Andrea B. Posted March 26, 2015 Share Posted March 26, 2015 Blum, A. G. (2015) Centaurea nigrescens Willd. (Asteraceae) Short-fringed Knapweed. Flowers photographed in ultraviolet and visible light. http://www.ultraviol...inged-knapweed/ Somesville, Maine, USA 06 August 2014 Wildflower Synonyms: Centaurea dubia Suter C. dubia Suter ssp. nigrescens (Willd.) Hayek C. dubia Suter ssp. vochinensis (Bernh. ex Reichenb.) Hayek C. transalpina Schleich. ex DC. C. vochinensis Bernh. ex Reichenb. Jacea nigrescens (Willd.) Soják Primary Pigment: Cyanidin, a sub-category of the Anthocyanins in the Flavonoids group. Comment: The truncate base of the ascending, fringed, dark apical appendage of the involucal bract distinguishes C. nigra and C. nigrescens from other Centaurea. The enlarged outer flowers of the capitulum indicate that this specimen is C. nigreacens. C. nigrescens pollen is UV-bright, the flowers are moderately UV-dark and the anthers are UV-dark. Reference: 1. New England Wild Flower Society (2015) Centaurea nigrescens Willd. Short-fringed Knapweed https://gobotany.new...rea/nigrescens/ Equipment [Nikon D600-broadband + Carl Zeiss 60mm f/4.0 UV-Planar] for the next three photos Visible Light [f/11 for 1/320" @ ISO-400 in Sunlight with Baader UVIR-Block Filter] Visible Light [unresized excerpt from a similar photo.] This C. nigrescens was covered with insects. Ultraviolet Light [f/11 for 1/2.5" @ ISO-1250 in Sunlight with Baader UV-Pass Filter] Equipment [Nikon D600-broadband + Nikon 105mm f/4.5 UV-Nikkor] for the next two photos Visible Light [f/16 for 1/40" @ ISO-400 in Sunlight with Baader UVIR-Block Filter] Ultraviolet Light [f/16 for 15" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter] Equipment [Nikon D600-broadband + Carl Zeiss 60mm f/4.0 UV-Planar] for the next two photos Visible Light [f/11 for 1/400" @ ISO-400 with onboard Flash and Baader UVIR-Block Filter] Ultraviolet Light [f/11 for 15" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter] Link to comment
nfoto Posted March 26, 2015 Share Posted March 26, 2015 Nice presentation, Andrea. I have seen C. montanum with a very similar UV signature so may be a common feature of the genus perhaps. The pictures and text appear to be out of order towards the end of the post. Link to comment
Andrea B. Posted March 26, 2015 Author Share Posted March 26, 2015 Thank you. I fixed the ordering. Link to comment
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