Anthochlor Pigments and Pollination Biology. II. The Ultraviolet Floral Pattern of Coreopsis gigantea (Asteraceae)

Abstract

Anthochlor pigments (chalcones and aurones) in the floral heads of C. gigantea were found to be responsible for the UV floral pattern present in this species. The pigments of primary importance in producing the UV floral pattern were marein, sulphurein, coreopsin, butein and sulphuretin. Presence of the anthochlor pigments and the UV floral pattern were determined by observing a visual color change (yellow to reddish-orange) when the floral heads were exposed to ammonia vapor. This color change, characteristic of anthochlor pigments, is suggested as a simple field test to detect UV floral patterns in those families where anthochlor pigments are known to occur. It was found that on drying and storage as herbarium specimens the floral heads of C. gigantea lost their UV pattern, with the entire floral head becoming UV absorptive. A cautionary note is suggested on the use of UV floral patterns from dried herbarium specimens without direct knowledge of the UV floral patterns in fresh material.