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Structure and Function of Tracheary Elements in Amborella Trichopoda

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Feild, TS and Zwieniecki, MA and Brodribb, TJ and Jaffre, T (2000) Structure and Function of Tracheary Elements in Amborella Trichopoda. International Journal of Plant Sciences, 161 (5). pp. 705-712. ISSN 1058-5893

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Abstract

Recent phylogenetic analyses have placed the root of flowering plants near Amborella trichopoda, a woody
plant restricted to cloud forest habitats in New Caledonia. A distinctive feature of A. trichopoda is its reported
lack of xylem vessels. Here we present observations of pit membrane structure and end wall morphology for
primary and secondary tracheary cells of A. trichopoda as well as field measurements of stem hydraulic
properties of A. trichopoda compared with five cloud forest species from New Caledonia. Observations of
stem radial sections revealed that the primary wall material in the protoxylem and metaxylem elements was
intact. No large porosities (such as those that have been observed in the pit membranes of Nymphaeales) were
observed. However, a few elliptical pits of tracheary cells in the secondary xylem appeared to lack pit membranes.
These observations are consistent with our measurements of functional conduit length, which indicate
that the longest open conduits are equal to the length of two secondary xylem elements joined end to end.
Thus, the xylem of A. trichopoda appears to be functionally vesselless, with the caveat that connections between
individual vascular elements may occasionally be open (i.e., lacking in at least one pit membrane). Sapwood
area and leaf area–specific hydraulic conductivities of A. trichopoda are similar to those of conifers and
angiosperms, with and without xylem vessels, growing in understory cloud forest environments. These findings
bear on discussions of the morphology and ecology of the first flowering plants as well as on the possible
causes of their diversification.

Item Type: Article
Keywords: Amborella, basal angiosperms, xylem hydraulic conductivity, vessel evolution.
Journal or Publication Title: International Journal of Plant Sciences
Page Range: pp. 705-712
ISSN: 1058-5893
Identification Number - DOI: 10.1086/314293
Date Deposited: 03 Dec 2007 04:11
Last Modified: 18 Nov 2014 03:25
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