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DUALEX

Optical absorbance meters for epidermal polyphenolics

DUALEX Series is the outcome of 15 years of research on plant UV and Visible spectroscopy of a CNRS interdisciplinary team of Photosynthesis and Optical Remote Sensing and of intensive R&D and industrialization by FORCE-A. The patented technology used in the DUALEX 3 Seriesis based on chlorophyll fluorescence screening. It is insensitive to variable chlorophyll fluorescence and it is independent of leaf chlorophyll content. The measurement is non-destructive, very rapid and simple. It does not need calibration or source adjustment. No preparation of the plant is required, and the measurement can be performed under ambient light outdoors.

DUALEX Series clips are portable instruments operating on rechargeable batteries. The epidermal absorption is displayed in real time on an alphanumeric LCD panel. Data are stored in the instrument memory (datalogger), and can be easily transferred to a computer for further statistical processing.

DUALEX Series leaf-clips measure quantitatively the absorption of the leaf epidermis:

• In the UV-B at 315 nm for the HCA version
• In the UV-A at 375 nm for the FLAV version
• In the Visible at 530 or 590 nm for the ANTH version

This epidermal absorption is directly linked to the concentration of leaf polyphenolics:

• Hydroxycinnamic acids for the HCA version
• Flavonoids for the FLAV version
• Anthocyanins for the ANTH version

ANALYSIS EXAMPLES
DUALEX FLAV
DUALEX FLAV is a valuable tool, either alone or in combination with the leaf chlorophyll content estimation. Indeed, in the framework of the protein competition model for polyphenolic allocation1, DUALEX 3 FLAVhas been used successfully in agricultural2 and forestry3 research. Information on epidermal flavonoids is complementary to the measurement of the leaf chlorophyll content. Figure: DUALEX 3 FLAV measures the isoorientin content in wheat, as an indicator of nitrogen deficiency. 1 Jones CG and Hartley SE (1999) A protein competition model of phenolic allocation. Oikos 86: 27-44 2 Cartelat A, Cerovic ZG, Goulas Y, Meyer S, Lelarge C, Prioul J-L, Barbottin A, Jeuffroy M-H, Gate P, Agati G and Moya I (2005) Optically assessed contents of leaf polyphenolics and chlorophyll as indicators of nitrogen deficiency in wheat (Triticum aestivum L.). Field Crops Res 91: 35-49 3 Meyer S, Cerovic ZG, Goulas Y, Montpied P, Desmotes-Mainard S, Bidel L, Moya I and Dreyer E (2006) Relationships between optically assessed polyphenols and chlorophyll content and the dry mass per leaf area ratio of woody plants: a signature of the carbon and nitrogen balance within leaf? Plant Cell Environ 29: 1338–1348
DUALEX ANTH
DUALEX ANTHcan be applied to assess the phenolic maturity of grapes. Figure: DUALEX ANTH-berry measures the anthocyanin content of berry peels; extraction with acidified 50% MeOH; extract absorbance expressed in absorbance units per cm² of skin.
DUALEX 3 HCA
DUALEX 3 HCAis especially useful for research on Arabidopsis thaliana known to contain more hydroxycinnamates than flavonols in its epidermis4 and for all plants grown in growth chambers and greenhouses lacking UV-B light. Figure: correlation curve between DUALEX UV absorbance and chlorogenic acid content of tobacco leaves. 4 Landry LG, Chapple CCS and Last R (1995) Arabidopsis mutant lacking phenolic sunscreens exhibits enhanced ultraviolet-B injury and oxidative damage. Plant Physiol 109: 1159-1166

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