Abstract/Summary:
A structural analysis of the chlorenchyma of Hakea suaveolens is presented based on light microscopy as well as on transmission and scanning electron microscopy. A cuticle is found covering most palisade cells of the very airy photosynthetic tissue containing large amounts of tannins. Intercellular pectic strands of a filamentous ultrastructure are found distended between palisade cells mutually and between palisade cells and sclereids. The strands are regarded as a casual structure with no obvious function, developed as a mechanical consequence of intercellular space formation. As the leaves get older, some palisade cells redifferentiate into tylosoids which often divide into 2 to 5 cells (Fig. lower left). Finally, they block the stomatal pores making stomatal function impossible, which reduces transpiration without a significant reduction of photosynthesis. In spite of the large volume of intercellular space, it is argued that the chlorenchyma is truly xeromorphic.