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green wavelength in plant photosynthesis

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green wavelength in plant photosynthesis

Postby dummy92 » Sat Aug 29, 2009 8:28 am

hi guys, i'm new around here.
I'm doing an experiment of how tomato seedlings of the same type response to different light spectrum. i read on the internet that green light is useless for plants. but what happens to those seedlings which are exposed only to green light. certainly they don't die. because i've done the experiment for 2 weeks and they're still alive. i really need some information on this head to write a bit in my report. will it change the colour of its leaves?
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Postby LostBio » Sat Aug 29, 2009 12:36 pm

Plants that grow under a green light will not died. Actually they grow a bit faster, BUT you will see a significant difference when comparing. The plant should come out weaker in some manner. Maybe the stem will be thinner or leaves might have a have more of a yellowish color in them.

If you compare this plant to your control you should see this with ease.

This should be somewhat of what you should see if you do the experiment right. I hope this helps.
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Re: green wavelength in plant photosynthesis

Postby robsabba » Tue Sep 01, 2009 3:59 pm

dummy92 wrote:hi guys, i'm new around here.
I'm doing an experiment of how tomato seedlings of the same type response to different light spectrum. i read on the internet that green light is useless for plants. but what happens to those seedlings which are exposed only to green light. certainly they don't die. because i've done the experiment for 2 weeks and they're still alive. i really need some information on this head to write a bit in my report. will it change the colour of its leaves?

Blue and Red are the major parts of the spectrum where chlorophyll absorbs light. This doesn't mean that green light isn't used at all, especially by other pigments such as carotenoids. I would expect that they wouldn't grow as fast, and that perhaps the leaves will produce less chlorophyll (less green).
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Postby MrMistery » Sat Sep 05, 2009 5:44 am

@robsabba: carotenoids don't really absorb much green light, look up an absorbtion spectrum if you don't believe me.

@dummy92
The plants will actually grow in green light for a while, and they will probably grow faster. Here's why: when a plant seed originally germinates, it doesn't need light to grow, at it is growing off its stored nutrients in the seed. The plant seed is originally in the ground (dark), so it will grow very fast until it reaches the sunlight so it can start photosynthesis (it needs to get to the light quickly). The plant detects that it has reached the surface by the presence of red light (sunlight has all colors, but the receptors are just adapted to detect red light). By growing a plant in green light, you are basically making it think it is deep down in the ground: the end result is the plant will grow really quickly until it runs out of stored nutrients and dies.

Cheers,
Andrei
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Re:

Postby robsabba » Tue Sep 08, 2009 3:29 pm

MrMistery wrote:@robsabba: carotenoids don't really absorb much green light, look up an absorbtion spectrum if you don't believe me.

@dummy92
The plants will actually grow in green light for a while, and they will probably grow faster. Here's why: when a plant seed originally germinates, it doesn't need light to grow, at it is growing off its stored nutrients in the seed. The plant seed is originally in the ground (dark), so it will grow very fast until it reaches the sunlight so it can start photosynthesis (it needs to get to the light quickly). The plant detects that it has reached the surface by the presence of red light (sunlight has all colors, but the receptors are just adapted to detect red light). By growing a plant in green light, you are basically making it think it is deep down in the ground: the end result is the plant will grow really quickly until it runs out of stored nutrients and dies.

Cheers,
Andrei

I think you are correct about plants under green light growing initially quicker.. I stand corrected on that. I would expect they would grow tall and spindly but also the leaves would turn yellow under green light. Carotenoids do shift the absorbance spectrum toward green, even if much of the green spectrum remains poorly absorbed.
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Re: green wavelength in plant photosynthesis

Postby lrost » Sat Sep 19, 2009 5:35 pm

I have a question related to this stream.
Would plants begin to produce different amounts of carotenoids if exposed to green light, so that they could absorb that more efficiently? If so, how could you detect those? Could chromatography be used to detect any changes compared to a control "white light" group? What about algae?
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Postby JackBean » Sat Sep 19, 2009 6:25 pm

If you kept enough of usable light, probably will be produced more carotenoids, but they will have more protective effect more likely than some use in photosynthesis.

Yes, you can definitelly use some sort of chromatography (basically some PC or TIC) for detection of all the pigments. Isolation into some nonpolar (or partialy polar, like some alcohols) solvent, separate by chromatography and detect by eye or some easy reaction and identify by retention time/volume/distance
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby MrMistery » Sat Sep 26, 2009 3:17 pm

jackbean is right, but I want to stress again: carotenoids don't absorb green light eficiently, they absorb only a very limited amount of the green light (that is why you see plants as green!). and even the few light they do absorb, they are not able to efficiently pass it off to chlorophyll, it is more of a mechanism of protection against photooxydation.
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