Agriculture Reference
In-Depth Information
The shoot system
Introduction
The configuration and productivity of the individual apple or pear tree is
determined by its height, the number and length of its branches and the angle
of these to the vertical.
The size, density and arrangement of the branch and shoot framework
determine the leaf area and light capture, and hence potential photosynthesis.
They also determine the number of fruit buds and fruits.
Manipulation of shoot growth begins in the nursery, with the objective of
producing trees with numerous lateral branches capable of bearing fruits in
their early years in the orchard. It continues throughout the life of the tree with
emphasis in the early years on branch initiation, development and training,
followed by emphasis on the renewal of fruiting wood and ensuring adequate
penetration of light into the canopy.
The stages in the development of an apple tree and the key elements of
its above-ground structure are shown in Figure
. Other tree forms may be
used but the essentials are the same for both apples and pears.
.
Buds
All shoots of apple and pear scions arise from buds. The first in the life of
the tree is the bud which is inserted into the rootstock stem by budding or
is present on scionwood grafted on the rootstock. The buds on the orchard
tree can be on the long (extension) shoots or the short (spur) shoots and may
be terminal, i.e. at the end of the shoot, or lateral, i.e. in the axil of a leaf. The
bourse bud which develops at the base of a flower cluster is considered as a
distinct category. Terminal bud formation can be considered as a continuation
of the axis after extension growth has ceased. Lateral buds develop from small
sections of the apical meristem remaining in the axils of leaves. In the early
