Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If you need an accessible version of this item please contact JSTOR User Support

Anatomy of the Thick Leaves in Dendrobium Section Rhizobium (Orchidaceae)

William Louis Stern, Michael Wayne Morris and Walter S. Judd
International Journal of Plant Sciences
Vol. 155, No. 6 (Nov., 1994), pp. 716-729
Stable URL: http://www.jstor.org/stable/2475331
Page Count: 14
  • Read Online (Free)
  • Download ($19.00)
  • Subscribe ($19.50)
  • Cite this Item
If you need an accessible version of this item please contact JSTOR User Support
Anatomy of the Thick Leaves in Dendrobium Section Rhizobium (Orchidaceae)
Preview not available

Abstract

Plants of section Rhizobium in the genus Dendrobium (Orchidaceae) are characterized by thick and fleshy leaves or by leathery leaves that are often terete or approach the terete form. The full description of foliar anatomy concentrates on the unusual epidermal features and internal canal. The exposed epidermis is abaxial, but in a few species, in addition to the abaxial epidermis, a small amount of adaxial epidermis is also exposed in a foliar groove. In those leaves covered entirely by abaxial epidermis, the adaxial epidermis is still present but immersed within and surrounded by the mesophyll. It flanks the walls of an internal canal represented as a lacuna on cross sections. The bilaterally symmetrical arrangement of the vascular bundles, a characteristic of all examined leaves in section Rhizobium, divides the leaf into equilateral halves, the canal being centered along the midplane. Xylem of all vascular bundles faces the midplane of the leaf. We postulate that the canal, lined with cells of the adaxial surface, is the product of an evolutionary sequence of events commencing with the grooved leaf lacking a canal, passing through a phase featuring an eccentrically located canal, and culminating in a centrally sited canal. Anatomical data support the monophyly of section Rhizobium, and the unifacial-leaved species constitute a distinctive clade within the section.

Page Thumbnails

  • Thumbnail: Page 
716
    716
  • Thumbnail: Page 
717
    717
  • Thumbnail: Page 
718
    718
  • Thumbnail: Page 
719
    719
  • Thumbnail: Page 
[720]
    [720]
  • Thumbnail: Page 
721
    721
  • Thumbnail: Page 
722
    722
  • Thumbnail: Page 
[723]
    [723]
  • Thumbnail: Page 
724
    724
  • Thumbnail: Page 
725
    725
  • Thumbnail: Page 
726
    726
  • Thumbnail: Page 
727
    727
  • Thumbnail: Page 
728
    728
  • Thumbnail: Page 
729
    729