The authors of “Seasonal changes of physiological parameters in sweet cherry (Prunus avium L.) buds“ (Scientia Horticulturae 172 (2014) 183–190) used data (biochemical analyses of sweet cherry buds with a temporal resolution of 1 week) to confirm their hypothesis that the date of the first peak (maximum) of the ABA concentration in winter (see their Fig. 2 A) is related with the “release of endodormancy”. Unfortunately, they did not explain sufficiently how they tested if this date really coincide with the “real” release date and how the “real” release date was identified, respectively. I assume that they determined this “real” release date as the first date after that some (or all??? This was not described!) buds of twigs, which were cut at this date, were able to reach the beginning of blossom under controlled conditions in a climate chamber.
Because of the temporal resolution of 1 week, there could be a random difference of some days between the “ABA-date” (peak of ABA) and the “climate chamber date”. Probably this difference will be increased by uncertainties in the determination of the “climate chamber date” and other unpredictabilities. Let us assume that the standard deviation s (of the yearly data, not of the mean values) of this date-difference is about 5 days (5 d), and that the difference is normal distributed with zero mean and that the data of different winters are statistically independent. In this case the 95% “confidence” interval (:=Conf95) for the mean difference is +/- t(0.975, n-1)*s/SQRT(n) (n=number of years; t(0.975, f) = 97.5% t-quantile with f degrees of freedom). For n=2 (the number of years used in the article) we get Conf95 = +/- 12.7 * 5 d/SQRT(2) = +/- 45 d. This means that the year to year deviations of both dates (even of the means over the n years) could be very large and the good coincidence in 2011/2012 and 2012/2013 could have been achieved by poor accident.
Therefore the conclusion that the ABA-peak defines the end of endodormancy is unreasonable. The authors had better waited until spring 2014 to involve a third year in order to decrease the uncertainty [see attached figure; with n=3 the Conf95 reduces to +/- 12.5 d (better but is yet very wide!), provided that s remains as small as 5 days].
For the validation of chilling models also more then two years of data are required. For a successful comparsion of two models, more than 5 (probably 10 and more) years are necessary. See my OpenReview of the present article.
By the way: There are a number of important publications dealing with this group of themes which are NOT mentioned in this article. These articles advocate different or even contrary hypotheses concerning the role of ABA for the release of dormancy. These articles are, e. g.:
Chao WS, Foley ME, Horvath DP, Anderson JV (2007) Signals regulating dormancy in vegetative buds. Int J Plant Dev Biol 1:49–56.
Faust M, Erez A, Rowland LJ, Wang SY, Norman HA (1997) Bud dormancy in perennial fruit trees: physiological basis for dormancy induction, maintenance, and release. HortScience 32:623–629.
Rinne P, Hänninen H, Kaikuranta P, Jalonen JE, Repo T (1997) Freezing exposure releases bud dormancy in Betula pubescens and B. pendula. Plant Cell Environ 20:1199–1204.
Horvath D (2010) Bud dormancy and growth. In: Pua EC, Davey MR (eds) Plant developmental biology—biotechnological perspectives.
Springer, Berlin Heidelberg, pp 53–70.
Article Seasonal changes of physiological parameters in sweet cherry...
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