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Hornwort Stomata: Architecture and Fate Shared with 400-Million-Year-Old Fossil Plants without Leaves.

Authors
  • Renzaglia, Karen S1, 2, 3, 4
  • Villarreal, Juan Carlos5, 6, 7, 8
  • Piatkowski, Bryan T5, 6, 7, 8
  • Lucas, Jessica R5, 6, 7, 8
  • Merced, Amelia5, 6, 7, 8
  • 1 Department of Plant Biology, Southern Illinois University, Carbondale, Illinois 62901-6509 (K.S.R., J.R.L.); [email protected].
  • 2 Département de Biologie, Université Laval, Quebec, Quebec, Canada G1V 0A6 (J.C.V.); [email protected]. , (Canada)
  • 3 Smithsonian Tropical Research Institute, Ancon, 0843-03092 Panama, Republic of Panama (J.C.V.); Department of Biology, Duke University, Durham, North Carolina 27708 (B.T.P.); and [email protected]. , (Panama)
  • 4 Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico 00901 (A.M.) [email protected]. , (Puerto Rico)
  • 5 Department of Plant Biology, Southern Illinois University, Carbondale, Illinois 62901-6509 (K.S.R., J.R.L.).
  • 6 Département de Biologie, Université Laval, Quebec, Quebec, Canada G1V 0A6 (J.C.V.). , (Canada)
  • 7 Smithsonian Tropical Research Institute, Ancon, 0843-03092 Panama, Republic of Panama (J.C.V.); Department of Biology, Duke University, Durham, North Carolina 27708 (B.T.P.); and. , (Panama)
  • 8 Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico 00901 (A.M.). , (Puerto Rico)
Type
Published Article
Journal
Plant physiology
Publication Date
Jun 01, 2017
Volume
174
Issue
2
Pages
788–797
Identifiers
DOI: 10.1104/pp.17.00156
PMID: 28584065
Source
Medline
Language
English
License
Unknown

Abstract

As one of the earliest plant groups to evolve stomata, hornworts are key to understanding the origin and function of stomata. Hornwort stomata are large and scattered on sporangia that grow from their bases and release spores at their tips. We present data from development and immunocytochemistry that identify a role for hornwort stomata that is correlated with sporangial and spore maturation. We measured guard cells across the genera with stomata to assess developmental changes in size and to analyze any correlation with genome size. Stomata form at the base of the sporophyte in the green region, where they develop differential wall thickenings, form a pore, and die. Guard cells collapse inwardly, increase in surface area, and remain perched over a substomatal cavity and network of intercellular spaces that is initially fluid filled. Following pore formation, the sporophyte dries from the outside inwardly and continues to do so after guard cells die and collapse. Spore tetrads develop in spore mother cell walls within a mucilaginous matrix, both of which progressively dry before sporophyte dehiscence. A lack of correlation between guard cell size and DNA content, lack of arabinans in cell walls, and perpetually open pores are consistent with the inactivity of hornwort stomata. Stomata are expendable in hornworts, as they have been lost twice in derived taxa. Guard cells and epidermal cells of hornworts show striking similarities with the earliest plant fossils. Our findings identify an architecture and fate of stomata in hornworts that is ancient and common to plants without sporophytic leaves. © 2017 American Society of Plant Biologists. All Rights Reserved.

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