Agriculture Reference
In-Depth Information
Effects of shoot vigour and orientation on flowering
Within an apple or pear tree the branches which are well exposed to light and
capable of average to vigorous growth usually produce the most, and the 'best
quality', fruit buds. Shaded parts of trees and trees whose growth is generally
below average for the particular stock/scion combination are usually poor in
terms of flower production and crop (Feucht,
). Paradoxically, induction
of flowering is often associated with a cessation or slowing of growth (Forshey
and Elfving,
).
) found that the major factor controlling floral initiation on long
shoots of 'Williams' Bon Chretien' pear appeared to be the pattern of growth.
Within any overall shoot length class the number of fruit buds which developed
per shoot was inversely correlated with the relative growth rate of the shoot
before harvest. He attributed this to the relative strength of apical dominance
by the different shoots.
Training, bending or placing apple shoots so that they become horizontal
both checks their growth and increases the proportion of the buds that become
floral (Tromp,
Huet (
; Robbie
et al.,
). Banno
et al.
(
a) found that within
days of shoot bending of Japanese pear in mid-June there was already an
increase in the number of nodes within the axillary buds compared with con-
trols. There was no effect on shoot growth at this time although it was evident
after
more days. The first visible signs of flower initiation were a month
earlier than on control shoots. The final proportion of buds becoming floral
was about
% on control branches.
Shoot bending led to an increase in the sorbitol, amino-acid, IAA and cyto-
kinin content of lateral buds and a decrease in these in shoot tips. Bending
was accompanied by a decrease in the gibberellin content of both shoot tips
and axillary buds. Tromp (
% following shoot bending but only
) found that shoots placed horizontally after
cessation of their growth produced more flowers than when left vertical.
Effects of shoot type and pruning on flowering
Flower initiation in the axillary or terminal buds of long shoots generally
does not begin until after extension growth ceases (Forshey and Elfving,
).
It therefore usually occurs later than on spurs. Dencker and Hansen (
)
found that flower initiation in axillary buds of 'Elshof' (a colour mutant of
'Elstar') was delayed by about
days compared with spur buds. Treatments
that stimulate growth and delay its termination may reduce flowering on long
shoots (Forshey and Elfving,
). Dencker and Hansen, however, found that
'fertigated' trees, with nutrients supplied daily in the drip irrigation system and
greater but earlier shoot growth, developed a greater proportion of, as well
as more in total, floral buds on the shoots. They also found that the critical
node number for axillary buds to become floral was
or
compared with
