Trying to Make Scents of Things

[Damon]

Andrea's recent question about a possible detectable change in flower appearance during the day caused by UVIVF got me thinking but along a different path. We humans rely so heavily on sight it seems natural to think UV signatures and UVIVF are sight related. But what if they are not?

 

Could it be possible this whole UV "bulls-eye" concept is flawed and the UV signatures are mainly helping to heat up the scent producing parts? Does UVIVF also play a role with heat/scents?

 

 

Here is where I am going with this:

Flowers use scent First then sight to attract insects. Maybe UV signatures are heating up the flower, aiding the production or enhancing the power of the scent? Skunk cabbage heats up in the snow to melt it's way out and this also heats up it's stink.

 

The Dark UV signature in the Gazania I measured was definitely warmer than the rest of the flower - so this could be aiding to enhance the scent. And maybe UVIVF, by emitting light at different levels, is helping to regulate the proper heat thus the proper release of scents. If it is a dark dismal day, weak UV and UVIVF effect - thus weak heat effect. Weak heat is good here because there is no need to blow scent around if there are hardly any insects flying around to detect it.

 

I need a way to detect scent levels. Is this possible? Some of this can be figured out with a laser thermometer I think or a good thermal imager.

 

From Wikipedia on skunk cabbage (it list sources) --

"Some studies suggest that beyond allowing the plant to grow in icy soil, the heat it produces may help to spread its odor in the air. Carrion-feeding insects that are attracted by the scent may be doubly encouraged to enter the spathe because it is warmer than the surrounding air, fueling pollination.

 

Could the heat shown in thermal pics on this site in the center of flowers be caused by the heat from a Dark UV signature/UVIVF? Yes.

 

It could be that most (all?) of the neat UVIVF we are seeing at night with our lights is just simply light caused by heat. Heat is a common way we see light. And I think heat always creates light. In this case, the heat is the primary useful product and the light is just a by-product, albeit a neat one. The severe low levels of UV at night always bothered me because it never seemed enough to produce any UVIVF that I could detect, even with ludicrous exposure times. Not only is there insufficient fuel to fluoresce, but there is no need to!

 

Most flowers are closed at night. These cool UVIVF flowers we are taking pics of are normally closed at night so this fluorescence is rarely, if ever, seen in nature. That's because the glowing we see is only beneficial during the day when it's function is related to heat/scents. Like anything there will be exceptions.

 

Flowers that heated up quicker in the AM via low ambient light could get their scent factories going quicker and they would also by default be warmer and insects need early warmth. A double incentive for pollinators..

 

I often find crab spiders right in the heart or near the heart of flowers. Must be really warm there. The ones I have photographed also fluoresce like mad. That's because during the day it helps them to regulate their body temperature! :)

 

Many mushrooms fluoresce well so they can give off heat during the day and not dry out prematurely.

These are initial thoughts and theories so keep that in mind.

 

-Damon

[Andy Perrin]

I need a way to detect scent levels. Is this possible? Some of this can be figured out with a laser thermometer I think or a good thermal imager.

Ok, I saw your comments on the other thead and I do think it's an interesting hypothesis, but you must be extremely careful in using thermal imagers or IR ("laser") thermometers to measure the temperature under sunlit conditions because the reflected IR component of the sunshine will cause a false reading. One way around it would be to let the flower be exposed to the direct sunshine till it reaches equilibrium, then very briefly shade it with some aluminum foil and take a measurement in the shade. Hopefully the actual temperature will not change very much but the foil will cut out the reflected sunshine that otherwise will contaminate your measurement.

 

It could be that most (all?) of the neat UVIVF we are seeing at night with our lights is just simply light caused by heat. Heat is a common way we see light. And I think heat always creates light. In this case, the heat is the primary useful product and the light is just a by-product, albeit a neat one. The severe low levels of UV at night always bothered me because it never seemed enough to produce any UVIVF that I could detect, even with ludicrous exposure times. Not only is there insufficient fuel to fluoresce, but there is no need to!

No. This is just wrong. While hot objects always radiate light, it depends strongly on the temperature, and we cannot see it with our eyes or with ordinary cameras until it is quite literally RED HOT. Since flowers are not red hot, UVIVF is not blackbody radiation. UVIVF is fluorescence, which has a totally different mechanism.

[dabateman]

You should check out this link:

https://www.ultravioletphotography.com/content/index.php/topic/3667-new-ideas-on-how-bees-see/page__pid__32379#entry32379

 

Bees only see blue and use it for contrast. So your hypothesis may have some weight.

[Stefano]

Well... I do believe that UV nectar guides are heated up more under sunlight than the rest of the flower, but by how much? Does this bit of more heat make a non-negligible difference?

[OlDoinyo]

Some checks on this hypothesis:

 

1) Do flowers whose pollinators cannot see UV develoo these patterns?

 

2) Since sunlight contains more IR than IV,do any flowers develop IR-dark nectar guides?

 

A yes answer to either question could be evidence in favor. I personally do not know of any examples.

[Damon]

Andy "No this is just Wrong"

 

Excellent! Thanks and I need definitive facts. I knew I was reaching with that. Appreciate the critique.

I like your temp check idea too.

 

Debateman - thanks I read that and it does have some compelling stuff.

 

Stefano - Great question! Some insects can detect hundredths of a degree in changes. Will need to look up common pollinators. But the change in scent is also what I am interested in.

 

OlDoiyno - Thanks for the questions. I will need to think about this

[Andrea B.]

***Could it be possible this whole UV "bulls-eye" concept is flawed and the UV signatures are mainly helping to heat up the scent producing parts?

 

Your question is right on a good an excellent one.

 

Here in the pages of UVP we have reported/discussed that UV-absorbing areas on flowers may be acting as protection against UV solar damage to floral reproductive parts (pollen/ovary DNA). This information is taken from scientific papers and (perhaps?) from Adrian Horridge's writing about bees.

 

So there are multiple possibilities for the presence of UV-absorbing areas on flowers: nectar guides, protection against DNA damage and, as you postulate, boosting scent via increased heat. Somewhere I also recall a brief mention or discussion here on UVP about the heat release as part of fluorescence and its possible benefit to the flower.

 

Added Later: Birna observed that many spring flowers have UV-dark stems/buds. So their absorption of heat might aid their survival in spring snows or against cold, possibly frozen ground.

 

Given the way evolution works, it is quite likely that there are multiple possible benefits for flowers having UV-absorbing areas and that different flowers have evolved to make use of different strategies or combinations of strategies.

 

I'm speaking here as a "reporter/editor" and not as a trained botanist, bee theorist or evolution expert. :grin:

You will, I hope, kindly forgive me if I do not post links and references right away as I'm a bit busy with some domestic activities today. There is a crew removing all the invasive Russian Sage from our 6 acres today and also doing other landscaping things. We want to keep our property "wild" outside the courtyard areas.

 

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***Since sunlight contains more IR than IV, do any flowers develop IR-dark nectar guides?

 

The Gazania is the best example I currently know of which has some IR-absorbing areas. I do not know whether those are considered to be nectar guides. I do not know if any pollinators have IR vision. It seems from our botanical collection that the presence of IR-absorbing areas is unusual or rare.

http://www.ultraviol...rigens-gazania/

https://www.ultravio...__fromsearch__1

 

In the photographs I made, I noted a slight fade from the IR-dark areas in the B+W 092 photos to the B+W 093 photos.

[Andrea B.]

Remembered where there was a cache of relevant links!! I'm going to copy/paste here, but do look thru the discussion also: https://www.ultravio...tive%20%20parts

 

The last link below is the one about UV-absorbtion protecting reproductive parts.

 

[copy from above link]

We have some examples here on UVP of UV-absorbing pigment change due to floral age. Here is an example.

Myosotis sylvatica As the little Forget-me-not flower ages, its UV absorption fades. A bit of research might reveal whether this is due to pollination.

 

Here is an example of pigment variation which is known to occur due to pollination and does not seem to be related to UV-absorption/reflection changes.

Lupinus sparsiflorus

Look at Set 1, photos 3 (visible) and 4 (bee vision), to see that after the lupine flower is pollinated it expresses magenta pink areas on the upper petals, called the standards. The Set 1, photo 4, example in bee vision shows quite a dramatic change, but looking at the photos in Set 2 we can't see any particular change in the UV-absorbing areas after pollination. So it is not always UV-absorbing pigments which are relevant to floral signatures.

 

Here is a reference to a paper which discusses UV bullseye size variation due to altitude.

Altitudinal cline in UV floral pattern corresponds with a beharioral change of a generalist pollinator assemblage.

In the flower Argentina anserina, the UV-bullseye increases with increasing altitude. Larger UV-bullseyes attracted more pollinators then smaller UV-bullseyes.

 

Here is a more general paper (it's really fascinating!!) by Koski & Ashman which discusses various geographic and bioclimatic factors affecting genetic expression of UV pigmentation in the Potentilla tribe.

Macroevolutionary patterns of ultraviolet floral pigmentation explained by geography and associated bioclimatic factors There is some mention in this paper of UV-absorbing areas being protective against UV damage but no mention of that as an anti-oxidant effect. Still, I think that partly answers what you were asking. This paper has quite a lovely list of references.

((I note in passing that Koski & Ashman make the typical reference to UV "patterns" rather than UV "signatures" as we do here. Absence of a "pattern" is a "pattern". But this is a minor quibble.))

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[Andrea B.]

I added another possibility to Post #7.

[Damon]

Thanks a bunch Andrea! Give me a bit to dig into this.