Trivial hypothetical - an research on turning lights on and off

albert_135(Sunset 2 or 3)February 6, 2008

Pardon me but this trivial hypothetical came to mind.

The question came to me thinking of an EEG machine in a neurology lab that had rapidly flashing lights.

Someone somewhere at some time must have researched how plants react to turning lights off and on rapidly?

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Absolutely! And you may be surprised at the results, especially the implications for growing under artificial lighing. I recently attempted to follow-up on this research, which I had read about nearly two years, but I did not figure out the right keywords to search by. I will try again, though. But first you need the background info:

Photosynthesis, which obviously occurs under light, actually consists of 2 stages: 1) The Krebs cycle, or Light cycle, which involves absorbing a photon, and 2) The Calvin cycle, or Dark cycle, which involves using an enzyme to process the result of that photon absorption. This is NOT ot be confused with the Light Period (daytime) and Dark Period (nightime). The Krebs/Calvin cycles occur continuously back-to-back during photosynthesis.

While I cannot describe the physical setup they used, what they did was to flash the plants with a 25%-75%, light/dark duty cycle, which was repeated in one second or less. They did do variations on pulse rate and duty cycle to determine optimal timings.

They found that, apparently, each chlorophyll is only using a photon for 25% of the Krebs/Calvin photosynthesis cycle, and is processing the energy for the other 75% of the time. They were able to grow several varieties of plants this way, and the resulting growth was exactly the same as the control group, which received constant radiation during the light period. The chlorophylls inadvertenly began acting in sync with one another - each was ready to receive another photon following cycle completion, all in unison.

The result of the this experiment suggests a very promising potential for reducing the enrgy required to grow crops. This hints at a system whereby the a plant light source could be redirected every 1/4 second (or whatever time length is determined optimal) to 4 separate sets of plants, since 75% of the photsynthesis event does not require a photon. This would reduce the light energy needed to only 1/4 of normal. In extreme living environments which might require a biosphere to generate sustenance, this will be an extermely useful technique to conserve energy.


    Bookmark   February 6, 2008 at 2:06PM
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A Follow Up:
As I recall, it was noticed that the plants also seemed very unstressed by this 25/75 duty cycle pulsing technique. The researchers discussed the fact that the function of some of the pigments which plants have evolved, is to protect the plant from excess radiation. This may be the radiation that cannot be used by the chlorophyll during the Krebs cycle. There are also some pigment(s) which have evolved to protect plants from UV. So, in this experiment, not only were the plants given only the light they could actually use, they did not need to deal with any unwanted radiation.

In this forum, you will often see people pointing to the total absorption spectrum which has been determined from research. They fail to distinguish that some of the absorption occurring is a protective process. The totally-in-error conclusion is that the plant NEEDS a good dose of all of these wavelengths. So they say things like "You need UV, or why would the plant absorb it?". The answer: NOT! No UV! Give your plant a reprieve!

An analogy would be this: What if you were collected by an alien zoo and they tried to determine your requirements. They see you have melatonin to absorb UV, so they think UV must be good for humans, so pour it on! A few months later they would be researching your skin cancer cells, and why you went blind. (although humans do need a bit of low energy UV to synthesize vitamin D).

So remember, not all of the absorption occurring involves sustenance, some involves protection. Get clued in! There is so much good information available on the net from university agricultural programs and other agricultural research sites. You can learn to use Google and keywords to find really great information. It is out there.


    Bookmark   February 6, 2008 at 2:55PM
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In the "alien zoo skin" reference above, I meant MELANIN! Not melatonin!

Melatonin is the hormone that our pineal gland produces to help regulate our circadian rhythms. I knew that. Really. I swear to you. I did. Bummer.

On the side, research done over a year ago determined that the 3mg doses that melatonin is usually sold in is agout 10 times too much and floods the regulatory system it is supposed to influence. So 0.3mg is the optimal dose. At least your 1 month supply will now last 10 months.


    Bookmark   February 6, 2008 at 7:17PM
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sinfonian(U8b A2 S5 SeaWA)

How about the energy it took to move the light to four different plants every second, or four different lights turning off and on every second (or one turning off and on four times a second). I'm not sure if turning on a light takes more energy than leaving it on (like a computer), but it still doesn't seem very energy efficient. I'm no scientist like Zink is, but since we're talking hypotheticals.

    Bookmark   February 12, 2008 at 1:33AM
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I recall they had several solutions for that. A rotating mirror was one. A space colony or biosphere garden would use a single light source, rotating mirrors, and a light pipe to carry the light to the plant sites.


    Bookmark   February 12, 2008 at 10:35AM
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