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Science 11 August 1972:
Vol. 177. no. 4048, pp. 528 - 530
DOI: 10.1126/science.177.4048.528
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Articles

Flavonols: Pigments Responsible for Ultraviolet Absorption in Nectar Guide of Flower

W. R. Thompson 1, Jerrold Meinwald 1, D. Aneshansley 2, and Thomas Eisner 2

1 Department of Chemistry, Cornell University, Ithaca, New York 14850
2 Section of Neurobiology and Behavior, Cornell University

The petals of the black-eyed susan (Compositae: Rudbeckia hirta) contain three flavonol glucosides (6,7-dimethoxy-3',4',5-trihydroxyflavone-3-O-glucoside, patulitrin, and quercetagetin). These compounds, which show intense spectral absorption at 340 to 380 nanometers, are restricted in distribution to the petal bases, which are ultraviolet absorbing as a result. Such ultraviolet-absorbing petal zones, known as "nectar guides," are invisible to us, but are visible and of orientation value to the pollinating insect that lands on the flower in search for food. This is the first time that ultraviolet absorption in a nectar guide has been interpreted in chemical terms. In view of the widespread occurrence of flavonols in flowers, it is suggested that these pigments serve specifically for demarcation of ultraviolet petal patterns visible and relevant to insects.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
A Small Family of MYB-Regulatory Genes Controls Floral Pigmentation Intensity and Patterning in the Genus Antirrhinum.
K. Schwinn, J. Venail, Y. Shang, S. Mackay, V. Alm, E. Butelli, R. Oyama, P. Bailey, K. Davies, and C. Martin (2006)
PLANT CELL 18, 831-851
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Ultraviolet Viewer.
T. Eisner and D. J. Aneshansley (1975)
Science 188, 782
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Attractive and defensive functions of the ultraviolet pigments of a flower (Hypericum calycinum).
M. Gronquist, A. Bezzerides, A. Attygalle, J. Meinwald, M. Eisner, and T. Eisner (2001)
PNAS 98, 13745-13750
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