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.