葡萄酒社

World of Wine—Vine anatomy

DR CASSANDRA COLLINS:
 

The grapevine is comprised of many key structures that are critical to its function.
The trunk, arms, root system, and shoot system all play an important role in producing grapes of the desired quality, which we then make into wine.
If we look at the trunk of a grapevine, this is comprised of older wood that has thickened with time and provides the support and translocation the vine needs for the growing shoots, roots, leaves, and fruit.
The trunk is trained to have one or more branches that are known as arms.
If these arms are long, they're known as cordons.
The trunk and arms of a grapevine are important for the storage of carbohydrates, water, and other chemical compounds, and for the transport of these to other parts of the plant.
As a storage organ, the trunk buffers the effects of unfavourable growing conditions on fruit production.
The amount of reserves in these organs therefore effects vine productivity.
While the trunk does not need support, most vines require a trellis system to support the arms, canes, and growing shoots of the vine.
The shoot system itself has an unusually complex developmental pattern, arising from the development of a node
containing a compound bud which is comprised of both primary and secondary buds.
Within a compound bud potential shoots, leaves, and bunches for that particular node are initiated for the following season.
This complexity provides the vine with a remarkable ability to adjust its development throughout much of the growing season.
Three or more successive sets of shoots may develop in a single year depending on the climate.
In addition, dormant buds from previous seasons may become active.
This is particularly important if there is a frost or a bushfire.
The components of the shoot system obtain their names from the type and position of the bud from which they are derived, as well as their age, position, and relative length.
For example, shoots can form on the current season shoots and are referred to as lateral shoots.
They provide an additional source of leaves for the production of photosynthesis, which may become more important if part of the main shoot is damaged through vineyard operations or adverse weather
conditions.
During the growing season, the outer epidermal tissues of a shoot can become lignified and turn brown.
At this stage of development, shoots are often referred to as canes.
Once canes or other stem tissue are two or more years old, they are classified as old wood.
At pruning, if a cane is pruned to only a few nodes, it is called a spur.
If left longer, then they remain a cane.
The spurs or canes provide the buds for shoot and fruit growth in the following season.
I will go into more detail about pruning in other sections of this course.
Grapevines also produce tendrils, which are twining organs that facilitate the climbing
habit of the vine.
Often tendrils will attach to trellis wires, which helps to support the rest of the vine and hold the shoots upright, helping to expose the leaves to sunlight.
The leaves of the grapevine are an integral part of the shoot system, as they are the main sites for photosynthesis and transpiration.
The sugars produced in the photosynthetic reactions are used for growth and metabolism of the vine.
Transpiration of water via the stomates acts as a cooling mechanism protecting the leaf from heat damage.
Leaves grow laterally along a shoot and have a distinct growth pattern.
Each shoot generally produces between one and four inflorescences.
The inflorescence is the structure that develops into a bunch.
This occurs when the flowers on an inflorescence are transformed into berries.
There is also a distinct patterning where the inflorescences form on a shoot.
Typically, they develop opposite the third and fourth, fourth and fifth, and fifth and sixth leaves on a shoot.
The grapevine inflorescence is a complex, highly modified branch system containing flowers.
The complete branch system is called the rachis.
And it is composed of a basal stem, otherwise known as the peduncle; two main branches, known as the inner and outer lateral arms; and various subbranches terminating in pedicels.
Pedicels give rise to the individual flowers, which once fertilised form into berries.
The flowers of most wine grape cultivars are hermaphroditic, meaning they contain both female and male parts on the one flower.
This allows the flowers to readily self-pollinate.
A bunch is essentially a fertilised inflorescence comprised of many berries.
The berries are made up of seeds, flesh, and skin.
And the number and weight of seeds are related to the berry growth.
Generally speaking, the greater the number of seeds, the larger the berry.
In most grape varieties, the coloured pigments are contained in the skins of the berry and therefore are responsible for the colour of the wine.
The composition of berries at harvest determines the style and quality of wine produced.
The overall hardiness of a grapevine may, to a large extent, be a function of the characteristics of its root system.
The root system also anchors the plant securely in the soil.
Roots are important sites for the uptake of water and nutrients from the soil; for storage of carbohydrates; and for the production of growth hormones, such as gibberellins, cytokinins, and ascorbic acid.
Another important function of grapevine roots is their role in propagation.
In most modern vineyards, cutting propagation is used to generate the vines used to establish a vineyard.
This is possible because grapevines readily form what we call adventitious roots.
These are roots that form on the aerial parts of the plant.
Large numbers of vines can be propagated with this method.
In many vineyards, the selection of desirable root stocks is also required to establish a hardy plant that is resistant to pests and environmental stress, such as drought or poor nutrition.
In this situation, the root stalk is then grafted to the required grape variety.
And cutting propagation methods again are used to generate adventitious roots.
As you can see, each structure of the grapevine has a very specific and important purpose.
已邀请:

要回复帖子请先登录注册