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Physiological correlations and bud dormancy in the apple
tree (Malus domestica Borkh.)
O. Bailly J.C. Mauget
laboratoire de Bioclimatologie, INRA, Domaine-de-Crouelle, 63039 Ctermont-Ferrand Cedex,
France
Introduction tember until January; or c) simultaneously
defoliated and pruned or pinched in September
and October.
During their autumn rest period, terminal Bud dormancy on control and treated shoots
was studied with the method of isolated node
and axillary buds of apple trees exhibit dif-
cuttings. For each treatment, about 10 shoots
ferent behaviours: the terminal bud is
were collected at intervals of 15 days and were
always much more dormant than the axil- cut into 8 cm cuttings on which a single node
lary ones so that one can wonder whether was left. The cuttings were stood in water at a
constant temperature of 20°C under long days
the latter are not simply inhibited by phy-
of 16 h. The time needed for budburst of each
siological correlations (Williams et al., bud was recorded by daily observation. The
1979; Mauget and Rageau, 1988). To
average state of dormancy of the population of
check this hypothesis, the following ex- sampled buds was quantified by the mean time
periment was carried out on apple trees, of budburst (MTI3) expressed in days; this was
the arithmetic mean of the time to budburst for
cultivar Golden delicious. Long shoots
each bud from a. given population and at each
were defoliated and/or pruned in fall and
date of collection. The higher the MTB, the
early winter in order to release buds from more dormant the buds. Distal, median or basal
all physiological inhibitive influences buds could be studied separately.
(apex, leaves). The subsequent dormancy Results are expressed as the change of
MTB during the vegetative rest period. This
of buds on control and treated shoots was
described the time course of dormancy.
studied from fall until budburst on the
trees.
Results
Materials and Methods
Effects of defoliation (Fig. 1a)
The trees (15 yr old) were grown in an orchard
located in the area of Clermont-Ferrand. in dormancy of lateral buds
Only changes
Groups of long shoots on the trees were: a) located near the apex part are shown.
defoliated in September and in October;
These buds became more dormant after
b) pinched (elimination of the terminal bud) or
defoliation, particularly after October treat-
pruned in their middle part monthly from Sep-
ment. Behaviour of other buds on the position of the lateral bud could be factors
stem was hardly affected by this treat- that prevent acquisition of strong dorman-
cy. The situation of the terminal buds
ment.
which exhibit strong dormancy, could be
different.
Effects of pruning and pinching (Fig. 1 b
Since the uppermost buds on apple
and c)
shoots pinched and defoliated in the fall
grow out rapidly when detached from the
the treatments done in September
Only trees (Paiva and Robitaille, 1978; Williams
and October modified the course of bud
et al., 1979; Latimer and Robitaille, 1981),
dormancy (i.e., before the peak MTB in a factor associated with the whole plant
late November). The intensity of dormancy
(and to a lesser extent low temperature) is
in the uppermost buds was considerably
necessary to increase the dormancy of
increased for treated shoots. These
lateral buds. The induction of strong dor-
effects were more important for buds on
mancy in the lateral buds can be consid-
shoots treated in September than on
ered a good means to study, using struc-
those treated in October. Both these treat-
tural and biochemical approaches, the
ments (and also defoliation) accentuated a
mechanisms involved in bud dormancy in
bud dormancy gradient along the stem.
apple trees.
The increase in intensity of lateral bud
dormancy was slightly more important on
simultaneously defoliated and pinched or
pruned shoots than on treated shoots (Fig. Acknowledgments
1a or b) (data not shown).
The main differences between MTB
Special thanks to J. Guinard, N. Frizot and R.
values for control and treated shoots in Mege for their technical collaboration.
mid-fall were statistically significant (Mann
and Whitney U test, 5% level).
References
Discussion
Barnola P., Charnpagnat P. & Lavarenne S.
(1976) Taille en vert des rameaux et dormance
Removing inhibitory influences from the des bourgeons chez le noisetier. C.R. Seances
apex and leaves did not decrease the Acad. Agric. Fr. 1, 1163-1171
I C
extent of dormancy; on the contrary, the Latimer J.G. & Ro!bitaille H.A. (1981) Sources of
variability in apple shoot selection and handling
intensity of bud dormancy was increased
for bud rest determinations. J. Am. Soc. Hortic.
by September and October treatments. Sci. 106, 794-798
The inhibited state of the lateral buds in
Mauget J.C. & Ra.geau R. (1988) Bud dorman-
apple could be responsible for the shallow cy and adaptation of apple tree in mild winter
dormancy exhibited by these buds. Never- climates. Acta Hottic. 232, 101-108
theless, the potential for these buds to Paiva E. & Robitaille H.A. (1978) Breaking bud
grow out remained weak. rest on detached apple shoots: effects of
wounding and ethylene. J. Am. Soc. Hortic.
These results are in agreement with the
Sci. 103, 101-104
hypothesis developed by Barnola et al. Williams R.R., Edwards G.R. & Coombe B.G.
(1976) for Corylus. These authors suggest (1979) Determination of the pattern of winter
that the correlative influence from the dormancy in lateral buds of apples. Ann. Bot.
apex and properties associated with the 44, 575-581
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