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Thread: UV light

  1. #1 UV light 
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    Hi, I had a discussion with a friend of mine wether or not UV-light was good for plants. I told him 'no' because I thought plants have certain mechanisms to protect them from UV-light, such as wax-layers. He thought plants needed the UV-light for fotosynthesis. Anyway, the things I was wondering :
    -Is UV necessary for plants (and what about other organisms)?
    -Is UVlight harmful for all organisms?
    -What is the effect of a greenhouse?( because I thought the glass kept UVlight out thus protecting the plants, let IR in so it was nice and warm inside...but my friend told me glass doesn't block UVlight, though I don't believe him there).
    Anyway, if there's anyone who could prove me right, I'd be very much obliged

    Thanks


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  3. #2  
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    Glass does block UV light definitely although you can get quartz glass which doesnt if you want.

    Wax layers are more for retaining water than keeping out UV although itmay have an effect.
    Lights definitely dont need uv light for photosynthesis, although perhaps they can use it
    Im no certain but I think it is damaging to plants Im only saying that because of how big a fuss climatologists were about ozone layer depletion destroying crops (so UV mus be harmful by that logic)


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  4. #3  
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    You're right about the photosynthesis. Only light from the visible spectrum is used for photosynthesis.

    http://www.botany.uwc.ac.za/ecotree/...rum.htm#middle

    As nearly as I can tell you are partly right about the glass, but it does let in some UVA (400–320 nm). "Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm." UVB is used to produce vitamin D in the skin.

    http://en.wikipedia.org/wiki/Ultraviolet
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  5. #4  
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    It's correct to say that plants don't use UV light for photosynthesis but many of them use it in a very important way - for reproduction.

    Pollinating insects see UV and use it to locate the flowers for nectar and pollen and pollinate the blossom as a result of their visit.

    But if you're speaking of plants in a greenhouse and are hand pollinating or not pollinating at all, then you don't need to supply it.
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  6. #5  
    Forum Cosmic Wizard paralith's Avatar
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    UV light is harmful for organisms because it can damage or mutate DNA. That's the major reason why you want to wear sunblock at the beach - not doing so can increase your risk of skin cancer, as all the cells in your skin will be exposed to UV light for a relatively long period of time. (and besides, sunburns are no fun either!) However, most organisms have molecular mechanisms to discover and take care of UV light mutations in their DNA.

    However, even excess visible light can be bad for a plant. Too much high intensity light can even damage its chloroplasts. Because of this some plants in environments with intense light use pigments other than chlorophyll that can better stand up to the intensity; other plants will keep their leaves thin and at a steep angle to the sun so that they get enough light, but not too much.
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  7. #6  
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    And what about reptiles or lizards? Do they benefit from UV light? Aren't you suposed to install a UVa and UVb light in the terrarium when you have one ... ?
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  8. #7  
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    well, too much UV light is usually bad, or at the very least increasing the odds of getting cancer, but we do need a certain amount. UVB light is required in order to make Vitamin D. This is why darker skinned people often get rickets when they live in higher latitudes (where the sunlight is less intense than it is near the equator) - their bodies can't make as much vitamin D as they need because the melanin in their skin is blocking the UV light.

    And as Old Geezer said, some insects, birds, and reptiles (such as lizards) can see into the ultraviolet spectrum.
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