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

Jim Metzger metzger.72 at OSU.EDU
Tue Oct 14 06:56:35 EST 1997

I really have to disagree with your suggestion that incandescent and
fluorescent lights are the same.  Unlike fluorescent lamps which produce
virtually no radiation with wavelenghts longer than 700 nm, incandescents
emit most of their radiation in the far-red region.  While this radiation
can not be used for photosynthesis, it does dramatically affect
photomorphogenesis: high proportions of far red (720-740 nm) light induces
stretching, loss of cholophyll, and inhibits leaf growth.  In other words
the plants look sick.  The bottom line is don't use incandescents for plant
growth.  Another point: do not waste your money on special plant growth
fluorescents either.  They do not really provide any benfits and cost about
four times as much as a regular cool white bulb.  

At 11:47 PM 10/13/97 -0400, you wrote:
>Scott, It really does not matter if you use incandescent or
>fluorescent light. What is important, however is the intensity and the
>wavelength of the light. Cacti, and all green plants, are incapable of
>utilizing green light. You want to supply red and violet light. These
>are the wavelengths that are useable by the chlorophyll. Plant lights
>are designed to supply these wavelengths.

Jim Metzger
Department of Horticulture and Crop Science
The Ohio State University
2021 Coffey Road
Columbus OH 43210

Voice:	614-292-3854
FAX:	614-292-7162
E-mail:	metzger.72 at osu.edu

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