Andrea B. Posted January 18, 2015 Share Posted January 18, 2015 Blum, A.G. & Rørslett, B. (2015) Calycoseris wrightii A. Gray (Asteraceae) White Tackstem. Flowers photographed in ultraviolet, visible and infrared light. http://www.ultraviol...white-tackstem/ Ajo, ArizonaThis Tackstem was growing in a weedy parking lot in Ajo, which is about 40 miles north of the US-Mexico border.10 March 2012Wildflower Comment:White Tackstem is a wildflower of the Southwestern US and Northwestern Mexico usually found in sandy, gravelly areas. The very similar Rafinesquia lacks the sticky glands which are present on the involucre and stem of this C. wrightii. The abaxial rays are often red-striped.The Tackstem rays are moderately UV-absorbing and exhibit UV-bright pollen and anthers. Reference:1. Jepson eFlora (2015) Calycoseris wrightii. Jepson Herbarium, U. of Cal.-Berkeley, Berkeley, CA. http://ucjeps.berkel...IJM.pl?tid=1892 Set 1 by Bjørn Rørslett Image reference: CALY_WRI_G1203103389_VISVisible light: NIKON D3X, 125 mm f/2.5 Voigtländer APO Macro-Lanthar lens, daylight Image reference: CALY_WRI_G1203104577_UVUltraviolet light: NIKON D40X, UV-Nikkor 105 mm f/4.5 lens, built-in Baader U2" (Venus) filter, SB-140 flash The ligules (ray flowers) are extensively dusted by pollen, which is pale yellow and difficult to discern in visible light. In UV, however, the pollen grains are highly UV reflective and stand out against the moderately reflective floral parts. The unopened buds are highly UV reflective so make a strong contrast to the opened flower heads. Set 2 by Andrea Blum Equipment [Nikon D300-broadband + Carl Zeiss 60mm f/4.0 UV-Planar] Visible Light [f/11 for 1/2500" @ ISO-800 in Sunlight with Baader UVIR-Block Filter] Ultraviolet Light [f/11 for 1/250" @ ISO-800 in Sunlight with Andrea-U UV-Pass Filter]The Andrea-U UV-pass filter passes a small amount of violet/blue light which slightly alters the typical false colour appearance seen above in Rørslett's photograph. UV dark and light relationships are not changed. The preceding photo after a slight turn of the colour wheel. Infrared Light [f/11 for 1/4000" @ ISO-800 in Sunlight with B+W 092 IR-Pass Filter] Visible Light [f/8 @ ISO-400 with Nikon D3S + Nikon 60/4 Micro-Nikkor]Details of the sticky tack-headed glands on the involucre and stem of C. wrightii. Dust and debris become caught in their sap. Visible Light [f/8 for 1/11250" @ ISO-400 with Nikon D3S + Nikon 24-70/2.8G AFS]The abaxial rays show red stripes. It looks like a candy cane effect.(Tucson, Arizona, 14 March 2012) Link to comment
Andrea B. Posted January 23, 2015 Author Share Posted January 23, 2015 Hey, our first joint post - cool !! Let's do more of these and maybe we can finish up the desert wildflowers? Link to comment
colinbm Posted January 23, 2015 Share Posted January 23, 2015 Excellent presentation, Andrea & Bjorn.Col Link to comment
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now