PL-11 Tubes

Discussion in 'Lighting' started by bugs, 24 Aug 2009.

  1. bugs

    bugs Member

    Messages:
    365
    Mu Aqua 40 came with a white/blue PL-11watt tube. I'm not overly keen on the blue light and I suspect it's not esp good for plant growth. However... I cannot seem to find anywhere selling alternatives. Anyone know of anywhere?
     
  2. baron von bubba

    baron von bubba Member

    Messages:
    333
    Location:
    stroud, glos
  3. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,953
    Location:
    Chicago, USA
    Well there are two issues here. Not being keen on blue light is the only thing that counts I guess, but the suspicion that blue light is bad for plants is absurd and is strictly mythological. Depending on the plant (and the type of measurement) chlorophyll "a" has Absorption peaks at around 430 nm (violet/blue) and around 660 nm (red). Chlorophyll "b" has Absorption peaks at around 450 nm (blue/green) and 640 nm (yellow/orange). A simplified absorption graph can be seen here: Absorption Spectra of Chlorophyll-a and Chlorophyll-b

    So in fact, blue light is fundamental to photosynthesis. :clap: The arguments are usually centered around whether green light is of any use....

    Cheers,
     
  4. bugs

    bugs Member

    Messages:
    365
    I was thinking that so much blue at the expense of other colours in the spectrum may not be esp good (as opposed to blue being bad). Can you have too much blue - so much so some is wasted? I don't really understand the science so forgive my ignorance. Thanks for the links, Baron.
     
  5. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

    Messages:
    8,953
    Location:
    Chicago, USA
    Well it's not really an issue of being exposed to certain wavelengths at the expense of others. No two plants in the same tank, or perhaps even no two leaves get exactly the same spectrum of light. The same can be said of plants in natural systems. The very quick growing tallest plants muscle out the slower plants and have access to the available energy and spectrum, i.e. whatever is being supplied. The medium speed plants receive filtered light, or the leftover spectrum. The slowest growers or bottom leaves get shaded light which is high in green/yellow content. In each case the plant customizes the various pigments to make use of whatever spectra and energy levels are available.

    This same pigment customization and reallocation occurs when you change the bulb type. So in other words, if you subject the tank to a lot of blue/violet the plant will optimize its usage of blue/violet. If you then decide that you prefer more red or orange light, the plant will develop other pigment types that are able to either convert red/orange light to another color to pass the energy on to the blue/violet loving pigment or will develop specific pigments that make direct use of red/orange. These other pigments are called Auxiliary Pigments.

    Pigments have two abilities; they absorb certain colors and they fluoresce other colors. The fluorescence has multiple functions. One function is to dissipate excessive light energy such as some UV and the other function is to convert one color to another. This is how plants are so incredibly adept at making use of whatever spectrum of light is available, and this explains why they can grow so well in hydroponic gardens and with the poor spectral quality of the bulbs we use. They really don't "need" full broad spectrum sunlight specifically. That's because they have had to adapt to variable lighting scenarios, whether in bright open savannas or in the muted light under a rain forest canopy. Obviously some plants are more adapted to certain spectral environments, but in general, our plants have an army of pigment types at their disposal, each pigment specialized to certain colors which enable them to make use of whatever colors we provide.

    This is why you should only think about what looks good to you because the plants will sort it all out automatically. If blue looks too dim or eerie to you then balance the "look" with some red or orange bulbs. Just play with different colors until you find something that agrees with your particular sense of aesthetics because whatever you choose the plants will adapt to with very little drama.

    Cheers,
     
  6. bugs

    bugs Member

    Messages:
    365
    Thank you for such a comprehensive explanation - makes a lot of sense. Since my original post I've installed a £1.73 PL from my local electrical distributor. It was a little yellow to start off with but seems to have cleaned up to what I hope will be pleasing once the tank has substrate, plants, etc.
     

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