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  [Aroid-l] Philodendrons produce infrared light???
From: Steve at ExoticRainforest.com (ExoticRainforest) on 2008.05.23 at 18:13:31(17605)
This morning Julius and I received a private response from Marc Gibernau in regard to the observation originally proposed by British engineer Chris Rennie on the University of British Colombia (UBC) plant discussion forum about "infrared light" and a spadix in anthesis. You can read Marc's original response to Aroid l just below this message. The possibility of whether infrared heat may or may not additionally serve to propel thermogenic attractants to aroid pollinators is obviously incomplete. As to whether or not infrared (IR) acts as any sort of homing device for the beetle pollinators of Philodendron or other aroid species, at least research is apparently being done. And there is a possibility it may assist!

It is known that many insects can and do use IR to find both light and prey. A private message from entomologist Christopher Rogers explains more and I've included that in this post. But can these beetles which are the natural pollinators of many aroids be attracted to the spadix of an inflorescence entering anthesis as a result of infrared heat as well? To a beetle does the "glowing" spadix appear as a beacon in the night with a sign yelling "eat here, rest here, have sex here?". If you read my post on UBC to Chris which I also posted on Aroid l you will see I proposed the long range attractant may be the pheromone and a short range attractant could be the infrared heat. I have no idea if that is possible! But work is apparently being done to learn more.

This is the message from Marc this morning, "Yes heating inflorescences are spot visible in the IR up to 15 meters according to our IR camera. Some beetles (laying in burnt woods) are known to have IR receptors to localize the forest fires. I sent some Cyclocephala (Philodendron pollinators) in Germany for detecting IR receptors but the results were negative. But the fact is that IR attraction is possible, I will continue on this topic, particularly with a Brazilian student.

All the best,


There was some very interesting input from folks to this possible idea posted on UBC. I personally believe all of you aroid enthusiasts might find the discussion on the University of British Colombia plant forum at least of interest. If nothing else, you may learn something more about aroid pollination.: http://www.ubcbotanicalgarden.org/forums/showthread.php?t8988

But before you read the several pages of discussion in which I began more than dubiously and subsequently began to see new possibilities with the urging of Julius, Leland Miyano and Christopher Rogers, watch Chris's time lapse photos of his inflorescence at this link:
http://www.ubcbotanicalgarden.org/forums/showthread.php?t9167&highlight=time+lapse I think you'll find it fascinating how the inflorescence bobs and changes its position.

At least I now have a much better understanding of the process of thermogenesis,, pheromone attractants, aroid pollination and how insects "see" as a result of feedback from a bunch of you sent privately. My special thanks to Julius and Leland as well as Christopher Rogers who is a regular on Aroid l. Dr. Croat's journals are of special value to me and always provide great information.

This message was sent to Julius, Leland and myself by Christopher Rogers as a result of this discussion, "An infrared thermometer works by detecting radiation in the IR spectrum. IR radiation is emitted by all objects depending on their temperature. IR is a colour like any other part of the electromagnetic spectrum, just like visible light, but we just cannot see it, although many insects and crustaceans can, as well as some birds. (Just an aside: some raptors can see the urine tracks in infra red left by rodents (who just dribble wherever they go) and so know which areas to concentrate on for prey items). So, there is IR colour and also IR radiation emitted by all objects. The higher an object's temperature, the greater the object's IR radiation. The IR thermometer does not tell you the colour of an object, it tells you the heat it is radiating by a correction factor multiplied times the IR radiation. This is exactly how the IR camera and thermometer work. But it must know what the basic background temperat
ure is to calibrate itself.

So, metabolic reactions will generate heat, which is measurable in the IR spectrum. One of my favorite aroids (which bloomed wonderfully for me this year) is Helicodiceros muscivorus, the Dead Horse Arum. The cells in the spadix are packed with mitochondria, which are the cell powerhouses. As a result, they raise the temperature of the plant to a wonderful 98.6 degrees F when they are in bloom and producing their macabre odors. It seems to me that anthesis is probably very costly (in energy) to the plant. So, the mitochondria are working hard to move anthesis along, spending lots of energy, much of which is lost as heat, and therefore generating an increase in IR radiation. Since insects do cue in on pheromones and the IR discharge in those pheromones, it seems a very logical step for the plant to exploit in the attraction of pollinators. Obviously, since Helicodiceros, Amorphophallus and Typhonium all produce heat from the spadix appendix (possibly to volitalize scent molecules as well as to add allure to t
he deathly perfumes) it seems that the ability would be found residing in other aroids as well."

I see Aroid l as a place to learn, and not just about the basics. That's why I often ask crazy questions! I get great information from a bunch of you and as you likely realize I am constantly filled with aroid questions! Those of you who are new to Aroid l may not know that many of the world's best aroid botanists and experts are right here with us! They read these posts and often make comments, so the information you receive here (free) is very valuable.

A couple of suggestions if I may. There is an incredible body of literature available out there to all of us. Just about anything worth reading on aroids can be read on the IAS website or acquired through the International Aroid Society. Every one of you should own copies of Dr. Croat's journals on Anthurium and Philodendron species as well as his journal on Central American Philodendron. These are quite inexpensive and I guarantee I read something in one or more of those every day. Another text which is incredible is Simon Mayo, J. Bogner and Pete Boyce's The Genera of Araceae. That one is costly but worth every penny. And if you don't have Deni Bown's book Aroids, Plants of the Arum Family, order it today! I rhink the price is only around $20. I'm virtually certain Tricia Frank can provide any of these to you through IAS. Tricia, if you read this will you post a note and let everyone know what texts you have in stock?

You don't have to be an IAS member to buy them, but you should join if you are still on the fringes!

To all of you who have sent private messages, and there were a bunch, if you feel your material will continue this discussion and perhaps spur more research, please post those here! We mentioned earlier Julius' article on the pollination of aroids and that is almost complete. I have been doing an edit for Julius and once he approves the final version I will post it on my website. I'll post the link here at that time. If you have even considered attempting to hand pollinate an aroid you need to read this! Julius is brilliant and his facts very easy to understand! He explains about both bisexual and unisexual inflorescences and offers tips on how to do pollination when the necessary beetle is still thousands of miles away in a rain forest! Sorry, no inside secrets, just science fact.

Thanks again to all of you and keep the information coming!

Steve Lucas

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