Báo cáo khoa học: "Physiological correlations and bud dormancy in the apple tree (Malus domestica Borkh.)"

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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