Stoma blocked by tylosoids

Heide-Jørgensen H S. 1978. The xeromorphic leaves of Hakea suaveolens R.Br. I. Structure of photosynthetic tissue with intercellular pectic strands and tylosoids. - Bot. Tidsskr. 72: 87-103.


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.

Rettelser/Corrigenda:
According to Flora of Australia, Hakea suaveolens R. Br. is now named Hakea drupacea (C. F. Gaertn.) Roem. & Schult.


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