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Hibbertia crinita

Fluorescence
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#1 DaveO

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Posted 05 February 2017 - 04:21

Oldfield, D. 2017. Hibbertia crinita Toelken (Dilleniacea) Flowers photographed in visible and ultraviolet light. http://www.ultraviol...bertia-crinita/

Maldon, Victoria, Australia
20 September 2016
Australian Native Wildflower as Garden Specimen

Synonyms

Hibbertia sericea (R.Br. ex DC) Benth. var. sericea
Hibbertia stricta var. canescens Benth.

Comment

Hibbertia crinita is found in South Australia, Victoria, New South Wales and southern Queensland. This species is closely allied to H. sericea and was treated as H. incana until described by Toelken in 2000.

Visible Light: Nikon D750 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens, Metz 15 MS-1 flash, 1/200 s @ f/16 ISO 200, Baader UV/IR Cut Filter.
Attached Image: Hibbertia_crinita_Vis.jpg
Image Reference: DO63250

Ultraviolet Light: Nikon D750 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens, Nissin Di866 Mark II flash, 1/200s @ f/16 ISO 200, Baader UV-Pass Filter.
Attached Image: Hibbertia_crinita_UV.jpg
Image Reference: DO63252

Ultraviolet Induced Visible Fluorescence: Nikon D750 Full Spectrum Modification, Nikon Rayfact PF10545 MF-UV 105 mm f/4.5 lens with Baader UV/IR Cut Filter, Nichia NCSU033A UV-LED with Baader UV-Pass Filter, 10.0 s @ f/16 ISO 1600.
Attached Image: Hibbertia_crinita_UVIVFL.jpg
Image Reference: DO63255

References:
Toelken H.R. 2000, Notes on Hibbertia (Dilleniaceae) 3. H. sericea and associated species, J. Adelaide Bot Gard., p. 19.

Published 5 February 2017

Edited by DaveO, 05 February 2017 - 04:21.


#2 DaveO

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Posted 06 February 2017 - 03:02

I have just found, in my dis-organised filing system, two previous references by Adrian Dyer to the UV properties of Hibbertia species:
Aus. J. Bot. 1996 473
Attached Image: Dyer 1996 Screen.jpg

You will see a reflection peak for H. obtusifolia at around 350 nm for the petal and NO reflection below 500 nm for the anther and leaf.

Proc. R. Soc.B (2012) 3606
Attached Image: Dyer 2012 Hibbertia Screen.jpg

This shows a similar, but better resolved, UV reflection for H. scandens

I will stick my neck out and propose that the same pigments are present in all Hibbertia species

Please can someone hazard a guess at the reason for the green UVIVFL petal colour

Wiki suggests that lutein is the most abundant yellow pigment in plants, I also found the absorption spectrum of lutein
Attached Image: Lutein absorbtion spectrum.JPG

and the fluorescence spectrum
Attached Image: Lutein fluorescence.JPG

What does it all mean?

#3 Andrea B.

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Posted 06 February 2017 - 17:39

Well, Dave, I'm not sure any of us knows the answer to that. :D


When I sample the colours on the petals, I'm getting samples like (94,118,43) or (71,92,35) in which the green is only slightly stronger than the red. So the fluorescence is a yellow-green, not a green. It is almost yellow. :rolleyes:
Green = 510nm = (0,G,0). Yellow = 570nm = (R,G,0), Yellow-green = 540nm = (R, g, 0).

Now, the Hibbertia spectral charts show strong reflection from about 525nm onward, approximately. But, the Hibbertia spectral charts do not indicate a strong UV reflectance -- so, the petals are absorbing between 60-75% of the UV portion of any illumination. Thus, under your Xenon flash, that is likely enough UV absorbance to trigger the dull yellow-green, almost yellow fluorescence seen in the photo.

Assuming the preceding is a reasonable observation, we should then remember that there are approximations induced by colour spaces, jpg conversions and possible white balance inaccuracies. If everything were perfect (!), then the fluorescent petals might be a bit more yellow looking. But they are not far off.

As for the pigments, it would be useful to know the exact yellow pigment of this Hibbertia. Just a little tweak here or there on those tricky organic chains can move the colour. Do we know Hibbertia has carotenoid pigmentation? Could it be flavonoid?

What was very interesting here, is that you had an actual spectral chart** for a flower petal against which to check the UV and UVIVF results. B)

**ADDED: Woops, I forgot this to qualify this. ==> The charts are for H. scandens and H. obtusifolia. The photographed flower is H. crinita. We are making an assumption that H. crinita has a similar spectral chart to the two shown. However, that kind of assumption can take one off the rails with some flower species.
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#4 OlDoinyo

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Posted 06 February 2017 - 18:27

I am no botanist; however, I suspect that the fluorescence is epiphenomenal (rather than serving any evolutionary purpose.) The lutein absorbance spectra do not look like a very close match to the flower's reflectance spectrum.

#5 DaveO

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Posted 07 February 2017 - 00:27

Andrea,

Suddenly a whole new world of questions has opened up. First off the UVIVFL was with a UV-LED filtered with Baader U to get a black SS spoon calibration, so it wasn't high powered Xenon flash. I'm a bit (like a whole year) behind in posting my studio shots which are the only ones that have the UVIVFL but I have found that other visible-Yellow flowers also show the same UVIVFL-green so I guess the pigments are similar. I wonder if visible-yellow flowers from your neck of the woods do the same thing, something to look for when summer returns and you can visit your hot little fluorescence space! I'm still looking for the key which will open the door to all the natural products studies done by Aussie chemists in the stone ages.

Here's another yellow to FL green:
http://www.ultraviol...a-hop-goodenia/

OlDoinyo,

I agree that the UVIVFL is just what happens and doesn't serve any evolutionary purpose - I can't see how insects can see it anyway as it only really becomes "visible" in the dark, I am coming to the view however that having the fluorescence info may held to pin down the pigments responsible since we then have the Visible, UV and UVIVFL to somehow juggle to get the answer. If I could find samples of the possible plant pigments at a sensible price then I would have a go with them, suggestions of suppliers gratefully received.

Edited by DaveO, 07 February 2017 - 01:05.


#6 Andrea B.

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Posted 07 February 2017 - 01:50

OK, you shot the UVIVF with a UV-Led. Those typically have a peak around 365nm. But you would still have UV absorbance at about the 70% level there -- a little less to the left of 365 and a little more to the right. That is a lot of UV absorbance.

I'll see what I have for UVIVF with UV-reflecting, yellow flowers and try to post something.

We also must remember how the insects or animals see this flower. The trichromatic bee, for example, sees the yellow Hibbertias as some kind of bee colour like "UV-yellow-green" because it reflects some of both UV and of yellow-green. Alternately, it might instead be seen by the bees as a dull "UV-green" because of the large green absorbance which only rises on the yellow side. (I'm never sure how much yellow vision is attributed to bees. Some authors seems to indicate it is possible.)

Dave, you can determine some of the underlying pigments in your flowers by performing a little bit of simple paper chromotography at home in your own kitchen. You simply mash up petals in different solvents, dip your paper and watch to see if the colour climbs or not. I will dig out the link for you. It may take me a while to find it. The resulting classification is only at a high level, but it might be fun to try.

https://www.biologyc...t_pigments.html

http://www.phschool..../concepts1.html

Word Doc file:
https://www.google.c...cn6UwXkN6cjyGKw
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#7 Andrea B.

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Posted 07 February 2017 - 02:18

My book Nature's Palette: the Science of Plant Color by David Lee (2007, U. of Chicago Press, Chicago) has a slightly different paper chromotography experiment in Appendix B to determine carotenoids, anthocyanins, flavonols and betalains. If there is interest, I will copy it and post it here. The solvents used there are 91% isopropyl alcohol, mineral spirits, clear vinegar or ammonium hydroxide.
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#8 DaveO

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Posted 07 February 2017 - 03:18

Andrea,

One of the "theories" I saw somewhere was that pigments could absorb UV and then emit it as fluorescence which may well be happening with the Vis-yellow flowers. These particular flowers are long gone so I would need to wait until they bloom again in our Spring. Way back in my student stone age I distinctly remember attending a packed lecture on the new wonder of the age Thin Layer Chromatography (which has by now gone the way of button-up-boots to be supplanted by High Pressure Chromatography etc) and I have contemplated that to sort out the witches brew of soluble compounds in petals. But I still need a fully equipped lab like I used to have, separation is always the key to working out what's going on.

#9 Andrea B.

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Posted 10 February 2017 - 21:33

Dave, here is a Ranunculus bulbosus visible fluorescence photo under made under a 365nm UV-Led in the dark. The torch did not have a filter so has leaked a tiny bit of violet light which you can see in the specular reflections off the very shiny R. bulbosus. This does not affect the basic fluorescence of R. bulbosus although I would have preferred a "purer" shot.

D200-broadband
Zeiss 60/4.0 UV-Planar
Baader UVIR-Cut Filter
Nichia 365 UV-Led Torch

The first version was finished for display. The exposure here has not been "pushed". The irrelevant blue fluorescent fibers have been cloned out. Clearly the pollen and the center portion of the flower show the strongest visible fluorescence.
Attached Image: ranunculusBulbosusUVIndVisFluor051309mt_29690proof0101.jpg

The second version is from Raw Digger. Here the raw colours have been captured in a raw composite. Then a daylight white balance was applied with a big boost to the exposure so that the petal colours can be better seen.
The petal fluorescence is rather weak when compared to the strong central orange-pink fluorescence (as seen in the first photograph). But after a push, we see that it is there and it is yellow.
Attached Image: ranunculusBulbosusUVIndVisFluor051309mt_29690rgbRenderDaylightpn0101.jpg
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#10 DaveO

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Posted 10 February 2017 - 22:36

That looks very much like what I see, often the pink chlorophyll (?) fluorescence is very dim and I have to really push to bring out any petal fluorescence. I think the blue fluorescence of the hairs on leaves etc is due to lignin or other cellulosic structural materials and I usually decide I've pushed the result far enough when that seems to be saturating.