title: A simple type of wood in two Early Devonian plants.
abstract: The advent of wood (secondary xylem) is a major event of the Paleozoic Era, facilitating the evolution of large perennial plants. The first steps of wood evolution are unknown. We describe two small Early Devonian (407 to 397 million years ago) plants with secondary xylem including simple rays. Their wood currently represents the earliest evidence of secondary growth in plants. The small size of the plants and the presence of thick-walled cortical cells confirm that wood early evolution was driven by hydraulic constraints rather than by the necessity of mechanical support for increasing height. The plants described here are most probably precursors of lignophytes.
authors.affiliation: Département de Géologie, Université de Liège (U.Lg), B18 Sart Tilman, B-4000 Liège 1, Belgium. P.Gerrienne@ulg.ac.be
authors.forename: Philippe
authors.initials: P
authors.lastname: Gerrienne
authors.forename: Patricia G
authors.initials: PG
authors.lastname: Gensel
authors.forename: Christine
authors.initials: C
authors.lastname: Strullu-Derrien
authors.forename: Hubert
authors.initials: H
authors.lastname: Lardeux
authors.forename: Philippe
authors.initials: P
authors.lastname: Steemans
authors.forename: Cyrille
authors.initials: C
authors.lastname: Prestianni
mesh_terms: D005075:Biological Evolution; D058506:Cambium / Q000033:anatomy & histology* / Q000166:cytology; D002170:Canada; D002473:Cell Wall / Q000648:ultrastructure; D005580:Fossils; D005602:France; D059828:Plant Cells; D010944:Plants / Q000033:anatomy & histology*; D014934:Wood / Q000033:anatomy & histology* / Q000166:cytology; D052584:Xylem / Q000033:anatomy & histology / Q000166:cytology