What is the optimal wavelength of light for growing plants (cacti indoors in a northern illinois climate)?

Benoit SCHOEFS schoefs at jcu.cz
Tue Oct 14 08:21:32 EST 1997

I do not know anything about how to grow cactus but I know plant pigment 
and I am not at all agree with the last sentences about sensibility of 
plants to green light. That completely wrong. If plants are green that 
because they are not absorbing green light efficiently. They are most 
absorbing blue and red lights.

Dr B. Schoefs
Biomembranes Lab
University of South Bohemia
Branisovska 31
370 05 Ceske Budejovice
Czech Republic

schoefs at jcu.cz

On 14 Oct 1997, Stan Goodman wrote:

> In message <pspopeXSPM-1310971949310001 at> -
> pspopeXSPM at shopchicago.com (Scott) writes:
> I am trying to accelerate the growth of my baby cacti by increasing their
> light exposure with fluorescent lamps.  I am wondering what would the
> optimal wavelength for promoting growth (i.e. photosynthesis).   My
> question, in part, stems from interest in growth lamps. 
> I have seen inexpensive (<$10) incandescent "plant lamps".  However,
> fluorescent lamps produce 4x visible light than their incandescent
> counterparts.  BTW, I don't want to use fluorescent plant lamps because I
> do not want to use special fixtures.  Modern compact fluorescent lamps
> work quite well.
> Pivotal question: 
> Which is better for growing cacti: incandescent plant lamps or compact
> fluorescent lamps?
> Fluorescent lamps are better. The light output of incandescent lamps is what
> is called "black-body radiation"; at the temperatures of incandescent lamps,
> this sort of spectrum will be heavy in red, infra-red, and longer wavelengths.
> The spectrum of the fluorescent powders with which the inside of fluorescent
> lamps is coated are more sclosely matched to the visible spectrum: this only
> one reason why fluorescent lamps give more light, watt for watt than
> incandescent lamps, and why they run cooler and consequently last longer.
> Plants, for the most part, are uninterested in red and infra-red radiation.
> They do their photosynthesis thing with the light from the sun; in order to do
> this most efficiently, they are most responsive to light at the wavelengths of
> the peak output from the sun, namely the middle of the visible spectrum, i.e.
> green -- not coincidently the color of peak visual acuity of the human (among
> others) eye, which is as efficient as it is because it, like plants, is at its
> best for the wavelengths most available in sunlight. The same evolutionary
> pressure has made eyes and plants most sensitive to green light, which is why
> the grass is green.
> %%%%%%%%%%%%%%%%%
> % Stan Goodman  %
> % Qiryat Tiv'on %
> % ISRAEL        %  
> %%%%%%%%%%%%%%%%%  

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