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The leafy stems of Sphagnum (Bryophyta) contain highly differentiated polarized cells with axial arrays of endoplasmic microtubules

Published online by Cambridge University Press:  01 November 1998

ROBERTO LIGRONE
Affiliation:
Facoltà di Scienze Ambientali Seconda, Università di Napoli, via Arena 22, 81100 Caserta, Italy
JEFFREY G. DUCKETT
Affiliation:
School of Biological Sciences, Queen Mary & Westfield College, Mile End Road, London, E1 4NS, UK
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Abstract

Contrary to the long-held belief that, internal to the cortical sterome, the central region of Sphagnum stems comprises unspecialized parenchyma, the present light- and electron-microscope study has revealed that these cells in fact have a highly specialized cytoplasmic organization. Their key features are: (a) the absence of large central vacuoles; (b) a spindle-shaped nucleus positioned internally; (c) a prominent axial system of endoplasmic microtubules associated with the nucleus, mitochondria, pleomorphic vacuoles, and membrane-bounded tubules and vesicles; (d) a distinct cytoplasmic polarization, with the cellular region near the capitulum being richer in organelles than the basal region; and (e) a high frequency of plasmodesmata in the cross walls with an enlarged median region containing no discernible desmotubule. Such a distinctive combination of cytological features has been hitherto only described for putative food-conducting cells in bryoid mosses. The results introduce a major new character common to Sphagnum and bryoid mosses and strongly suggest that this cytological organization underlines cellular specialization in symplasmic transport.

Type
Research Article
Copyright
© Trustees of New Phytologist 1998

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