Agriculture Reference
In-Depth Information
Table
.
The effects of seeds and spur leaf area on floral initiation
in 'Williams'' pear
Tree with
Tree with
seeded fruits
seedless fruits
Yield (kg)
.
.
Number of fruits
Seeds per fruit
.
% floral initiation
on spurs with the
following leaf area (cm
)
Less than
( leaves) -
.
( leaves) -
.
( leaves) -
.
Greater than
.
From Huet (). Reproduced with permission.
hormones, especially gibberellins, play a major role (Fulford,
; Luckwill,
) found that more GA and other plant hormones move
out of the fruitlets of biennial flowering cultivars than from those which flower
regularly. Within any one cultivar, but not between cultivars, the amount of
gibberellin in diffusates from excised fruitlets via their cut pedicels is depen-
dent on the number of seeds in the fruitlet. Diffusion out of the fruits continues
at a variable rate but without any clear trend with time for at least the first
,
). Hoad (
weeks after full bloom (Hoad,
). Fruits of 'Spencer Seedless' export much
less GA
than those of the seeded cvs. 'Elstar' and 'Golden Delicious', with it
being undetectable at some dates in June. They can, however, export consid-
erable amounts of GA
which does not inhibit flowering (Prang
et al.
,
).
Exogenously applied GA can inhibit flowering, as discussed later. Hoad (
)
also found more auxin activity in fruit diffusates of the strongly biennial cv.
'Laxton's Superb' than in the less biennial 'Cox's Orange Pippin'. Grochowska
et al.
(
) found no difference in auxin content between fruiting and non-
fruiting (i.e. potentially flowering and non-flowering) spurs of 'Jonathan' and
'McIntosh' apples, but a high content of gibberellins in the former while cyto-
kinins predominated in the latter. Grochowska (
) also found less starch in
fruit-bearing than non-bearing apple spurs and attributed this to an effect of
hormones from the seeds.
Effects of leaves on flowering
Defoliationexperimentshaveshownthatleavespromoteflowerbudformation.
Ryugo (
) reported that no flowers formed on apple spurs that had been
