Wood anatomy of brazilian Viscaceae: a comparison with wood of other mistletoes

Abstract

Among the huge diversity of life forms within angiosperms, one of the most peculiar is the parasitism, which has emerged 12 times throughout the evolutionary history of this group. All these clades have in common a special organ called haustorium, a structure adapted for acquiring nutrients from a host. Of all these parasites, the largest group is Santalales, order in which the mistletoe habit, described as arbustive hemi- or holoparasites that germinate directly above the shoot of a host, is very frequent. Many studies have been made regarding the morpho-anatomy of haustoria, especially in families Loranthaceae and Viscaceae, but there are still few wood anatomy analyses within these families.Variables such as measurements of each cell types present in the wood, vessel and parenchyma dispositions, fibre density, fibre-wall thickness among others, are useful not only for complementing and expanding what is understood of the wood anatomy of these species and families, but also for elucidating questions regarding evolution, hydraulics, development and mechanics of these parasites. Given all this, the following study aims performing such anatomical analyses in mistletoes, with focus on Brazilian Viscaceae and comparing them with foreign species from the same family and with Loranthaceae species, in order to ascertain if there exists an anatomical wood pattern for this very habit, mainly within these families.