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Acclimation of Leaf Anatomy, Photosynthetic Light Use, and Xylem, Hydraulics to Light in Amborella Trichopoda (Amborellaceae)


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Feild, TS, Brodribb, TJ, Jaffre, T and Holbrook, NM 2001 , 'Acclimation of Leaf Anatomy, Photosynthetic Light Use, and Xylem, Hydraulics to Light in Amborella Trichopoda (Amborellaceae)' , International Journal of Plant Sciences, vol. 162, no. 5 , pp. 999-1008 , doi: 10.1086/322889.

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Recent phylogenetic analyses place Amborella trichopoda, a semiclimbing premontane rain forest shrub
endemic to New Caledonia, as sister to all other extant flowering plants. Here we present new observations
on leaf anatomy and morphology, leaf photosynthetic physiology, and xylem hydraulic function for Amborella
in the field. We focus on experimental measurements of the degree of photosynthetic and xylem hydraulic
acclimation to sunlight by examining Amborella plants growing in deeply shaded understories (0.7% full
sunlight) compared with individuals from exposed montane ridge crests in New Caledonia. Amborella leaves
exhibit few anatomical differences between sun and shade. Instead of primarily adjusting leaf anatomical
characters to irradiance, A. trichopoda leaves exposed periodically to full sunlight modify their orientation,
becoming folded up along the midvein, presumably to avoid increases in light interception. Chlorophyll a
fluorescence measurements demonstrate that the photosynthetic apparatus of A. trichopoda is shade adapted,
based on a low capacity for excess light energy dissipation and low photosynthetic electron transport rate. In
addition, these characteristics exhibit limited upregulation in response to increased irradiance. In parallel,
there are small or no differences in leaf area-specific hydraulic conductivity between sun and shade shoots of
A. trichopoda. Taken together, A. trichopoda appears to possess limited developmental and physiological
flexibility to light flux density. The bearing of these observations, in the context of other early-diverging clades
of angiosperms identified by recent phylogenetic studies, on the physiological ecology of the first angiosperms
is discussed.

Item Type: Article
Authors/Creators:Feild, TS and Brodribb, TJ and Jaffre, T and Holbrook, NM
Keywords: Amborella, angiosperm phylogeny, basal angiosperms, shade adaptation, xylem hydraulics.
Journal or Publication Title: International Journal of Plant Sciences
ISSN: 1058-5893
DOI / ID Number: 10.1086/322889
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