The vine

Question 1

Vitis vinifera

Answer 1

Indigenous to Eurasia, and most common rootstock varieties in the world. Grafted onto American rootstocks

Question 2

Name the most important North American species

Answer 2

Vitis labrusca
Vitis riparia
Vitis berlandeiri
Vitis rupestris

Question 3

Explain the anatomy of the vine (4 sections)

Answer 3

All vines have a similar structure. This structure can be divided into four sections

• Main shoots
• One-year-old wood
• Permanent wood
• Roots

Question 4

Describe the structure of the main shoots

Answer 4

The main shoots on the vine grow in spring from buds retained from the previous year. The major structures of the main shoots are:

• The stem
• Buds
• Leaves
• Tendrils
• Lateral shoots
• Leaves
• Inflorescences/grape bunches

Question 5

The stem

Answer 5

The stem is essentially the structure to which all the other structures are attached. It transports water and solutes (substances that dissolve in a liquid to form a solution and in this instance include sugars and minerals) to and from the different structures. The stem also stores carbohydrates.

The little swellings along the stem, where the other structures are attached, are called nodes. The lengths of stem in between the nodes are called internodes.

In late summer, the leaves fall from the vine and the green shoots become woody and turn brown; from this point they are called canes.

Question 6

Buds

Answer 6

Buds form between the leaf stalk and the stem. As they mature they contain all the structures in miniature that will become green parts of the vine. Including the stem, buds, tendrils, leaves and often inflorescences.

There are two main types of buds:

Compound buds;

• Also called latent buds, from in one growing season and break ope in the next growing season (provided they are retained during winter pruning). They produce the main shoot in the next growing season.
• Within a compound bud, there is typically a primary bud (the main growing point) and smaller secondary and tertiary buds. The later two buds usually only grow if damage has occurred to the primary bud (e.g. spring frost).

Prompt buds

• From and break open ins the same growing season. They form on the main shoot (that has just grown from a compound bud) and produce lateral shoots.

Question 7

Lateral shoots

Answer 7

Grow from buds formed in the current year (prompt buds)

They are smaller and thinner than the main shoots. Lateral shoots have a stem, leaves, buds and sometimes inflorescences. Their main function is to allow the plant to carry on growing if the tip of the mains shoot has been damaged or eaten.

They can provide an additional source of leaves for photosynthesis (the process by which green plants use sunlight to produce sugars from carbon dioxide and water), which can be useful if the laterals are near the ends of the main shoots and able to benefit from sunlight.

Growth of laterals nearer the base of the main shoot can be undesirable as they impede air flow and can shade the fruit too much. They may be removed in summer pruning.

Lateral shoots often produce inflorescences, which can be known as a second crop. However, this can depend on the variety and canopy management techniques. Pinot Noir is a variety that often forms inflorescences on lateral shoots. The second crop may be removed during the growing season by green harvesting; a techniques to enhance the ripening process and improve the uniformity of ripeness of the remaining bunches.

Alternatively, if fruit is hand harvested, the ability to be selective means the second crop need not be picked or can be separated. However, this is not possible when fruit is machine harvested, and the second crop may therefor have an impact on the must and finished wine.

Question 8

Tendrils

Answer 8

The shoot cannot support itself, therefor vines have tendrils.

In the wild, these tendrils would have been used to attach the vine to other plants or trees, providing support.

In viticulture, grape growers can use a trellis to position the vine canopy. The tendrils curl around trellis wires and keep the canopy in place.

However, grape growers typically do not trust the tendrils to hold the vine to the trellis on their own and therefore they tie in canes and shoots as necessary

Question 9

Leaves

Answer 9

The leaves are the main site of photosynthesis in the vine. The sugars produced in photosynthesis are used for vine growth and metabolism.

Stomata (pores) open on the underside of the leaves, letting water diffuse out and carbon dioxide for photosynthesis to enter.

As water diffuses from the leaf, a process called transpiration draws water and nutrients from the soil up through the vine to the leaves.

These stomata partially close if the vine is water stressed. This can help to conserve water, but limits photosynthesis by preventing carbon dioxide from entering the vines and therefore slows down growth.

Question 10

Inflorescences

Answer 10

The inflorescences is a cluster of flowers on a stem, which becomes a bunch of grapes at fruit set. The number of inflorescences on each main shoot can depend on the grape variety, but is usually between one and three.

Question 11

Bunches

Answer 11

A bunch of grapes is a fertilsed inflorescences. usually, not all the flowers in the inflorescences will successfully become grapes, as well as the size and shape of the bunch, varies between grape varieties and even between different clones of the same grape variety.

Some grape varieties can have very tight bunches (Pinot Noir), which are more prone to fungal diseases inside the bunch due to damage to the grape skins.

Question 12

Grapes

Answer 12

A grape is a type of berry

In broad terms a grape is made up of pulp, skin and seeds.

Pulp:
- The pulp makes up the majority of the grapes weight and volume. It contains water, sugars, acids, and some aroma compounds and aroma precursors. The pulp of most grapes is colourless. Exceptions include Alicante Bouschet, however, these are not common.

Skin:
- The skin of the grape contains a high concentration of aroma compounds and aroma precursors, tannins and colour compounds. The amount of tannins and colour in black grapes is significantly higher than in white grapes

Seeds:
- Seeds mature inside the grape, turning yellow to dark brown. Seeds contain oil, tannins an the embryo, which an grow into a new plant.

A powdery waxy coating, called the bloom, covers th surface of the grape. The grape is attached to the vine by a stem, which contains tannins.

Question 13

One year old wood

Answer 13

Refers to the main shoots from last growing season that were kept at pruning.

The amount of one year old wood will depend on the pruning and training decisions made by the grape grower.

Importantly, the one year old wood supports the compound buds that will break to release the main shoots for the upcoming growing season.

Depending on how the vine is pruned the one year old wood will either be called a cane or a spur

Question 14

Permanent wood

Answer 14

These are the woody parts of the vine that are older than one year, including the trunk.

Depending on pruning and training decisions, some vines also have one or more horizontal arms of permanent wood, often called cordons.

The trunk and cordons provide support to the other parts of the vines. They transport water and solutes to and from different parts of the vine and store carbohydrates and nutrients

Question 15

Roots

Answer 15

Roots are important for anchoring the vine and also for the uptake of water and nutrients and are also a store of carbohydrates and produce hormones that have important functions within the vine growth and grape ripening.

In most cases, vines are grafted onto a rootstock.

Most of the vine’s roots are found in the top 50cm of the soil, although vine roots have been found that reach over six meters down into the soil.

Distribution of the main framework of roots is influenced by the soil properties, irritation, cultivation and the type of rootstock.

Question 16

Vine Propagation (voortplanting)

Answer 16

In modern viticulture, vines are propagated by cuttings or layering.

These two methods create new plants that are usually genetically identical to the parent plant, and therefore have the same characteristics.

In viticulture vines are not propagated through seeds, vines that grow through seeds are not genetically identical to the parent vines and although they can show similar characteristics to their parents, more often they are notably different.

Question 17

Cuttings

Answer 17

A cutting is a section of a vine shoot that is planted and then grows a new plant. This is by far the most common propagation technique as many small cuttings can be taken from a vine and propagated at the same time.

It also permits the use of rootstocks, which can easily be grafted onto the vine cutting before it is planted. In addition, nurseries are able to treat vine cuttings to avoid spread of diseases.

Question 18

Layering

Answer 18

Is a method of filling gaps in a vineyard (e.g. due to a death of a vine) by using shoots from an established neighboring vine to produce a new vine.

A cane is bent dons and a section of it is buried in the ground. The tip of the cane points up out of the ground. The section that is buried takes root and, once these roots are established, the cane linking the new growth to the original plant is cut.

The new vine grows on its own roots, not those of a rootstock, and this method is therefore not always suitable. The new vine will have no protection against phylloxera or have the qualities (such of desired yield) that a choice of rootstocks offers

Question 19

Clones

Answer 19

The methods of cutting and layering usually produce vines that are genetically identical to the parent vine. However, at each cell division during plant growth there is the res that random mutations in the genetic code will occur.

Many of these mutations have no effect on the vine but sometimes slightly different characteristics (larger grapes/thicker or thinner skins) will occur.

Clones cause diversity within the vines of the same grape variety.

On rare occasions, a mutation might be so significant that the new vine is classified as a new variety. For example, Pinot Noir, Pinot Meunier (etc) are all mutation of the grape variety Pinot.

Question 20

Clonal selection

Answer 20

Vines with particularly favorable characteristics that are selected by vine nurseries or grape growers for propagation by cuttings in order to grow new vines with these favorable characteristics.

Each slightly different vine is known as a clone.

Question 21

Obtaining new planting material

Answer 21

The most common way to obtain new planting material is to buy young vines form a nursery, which will typically offer particular clones of grape varieties.

One of the reasons for this is that young vines purchased from nurseries have been tested to be free from virus infections. However, depending on the region and the grape variety, only a very limited number of clones may be available from the nurseries, and is some cases these clones may have been chosen to maximize yields rather than fruit quality. Meaning vines planted across a vineyard or even a region can be relatively uniform, especially if natural factors are consistent across the region.

This may have some benefits; if all of the vines grow in similar way and ripen grapes at the same time as each other, management of the vineyard becomes simpler.

However it can also be disadvantageous; meaning there is less diversity in the fruit and hence potentially producing a wine that is less complex. It also makes the vineyard more susceptible to disease because the identical vines are likely to all be equally susceptible to a disease or pest. Therefore a grape grower will often buy and plant a number of different clones of the same grape variety.

Question 22

Mass selection (advantages/disadvantages)

Answer 22

Also called Slection Massage, a technique regaining popularity with some vineyard growers.

The technique requires growers to take cuttings from the vines in their own vineyards and cultivate these cuttings (the cuttings are send to a nursery for grading onto rootstocks were necessary).

Cuttings are taken from several different vines. Generally, the best performing vines are selected (yields, desired characteristics) and are selected after several years of monitoring and recording their performance.

Advantages of mass selection:

• It increases the diversity of planting material in the vineyard and throughout the region
• Vineyard owner is using their own unique planting material (different form that being both from the local nurseries) which can enhance fruit quality and/or yield
• Can be used as marketing asset

Disadvantages of mass selection:

• The selection and monitoring of vines to ensure the propagation of the best vines is costly in terms of time and labour
• If the parent vine is infected by disease this is likely to be passed onto the new vines, and therefore this technique can increase the pared of vine diseases

Question 23

New grape variety

Answer 23

Typically produced from seeds. The pollen from the stamens of the flowers of one vine is transferred tot he stigmas of the flowers of another vine and fertilization occurs; called cross fertilization.

Grapes develop and the seeds from these plants are planted and grown. The new vine that grow form the seeds will all have different characteristics (in a way that siblings in a family are not identical to each other or their parents). If one of the new vines has desirable characteristics, it may be propagated by cuttings to create identical vines.

In modern viticulture, scientist actively try to create new grape varieties by carrying out cross fertilization in a laboratory environment. The aim is usually to create an offspring that has the favorable characteristics of the two parent vines, but in reality this often does not happen (Muller Thrugau: Riesling X Madeleine Royal to have the fruit quality of Riesling and high yield of Madelaine Royal).

Although knowledge of grapevine genetics has increased still new grape varieties rarely come to market; the main reason is consumer resistance.

Question 24

Cross

Answer 24

When the two parent vines are from the same species, the offspring is called a cross. For example, Pinotage is a cross of Pinot Noir and Cinsault.

The potential and long-term value of the new vine will be assessed over a long period of time. If there is thought to be value in making this new variety available commercially, it will need to be registered on the OIV catalogue as a new variety.

Question 25

Hybrid

Answer 25

When the two parent vines are from different species, the offspring is called a hybrid.

Possibly the best known hybrid for wine production is Vidal Blanc, from Ugni Blanc (V. vinifera) and a member of the Seibel family (American parentage).