Appearance of vegetation in ultraviolet light: absorbing flowers, reflecting backgrounds.
Flowers that uniformly absorb ultraviolet light may contrast strikingly with a bright ultraviolet-reflecting background, such as densely hairy or glaucous foliage, white soils, or the sky. Shadows will not resemble these flowers if the appearance of each in visible light is also considered. Examples are shown from Mexican heliotropiums and Michigan dune plants.
Frohlich
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MW