Far-red light box
"KONING,ROSS E. Biology
KONING at easternct.edu
Fri Aug 18 08:25:33 EST 2000
I do this lab every semester...
A few years ago I inquired of a leading electronics guy
about using FR diodes rather than lamps for this project.
They were not available then, but ARE available now.
Last I knew, though, they were VERY expensive (I guess
a custom-production deal). Perhaps now that has changed...
I had hoped that this person and I could design an easy
and inexpensive circuit involving a high-output diode or
diode array that teachers could build and use. I was
hoping to put a How-To article on that in the ABT. If I
get some time, I'll look into that possibility again.
I am using the filters formerly (but I fear no longer) sold by
Carolina Biological. I built wood frames to hold them and
six standard-sized (10 cm) disposable Petri dishes fit inside
each box. For my red treatment I use a fluorescent lamp
as you do...mine are two 40-watt tubes at a distance of
about 40 cm above the dishes in the box. For my far-red
treatment I use a 40-watt incandescent bulb in a goose-
neck lamp also about 40 cm above the dishes in the
box. I have not had heat problems, and I have the students
put the foil-wrapped control dish UNDER the far-red dish inside
the box to provide for suitable temperature in the control.
BTW: it is critical to have the control dish wrapped up within
10 seconds of the seeds hitting the moisture...any longer
than that and the embryos start "perceiving" the room light
and the germination percentage in the dark controls will
Also: I use continuous illumination rather than bursts of
a few seconds or whatever. We count lettuce seed germination
after two or three days (destructive sampling method), then
move all treatments to white light for four days or so and
add to our counts any newly germinated seeds. This
further treatment gives us something interesting to talk
about in terms of what treatments do or do not do...inhibition
vs "death" and so on.
Species: we use cultivar 'Salad Bowl' from Agway (a local
chain of farm-stores) and these have given about 30%
germination in dark, 90% in red or white, 0% in far-red...
the re-exposure brings dark-treated up to 90% but brings
the far-red-treated only up to about 70%.
I'd be interested in knowing if anyone has found a species
that is dark-stimulated or FR-stimulated...I have tried a few
that seed catalogs list as needing a "dark" treatment, but
without anything measurable to report. Peas seem to be
delayed by light, but still germinate in light.
Ross Koning | koning at easternct.edu
Biology Department | http://koning.ecsu.ctstateu.edu/
Eastern CT State University | phone: 860-465-5327
Willimantic, CT 06226 USA | fax: 860-465-4479
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> From: nartus at wcupa.edu
> Sent: Wednesday, August 16, 2000 3:33 PM
> To: plant-ed at hgmp.mrc.ac.uk
> Subject: Far-red light box
> I am designing red and far-red light boxes for use in the classical
> phytochrome experiments. The red box is straight forward since it uses a
> fluorescent bulb and won't require cooling. I am having a harder time
> the far-red box that requires incadescent bulbs. I am interested in
> about the designs of far-red set-ups that have worked for you.
> Nancy Artus
> Department of Biology
> West Chester University
> West Chester, PA 19383-2130
> (610) 436-3546
> nartus at wcupa.edu
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