Small buds are formed in the axils of all leaves on a young, green grapevine shoot. As the shoot grows, these axillary buds are revealed to be double: one of them initiates immediate development, giving rise to a short lateral branch — known as a lateral shoot, while the second one gradually increases in volume but remains dormant throughout the entire vegetative period, constituting a dormant bud.

Developmental Features of Lateral Shoots

Lateral shoots achieve significant length primarily on the lower section of the grapevine shoot; in certain instances, they lignify and persist on the vine as lateral branches. The upper lateral shoots, which develop sequentially throughout the summer, exhibit weaker growth, remain herbaceous, and abscise along with the leaves in autumn.

Early removal of the terminal growing point of the primary shoot can stimulate vigorous development in all lateral shoots. Under these conditions, the topmost lateral shoot grows with particular intensity, replacing the lost shoot apex. After a short period, it becomes difficult to identify the exact position where the apex of the primary shoot was removed.

Morphological Differences Between a Lateral Shoot and an Annual Shoot

A comparative analysis of a lateral shoot and its bearing annual shoot reveals the following distinct morphological differences:

  • At the base of a lateral shoot, there is only a single scale, which represents an underdeveloped leaf, whereas the primary shoot possesses two such scales.
  • In lateral shoots, tendrils emerge opposite the second leaf, while the lower 3–5 leaves of the primary shoot do not have tendrils positioned opposite them.
  • The plane of phyllotaxis of a lateral shoot always intersects at a right angle with the plane of phyllotaxis of the primary shoot that bears it.

Fruiting of Lateral Shoots and Their Anatomical Relationship

In most grapevine cultivars, lateral shoots are typically sterile. However, certain cultivars are known to annually produce small clusters on their lateral shoots, some of which manage to ripen successfully before the onset of frost (e.g., Madeleine Angevine, Portugieser, Muscat Saint-Laurent, etc.).

A large bud is situated at the base of the lateral shoot within the leaf axil. The viticultural researcher Braun was the first to conclusively demonstrate that this bud actually represents the lowermost bud of the lateral shoot, seated in the axil of its first underdeveloped, scale-like leaf. This anatomical arrangement becomes visually evident in rare cases where a small green leaf develops instead of this scale.

While the lateral shoot generally perishes in autumn, its lowermost bud is invariably preserved as a so-called wintering bud. In the subsequent vegetative period, it gives rise to a new shoot, which in turn develops its own lateral shoots. Consequently, a strict and continuous alternation between two types of shoots is observed in the grapevine: primary shoots developing from wintering buds, and lateral shoots.