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artificial light foliage effects or virus ?

This is a discussion on artificial light foliage effects or virus ? within the General Orchid Culture forums, part of the Orchid Culture category; ...

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  1. #1
    sunset's Avatar
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    Default artificial light foliage effects or virus ?

    Hi

    I would like you to have a look at the following photographs.

    The blc had perfect green foliage before its culture under artificial light.

    Under an intense artificial light (fluorescent), its foliage developed purple spots (photograph 1 – 2005 November).
    Then, after November, I gave blc less light intensity and the spots are completely disappeared and foliage is beautiful (photograph 2 – January 28 - 2006).

    In short, these spots are reversible and depend on light.

    What can we think about that? I also thought it was virus spots but why is it reversible?.

    Thanks, Philippe
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  2. #2
    bench72's Avatar
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    Philippe... I find that with phalaenopsis as well, they will develop a purplish hue to the leaves when they are getting more light than necessary...

    I didn't realise that the colour change was reversible though...

    good info... thanks... means we don't have to worry too much about it.

    cheers
    tim

  3. #3
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    Interesting...I also find the reversible nature weird. I would have said sunburn - I have a mini-cat with not dissimilar spots (but brown streaks, not purple), but in lower light (all natural), it hasn't reversed.

    Julie

  4. #4
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    a lot of catts and phals will develop that purple coloration from anthocyanin pigments (which, I'm told, protect the plants from excess UV light). drop them into lower light, and the pigment fades. sunburn may start out looking similar, but the cells actually die and form those brown/black areas.

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    Wow - very interesting, Jason. Thanks!

    Julie

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    Well, Philippe, your plants look fine to me. The dark areas appear to be responses to intense light. My catts do this a lot and I think they like it!
    Cheers. Hoa.

  7. #7
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    Quote Originally Posted by Hoa Tony Nguyen
    Well, Philippe, your plants look fine to me. The dark areas appear to be responses to intense light. My catts do this a lot and I think they like it!
    Cheers. Hoa.
    Really - I have a couple that have started the purple thing when I got home, so I moved them to a place where they are further from the light source.... perhaps I should put them back???

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    What Jason said make sense!
    Anthocyanin compounds are what give flowers their colors ranging from red, purple, "blue", etc.. So when an orchid develops these purplish spots, that means the biosynthesis of these antioxidants increases, i.e. these compounds are overexpressed under these conditions. With the extra doses of these color pigments, certainly, we will get more vibrant blooms with deeper and more intense color! And the plants are healthier since they get more light!
    I see this a lot in catts having purple/pink/lavender blooms and the darker they turn, the better the blooms will be! I have never seen this in blue catts. (That also makes sense since the coerulea color comes from a different group of pigments and this one is strongly dependent on internal pH (vacuoles) of the cells.)
    So no need to panic or anything. Just as long as you don't burn the leaves, which I do now and then with my catts! (This year, three of them got burned since I forgot to provide more cover or lower the plants so they don't get exposed too much. I wish I did not do that but it happened! But at least they got panic and just set buds!)
    Cheers. Hoa.

  9. #9
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    thank you for your help !

    Now i beleave that it is not a virus

    Florewing is begening today. Flowers seem to be smaller under artificial light than natural one. I will show you a photograph later

    Philippe

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