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lettuce seed germination

Ross Koning koning at ECSUC.CTSTATEU.EDU
Tue Feb 3 12:04:23 EST 1998

At 11:04 AM -0500 2/3/98, Grant R. Cramer wrote:
>>At 6:46 PM -0500 2/2/98, wise at vaxa.cis.uwosh.edu wrote:
>>>Dear Plant Edders,
>>>        I am hoping to do the classic lettuce seed germination experiment
>>>in plant phys lab next week.  The standard procedure is to use the Grand
>>>Rapids variety.  However, all I can get locally and quickly are Romaine a=
>>>Summertime.  Does anyone know if these latter two varieties will work?
>>The best way is to try them...In my hands the lettuce
>>germinates in red/white light within two days time.
>>Under continuous far-red they fail to germinate above
>>4% and in darkness the results vary among seed batches
>>in my experience.
>>I routinely use 'Salad Bowl' because it is cheap and
>>abundant at our local AGWAY.  I can get several ounces
>>of the same seed lot.
>>I guess my point is that if you simply test one packet
>>(note the seed lot printed on the envelope), you can then
>>buy the bulk you need of the lot you have available that
>>I have had 'Grand Rapids' that was great...I have had
>>lots that were miserable (98% germination in the dark!).
>I believe most of today's lettuce varieties will germinate in the dark.

I'm sorry that I failed to mention that
the lots of 'Salad Bowl' I have bought routinely
from Agway germinate at about 30% in darkness.
This has been true of seed lots over the past
ten years.

This is quite good considering that the Pfr and Pr
ratio in the batch could be just about anything
prior to your first exposure in vitro.

I believe expecting 0% germination in darkness
without a pre-treatment is indeed unjustified.

I'd bet, though I have not needed to actually test
this, that the dark germination could be brought
to 0% by a brief FR exposure after imbibition.
Such a pre-treatment would allow you to demonstrate
the effects of subsequent exposures to R and FR light
sequences with a 0% control.  Frankly I've never been
interested in 0% germination in the dark.  I think
the story is told best when the FR exposure results in
the 0% germination.  In my hands this is how it has
worked for a decade using 'Salad Bowl':

white 85-90%
red 90-95%
darkness 20-35%
far-red 0-4%


Ross Koning                 | koning at ecsu.ctstateu.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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