Journal Article

Developmental changes in spatial distribution of <i>in vivo</i> fluorescence and epidermal UV absorbance over <i>Quercus petraea</i> leaves

S. Meyer, J. Louis, N. Moise, T. Piolot, X. Baudin and Z. G. Cerovic

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 104, issue 4, pages 621-633
Published in print September 2009 | ISSN: 0305-7364
Published online June 2009 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcp144
Developmental changes in spatial distribution of in vivo fluorescence and epidermal UV absorbance over Quercus petraea leaves

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Epidermal phenolic compounds (mainly flavonoids) constitute a vital screen that protects the leaf from damage by natural ultraviolet (UV) radiation. The effectiveness of epidermal UV-screening depends on leaf anatomy, the content of UV-screening compounds and their spatial uniformity over the leaf area. To investigate in vivo the spatial pattern of the epidermal UV-screen during leaf development, a fluorescence imaging method was developed to map the epidermal UV-absorbance at a microscopic scale. This study was done on oak (Quercus petraea) leaves that were used as a model of woody dicotyledonous leaves.

Methods

The leaf development of 2-year-old trees, grown outdoors, was monitored, at a macroscopic scale, by in vivo measurements of chlorophyll content per unit area and epidermal UV-absorbance using two optical leaf-clip meters. The distribution of pigments within leaves was assessed in vivo spectroscopically. The microscopic images of UV-induced fluorescence and UV-absorbance acquired in vivo during leaf development were interpreted from spectral characteristics of leaves.

Key Results

At a macroscopic scale, epidermal UV-absorbance was high on the upper leaf side during leaf development, while it increased on the lower leaf side during leaf expansion and reached the adaxial value at maturity. At a microscopic scale, in immature leaves, for both leaf sides, the spatial distribution of epidermal UV-absorbance was heterogeneous, with a pattern depending on the flavonoid content of vacuoles in developing epidermal cells. At maturity, epidermal UV-absorbance was uniform.

Conclusions

The spatial pattern of epidermal UV-screen over the area of oak leaves is related to leaf anatomy during development. In vivo spectroscopy and fluorescence imaging of the leaf surface showed the distribution of pigments within the leaf and hence can provide a tool to monitor optically the leaf development in nature.

Keywords: Blue-green fluorescence; chlorophyll fluorescence; epidermis; flavonoids; leaf development; microscopic imaging; polyphenols; Quercus petraea

Journal Article.  6765 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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