Distinctive wood anatomy of basal Asteraceae: Barnadesioideae

CARQUIST, S; STUESSY T. F.; URTUBEY, ESTRELLA

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022 vol. 198 p. 259 - 284

0024-4074

The subfamily Barnadesioideae (10 genera, ~90 species), confined to South America, is sister to the remainder of the family Asteraceae. The relative antiquity of barnadesioids might lead one to expect that they contain more wood features plesiomorphic for the family, but only one character clearly falls in that category. Pits on imperforate tracheary elements are bordered (except for annuals), whereas simple pits occur in two related families, Calyceraceae (part) and Goodeniaceae (bordered pits also occur). By attaining fully bordered pits in Chuquiraga, the imperforate tracheary elements qualify as an apomorphy, ?neotracheids,? valuable for resisting embolism formation in dry and cold South American habitats. Neotracheids are found also in Loricaria (Asteraceae: Inuleae), also from these habitats. Neotracheids, like plesiomorphic tracheids, are conductive, unlike fibre-tracheids and libriform fibers. Other barnadesioid wood characters adapted to cold and drought include grouping of vessels, high vessel density, shorter vessel elements, and helical sculpture (including helical thickenings on lumen-facing walls) of secondary xylem vessels. In Chuquiraga and Dasyphyllum, these helical thickenings are bordered in some species (new report for angiosperms). Some of the barnadesioid adaptations to cold and drought can be found in North American species of Artemisia (Asteraceae: Anthemideae), especially in montane and desert areas. Wood features of barnadesioids match their respective habits and habitats: a few trees, shrubs of humid, dry, or desert areas, a distinctive rhizomatous succulent in the pampas (Schlechtendalia), a scree/gravel perennial (Huarpea), and two genera of annuals, one with succulent leaves Duseniella) and one with rayless (at least at first) stems in arid and open soils (Doniophyton). Diversity is unusual considering the small size of the subfamily. Examples of endodermal crystals (Arnaldoa only), pith sclereids, and primary xylem fibers are cited.