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Chris, it appears possible you may have opened a new door in understanding more of the pollination of Philodendron species. Whether you have simply made an observation or a discovery is yet to be determined and I am certainly not qualified to comment. I am now receiving a stream of mail from researchers and skilled aroid experts who find your observations of interest.
The one thing that would have been of greatest benefit would have been that you had a better understanding of what you were observing at the time you took your measurements. By understanding what was happening you would have been better able to more accurately record information at the critical phases during anthesis.
Now, let me state I am not an expert in this field. I just study it a great deal and spend a lot of time discussing information with people who are experts. Don't take everything I write here as science fact, just take it as a basis for your own studies. Since you are apparently relatively close to the Royal Botanic Garden Kew in London I would strongly recommend you attempt to seek an appointment with Dr. Simon Mayo who is one of the world's top aroid botanists and experts in Philodendron species, especially those from Brazil. Your specimen of Philodendron bippidifidum is a Brazilizian Philodendron species. Simon is one of the authors of a scientific text entitled The Genera of Araceae. That text is quite costly, around $180 per copy U.S., but if you are interested in persuing this endeavor you will learn a great deal about pollination within that text written by Simon, J. Bogner and Pete Boyce. It is the single most comprehensive such text available. In addition, secure a copy of Deni Bown's text,
Aroids, Plants of the Arum Family. This book is relatively inexpensive and available from Amazon.com. Deni's book is jam packed with aroid information with more than a single discussion of the processes you observed.
I have several follow ups which I will be posting but for now I'd like to give you some "food for thought" regarding what you observed.
Aroids are pollinated by insect species, often very specific "assigned" species. The vast majority of Philodendron are often visited by the male of a beetle species found within the genus Neelia, although these beetles do not appear to feed nor mate on the inflorescence. It appears only larger beetles actually do the work of pollination. The pollinators appear to be members of subfamily Dynastinae in the family Scarabaeidae. Many belong to the genus Cyclocephala and have been recorded as pollinators of Philodendron and other aroid genera. Some of these beetles are not particularly species specific and visit more than a single Philodendron species, however it is surmised the height of the plant may be a particular attractant to individual beetles thus causing them not to cross pollinate other Philodendron. Those beetles are generally drawn to the Philodendron inflorescence in the late day or at dusk and are apparently attracted by a combination of pheromones (scent) and a source of food and shelter whi
ch is composed at least in part of an oil produced on the staminate flowers containing lipids along with the enclosure of the spathe. Shelter may play a part since the male often brings along his mate in order to breed at the same time.
Some Philodendron species have sweet smelling pheromones while others show no noticeable aroma. The one you observed, Philodendron bipennidifidum, appears to have been attractively scented. This aroma is produced by the sterile male flowers on the inflorescence which are attempting to entice a pollinator, and to the male of that insect species that scent may be similar to the same pheromone that attracts him to a mate when she is ready to be impregnated. This point is not factually certain within Philodendron. Anthesis is composed of two primary stages, female anthesis at which time the pollinator is attracted and male anthesis during which time pollen is produced to be carried to another plant. Some species are capable of self pollination, but not all. And as you will read later, a very unusual but common chemical source may also help to prevent self pollination.
During anthesis (both female and male) the open spathe of the Philodendron provides space for protection and often entices these beetles to use that area for feeding along with a place to safely copulate. The plant provides a source of nutrient rich lipids which is an excellent food source for the beetles, but the plant also benefits. It is not uncommon for the beetles to spend the night within the spathe and spadix of the host Philodendron and they frequently mate during this period. So why do they spend the night? Thermogenisis! Quite simply, the spadix can warm enough to be noticeable to the touch and for the insects that may be tired from traveling long distances to perform their required tasks this additional source of heat in the rain forest creates a microclimate and may actually increase their metabolism and encourage them to explore all portions of the spathe and spadix. Quite simply, a microclimatic zone of warmth is now being generated within the spathe that offers both comfort and protecti
on along with food. This feature alone may increase the chance of self pollination within the specimen, but another may inhibit the same.
The thermogenesis produced by the plant during anthesis, which is simply a natural heat produced by many living beings, appears to stimulate the beetles into this period of copulation. Of major interest, even though the effects of thermogenesis have been observed for over 200 years, not until relatively recently did anyone know the cause. So what is the chemical cause? Salicylic acid, the same compound used to manufacture aspirin! The salicylic acid begins not only the heating process but also the production of the pheromones (scent). This unique process is not limited to Aracea (aroids) but is also found in other plant genera. Read Deni Bown's book for a more complete explanation. Of interest, salicylic acid may also help to prevent self pollination which is an interesting contradiction in and of itself.
The thermogenesis (thermo genesis. "Heat Birth" or heat production) caused by the salicylic acid appears to be one of the stimulators to cause the beetles to be active and as a result to both feed and copulate. It is known the rate of thermogenesis (heat rise) is sometimes dramatic. And that may be what you observed with your IR thermometer. However, thermogenesis does not produce a consistent temperature since the highest temperatures appear to last only 20 to 40 minutes. In fact, it may be the visit of the beetles that contributes to the effect botanists know as thermogenisis.
I'm sure you are now questioning why you didn't see any beetles, and that raises a new group of questions since scientists have known for a long time they don't need to be present for thermogenisis to manifest itself. But the presence of beetles does appear to increase the temperature produced by the event. The temperature increase appears to increase the amount of pheromone being exuded by the tiny flowers, thus the strength of the pollinator attractant. Up to 200 beetles at a single time have been observed on a single inflorescence during anthesis! However, the normal number is closer to 5 to 10. Researchers have noted the highest temperatures appear to occur during the period when the highest number of beetles are present. However, the exact role of thermogenesis is still not well understood and your observations "may" have opened the door for additional research. Right now, no one appears to know if research on infrared heat in relationship to an attractant role is being done.
You just observed both female and male anthesis without fully understanding what you were watching. The first stage is when the female flowers are ready to be pollinated and the production of the attractant pheromone along with thermogenisis begins. Female anthesis in Philodendron can last approximately 2 days. That stage is followed often a day or so later by male anthesis which is the point when pollen is produced. The pollen often appears to be a stringy substance as you observed. The beetles often visit a separate inflorescence in the male stage of anthesis prior to visiting an inflorescence beginning female anthesis and thus collect pollen on their bodies and transfer that pollen from one healthy specimen to another in need of pollination. All of this is within Nature's ingenious design to keep the ecosystem strong and healthy.
Now, here are the questions at hand. Is the infrared heat you observed directly related to thermogenesis or something entirely different? Does the infrared heat have any impact as an attractant on the assigned beetle pollinator? I really cannot offer an opinion although it certainly appears plausible. I asked several interested experts as explained in another post and these interesting responses I received from D. Christopher Rogers, Senior Invertebrate Ecologist/Taxonomist, EcoAnalysts, Inc. stood out, "Infrared thermometer works by detecting radiation in the IR spectrum. IR radiation is emitted by all objects depending on their temperature. IR is a color 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, ther
e is IR color 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 color 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 temperature is to calibrate itself.
So, metabolic reactions will generate heat, which is measurable in the IR spectrum. One of my favorite aroids 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 the deathly perfumes) it seems that the abil
ity would be found residing in other aroids as well."
Christopher then continues responding to the question of the possibility infrared is involved in the process of anthesis as an attractant, "YES!!! Many insects respond to infrared. This is why the moth (and some many other insects) come to the flame (porch light, candle, mercury vapor bug collecting light, et cetera). One paper I remember reading discussed how certain moths produce IR. The female corn ear worm rubs her body building up a static electricity charge through friction. She releases her pheromones in a cloud and then discharges the static charge into the cloud giving an IR flash, attracting mates (and a few predators and parasites!!) towards her. So again, plants could easily be using IR as well as pheromonal tricks to attract pollinators.
Mosquitoes do a similar thing; when I was working for the State Health Department on mosquito borne diseases, I used a CDC trap. This trap is a bucket filled with dry ice (carbon dioxide) over a very small ?wheat grain? light. Female biting mosquitoes follow the CO2 (assuming it to be exhaled breath) to find a good host, but then focus on the IR glow of the tiny light as the exact source, after following the CO2 trail. When they approached the light, they were then sucked into a chamber by a small fan."
So, now that we can establish the fact infrared can act as an attractant we are still left to ponder whether or not it will act as an attractant to the specific beetle species involved with Philodendron. I'm not sure if anyone knows the answer. But here is some conjecture that is being batted around as a result of your post. The current questions are asking if it could be possible if the initial attractant is the pheromone which acts more like a long range invitation and "aims" the beetles toward the plant that is now nearing female anthesis? It is known from the study of orchids that many of these assigned insects can sense a single molecule of the pheromone from up to one mile away. But that leads to a another question. Is it the thermogenesis that is the final attractant attracting the beetle and his mate to a source of food? Or is it possible the infrared heat also severs in addition to the pheromone attractant. In other words, the infrared heat could possibly act as a "neon sign" which is basica
lly blinking "Eat Here, Sleep Here, Have Sex Here"! Is that possible? I just do not know! But you have posed some interesting thought.
Again, I strongly recommend you consider buying and reading the text by Dr. Mayo, J. Bogner and Pete Boyce as well as Deni Bown's text. These three scientists are among the best in the world when it comes to aroid species. Deni is an accomplished writer but the facts posed in her text are well researched. Additional great information can be found in the Annals of the Missouri Botanical Garden 1997, volume 84, #3 by Dr. Thomas B. Croat. Pose your theories to Simon if you can manage an appointment at the Kew. In the meantime, I can assure you there are now some in the United States who have shown interest. Will it prove anything to which you can claim credit? I have no idea. I'm just a writer/photographer who loves to study aroid species.
Just one additional note. The information presented here was gathered from the International Aroid Society website http://www.aroid.org/ as well as from the texts mentioned. Input on this was given by aroid experts Julius Boos and Leland Miyano in addition to the named sources. If you are truly interested in learning more about your aroid specimen I would urge you to consider joining the IAS. You can do so by clicking on the link above. The $20 per year you will spend on membership will come back to you many times in journals and information alone. You will quickly learn many of the members of the International Aroid Society are extremely knowledgeable about the plants they grow and they are quite willing to share information.
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