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The Photoprotective Role of Anthocyanin Pigments in Leaf Tissues

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The Photoprotective Role of Anthocyanin Pigments in Leaf Tissues
Hughes, Nicole M
Anthocyanins are vacuolar pigments most commonly responsible for red to purple coloration in plant tissues. Because they absorb strongly in the blue-green waveband, anthocyanins effectively reduce internal light within the leaf, which may be beneficial under high-light stress conditions. However, pigment patterns in natural systems often appear inconsistent with a photoprotective function (e.g. anthocyanins in abaxial leaf surfaces), and their absence in many species exposed to high-light stress suggests that anthocyanins may not be necessary for photoprotection. Furthermore, the presumed dynamic interaction between anthocyanin synthesis and relative need for photoprotection has yet to be quantitatively described. These issues, among others, have stalled acceptance of a photoprotective function of anthocyanin pigments, and are addressed in the studies presented here. Measurements of leaf optics and chlorophyll fluorescence were used to compare optical and photosynthetic effects of abaxial anthocyanins in vivo. In a species where abaxial leaf surfaces are naturally exposed to high light stress in the field (Galax urceolata), anthocyanins appeared to function similarly to anthocyanins in adaxial surfaces—absorbing strongly in the blue-green wavelengths, and reducing high-light stress (i.e. photoinhibition of photosynthesis). In a shade-adapted, abaxially-red understory species (Begonia heracleifolia), a photoprotective function was also supported, but through attenuation of internally-scattered green light transmitted through the upper leaf surface. This function may be adaptive during periodic exposure to high intensity sunflecks or sun-patches, which are potentially damaging to shade-adapted plants. In developing leaves of three deciduous-tree species, anthocyanin disappearance corresponded with development of ~50% mature photopigment concentrations, ~80% lamina thickness, and differentiation of the mesophyll into palisade and spongy layers. This conserved pattern in anthocyanin loss during development between species is consistent with a controlled coupling of anthocyanin concentration and relative need for photoprotection. Relative photosynthetic capacity was compared for five species exhibiting anthocyanin production in winter leaves and five species lacking anthocyanin. It was expected that species with red winter leaves would correspond with those exhibiting diminished photosynthetic capacity, rendering them in greater need for photoprotection. This hypothesis was not supported, however, and the reason why some species require anthocyanin pigments while others do not during winter remains unknown. In conclusion, these studies are generally consistent with a photoprotective function of anthocyanins in leaf tissues.
William K Smith (committee chair)
Gloria Muday (committee member)
Peter Weigl (committee member)
Kathleen Kron (committee member)
Taylor Feild (committee member)
2009-01-14T21:23:32Z (accessioned)
2010-06-18T18:58:46Z (accessioned)
2009-01-14T21:23:32Z (available)
2010-06-18T18:58:46Z (available)
2009-01-14T21:23:32Z (issued)
Biology (discipline)
http://hdl.handle.net/10339/14794 (uri)
en_US (iso)
Wake Forest University
Release the entire work immediately for access worldwide. (accessRights)

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