X-Message-Number: 29903
Date: Wed, 10 Oct 2007 22:08:02 -0700 (PDT)
From: 
Subject: Fully reversible cryopreservation of...

Cryo Letters. 2006 May-Jun;27(3):169-78.
New determinants for tolerance of coffee (Coffea arabica L.) seeds to
liquid nitrogen exposure.
    Dussert S, Engelmann F. IRD, UR 141, 911 Av. d'Agropolis, BP 64501,
F-34394 Montpellier, France.
    The present work establishes for the first time that tolerance of
coffee seeds to liquid nitrogen (LN) exposure depends on the initial
quality of the seedlot and on the rewarming regime employed. Seedlot
quality was estimated by the parameters of a quantal response model of
desiccation sensitivity developed previously. The percentage of seedlings
recovered from cryopreserved seeds was very well correlated with the
relative humidity (RH) at which 90 percent of the initial viability was
retained, RH90, as estimated by the model. Whatever the cooling regime
employed, rewarming the seeds slowly by exposing them to ambient air was
highly detrimental. Slow rewarming-induced viability loss was not due to
imbibitional damage since seeds pre-heated at 37 degree C after slow
rewarming to 0 degree C exhibited a survival percentage lower than seeds
thawed rapidly to 0 degree C before sowing. The optimal hydration status
for coffee seed cryopreservation was also re-examined. Drying seeds in 81
percent RH provided survival percentages considerably higher than those
obtained using the drying RH always employed until now, i.e. 78
percent. A new procedure for slowly precooling the seeds prior to
immersion in LN was also established. It consisted of placing the vials
containing the seeds in a dry ice-bath for 25 min. Using this procedure
in combination with seed drying in 81 percent RH and rapid rewarming in a
37 degree C water-bath for 30 min ensured the highest survival percentages
ever obtained with coffee seeds, i.e. 89 percent, a value which was not
significantly different from the initial viability percentage.
PMID: 16892165

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