Developmentally Variable, Polymorphic Woods in Cacti

Abstract

Sixteen genera of cacti were discovered to have polymorphic wood, that is, the plants produce one type of wood while young but a different type when older. The polymorphisms are: fibrous wood (with vessels and scanty paratracheal parenchyma) followed by parenchymatous wood (with vessels but few or no fibers) (Hylocereus venezuelensis, Dendrocereus nudiflorus, Borzicactus humboldtii, Haageocereus australis. Morawetzia sericata, Stephanocereus leucostele, Trichocereus schickendantzii); WBT wood (with wide-band tracheids, vessels, and apotracheal parenchyma but few or no fibers) followed by fibrous wood (Buiningia aurea, Oreocereus celsianus, Vatricania guentheri); WBT wood followed by parenchymatous wood (Echinopsis tubiflora, Gymnocalycium marsoneri, G. oenanthemum, Notocactus warasii, Parodia maassii); trimorphic wood in which WBT wood is followed by fibrous wood, which is followed by parenchymatous wood (Melocactus intortus, Arrojadoa braunii). The different phases within each plant may differ in vessel cluster size, percentage of the vessels that are solitary, diameter of vessels, and lignification of ray cells. Several of these genera are not closely related to the others, so wood polymorphism may have arisen several times.

Increased Water Storage Capacity in Cactus Wood: A Study in the Tribe Cereeae (Cactoideae, Cactaceae)

“…The extreme diversification seen in this subfamily probably has something to do with increase in succulence and is also reflected in the wood anatomy. In that sense, although subordinated to succulence in many species of Cactoideae, the fibrous wood has developed several strategies to improve storage and efficiency in conduction (Gibson 1973;Mauseth and Plemons 1995;Plemons-Rodriguez 1997, 1998;Terrazas and Arias 2003;Mauseth 2006;Angyalossy 2005, 2007;Yoshikawa and others 2004).…”

“…A peculiar situation documented in several groups of cacti is the occurrence of unlignified parenchyma in the wood (Gibson 1973(Gibson , 1977Mauseth and Plemons 1995;Plemons-Rodriguez 1997, 1998;Mauseth 2006;Angyalossy 2005, 2007). Carlquist (1988) devised the term parenchymatization for imperforated elements, such as libriform fibers, that substitute for axial parenchyma cells.…”

“…fibrous wood, which is represented by thinwalled unlignified cells distributed amongst the lignified elements of the secondary xylem (Gibson 1973;Gibson and Nobel 1986;Mauseth 1989;Mauseth and Plemons 1995;Plemons-Rodrigues 1997, 1998;Angyalossy 2005, 2007;Yoshikawa and others 2004).…”

“…Non-fibrous wood is exclusive to Cactaceae, characterized by wide-band tracheids and vessels, where fibers are absent, and is commonly present in globose species (Gibson 1973(Gibson , 1978Mauseth 1989;Mauseth and Plemons 1995;Plemons-Rodrigues 1997, 1998;Terrazas and Arias 2003;Yoshikawa and others 2004). Non-fibrous wood is found in most derived clades in the family, and indicates an extremely adapted wood for storage and drought.…”

“…Although subordinate to the succulent tissues (Carlquist 1988), a lot of variation in wood anatomy occurs in cacti, especially in Cactoideae (Gibson 1973;Mauseth and Plemons 1995;Plemons-Rodrigues 1997, 1998), the most diversified subfamily, where each lineage develops a different strategy to improve xylem conduction safety and storage capacity. In the Cactoideae, fibrous wood is more adapted not only to provide mechanical support and efficient conduction, but also water storage, thus allowing the survival of the species during long periods of drought (Gibson and Nobel 1986;Mauseth 1991Mauseth , 1993b.…”