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Agricultural Information Technology in Asia and Oceania 1998 161-161
© 1998 by The Asian Federation for Information Technology in Agriculture
- 161 -
Abstract
Peach trees development is yearly subject to many
influences from which temperature, as an exogenous
factor, is of utmost importance during the active growing
season and also in the cold one (rest period).
The study is focused on a main stage in bud
development, by modelling endodormancy release on a
temperature basis; the corresponding chilling
accumulation (in portions), with an hourly basis of time
and hourly temperatures recorded under shelter, are
calculated according to the dynamic model (Erez A,
Svetlana Fishman, Zipora Gat, G. A. Couvillon, 1988).
The principle of the model is that endodormancy is
considered to be broken when a certain amount of
chilling (requirement specific for each variety) has been
accumulated. Detailed researches were already carried
out, in order to approach the subject in different climatic
conditions. The results of the present paper are obtained
by running the model on typical cases, with the values of
parameters given by the authors and also in the different
years in climatic conditions of the extreme South East
part of Romania. An attempt is concerned to modify the
program for these specific temperate cultivation areas, of
South-Eastern Europe. The program was tested in this
cultivation area, with the purpose of more accurate
phenological forecasts for peach trees vegetation
resuming (floral and leaf bud break of Redhaven variety)
aiming a better management of the orchards as against
spring frosts events. Due to the trend of “milder“ of the
winters, to quantify winter chilling conditions represents
a first necessary step in optimizing them (by breeding
methods, etc.). Also it is allowed a possibility of survey
on the potential climate changes impacts on trees - as
perennial indicators, subject of W.M.O. interest.
Key words: trees rest period simulation, dynamic two
steps period model, peach bud breaking, hourly
temperature accumulation, endodormancy release, etc.
*
To whom correspondence should be addressed. Fax.: +40-1-2303143;
E-mail: romana@meteo.inmh.ro
Introduction
The plants development is biologically controlled by
a number of hormones acting on the various
morphological changes which are developing inside the
plant cells. The production of promoting and inhibiting
hormones is a genetic characteristic of each plant species
and variety, their production or destruction being
strongly influenced by the environment.
The predominating influence is by temperature,
which controls the rate of chemical reactions producing
the hormones. The temperature effect on the hormones
production may vary from one genotype to another. High
temperature may destroy certain hormones.
Crop development models have a wide range of
applications in agricultural activities, including crop
zoning land-use planing, orchard management,
characterising genotype response to the environment and
forecasting phenologic phases during the development of
the crop ( Robertson 1983 and others).
The principle of the model is that endodormancy is
considered to be broken when a certain amount of
chilling (requirement specific for each variety) has been
accumulated. Detailed researches were already carried
out, in order to approach the subject in different climatic
conditions (R. Guerriero 1976, 1985; R. Rageau 1982, T.
Sugiura 1991, N. Kume & K. Takezawa 1994, A.
Pitacco 1995 and others).
The interests of the present investigation involve the
above mentioned applications, being due to the necessity
of an annual assessment of dormancy completion process,
especially for tree species with a short rest period, in
South Romania climatic conditions, representing also a
specific tool for climate change survey through the
impact on fruit-trees annual development.
Material and methods
In this purpose a two-steps model describing the
response of dormant buds in deciduous fruit trees to
temperature ( Erez et al. 1988, Fishman et al., 1987, Gat
et al., 1994), was analysed. According to these authors,
Testing the Dynamic Model of Chilling Portions in the Extreme
South-East Part of Romania
Ana Maria Roman
*1)
, V. Cuculeanu
1)
, Beatrice Cusursuz
1)
, Liliana Dumitru
2)
,
Elena Topor
2)
and Gh. Alexe
3)
1) National Institute of Meteorology and Hydrology, *NIMH, Applied Meteorology Department, Agromodelling
Division, Sos. Bucuresti - Ploiesti 97, 71552 Bucharest, ROMANIA Soseaua Bucuresti-Ploiesti, No 97, sectorul
1cod 71552, Bucharest, Romania
2) Fruit Tree Station for Research and Production -Valu lui Traian -, Constantza; Romania
3) University of Agricultural Sciences and Veterinary Medicine, Bucharest, Romania
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