A comparative study of the structure of cell wall surfaces: air spaces in leaves are exceptional in having exposed microfibrils

Abstract

The study compares the appearance of cell wall outer surfaces adjacent to air spaces in cereal leaves (wheat and rye) with other cell wall surfaces (root hair, water-filled root intercellular space, root gas space) using replica specimen-preparation techniques for electron microscopy, particularly freeze-etching. While all other cell wall outer surfaces are heavily impregnated with materials which fill intermicrofibrillar interstices, those associated with cereal leaf air spaces are impregnated to a lesser extent and are described here as "open." This openness appears to continue at least into the centre (in the radial sense) of the cell wall. There was some evidence for puddling of water at certain sites. The results are discussed in terms of their significance for understanding the nature of leaf air-space cell wall surfaces (it is argued that there is no "cuticle" equivalent to that covering the leaf outer surface), and by consequence the discussion extends to the roles of these surfaces in transpiration and gas exchange.