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Re: Red light, green light

On Jul 23, George Booth wrote:

> So, any comments?  I mean about green wavelengths being useful to
> plants with red leaves, not about my ponderous prose.

and Louis Lin subsequently replied:

>Given the high green value reflected.  If these red plants uses green light,
>they are using it in a very inefficient way.  My wild guess is the natural
>habitat of these plants are brightly lighted but limited in some essential
>nutrient (CO2 or N, perhaps?).  The plants simply cannot utilize all the
>light available and evolved to only take the blue light.  This hypothesis
>seems to agree with the observation that red plants do better under very
>strong light in aquarium.
>This is of course utterly unscientific.

Continuing in this utterly unscientific vein, is it possible that we 
could view different parts of the light spectrum in a manner analagous to 
different nutrients?

I think we all accept the following facts:
- the light levels we supply artificially are nowhere near as intense as 
natural light;
- different artificial light sources (eg metal halide vs fluoros) vary in 
intensity and spectra;
- different bulbs of the same sort vary in intensity and spectra.

Now, if certain plants utilise a particular bandwidth inefficiently, 
perhaps the benefit they receive from that bandwidth is proportional to 
its intensity. If so, then a light source that accurately duplicated 
natural daylight's spectra would need to deliver a certain minimum 
intensity to be really effective. If it fell short of that intensity, as 
our artificial light sources do, it might still meet all bandwidth 
requirements except, say, green bandwidths and increasing the lamp's 
output in that area while maintaining the same overall intensity might be 

If this sort of reasoning is correct, it might explain one aspect of why 
different aquarists are happy with different bulbs - the bulb they use 
might have an emmission spectrum which provides enough light at each of 
the bandwidths that the plants they keep grow well in the nutrient 
conditions they maintain.

Of course, aquarists don't go around swapping lights all that frequently 
in a search for the perfect bulb because of expense and other reasons. 
They do, however, change their plant species whenever they throw out what 
doesn't grow in their tank and try something else.

Perhaps part of being a successful aquatic plant grower is finding the 
plants that work with the bulb you happen to choose.

David Aiken