Agriculture Reference
In-Depth Information
Fig. 7.4
Shiraz shoot (
a
) and latent bud section at flowering (
b
). Labels indicate main shoot axis
(
S
), petiole (
P
), lateral shoot (
LS
), latent bud (
LB
), stipule (
St
), inflorescence primordia (
Ip
), and
bud apex (
A
). Shoot generations indicated by N, N + 1, N + 2, N +
of each leaf during the spring of the first season, and then undergo several orders of
branching before entering the winter dormancy period. Inflorescence development
resumes at bud break with the growth of the shoot primordia and the development
of individual flowers, and continues through from flowering to berry maturation
and harvest in mid-summer to mid-autumn.
Fruit yield at harvest in the following season is a function of bunch weights and
the number of bunches per vine, and both parameters can be influenced by geno-
type, environmental conditions and viticultural management practice during the re-
productive cycle. Bunch weights are determined by berry weight and berry number
per bunch, and in turn by inflorescence flower numbers, the proportion of flowers
that are successfully fertilized at anthesis, and by the growth and final weight of
berries at harvest. Bunch numbers per vine are determined by shoot numbers and
the fruitfulness of those shoots, with the number of buds retained at pruning and
percentage bud-break determining shoot numbers, and the number of inflorescence
primordia initiated by these buds in the previous season determining shoot fruitful-
ness.
The Grapevine Bud
Grapevine buds consist of a prompt bud that usually bursts through late spring and
summer to form a small lateral shoot, and a latent or compound bud that forms in
the axis of the first bract of these summer laterals (Fig.
7.4
).
The latent bud typically develops six to twelve leaf primordia and initiates be-
tween one and three inflorescence primordia before entering the winter dormancy
period (May
2004
). The fruitfulness of these buds, together with the number buds
retained at pruning, are one of the key yield determinants for the followed season.
Within the latent bud, second order buds are also formed in the axis of the basal
bracts. These buds are generally smaller and less fruitful than the primary shoot
meristem, but if the primary bud is damaged or dies during the season, one of more
