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Re: Light Intensity vs Spectrum

> Aquatic Plants Digest     Wednesday, July 1 1998     Volume 03 : Number 357

Neil Frank wrote:

>  Also, unfiltered flat spectrum sunlight may not be better. I recently
> collected some Ludwegia palustris in South Carolina. Gorgeous red leaves
> that rivaled my Rotala macrancra at its best. I set up a 55g peat bottom
> tank (with a little soil covered with coarse sand) on my patio. It gets
> eastern exposure, including a few hours of direct sunlight. I haven't yet
> measured the light intensity, but I am betting it is brighter than any of
> my indoor tanks. The results were disappointing!! The plant lost all of its
> nice red color (otherwise, it has been growing nicely for approximately 2
> months outside). I connected a yeast CO2 generator... this increased the
> growth rate and got the plants to pearl... but  no change in color(not
> surprising). The CO2 really made the collected chain swords really take
> off!!(a wide leaf variety of tenellus that I have never prevously seen).
> Last month I brought some Luwegia indoors and got it to regain most of its
> original red brilliance in my 70g with the growlux/triton combination, but
> NOT in the 125g. I am guessing that the peaty water of its native pond
> absorbed much of the blue light and gave it a "natural" light heavily
> weighted towards the reds. It would be great to have research to examine
> the results of pigment production and growth rate as a function of color
> AND intensity. They both need to be considered.  The spectral studies need
> to consider bulbs with both blue, red and far red in different
> combinations. Their effects on plants and on algae (G, BG, red, etc) are
> needed. This may have already been done in Germany or elsewhere in Europe.
> Please provide references, if known, so we can get them translated.

Light is captured by mainly two photosynthetic pigments (with the
exception of
Cyano bacteria and Red Algae)

1. Chlorophyll pigments

     Abosrbs 90% at blue peak, reflects most greens and absorbs 50% at
red peak.
    350-500 and 620-700 nm wavelengths.

2. Carotonoid pigments

    Absorbs 45% at blue peak but also absorbs part green at 50% at peak,
no red.
    350-550 nm wavelengths.

Can we conclude that aquatic plants that turn red, are depending more on
the green
spectrum for photosynthesis (maybe in forest shade/green water
at high light levels turn red to reduce their absortion efficiency ?

Bangalore, South India

Ref: Biology: Exploring life byGil D Brum, Larry K. McKane
Page 123