The Vine Growth Cycle

Question 1

Grape vines stay dormant when the average air temperature stays below ______

Answer 1

10°C / 50°F

Question 2

V. Vinifera plants are susceptible to cold temperatures. At what temperature do most V. vinifera plants begin to die?

Answer 2

-25°C /-13°F

Question 3

Budburst happens in which type of bud?

Answer 3

Compound buds

Question 4

What is a major concern for growers right after budbreak?

Answer 4

Spring frost

Question 5

How does soil type effect budbreak?

Answer 5

high soil temperature around the roots can encourage bud break.

Dry, free draining soils tend to warm up quicker than water storing soils

Question 6

True or False,

Late winter pruning can delay budbreak

Answer 6

True!

Question 7

List some of the reasons a vine could have low vigour after bud break

Answer 7

low carbohydrate levels caused by excessive leaf removal, water stress, mildew infections, or high crop loads from the previous growing season.

Water Stress

Question 8

What are some of the side affects from stunted shoot growth

Answer 8

Small, weak shoots
reduction in leaf number / Small leafs
improper flowering / grape bunches that do not fully ripen

Question 9

what conditions are needed for successful fruit set?

Answer 9

Warm temperatures between 79°- 90°F

Question 10

Name the adverse weather conditions that can affect fruit set

Answer 10

Rain
Overcast
Windy

Cold temperatures

Question 11

What are the two common forms of irregular fruit set?

Answer 11

Coulure and Millerandage

Question 12

Define Coulure

Answer 12

Coulure is a condition of the grape bunch in which fruit set has failed for a high proportion of flowers.

It is caused by an imbalance in carbohydrate levels.

Question 13

Give some examples of grape varieties that are more susceptible to Coulure

Answer 13

Grenache, Cab Sauv, Merlot, Malbec

Question 14

Define Millerandage

Answer 14

A condition of the grape bunch in which there is a high proportion of seedless grapes.

Question 15

What are some of the negative side affects of millerandage?

Answer 15

Potential loss in volume of wine produced due to smaller grapes

Some of the seedless grapes will stay small, green and unripe.

Question 16

What causes Millerandage?

Answer 16

Cold, wet and windy weather at pollination and fruit set.

Question 17

What things begin to accumulate in the berry before veraison starts?

Answer 17

Tartaric and Malic acids
Aroma compounds and precursors
Tannins
Water

Question 18

Why would having too much water and nitrogen delay ripening?

Answer 18

Water and Nitrogen promote shoot growth instead

Question 19

What causes the red coloring in the grape skins?

Answer 19

Anthocyanins

Question 20

What happens to the grape during veraison?

Answer 20

Grape growth slows down for a few days
The cell walls become more stratchy and supple
the green-colored chloropyll in the skin cells break down

Question 21

What happens internally during the ripening phase?

Answer 21

The cells expand rapidly
Sugar and water accumulate
Acid levels fall
Tannins, color and a number of aroma precursors and aroma compounds develop

Question 22

How are the sugars for the grapes produced?

Answer 22

Photosynthesis in the leaves of the vine.

Question 23

What is the ideal range for photosynthesis?

Answer 23

64 - 91°F

Question 24

What two prolonged weather conditions can hinder sugar production/photosynthesis?

Answer 24

Cold weather and constant cloud cover

Very hot and dry conditions that lead to extreme water stress

Question 25

Name the two types of acid naturally found in grapes?

Answer 25

Malic and Tartaric

Question 26

Which acid will fall off as the growing season goes on?

Answer 26

Malic acid

Question 27

Why do levels of Malic Acid decrease as the season goes on?

Answer 27

Malic acid can be used for respiration during the ripening phase instead of sugar

Question 28

What part of the vine moves sugar from the leaves into the grape?

Answer 28

the Phloem

Question 29

Can the grapes themselves transpire?

Answer 29

Yes, even though the grapes do not have stomata, a small amount of water can transpire through the grape skin

Question 30

Sugars accumulate faster in warm dry conditions, but what is a potential side effect of rapid sugar accumulation?

Answer 30

Even though the grape may reach physiological ripeness, it may not have fully ripe phenolics

Question 31

Respiration is slower at cooler temperatures, how can this affect the final wine?

Answer 31

Due to respiration slowing down in cooler weather, the grapes can retain more Malic acid, making the wine naturally more acidic.

Question 32

How does sunshine influence tannins in black grape varieties?

Answer 32

Pre-veraison, sunshine on the grapes will promote tannin accumulation Post-veraison, sunshine will promote greater tannin polymerisation (become less bitter or astringent)

Question 33

The length of grape ripening is dependent on what factors?

Answer 33

Grape Variety Climatic Conditions Vine and Vineyard Management Time of Harvest

Question 34

Explain what happens to the grapes if they are left on the vines for an extended period of time?

Answer 34

They will begin to shrivel since no more water of sugar is brought into the grape, even though there is water loss due to transpiration. This can lead to extra-ripe aromas.

Question 35

Where are the plants carbohydrate reserves stored?

Answer 35

In the roots, trunk, and branches