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UltravioletPhotography

First Tussilago of 2014


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In my neck of the woods, which is the cold Nordic kingdom of Norway, the first native spring flower* is Tussilago farfara (Asteraceae). It is a heterophyllous species occurring with flowering shoots that only have vestiges of scale leaves and carry a terminal composite flower head. A few weeks later, sterile summer shoots emerge with basal rosettes of medium to large leaves. The shape of these leaves can, with the imaginative powers of our forebears, be likened to small horse hoofs hence the vernacular name Colt's foot.

 

* Alder, hazel, and willows trees can flower earlier (some years in January), but they have catkins. Winter Aconite and Helleborine can flow already in February, but they are not native and are mainly found in gardens.

 

I shoot Tussilago flowers every year, because they are the first UV subject of a botanical kind to appear in the season and also have a lot of UV details that can be explored. Like so many members of the Asteraceae, the Colt's foot flower heads go through a female to male development. The female ray flowers are peripheral on the central disc and the styles wither rather quickly. The disc flowers are all male and open gradually from the periphery towards the centre. Thus one usually observes flowers in all stages of development in any given capitulum. The pollen fluoresces brightly under UV with a cold blue rendition. In UV, the disc corolla and stamen columns are rendered very dark, almost black hues. The ray flowers reflect significantly in UV so a classic 'bull's eye' effect is manifested. Towards the end of life of the capitula the rays become first UV dark at their tips then they lose their turgor and wilt rapidly.

 

I found these Tussilago specimens hanging literally mid-air in a road embankment. They made a spectacular sight amongst rusting rebars in the support structure. Just goes to show the tenacity of nature and its life forms.

 

The plants were too far above me to be captured using a flash, so I used available subdued sun light instead. Exposures still were around f/11 @ 1-1.3 sec and ISO 200, so the UV response of my modified Nikon D3200 is excellent. The D3200 has a cut-to-shape Baader U2" inside it.

 

UV_Tussilago_DSC1443_v1.jpg

 

As Tussilago is a perennial species, remains of the decayed foliage of last summer still cling onto the rhizome. Usually the decay is completed before the next season of growth, but in this instance there is hardly any soil substrate present so decomposition slows down. One observes the same behaviour when the plants grow on pure sand or gravel. The genus itself is monotypic and may be very ancient as there are several specialised parasite fungi associated with it. These fungi mostly are restricted to the summer foliage so won't influence seedset.

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Wonderful story Bjorn

The photo is great, just growing out the side of some geo-textile beside a road.

Yes the camera is doing a good job, we wouldn't expect anything less from you :D

Col

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Later I found a way to scale the steep embankment so got better close-ups. Here is one with a CC Passport included. Note how the flower heads change in appearance according to their development stage.

 

UV_Tussilago_DSC1454_v1.jpg

 

A precarious balancing act in which my SB-140 UV flash and an EL-Nikkor 80 mm f/5.6 participated netted me this 2.4X close-up,

 

UV_Tussilago_2,4X_DSC14692_v1.jpg

 

I'll have to dig up a few plants and bring them with me into a studio set up, as the depth of field is too limited at these magnifications and in fact, getting something in sharp focus is a miracle anyway under field conditions. Focus stacking might, repeat might, be the answer to solve these issues.

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Now we know that Spring really will return to the Northern hemisphere if the Tussis have appeared !!

 

I love the tough little Tussilagos. Every year I look here for some, but I haven't seen them for years now. Time to go try again.

 

The first photograph is cool. I love seeing how wildflowers can grow in the strangest places.

 

*****

 

Who cut the Baader-U ??

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Sadly, no. They were left behind in an Anza-Borrego trashcan.

 

I once fitted an uncut 1.25" Venus filter in my D300.

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