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A unique mode of parasitism in the conifer coral tree Parasitaxus ustus (Podocarpaceae)

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Feild, TS and Brodribb, TJ (2005) A unique mode of parasitism in the conifer coral tree Parasitaxus ustus (Podocarpaceae). Plant, Cell and Environment, 28 (10). pp. 1316-1325. ISSN 0140-7791

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Abstract

Almost all parasitic plants, including more than 3000 species,
are angiosperms. The only suggested gymnosperm
exception is the New Caledonian conifer,
Parasitaxus
ustus
, which forms a bizarre graft-like attachment to the
roots of another conifer
Falcatifolium taxoides
. Yet, the
degree of resource dependence of
Parasitaxus
on
Falcatifolium
has remained speculative. Here we show that
Parasitaxus
is definitively parasitic, but it displays a physiological
habit unlike any known angiosperm parasite.
Despite possessing chloroplasts, it was found that the
burgundy red shoots of
Parasitaxus
lack significant photosynthetic
electron transport. However unlike nonphotosynthetic
angiosperm parasites (holoparasites),
tissues of
Parasitaxus
are considerably enriched in
13
carbon
relative to its host. In line with anatomical observations of
fungal hyphae embedded in the parasite/host union, stable
carbon isotopic measurements indicate that carbon transport
from the host to
Parasitaxus
most likely involves a
fungal partner. Therefore,
Parasitaxus
parallels fungusfeeding
angiosperms (mycoheterotrophs) that steal carbon
from soil mycorrhizal fungi. Yet with its tree-like habit,
association with fungi residing within the host union, high
stomatal conductance, and low water potential, it is demonstrated
that
Parasitaxus
functions unlike any known
angiosperm mycoheterotroph or holoparasite.
Parasitaxus
appears to present a unique physiological chimera of mistletoe-
like water relations and fungal-mediated carbon trafficking
from the host.

Item Type: Article
Keywords: Parasitaxus ustus ; carbon isotopic; holoparasitic; mistletoe; mycoheterotroph; parasitic plants
Journal or Publication Title: Plant, Cell and Environment
Page Range: pp. 1316-1325
ISSN: 0140-7791
Identification Number - DOI: 10.1111/j.1365-3040.2005.01378.x
Additional Information:

The definitive version is available at www.blackwell-synergy.com

Date Deposited: 29 Nov 2007 03:37
Last Modified: 18 Nov 2014 03:25
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