The Vine Growth Cycle

Question 1

When is Dormancy in the northern and southern hemispheres, and what temperature does the vine need?

Answer 1

November- March in the northern, and May-September in the southern.
10 degrees/50 F
Below -20, damage or kill vine

Question 2

Briefly describe dormancy

Answer 2

No leaves, no photosynthesis, vine relies on carbs (starch) from previous growing season.

Question 3

When is budburst in the northern and southern hemispheres, and what temperature does the vine need?

Answer 3

March- April- northern
September-October- southern
Above 10c, 50 F

Question 4

Describe how air temperature can affect budburst

Answer 4

Regions with large differences between winter and spring good with uniformity of budburst and ripening.
Regions with less difference, can make budburst uneven, and if have mild winter days, budburst can be early, and then be later affected by spring frosts.

Question 5

Describe how soil temperature can affect budburst

Answer 5

The warmer the soil temperature, the earlier budburst.
Sandy soils are warmer than clay soils, can be an advantage in cooler climates- improves ripening.

Question 6

Give some examples of early and late budding grape varieties

Answer 6

Early budding- chardonnay, merlot, pinot noir, grenache.
Merlot- below 10c, ugni blanc, above 10c.
Late budding- Sauvignon blanc, cabernet sauvignon, syrah
Early budding- risk of frost

Question 7

Name a human factor that affects budburst

Answer 7

Late winter pruning in dormant period- postpones budburst

Question 8

When is shoot and leaf growth in the northern and southern hemispheres?

Answer 8

March-July- northern
Sept-January- southern

Question 9

What does the vine need for shoot and leaf growth, and what are the adverse conditions?

Answer 9

Stored carbs, water, nutrients, warmth, sunlight.
Water stress, low carbs

Question 10

How does vigour affect shoot and leaf growth?

Answer 10

Implications on yields and ripening
Depends on:
Natural resources

Question 11

How do low levels of carbohydrates affect shoot and leaf growth, and why would they be low?

Answer 11

If carbs low, reduces shoot and leaf growth.
Due to excessive pruning, excessive high yields, water stress, mildew infections
As leaves develop and mature, provide energy for photosynthesis- need warmth and sunlight.
Carbs stored in roots, trunk, branches, support initial shoot growth.

Question 12

Which nutrients does the vine need during shoot growth?

Answer 12

Nitrogen, potassium, phosphorus.
Also needs water- important there is no water stress.

Question 13

What happens to the vine if there is stunted shoot and leaf growth?

Answer 13

Small weak shoots, reduction in leaves, inflorescences don’t ripen properly= poor quality and lower yields

Question 14

When is flowering and fruit set and what does the vine need?

Answer 14

May-June- northern
Nov-Dec- southern
The vine needs water, warmth (min 17c), sunlight and nutrients
Adverse- rainy, cloudy, wind, cold

Question 15

Describe the process of flowering

Answer 15

New buds develop at base of petiole on new growing shoots.
Prompt buds burst within growing season- produce lateral shoots.
Compound buds dormant until following season.
Flowering= opening of individual flowers within an inflorescence.

Question 16

What is pollination?

Answer 16

The pollen-laden stamens (consisting of anther and filament) are exposed, and the pollen grains shake on the moistened stigmas.
They germinate, each pollen grain produces pollen tube. Pollen tube penetrates the stigma, then ovule in ovary.
Pollen tube delivers sperms cells to ovulate egg- leads to formation of grape berry.

Question 17

What is fruit set?

Answer 17

When the fertilised ovule forms seeds- 4 per grape.
The wall of ovary enlarges to form skin and pulp of grape.

Question 18

What are the conditions for successful flowering?

Answer 18

Flowering usually within 8 weeks of budburst (temp dependent).
Warm conditions (above 17)= individual inflorescence can start and finish within few days,
Cold= takes few weeks= bad for even ripening

Question 19

What are the conditions for successful fruit set?

Answer 19

Warmth- 26-32 degrees
To windy, wet, cold= bad- irregular fruit set, low yields
Too hot, arid, dry= bad- reduced yields

Question 20

What is coulure?

Answer 20

Fruit set failed for a high proportion of flowers.
Occurs when ovule fertilisation unsuccessful- no grape develops.
Caused by imbalance in carbs level- due to cold weather (photosynthesis), hot weather- water stress. And vigorous shoot growth diverting carbs from inflorescence.
Susceptible- grenache, cab sav, merlot, malbec

Question 21

What is millerandage?

Answer 21

A high proprtion of seedless grapes. Berries remain small green and unripe- reduce vol of wine.
Cold, wet, windy weather at fruit set.
Chard, merlot.

Question 22

Describe early growth in Grape Development

Answer 22

Hard green grapes grow, tartaric and malic acid increases.
Aroma compounds and precursors develop- methoxypyrazines.
Tannins accumulate, low sugar.
Water flow- high- Xylem tissue
Too much water and nutrients- bad- too much shoot growth instead of ripening grapes= delay in ripening.
Mild water stress- good- reduced yields but greater concentration- good quality.
June-Sept
Dec-March

Question 23

What happens during veraison?

Answer 23

Grape growth slows down- ‘lag phase’
Grape cell walls become more stretchy and supple- green coloured chlorophyll in skin cells break down
Black- red in synthesis of anthocyanins.

Question 24

What happens during the Ripening stage?

Answer 24

Shoot growth slows, grape cells expand rapidly.
Sugar and water accumulate, acid falls.
Tannins, aroma cs & ps develop.
Water flow via xylem slows, and sugar transported from leaves to to grape by phloem tissue.
Tartaric acid falls, malic falls even more.
Mean temp of above 21 in final month of ripening= rapid loss of acidity.
Mean temp of below 15= acid loss- too much.
Methoxypyrazine levels fall, terpenes increase.

Question 25

What does the length of ripening period depend on?

Answer 25

Grape variety- chardonnay an pinot noir
Climactic conditions
Management of the vineyard
Time of harvest- human influence and style wanted etc.