A cryo-scanning electron microscope study of the water relations of the remarkable cell wall in the moss Rhacocarpus purpurascens (Rhacocarpaceae, Bryophyta)
Abstract:The functional properties of the unique trilamellate walls in Rhacocarpus purpurascens revealed by cryo-scanning electron microscopy are interpreted as a supreme adaptation to exposed habitats that experience frequently alternating periods of drought and heavy precipitation. The porous outer layer ensures rapid water uptake and retention whilst its highly hydrophobic cuticle-like layer prevents waterlogging. Thus, R. purpurascens is unlikely to suffer from depressed metabolism like that recorded in waterlogged Sphagnum. Water retention by the middle lamellar stratum extends the periods of protoplast hydration and active metabolism under drying conditions. Comparisons between the wall layering in Rhacocarpus and papillate moss walls indicate that, whilst both are adaptations associated with rapid water uptake, the presence of papillae accelerates water loss and hence the shutting down of stressed metabolism under drying conditions. Unlike the intermittent soaking and dry conditions experienced by Rhacocarpus, taxa with surface waxes are found either in habitats with constantly flowing aerated water or beneath underhangs where waterlogging would depress gaseous exchange.
Document Type: Research Article
Publication date: November 1, 2010
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- Nova Hedwigia is an international journal publishing original, peer-reviewed papers on current issues of taxonomy, morphology, ultrastructure and ecology of all groups of cryptogamic plants, including cyanophytes/cyanobacteria and fungi. The half-tone plates in Nova Hedwigia are known for their high quality, which makes them especially suitable for the reproduction of photomicrographs and scanning and transmission electron micrographs.
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