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UltravioletPhotography

Centaurea nigrescens [Short-fringed Knapweed]


Andrea B.

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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]

centaureaNigrescens_Vis_20140803somesvilleME_25075pn.jpg

 

Visible Light [unresized excerpt from a similar photo.]

This C. nigrescens was covered with insects.

centaureaNigrescens_Vis_20140803somesvilleME_2505501.jpg

 

Ultraviolet Light [f/11 for 1/2.5" @ ISO-1250 in Sunlight with Baader UV-Pass Filter]

centaureaNigrescens_UVBaadSun_20140803somesvilleME_25083pf2.jpg

 

 

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]

centaureaNigrescens_Vis_20140806somesvilleME_25486pn.jpg

 

Ultraviolet Light [f/16 for 15" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

centaureaNigrescens_UVBaadSB14_20140806somesvilleME_25507pf.jpg

 

 

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]

centaureaNigrescens_VisFlash_20140805somesvilleME_25459pn.jpg

 

Ultraviolet Light [f/11 for 15" @ ISO-400 with SB-14 UV-modified Flash and Baader UV-Pass Filter]

centaureaNigrescens_UVBaadSB14_20140805somesvilleME_25474pf.jpg

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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.

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