Two zones can easily be distinguished in the anatomy of the grapevine: the part buried below the soil surface, which is the plant’s root system, and the part above ground, generally called the canopy, which is made up of several structures such as the trunk, the arms (if any), the canes or shoots, the leaves, the tendrils, the buds and the inflorescences.
Each of these structures plays a specific role in the life of the plant.
The roots
The roots of the grapevine play several roles in the plant, chief among them:
- Absorbing water and mineral nutrients, such as nitrogen, phosphorus, potassium and other micronutrients essential to the plant’s survival.
- Anchoring the plant.
- Storing reserves during the winter.
Depending on the type of soil and the climate, these roots can reach depths of anywhere between 50 cm and 12 meters. Rooting depth depends on factors including:
- The age of the plant
- The irrigation system (frequency, duration, method)
- The effective depth of the soil, that is, whether the profile contains layers the roots cannot penetrate.
As a general rule, vineyards irrigated with either modern or traditional systems tend to have shallower root systems, since the vines don’t need to explore deep down for water: it is near the surface whenever they are irrigated. By contrast, in dry-farmed vineyards (in regions where water comes naturally from rainfall) where irrigation is not allowed or not needed, vines tend to send their roots deeper in search of rainwater stored in the soil profile.
The root system can be divided into two types: the older, thicker roots, which mainly transport nutrients, anchor the plant and store reserves during the winter; and the system of rootlets, or tertiary roots, which is responsible for absorbing nutrients and water from the soil.
The rootlets grow each year from the older roots, and some of them keep growing throughout the season. They are very sensitive to extreme environmental conditions, such as excess salts or severe drought.
During the growing season, each rootlet has a zone of elongation, a zone of absorption, a growing tip and a protective structure called the root cap. The zone of absorption is where most of the water and mineral nutrients are taken up, and it is where the root hairs are concentrated. Root hairs are outgrowths of epidermal cells that come into contact with soil particles and absorb the growth factors available in them, increasing the plant’s absorptive surface and the volume of soil it actually uses.
Rootlets that survive a growing season become part of the plant’s older roots and give rise to new rootlets the following season.
During autumn and winter, when the plant is dormant, root growth stops almost completely, resuming in late winter as soil temperatures begin to rise.
Trunk and Arms
The trunk and arms of the grapevine serve two fundamental purposes for the plant. The first is to support the rest of the plant’s structures (arms, spurs, canes, shoots, etc.). The second is to act as a channel that carries nutrients from the roots to the plant’s other structures, and carries the nutrients synthesized in the leaves to the rest of the plant.
The trunk and arms of the vine grow radially, that is, in thickness, only during the growing season, through the multiplication of the cells of the vascular cambium, which are responsible for forming the conducting tissues known as xylem and phloem.
The bark of the trunk is thick and rough and constantly peels off in long strips, all caused by the growth of the trunk itself.