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1 June 2006 Wood in the cactus subfamily opuntioideae has extremely diverse structure
James D. Mauseth
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Members of the cactus subfamily Opuntioideae have adapted to numerous types of xeric habitat. Wood evolution was extensive and affected most wood characters. There was a reduction or elimination of xylary fibres, accompanied by a large increase in water storage cells within the wood itself in many of the most xericadapted clades. In all species at least some water storage tissue consists of living parenchyma cells but in most there is also a significant amount of non-living wide-band tracheids (WBTs). Depending on the species, both parenchyma and WBTs occur in the axial tissues alongside vessels or in rays or in both locations. In almost all species, primary xylem is surrounded by a mass of WBTs in the pith and innermost regions of medullary rays. Xylary water storage tissues are especially important to opuntioids because they lack many extraxylary adaptations present in other cacti, so water must be stored in the wood itself. Also, because most opuntioids have only rudimentary leaves and lack cortical bundles, water must be unloaded directly from wood vessels rather than from an extensive network of primary vascular bundles; this adds importance to having parenchyma cells adjacent to wood vessels.

James D. Mauseth "Wood in the cactus subfamily opuntioideae has extremely diverse structure," Bradleya 2006(24), 93-106, (1 June 2006).
Published: 1 June 2006
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