plant growth in different light spectra

Kieth E Henderson keith.e.henderson1 at
Mon Mar 16 12:30:55 EST 1998

Interesting experiment.  I will give some rather basic information that
might help you.  First of all you are right to assume the blue and red
wavelengths are the ones most essential for photosynthesis.  I do not
belive the violet will contribute much to the plants photosynthetic level.
A second point is that one must condider the intensity of the radiation.
When comparing normal light to red light for example, one most provide the
red light in the same intensity a the red light would occur in the natural
light.  Otherwise, the effects on growth may be only due to the intensity
rather than the color or wavelength.  Finally, I would predict that the
normal light would always provide better growth conditions than any single
wavelength.  If one were to use several spectra (red, blue, orange, etc.)
you should be able to get close.  Using red and blue one may be able to
provide 80-90 percent of the requried photosynthetic active radiation but
not 100 percent.  This is especially true for certain aspects of plant
growth like stem elongation, flower initiation, and other reproductive

Keith H.

Husain Qutbuddin <tahiyyat at> wrote in article
<6e5m1a$7fh at>...
> I am doing an experiment in which I am exposing plants to different =
> spectra of light for a length of time (a few days) and then measuring =
> their length increase in that period of time. Although growth is not a =
> direct effect of photosynthesis it would be expected that the plants =
> will grow more when they are exposed to the violet, blue and red =
> spectra, because the plant pigments absorb these ranges most.

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