Agriculture Reference
In-Depth Information
3500
Terminal buds
Axillary buds
2500
1500
500
0
27
Aug Sep
10 24 8 22 5 19 2 17 30 14 27 11 25 10
8 15 (dates)
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Figure 6.11
Bud dormancy of 'Golden Delicious',measured as
mean time to budburst (MTB) of single-node cuttings under forcing
conditions,throughout the winter in central France. From Mauget and
Rageau (1988). Reproduced with permission.
P. communis
buds on
P. calleryana
could lose their dormancy through exposure
to a chilling regime inadequate to satisfy the chilling requirement of 'Bartlett'
on
P. communis
and that the dormancy level was then intrinsic to the bud
(Westwood,
).
Chilling requirements of lateral buds
Under conditions of limited chilling, terminal buds on intact shoots may break
longbeforelateralbuds(Saure,
).Fromthisithasbeendeducedthatlateral
buds have a much greater chilling requirement than terminal buds. However,
in numerous studies (Latimer and Robitaille,
; Williams
et al.
,
; Skene,
b) it has been
shown that the uppermost lateral bud on a decapitated shoot, or a lateral bud
on a single-node cutting, can be induced to break out quickly at any time
during the winter under forcing conditions (Figure
; Mauget and Rageau,
; Hauagge and Cummins,
). Subsequent to the
period over which terminal buds show endodormancy, terminal and lateral
buds are influenced by growing temperature in an identical way (Mauget and
Rageau,
.
).
Paiva and Robitaille (
) also found that notching above a lateral bud
could induce it to grow out readily even during the period of terminal
bud endodormancy. This strongly suggests that the major cause of lateral
bud dormancy in winter is continued correlative inhibition combined with
