Agriculture Reference
In-Depth Information
Figure 3.3
The effect of splitting the base of a cutting on root
emergence: roots emerging in ranks from the wound. From Howard
et al.
(1984). Reproduced with permission.
Root emergence from layered shoots of
Malus
rootstocks is largely confined
to nodal positions near lateral buds (Doud and Carlson,
). It is closely
associated with parenchymatous, starch-rich tissues in bud and leaf gaps in
the stem.
Wound-induced roots
are produced by cuttings. In some cases cuttings
already have pre-formed roots. This is so with quince (
Cydonia oblonga
), where
a small slice of older wood (a 'heel') with pre-formed root initials is retained
at the base of the cutting to obtain maximum rooting (Hartmann
et al.
,
).
In other cases the presence of nodal rooting sites on the cutting is important.
Rooting potential of apple cuttings is highest if they are from the basal part
of the annual shoot as the result of a rosette of buds with their associated
nodal sites (Howard,
). In general, however, rooting of cuttings is
stimulated by wounding, which is especially important when the cutting base
is of internodal tissue. Outward-pointing cambial salients develop in the callus
which arises following stem wounding. The wounding which stimulates this is
the cut across the base of the hardwood (winter) cutting, which has separated
it from the parent plant, or a vertical cut which splits the base of the cutting
(Figure
,
.
).
