Agriculture Reference
In-Depth Information
and its subsequent development is relatively rapid. The order of appearance
of the tissues is: sepals, petals, anthers and ovaries; and by leaf fall all parts are
present in a large proportion of the flowers (Abbott,
). The
stage of flower bud development at any given time during summer and autumn
varies with type of bud (basal shoot bud, middle shoot bud, upper shoot bud
and terminal bud) and with cultivar (Crabbe,
; Faust,
b). Buds
continue to develop through the winter: apple buds increase in size by
; Banno
et al.
,
-
% during December and January and by an additional
-
% between
mid-February and mid-March.
A considerable degree of differentiation of tissues takes place over this per-
iod (Faust,
). At budbreak, which follows satisfaction of the winter-chilling
and heat-unit requirements discussed in Chapter
, the apical or king flower of
apple opens first, followed by the lateral flowers. In the southern hemisphere
Bergh (
a) found that flattening of the apex, marking the change from
the vegetative to the reproductive phase, occurred during the first week of
January in 'Starking' apple. Sepal primordia of the terminal and lateral
flowers were formed simultaneously during the second week of January. The
full complement of five sepals of the terminal flower had formed by the last
week of January and development of the petal primordia and the first whorl of
ten stamens of the terminal flower was completed during the second week of
February. The sepals and bracts of lateral flowers were also evident at that time
and carpel primordia of the terminal flower could be detected. The first whorl
of ten stamens, first and second whorl of five stamens and developing carpels
were found in all samples collected during the second week of March, well
before leaf fall in May. Floral organs developed slowly during the mid-winter
months of June, July and August. Carpels and pollen sacs developed rapidly in
Septemberandovuleprimordiaweredistinguishedtowardstheendofthisper-
iod, approximately
days before anthesis. From the third week of September
until anthesis in mid-October rapid swelling of the buds coincided with accel-
eration of elongation of the carpels, formation of pollen sacs and elongation
of the filaments of stamens. Development of the bud from the green tip stage
to the opening of the terminal flower coincided with further elongation of the
floral organs and rapid development of the ovule. Stages of bud development
are shown in Figure
.
Flower bud differentiation and development in Japanese pear (
Pyrus serotina
Rehder) follows a similar pattern to apple and to
P. communis
but Banno
et al.
(
.
and the structure of the mature flower in Figure
.
) reported relatively early initiation and differentiation. The first visible
signs of flower bud differentiation on spurs of cv. 'Nijisseiki' in Japan (northern
hemisphere) were on
June, petal and stamen primordia were initiated by
late July and carpel primordia by mid-August.
The whole process of flower bud and flower development, taking place
over two consecutive years, is influenced and modified by a large number of
