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Re: Seeds Under Lights Versus Greenhouse

I've read with interest the stuff on lights. We do a lot of research here
on plant responses to light (especially phytochrome, flowering and
development), and perhaps I can offer some advice.
We grow in glasshouses, phytotron chambers, controlled environment cabinets
and outside. In terms of seed germination, I would say temperature is the
more important factor- ie keep 'em warm and they will germinate faster.
After germination, light becomes important. There are 2 parts to this-
light intensity and light spectrum.

The light source (spectrum) is very important. Plant responses are
controlled by the red-far red end of the light spectrum (this is the
phytochrome bit).  They also respond at very low light levels, but you need
the right spectrum, ie the red end. You don't need anything fancy, ordinary
incandescent bulbs will do the job. Flourescent tubes will not. So if you
are looking at extending photoperiod, all you need are a few incandescent
bulbs, nothing fancy.

Light intensity is the other part. Artificial lights are nowhere near as
bright as the sun. Most of our cabinets have intensities about 1/10 of
sunlight, but this is enough for most things. If you are looking at
replacing sunlight, you need a lot of fluorescent tubes or high intensity
lamps. You don't need fancy light types (eg Gro-Lux), you need lots of
light. The other part of this is you need light of the right spectrum. We
use a mix of incandescent and ordinary fluorescent because it's cheap and
gives the right mix for good growth.

Hope this adds to the debate, if you want more specific details, (or just
think I'm talking crap) let me know.

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Ian Cummings                             fax: 61 3 62 262698
Plant Science Department                 phone: 61 3 62 262648
University of Tasmania                   email: Ian.Cummings@plant.utas.edu.au
G.P.O. Box 252-55
Hobart, Tasmania
AUSTRALIA 7001
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