Agriculture Reference
In-Depth Information
Flowers and fruits
The defining characteristics of apple and pear flowers and fruits were sum-
marized in Chapter
and the morphology and anatomy of apple flow-
ers and fruits comprehensively reviewed by Pratt (
). Flowers are initi-
ated and develop within the buds borne terminally on fruiting spurs (short
shoots) and terminally or laterally on long shoots. These buds, as discussed
in Chapter
, consist essentially of a shortened shoot axis with a 'leaf for-
mation' inserted at each node. These 'leaf formations' in apple commonly
consist of about nine bud scales, three transition leaves, sixtrue leaves and
three bracts (cf. Figure
). Flower primordia may form at the apex
and in the axils of the bracts and the three uppermost leaves (Abbott,
.
,p.
).
Alternatively, the buds may fail to develop far enough to produce flowers and
remain vegetative.
Juvenility
Seedling apple and pear trees usually remain vegetative for several years after
seed germination. During this 'juvenile' phase they readily form adventitious
roots, as discussed in Chapter
, are often thorny and have a distinctive leaf
shape and, especially, cannot be induced to flower (Zimmerman,
). They
emerge from this juvenile state after reaching a minimum size, characteristic of
the cultivar, measured as height or number of main stem nodes. The duration
of the juvenile phase can be shortened by growing the seedling tree under
conditions which speed up its growth or by specific horticultural practices
such as grafting the seedling on to a dwarfing rootstock. Failure to flower as
a result of juvenility is primarily of importance to fruit breeders. Apple and
pear trees in the orchard are usually compound trees in which the scionwood
grafted or budded on to the rootstock was taken from trees already in the
mature, non-juvenile phase.
