THE STOMATAL COMPLEX OF PODOCARPUS OBSERVED IN CROSS-SECTION USING CRYOFRACTURE: A PRELIMINARY STUDY

Abstract

Cryofracture of living material and fracture at room temperature of herbarium material were used to obtain cross-sections of the stomatal complexes of four species of Podocarpus (Podocarpaceae) for scanning electron microscopy. Cross-sections of the stomata of one species in Podocarpus subgenus Foliolatus section Foliolatus (Podocarpus rubens), one in Podocarpus section Globulus (Podocarpus beecherae), one in Podocarpus subgenus Foliolatus section Longifoliolatus (Podocarpus insularis) and one in subgenus Podocarpus section Australis (Podocarpus nivalis) were studied. The architecture of the stomatal complex, including the wax plug, is described. It was found that the wax plug sits high in the stomatal antechamber in Podocarpus rubens, P. beecherae and Podocarpus decipiens and about halfway up the chamber in P. nivalis. A ridge, which appears to correspond to the crease where the guard cells meet, exists on the underside of the wax plug in Podocarpus beecherae, P. decipiens and P. rubens; its presence in P. nivalis requires confirmation. In addition, ridges within the stomatal antechamber were observed when viewing the cross-sections of Podocarpus decipiens and P. rubens, the internal surface of the cuticle of P. decipiens, Podocarpus teysmannii, P. insularis and Podocarpus milanjianus, and the external surface of the cuticle of Podocarpus chinensis, Podocarpus macrophyllus and Podocarpus pilgeri. These ridges may consist of wax and be a result of epitaxis.