Leaf architecture and direction of incident light influence mesophyll fluorescence profiles

Light propagation and distribution inside leaves have been recognized as important processes influencing photosynthesis. Monochromatic light absorption across the mesophyll was measured using chlorophyll fluorescence generated from illumination of the cut edge (epi-illumination), as well as the adax...

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Bibliographic Details
Published in:American journal of botany 2005-09, Vol.92 (9), p.1425-1431
Main Authors: Johnson, Daniel M, Smith, William K, Vogelmann, Thomas C, Brodersen, Craig R
Format: Article
Language:English
Subjects:
Abies fraseri
Anatomy and Morphology
chlorophyll
Chlorophylls
conifer needles
Cotyledons
Ericaceae
Flowers & plants
Fluorescence
forest trees
green light
high‐altitude species
leaf angle
leaf orientation
Leaves
Light
Mesophyll
Mesophyll cells
palisade layer
photosynthesis
phototransduction
Picea rubens
Pinaceae
plant architecture
Plant cells
Plants
Rhododendron catawbiense
Sunlight
Wavelengths
wild plants
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Summary:Light propagation and distribution inside leaves have been recognized as important processes influencing photosynthesis. Monochromatic light absorption across the mesophyll was measured using chlorophyll fluorescence generated from illumination of the cut edge (epi-illumination), as well as the adaxial or abaxial surfaces of the leaf. Species were selected that had basic leaf types: laminar leaf with adaxial palisade layer (Rhododendron catawbiense), needle with palisade (Abies fraseri), and needle without palisade (Picea rubens). Fluorescence was more evenly distributed across the mesophyll for adaxially illuminated leaves with a palisade cell layer, as well as for the needles (cylindrical) without palisade, when compared to fluorescence generated by abaxial illumination. Moreover, fluorescence from green light illumination remained high across the mesophyll of adaxially illuminated R. catawbiense, indicating a possible influence of mesophyll structure on internal light distribution beyond that of chlorophyll levels. These data support the idea that light propagation within the mesophyll is associated with asymmetric mesophyll structure, in particular the presence of palisade cell layers. In addition, we propose that the evolution of a more cylindrical leaf form, such as found in conifer species, may be a structural solution to excessive sunlight that replaces the highly differentiated mesophyll found in most laminar-leaved species.
ISSN:0002-9122
1537-2197
DOI:10.3732/ajb.92.9.1425