D1 Viticulture: Anatomy and Growth Cycle Flashcards
In-depth learning of the vine's anatomy and growth cycle. (134 cards)
1
Q
During what months are vines dormant in the Northern and Southern Hemispheres?
A
Northern Hemisphere: November - March
Southern Hemisphere: May - September
2
Q
Below what temperature do vines go dormant?
A
10ºC (50ºF)
3
Q
At what temperature does freeze injury/damage occur?
A
-20ºC (-4ºF)
4
Q
Temperatures below −___°C (−___°F) will kill most V. vinifera.
A
−25°C (−13°F)
5
Q
Vineyards facing west, which get afternoon sun, can experience what issues?
A
- Vineyard may become too hot, particularly if it’s in a warm climate;
- Grapes face increased risk of sunburn.
- In certain climates, west-facing vineyards tend to endure damper, cooler weather conditions.
6
Q
What are 3 advantages of sloping vineyards?
A
- Cold, dense air moves downhill displacing warmer air to higher levels, which produce warm thermal layers on the slope (like the Côte d’Or).
- Soils on slopes tend to be poorer, more coarsely textured and better drained;
- Slopes increase the angle at which solar radiation hits the Earth’s surface, thereby increasing the intensity of heat and light which in turn helps the grapes achieve greater ripeness and concentration.
7
Q
What are some disadvantages of sloping vineyards?
A
- Increased risk of erosion;
- Higher costs as it requires hand harvesting.
8
Q
What are four advantages of vineyards being planted close to a body of water?
A
The body of water:
- Reflects the sun’s rays;
- Provides source for irrigation;
- Reduces risk of ground frost;
- Can provide morning mists to encourage development of noble rot.
9
Q
What are the advantages of a vineyard being planted close to a forest?
A
The trees can act as a windbreak, store heat in cold weather, and reduce erosion.
However, forests can also harbor flocks of birds, which are pests.
10
Q
Temperature directly affects the yield of a vineyard by influencing:
A
- Vigor of the vines;
- Number of flower clusters and their size;
- Fruit set.
11
Q
Temperature directly affects the quality of a vineyard by influencing:
A
- Yield level;
- Accumulation of sugars and the reduction of acidity in the berry;
- Development of wine aromas.
12
Q
What is something a winegrower can do in a cool climate to increase the rate of photosynthesis?
A
Increase the amount of leaf area and canopy to compensate for slowed photosynthesis.
13
Q
List 5 major soil types.
A
- Limestone
- Chalk (lower density than limestone, so more free draining)
- Slate
- Granite
- Volcanic
14
Q
Why aren’t vines often planted as seeds?
A
Propagation from cuttings is quicker and easier;
- plus, propagation allows for grafting onto phylloxera-resistant rootstock
Vines grown 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
15
Q
What is the most important aspect of winter pruning?
A
Winter pruning dictates the number and location of buds that will form shoots in the next growing season.
Heavily pruned vines will grow fewer shoots the following summer (and so grow fewer leaves).
16
Q
What does the term ‘vine vigor’ refer to?
A
It refers to the general growth of the vine, and a vine’s vigor has ramifications on the yield and ripening of the grapes.
17
Q
What are three factors that influence a vine’s vigor?
A
- Available resources for the vine (water, nutrients, temperature);
- The vine’s variety, clone, and rootstock;
- Whether disease lives in the vineyard where the vine is planted, which can lower vigor.
18
Q
What are three things that can cause excessively low vigor, and what is the solution for each?
A
- Drought stress –> solved by irrigation (where allowed);
- Low soil fertility –> solved by increased fertilization and drainage;
- Disease –> solved by diagnosis and treatment.
19
Q
Chlorosis, yellowing of the foliage, is caused by what?
A
A deficiency of iron, nitrogen, magnesium, and/or sulfur.
20
Q
Chemical weed control (herbicides) can be organized into three groups:
A
- Pre-emergence herbicides;
- Contact herbicides;
- Systemic herbicides.
21
Q
Pre-emergence herbicides:
- Where and when are they best applied?
- How are they absorbed?
- What do they inhibit?
A
- Pre-emergence herbicides are sprayed to surface soil before weeds establish;
- They persist in the
surface layers of the soil but are absorbed by the weeds’ roots; - Inhibit the germination of young seedlings.
22
Q
Contact herbicides:
- To what are they applied?
- What do they destroy?
A
- Sprayed onto established weeds;
- Destroy the green parts of the weed that are sprayed, resulting in the death of the plant.
23
Q
Systemic herbicides:
- What are they sprayed onto?
- How are they absorbed?
- What do they destroy?
A
- Sprayed onto established weeds;
- Absorbed by the leaves and translocate in the sap (move upward and downward in the plant);
- These destroy the whole plant.
24
Q
How can wind damage be mitigated?
A
- Artificial Wind Breaks - mobile structures that provide instant protection. Expensive and will need to be replaced;
- Natural Wind Breaks - must be planted before vineyard is planted and established, e.g. trees with dense foliage. Trees can harbor pests and disease, and may need pruning and other maintenance.
For maximum effect the crop should be within 10x the height of the break.
25
What is lutte raisonée (aka integrated viticulture, or integrated pest management)?
* Synthetic agrochemicals are permitted but only when there is a clear need;
* Vineyards must be constantly monitored for pests and disease;
* Complete list of fertilizers, pesticides, and cultural practices are submitted and grower is inspected at least once per year.
26
Are biodynamic growers permitted to use Bordeaux mixture and/or sulfur?
Yes, biodynamic growers are permitted to use Bordeaux mixture and/or sulfur.
Bordeaux mixture: **3 kg/ha**
Sulfur: **7 kg/ha**
Sometimes dynamized ashes of target pests are sprayed onto the foliage in an attempt to control the pest.
27
What are the main sugars found in grapes?
**Glucose** and **fructose**, both metabolized by yeast.
28
Fructose is found in what kind of grapes?
**Late harvested**. Fructose is more difficult to ferment.
29
What happens if you have high concentrations of pectins in your grape juice?
How do you handle it?
**Pectins make it difficult to extract and/or clarify grape juice** (many aromatic varieties are high in pectins, e.g. Gewürztraminer and Viognier).
Remedy this by **adding pectolytic enzymes during grape processing**.
30
What are phenolic compounds?
A group of **chemical compounds that affect a wine's color, texture, astringency and bitterness**.
Smaller phenolic molecules (catechins and epicatechins) can taste bitter or waxy, or develop bitter tastes with oxidation.
31
Are anthocyanins phenolic compounds?
What are anthocyanins responsible for?
Yes, anthocyanins are phenolic compounds.
They are **responsible for red wine color**, and are found in the skins.
32
Are tannins phenolic compounds?
What are tannins responsible for?
Yes, tannins are phenolic compounds.
They are **responsible for** **astringency and contribute to the weight and body** of the wine.
## Footnote
(They are also antioxidants and preservatives.)
33
What is the difference between aspect and slope?
Slope is the angle of incline of the terrain.
Aspect is the direction the slope faces (east facing, west facing). Aspect relates to the degree of solar exposure.
34
Even though grapevines are drought resistant, they still need a minimum of __ mm of rain per year in cool climates and __mm of rain per year in warm climates.
* **500mm** in cool climates;
* **750mm** in warm climates.
35
Approximately how many hours of sunlight does a vine require during the growing season?
1300 hours
36
High soil pH (limestone-rich) contributes to higher \_\_\_\_ in grapes.
Low soil pH (acidic soils) can be a deterrent to viticulture. This can be countered by adding \_\_\_\_ to your soil.
High soil pH (limestone-rich) contributes to **higher acidity (low pH)** in grapes.
Low soil pH (acidic soils) can be a deterrent to viticulture. This can be countered by **adding lime** to your soil.
37
What are the four most important North American vine species?
1. Vitis **berlandieri**;
2. Vitis **labrusca**;
3. Vitis **riparia**;
4. Vitis **rupestris**.
38
What are the four anatomical structures of the vine?
1. Main shoots;
2. One-year-old wood;
3. Permanent wood;
4. Roots.
39
What are the parts that collectively make up the canopy?
1. Stem;
2. Buds;
3. Leaves;
4. Lateral shoots;
5. Tendrils;
6. Inflorescences/grape bunches.
## Footnote
*These are all structures of the main shoots*
40
In the spring, the main shoots of a vine grow from \_\_\_\_ retained from the previous year.
Buds
| Compound Buds would also be an appropriate answer
41
What role does the main axis of the shoot have in regards to how a vine functions?
* Transports water and solutes to and from the various vine structures;
* Stores carbohydrates.
## Footnote
see p.1, The Structure of the Shoots
42
What are solutes?
In regards to viticulture, they are sugars and minerals -- substances that dissolve in liquid to form a solution.
43
What is the difference between a node and an internode?
Node
* The swelling on the stem where other structures of the vine are attached.
Internode
* the area, or distance, between nodes.
## Footnote
*Fun Fact: The distance between nodes is an indicator of the rate of shoot growth, so internode length varies along the cane corresponding to varying growth rates during the season.*
44
What does it mean when shoots lignify?
When green shoots turn brown, and become woody and rigid.
Once this happens, that shoot is now referred to as a cane.
45
Where do buds form on the vine?
Between the leaf stalk (petiole) and the stem
46
What are buds made of (read: what do they become)?
Buds become all the green parts of the vine:
* Stem;
* Buds;
* Tendrils;
* Leaves;
* Inflorescences.
47
What are the two main types of buds?
1. **Compound** buds (also known as latent buds);
2. **Prompt** buds.
48
What is the main difference between compound buds and prompt buds?
Compound buds form in one growing season and break open in the next growing season;
Prompt buds form and break open in the same growing season.
49
What do compound buds produce?
Briefly describe what is inside a compound bud.
Compound buds produce **the main shoots in the next growing season**.
Inside a compound bud there is a **primary bud (the main growing point) and smaller secondary and tertiary buds**; *the latter buds usually only grow if the primary bud has suffered damage (e.g. spring frost).*
50
What do prompt buds produce?
Lateral shoots
51
On what do prompt buds grow?
They grow on the main shoot which had just grown from a compound bud.
52
Lateral shoots grow from buds formed in the:
* Current year
* Previous year
**Current year** (because they grow from Prompt buds)
53
Compared to main shoots, lateral shoots are:
* smaller and thinner
* larger and thicker
* the same size
Smaller and thinner
54
What structures do lateral shoots have?
1. Stem;
2. Leaves;
3. Buds;
4. Tendrils;
5. Sometimes inflorescences.
55
What is the main function of lateral shoots?
To allow the vine to continue growing if the tip of the main shoot has been damaged or eaten; they're especially helpful being an additional source of photosynthesis.
56
Why is it undesirable to have lateral shoots near the base of the main shoot?
They can **impede air flow and shade the fruit too much**.
## Footnote
*They're usually removed during summer pruning.*
57
What are the Pros of keeping the inflorescences on lateral shoots and letting them develop into clusters (also known as a 'second crop')?
* If they grow into clusters and are green harvested, **their removal is thought to improve the ripening process and enhance the uniformity of ripeness** of the remaining bunches;
* If they grow into clusters and are hand-harvested, the vineyard manager **can be selective and either give them a longer hang time or the clusters can be separated**.
58
What is the profile of bunches from a 'second crop' harvested at the same time as the main crop?
* Higher in acidity;
* Lower in potential alcohol;
* Potentially unripe tannins, aromas, and flavors;
* In black grapes, the bunches will have less color development.
59
What role do the tendrils have?
* Provide support for the vine;
* Help position the vine canopy;
* Help keep canopy in place.
60
What are stomata?
Stomata are pores on the underside of leaves that **allow a plant to** **take in carbon dioxide,** which is needed for photosynthesis;
They also allow **water vapor to** **diffuse out of the plant**, but when conditions are hot or dry they can close to reduce water loss, but limits photosynthesis by preventing carbon dioxide from entering the vine.
61
Where in the vine does photosynthesis mainly happen?
In the **leaves**
62
What is inflorescence?
A cluster of flowers on a stem which, when fertilized, develops into a bunch of grapes at fruit set.
63
How many inflorescences develop on each main shoot?
Between 1 and 3
64
What are the three main parts of a grape?
1. Pulp;
2. Skin;
3. Seeds.
65
What is a teinturier grape variety?
One that has **red-colored pulp**, as opposed to the majority of grape pulp which is colorless.
66
What does grape pulp consist of?
* Water;
* Sugars;
* Acids;
* Some aroma compounds and aroma precursors.
67
What does grape skin consist of?
* High concentrations of aroma compounds and aroma precursors;
* Tannins;
* Color compounds.
68
What do seeds consist of?
* Oils;
* Tannins;
* The embryo, which can grow into a new plant.
69
As seeds mature, their color goes from ___ to \_\_\_.
Yellow to dark brown
70
What is the powdery, waxy coating on grapes called?
Bloom
71
What does 'one-year-old wood' refer to?
The main shoots from the last growing season that were kept at pruning.
72
What is the most important function of one-year old wood?
It has the compound buds that will release the main shoots for the upcoming growing season.
73
One-year-old wood will either be called a ___ or a \_\_\_, depending on how the vine was pruned.
A **cane** or a **spur**
74
Any of the woody parts of the vine, including the trunk, that are older than one year are called ___ \_\_\_.
Permanent wood
75
What are cordons?
Horizontal "arms" of a vine made of permanent wood
76
What functions do the roots of a vine have?
* Anchor the vine to the soil;
* Uptake water and nutrients;
* Store carbohydrates;
* Produce hormones for growth and ripening.
77
Most of a vine's roots are found:
* In the top 25 cm of the soil
* In the top 50 cm of the soil
* In the top 100 cm of the soil
In the **top 50 cm of the soil**
78
How are vines propagated in today's viticulture?
By **cuttings** or **layering**
79
What is a cutting?
A section of a vine shoot that is planted which then grows as a new plant.
80
What is layering and how is it done?
Using a shoot from an established, neighboring vine to produce a new vine.
The shoot is bent down and a section of it is buried in the ground with the tip of it pointing up out of the ground. The buried part of the shoot takes root. Once the new roots are established, the cane linking the new growth to the original plant is cut.
The new vine now grows on its own roots, not those of a rootstock, which can be problematic in that the new roots don't offer any kind of resistance to phylloxera.
81
Why is layering done?
To fill in gaps in the vineyard, like when a vine is pulled or dies.
82
Cutting and layering generally produce vines that are:
* genetically identical to
* completely different from
the parent vine.
Genetically identical
83
During plant growth, random mutations in the genetic code of a vine create \_\_\_\_\_.
Clones
84
What is clonal selection?
When vine nurseries or grape growers propagate a vine that has somewhat different but desirable characteristics, or mutations, by using cuttings from that vine to grow new vines which will then have the same desirable and somewhat different characteristics (mutations).
Some clones have mutations such as higher yields, bigger or smaller grapes, and varying tannin levels, all of which can be applied to the needs of the grape grower and what style of wine they want to produce.
85
Why would a grape grower plant a number of different clones of the same grape variety rather than planting vines that are all the same clone?
* To increase diversity in the vineyard;
* To make the vineyard less susceptible to disease.
86
What is Mass Selection (also known as Sélection Massale)?
A term used to describe a traditional method of vineyard propagation.
Grape growers make a selection of particular vines within an old vineyard, and use this subset as the genetic stock to plant a new vineyard.
The vines selected for propagation have attributes which are important to the producer, whether that be yield, hardiness or sensory qualities.
87
What is a major downside of Mass Selection?
If the parent vine carries any disease, that disease will be passed down to the new vines through its cuttings, increasing the spread of the disease.
88
Describe the difference between Mass Selection and Clonal Selection.
Clonal selection and mass selection are often confusing. Simply put, mass selection is the old way – done ‘at home’ in the vineyard -- and clonal selection is done deliberately at a grapevine nursery. Both methods have their supporters and opponents, but many believe that massale selection preserves more diversity in the vineyard.
With mass selection a grower selects the vines from their vineyards that exhibit more desirable attributes and they use cuttings from these to plant new vines. So while these selected vines produce the finest fruit they are not necessarily totally identical.
Clonal selection takes mass selection to a deeper level, where better vines are selected for propagation again and again until there is a more precise vine that can be replicated at the nursery, be officially recognized, registered and made available for sale from the nursery. Clones are identical to their parent. The idea of clonal selection is to have an army of the same vine showing the same characteristic(s).
89
Generally, new grape varieties are typically produced from:
* Roots
* Seeds
* Cuttings
Seeds
90
What are the steps a grape grower would take to create a new grape variety?
1. Cross fertilize two vines;
* pollen from the flowers of one vine is transferred to the stigmas of the flowers of another vine;
2. Plant the seeds from this new plant and grow new vines;
3. These new vines that grow from the seeds will all have different characteristics, and if one of the new vines has desirable characteristics it may be propagated by cuttings to create identical vines.
91
What is the difference between a cross and a hybrid?
A cross is a plant offspring that has **two parent vines from the same species**.
A hybrid is a plant offspring that has **two parent vines from different species**.
92
What are the differing aims of creating and breeding crosses and hybrids?
The aim of creating and breeding a cross is usually to create an offspring that has favorable characteristics of the two parent vines;
The aim of creating and breeding a hybrid is usually to create an offspring that combines the resistance of non-vinifera species (to diseases, pests or climatic extremes) and the quality of fruit from V. vinifera.
93
When does budburst (also known as budbreak) occur in the Northern and Southern Hemispheres?
Northern Hemisphere: March - April
Southern Hemisphere: September - October
## Footnote
*Budbreak marks the end of winter dormancy*
94
What does the timing of budburst depend on?
1. Air temperature;
2. Soil temperature;
3. Grape variety;
4. Human factors.
95
What are the buds that are bursting during budbreak (prompt buds or compound buds)?
What air temperature do they need to burst?
* Budbreak buds are the **compound buds formed in the previous year's growing season**;
* The buds need a sustained average air temperature of **~10°C / 50°F**.
96
Why do regions that have a marked contrast in their seasonal temperatures (e.g. Continental climate) typically have a greater advantage of homogenous budbreak and subsequent growing phases, and even ripening over regions that have *less* contrast in their seasonal temperatures (e.g. Maritime climate)?
Rapidly increasing temperatures in the spring mean that the vines benefit from the rise in temperature and are in sync with each other development-wise, whereas a region that has less contrast between winter and spring temperatures can be confusing for the vines, particularly when there are mild days during winter when the vine is supposed to be dormant. This can lead to uneven budburst, and if there's a frost, uneven yields.
97
Higher soil temperatures around the roots encourage budburst to happen:
* Earlier
* Later
Earlier
## Footnote
*Dry, well-draining soils (e.g. sandy soils) tend to warm up more quickly than water-storing soils (e.g. clay-rich soils).*
98
Grape varieties that require relatively low temperatures at budburst are referred to as:
* 'early budding’
* 'early ripening'
* 'early rising'
'Early budding'
## Footnote
e.g. Chardonnay, Pinot Noir
99
Grape varieties that require higher temperatures are referred to as:
* ‘late budding’
* 'late ripening'
* 'late rising'
'Late budding'
## Footnote
e.g. Sauvignon Blanc, Cabernet Sauvignon
100
If vines are winter pruned late in the dormancy period, what can this do to budbreak?
* Encourage budbreak
* Postpone budbreak
* It doesn't affect budbreak
**Postpone** budbreak
## Footnote
*This technique can be used in areas where spring frost is known to be a problem.*
101
When do vines have shoot and leaf growth in the Northern and Southern Hemispheres?
Northern Hemisphere: March through June
Southern Hemisphere: September through December
## Footnote
see p.10 of version D1_Aug2024
102
The fastest rate of vine growth generally occurs:
* Between budburst and flowering
* Between flowering and fruit set
* Around véraison
Between budburst and flowering
103
What drives initial shoot growth?
Carbohydrates stored in the vine's roots, trunk and branches
104
What stimulates further shoot, leaf, and vine growth?
Photosynthesis, which increases with leaf development
## Footnote
*Remember: the vine needs adequate warmth and sunlight to photosynthesize*
105
What are the principal nutrients a vine needs to grow?
* Nitrogen;
* Potassium;
* Phosphorus.
106
What are some consequences if a vine experiences stunted shoot growth (which can happen from dry soils, poor nutrient availability, or water stress)?
* Small, weak shoots;
* Reduction in leaf number or smaller leaves;
* Inflorescences that don't flower properly;
* Grape bunches that do not ripen fully.
* this can lead to poor fruit quality and lower yields.
107
When is flowering and fruit set in the Northern and Southern Hemispheres?
Northern Hemisphere: May–June
Southern Hemisphere: November–December
108
What are some conditions in the present growing season that can limit bud fruitfulness for the next growing season?
* Shading of compound buds;
* Low temperatures (under 25°C / 77°F);
* Water stress;
* Nutrient deficiency.
109
The yield and quality of grapes in the current growing season are strongly influenced by:
* Flowering and fruit set
* Harvest date
* Aspect of the vineyard
Flowering and fruit set
110
In pollination, pollen grains are shed from the \_\_\_\_ and land on the moistened \_\_\_\_ surface.
Shed from the **stamen** (or anther) and land on the **stigma** surface
111
Flowering typically takes place within:
* 8 hours
* 8 weeks
* 18 weeks
weeks of budburst.
8 weeks
112
Fruit set is the term used to describe the transition from \_\_\_\_ to \_\_\_\_.
Flower to grape
113
For successful flowering, temperatures must be warm (~17°C / 63°F).
What happens if there are low temperatures during flowering?
* The duration of flowering is lengthened;
* The consequence of which is a negative effect on the evenness of ripening.
114
Typically, what percent of flowers become grapes?
30% (it can range from 0-60%)
115
The two common forms of irregular fruit set are:
1. Coulure
2. Millerandage
116
What is coulure, and what causes it?
A high proportion of **failed fruit set** in grape bunch (unsuccessful fertilization).
Coulure is **caused by an imbalance in carbohydrate levels**, and that imbalance can be caused by:
* **low photosynthesis** (cloudy conditions or water stress);
* **improper canopy management** (vigorous shoot
growth diverting carbohydrates
from the inflorescence);
* **overly-fertile soil**.
## Footnote
Some coulure is normal; excessive coulure can reduce yield.
117
Millerandage:
1. What is it?
2. What causes it?
1. It's when a high percentage of grapes within a bunch are seedless and, usually, smaller than the normal berries with properly formed seeds;
* these smaller grapes can either ripen normally or stay unripe, which can affect the quality of the crop;
2. Caused by unfavorable weather (cold, wet, windy) at fruit set.
118
When does grape development occur in the Northern and Southern Hemispheres?
Northern Hemisphere: June–September
Southern Hemisphere: December–March
119
What are the four stages of grape development?
**Which stage** is the most important in determining final grape quality?
1. Early Grape Growth;
2. Véraison;
3. **Ripening**;
4. Extra-Ripening.
120
Berry formation starts soon after:
* Flowering
* Fruit set
* Harvest
Fruit set
121
What is happening inside the grape during berry formation (early grape growth)?
* Accumulation of tartaric and malic acids;
* Accumulation of tannins;
* Development of aroma compounds and aroma precursors;
* High water flow into the grape;
* Low sugar levels.
122
What does the vine need during berry formation?
1. Sunlight;
2. Warmth;
3. Mild water stress.
123
What happens if a vine gets too much water and nutrients during the berry formation stage?
**Shoot growth is encouraged over grape ripening, which delays the onset of the ripening stage** which means that the grapes might not ripen fully in time for harvest.
124
Grape varieties with tight bunches, such as Sémillon and Pinot Noir, can be prone to fungal disease. Why?
* The possibility of their grape skins splitting during the growth cycle is increased due to the very nature of their tight, compact bunches;
* Lack of air flow in the crowded bunches increases humidity, and if the skins split then disease is difficult to avoid.
125
What is véraison?
When grape berries change color signaling the onset of final ripening.
White grapes go from green to yellow, and red grapes go from green to red.
126
What's happening inside the grape during the ripening stage?
1. Cells in the grape expand rapidly;
2. Sugar and water accumulate;
3. Acid levels fall;
4. Tannins, color, aroma precursors and aroma compounds develop.
127
How can excessively cloudy or excessively hot and dry conditions affect the ripening stage?
If cloudy conditions, photosynthesis slows and can interfere with sugar accumulation (read: lead to under-ripe grapes);
If hot and dry conditions, photosynthesis slows or can even stop, also interfering with sugar accumulation.
128
In warm, dry conditions grape transpiration (and sugar accumulation) is:
* faster than in cool, humid conditions
* slower than in cool, humid conditions
* grape transpiration and sugar accumulation never fluctuate
Faster than in cool, humid conditions
129
What is respiration?
Vines produces energy by combining sugars (from photosynthesis), oxygen, and other compounds with water and carbon dioxide.
During respiration, that **energy stored by the vine is released**.
130
Why do wines from cooler climates tend to have higher natural acidity?
Because malic acid is used in respiration during the ripening stage, and **respiration is slower at cool temperatures** than warm ones.
This is also why cooler nighttime temperatures are important for producing balanced grapes with fresh acidity.
131
During the ripening stage in a normal year, which compound levels increase and which compound levels decrease in the grapes?
Increase:
* Aroma compounds and aroma precursors
* Anthocyanins
Decrease:
* Methoxypyrazine
* Tannins (they polymerize)
132
What are the two biggest differentiators in how grapes ripen during the ripening stage?
1. Heat;
2. Sunlight.
133
What are four factors that determine the length of the ripening stage?
1. Grape variety;
2. Climatic conditions;
3. Vine and vineyard management;
4. Time of harvest.
134
What happens inside the grape during the extra-ripening stage?
Sugars accumulate (and water is lost) from grape transpiration
