jjc4 at PO.CWRU.EDU
jjc4 at PO.CWRU.EDU
Mon Apr 17 14:09:19 EST 1995
Some of you may remember that about 3 weeks ago I posted
a question about the correct usage of vernalization,
cold-treatment, and stratification. I want to thank all
the kind folks who sent me answers. I'd like to post all
of them, but for those of you who want a quick answer
that would waste your time. I think that the best, most
concise, and elegant answer came from Jan Zeevaart-- and
I will post her letter here-- since it pretty much sums
up all the other answers:
In answer to your question concerning the correct usage of the
terms vernalization and stratification the following:
Vernalization. A good definition can be found in P. Chouard, Annu.
Rev. Plant Physiol. 11, 191-238 (1960): "The acquisition or
acceleration of the ability to flower by a chilling treatment".
Thus, vernalization refers to promotion of flower formation by a
period of low temperatures. The flowering response is usually
observed at subsequent higher temperatures. Thus, the effect of low
temperature on flowering in cold-requiring plants is inductive.
Vernum = spring. The term vernalization was coined to indicate that
cold-treated winter cereals (sprouted seeds kept at 0-5C for 6
weeks) will flower when sown in spring, like spring varieties that
do not require a cold treatment for flowering.
Stratification is the breaking of seed dormancy by exposure of
moist seeds to low temperature.
Stratum = layer. Nurserymen used to place layers of rosaceous seeds
(such as apple, peach, etc.) between layers of sand to expose them
to the cold of winter. Hence the term stratification.
Dry seeds do not respond to a cold treatment, although storage at
low temperature and low humidity greatly increases their longevity.
In the case of stratification, seeds must be moist. Cold treatment
to induce flowering (vernalization) is only effective in germinated
seeds, or in plants in case there is a juvenile phase for response
to low temperature.
I hope this clarifies the terminology.
The upshot is that most of us use the term "vernalization"
incorrectly when we are actually mean simple, overnight
cold treatment/imbibition. We should probably just call
it "cold-treatment" and not vernalization when our goal
is to increase germination frequencies. It is clear in the
flowering literature what people mean by vernalization, but
it only confuses the Arabinauts at large to use the term
in other circumstances. It's just something to think about.
Thanks once again for the replies.
Case Western Reserve University
Dept. of Biology
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