Agriculture Reference
In-Depth Information
Apple and pear root systems:
induction, development,
structure and function
Introduction
In field crops grown from seed the root system develops, in general, in an
uncomplicated way so as fully to exploit the soil to a depth characteristic of
the crop. In crop physiological analysis, and for irrigation scheduling, the root
system is considered to be defined fully in terms of rooting depth and density,
the roots usually being considered to be evenly distributed.
Root development and distribution is much more complexin apple and
pear trees as grown commercially. It involves, and relates to, very distinctive
technologies of propagation, tree establishment, and nursery and orchard soil
management and irrigation. Prior to consideration of the biological basis of
these technologies it is best to consider the general anatomy and structure of
the roots of the orchard tree.
The essential root system of the mature tree consists, as a rule, of an under-
ground rootstock stem from which arises a system of permanent, thickened,
scaffold roots spreading almost horizontally, usually less than
cm from the
surface, and numerous more or less vertical 'sinkers' descending as a rule
to either an impermeable layer or a water table (Rogers and Head,
;
Atkinson,
). These woody 'skeletal' roots are long-lived, provide anchor-
age and form the framework which bears the fine (fibrous) roots. New roots
can emerge from the underground rootstock stem, from coarse roots (
mm
diameter) or from fine roots. They are initially white and most are ephemeral
with only a proportion thickening and becoming perennial roots. Figure
>
illustrates the root system of an apple tree. Transverse sections of pear roots
are shown in Figure
.
.
There are three main stages in the development of such a root system: the
initiation of roots on rootstock shoots, the development of roots on lined-out
rootstocks and grafted or budded trees in the nursery, and the development of
a root system after transplanting into the orchard.
.
