Thank you for the wonderful response (I had over 10). This is a summary
and conclusion of the response plus my investigation of most of the
To start with I must clarify my objectives a little better than I did in
my first message. I am a physiologist interested in characterizing growth
responses to different environmental stresses. Since Arabidopsis is so
small I was looking for conditions that would optimize growth conditions
to produce the greatest amount of leaf biomass for analyses. (I think
there might be a few people out there who might also be interested in
this). I have found that growing plants hydroponically is by far the best
way to get big plants (no root restriction, well-watered all the time,
ample nutrient supply).
We are also interested in delaying flowering to get larger plants. We are
using both the Columbia and Ler ecotypes (hence my interest in
photoperiod). Shorter days delay flowering in our two ecotypes and
produce much larger plants before flowering. The longer the day the
earlier the plant will flower. The question is what is the optimum
daylength that will delay flowering and provide optimum light to produce
big plants. We have been using 8 h daylengths. Another person here was
using 10 h. So we started to explore what might be the optimum. Now for
the summary and conclusions.
First of all, there are many references regarding photoperiod effects.
Most just choose arbitrary daylengths without reference or justification.
I could not find any hard data on critical daylengths. However there are
some references to it.
It is mentioned in a review by Klaus Napp-Zinn, 1985, Arabidopsis
thaliana. In CRC Handbook of Flowering, Vol 1, pp 492-503.
There was also very useful information on the Columbia ecotype in a brief
note by A. Corcos, Vol 18, of the Arabidopsis Information Service. It is
reported that 8 h is required for bud formation, but indicates that
daylengths below 5 h may restrict growth. This is the only report that I
have found that looked at a number of different short daylengths.
However, no data are presented.
Two other potentially useful references were either in journals we do not
have easy access to or are in a foreign language. They are:
Gregory F.G. and Hussey G.G. 1953. Photoperiodic responses of A.thaliana.
Proc. Linn. Soc. London 164, 137
Laibach, F. 1951. Uber sommer- und winterannuelle Rassen von Arabidopsis
thaliana (L) Heynh. Ein beitrag zur atiolgoie der blutenbildung. Bietr.
Biol. Pflanzen. 28:173
If you have access to these or can make comments about these, it would be
Also, if you have comments about optimum conditions, please do so. We are
probably going with 23 C temperatures and 8 h daylength.
Thanks in advance,