Super-ultrastructure of the Envelope Membranes of Spinach Chloroplasts

Abstract

Super-fine structure of the envelope membranes of spinach chloroplasts was observed with ultrathin sections fixed in glutaraldehyde and osmic acid. Both inner and outer membranes are not composed of unit membranes, but of a number of fine grains which are 13 to 16Å in diameter and 14 to 16/100nm² in density and of a matrix between them. The grains do not appear to be regular in distribution. The outer membrane of the envelope is different from the inner membrane in both electron density and thickness, that is, the former is less dense and 60 to 70 A thick, and latter is dense and 75 to 85Å thick, Both membranes are separated by a electron transparent zone of 40 to 60Å in width.