the ATPase activity and the ATP-dependent H+ transport associated with this fraction. Both activities were almost completely inhibited by vanadate and stimulated by cations. Both activities displayed a pH- optimum of 6.5–7.0 and were insensitive to nitrate and Bafilomycin.