Optical effects of abaxial anthocyanin on absorption of red wavelengths by understorey species: revisiting the back-scatter hypothesis

A red/purple coloration of lower (abaxial) leaf surfaces is commonly observed in deeply-shaded understorey plants, especially in the tropics. However, the functional significance of red abaxial coloration, including its role in photosynthetic adaptation, remains unclear. The objective of this study...

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Bibliographic Details
Published in:Journal of experimental botany 2008-09, Vol.59 (12), p.3435-3442
Main Authors: Hughes, Nicole M, Vogelmann, Thomas C, Smith, William K
Format: Article
Language:English
Subjects:
Abaxial
Absorption
anthocyanin
Anthocyanins - physiology
back-scatter
Begonia
Begoniaceae - physiology
Begoniaceae - radiation effects
Biological and medical sciences
Chlorophylls
Colors
Fluorescence
Fundamental and applied biological sciences. Psychology
Leaves
Light
Optical reflection
photoprotection
Photosynthesis
Plant cells
Plant Leaves - physiology
Plant Leaves - radiation effects
Plants
Research Papers
shade
understorey
Understory
Wavelengths
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Summary:A red/purple coloration of lower (abaxial) leaf surfaces is commonly observed in deeply-shaded understorey plants, especially in the tropics. However, the functional significance of red abaxial coloration, including its role in photosynthetic adaptation, remains unclear. The objective of this study was to test the back-scatter hypothesis for abaxial leaf coloration, which posits that red pigments internally reflect/scatter red light transmitted by the upper leaf surface back into the mesophyll, thereby enhancing photon capture in light-limited environments. Abaxially red/non-red variegated leaves of Begonia heracleifolia (Cham. & Schltdl.) were used to compare reflectance spectra and chlorophyll fluorescence profiles of abaxially anthocyanic (red) and acyanic (non-red) tissues under red light. Photosynthetic gas exchange in response to red light was also compared for abaxially red/non-red leaf sections. The results did not support a back-scattering function, as anthocyanic leaf surfaces were not more reflective of red light than acyanic surfaces. Anthocyanic tissues also did not exhibit any increases in the mesophyll absorbance of red light, or increased photosynthetic gas exchange under red light at any intensity, relative to acyanic tissues. These results suggest that abaxial anthocyanins do not significantly enhance the absorption of red light in the species tested, and alternative functions are discussed.
ISSN:0022-0957
1460-2431
DOI:10.1093/jxb/ern193