Chapter 2 - The Vine Growth Cycle Flashcards
Dormancy:
Months
Needs
Adverse Conditions:
November - March (leaf fall - budbreak)
Temp below 10C
Extreme cold or mild temps
During dormancy, temps below what will kill vines?
-25C
Budburst:
Months
Needs
Adverse Conditions:
March - April
Avg air and soil temps above 10C
Frost, cold soils
Factors that affect when budburst happen
Air temp
Soil temp
Grape variety
Human factors
Why is continental climate beneficial for bud burst? Why is mediterranean climate not?
Because it has marked differences in temperature between seasons
Rapidly increasing temps in the spring means uniform budburst, means even ripening later on
Mediterranean climates don’t have a marked difference in temp
Also, mild winters are often and they can cause early budburst. Any frost or dip in temp after that can harm/kill the buds. Leads to lower yields
What kind of soil is advantageous for budburst? Why?
Sandy soils - bc it is dry, free-draining, and warms up quicker than water storing clay. Especially advantageous in cool climates
What are early budding varietals? Example?
Ones taht require relatively low temps at budburst (ie Merlot)
What are late budding varietals? What’s the pro of them?
Late budding: Sauv Blanc, Cab, Syrah
Less risk of spring frost
What is a human activity that can delay budburst?
Carrying out winter pruning later in the dormant period. Can be used to prevent spring frost
Shoot & Leaf Growth
Months
Needs
Adverse Conditions
March-July
Stored carbs, warmth, sunlight, nutrients, water
Low carb levels, water stress
What is plant vigor dependent on?
Natural resources available (sunlight, water, nutrients, warmth)
Planting material (varietal, rootstock, clone)
Presence of disease
How do low carb storage and water stress negatively affect vine growth?
Stored carbs are important for initial shoot growth and providing the necessary sugars until the leaves grow and are able to perform photosynthesis
Vines that suffer from water stress at this time can limit photosynthesis and shoot growth
Shoot growth is MOST IMPORTANT at this stage
What can cause low carb storage levels?
In the previous growing season: Excessive leaf removal Water stress Mildew infections Excessively high yields
Flowering & Fruit Set
Months
Needs
Adverse Conditions
May - June
Warm temp (min 17C)
Sunlight, warmth, water, nutrients - for bud fruitfulness in the next growing season
Cold temp, wind, rain, cloudyness
What will cause limited bud fruitfulness?
Shading of the compound buds, water stress, nutrient deficiency, low temps under 25C
Describe the process from flowering to fruit set
- Flowers open in an inflorescence
- Pollen-laden stamens are exposed
- Pollen grains are shed and land on the surface of the stigma (POLLINATION)
- Pollen germinates and each pollen produces a pollen tube
- Pollen tube penetrates the stigma and ovule (in ovary)
- Pollen tube delivers sperm cells to egg (FERTILIZATION)
- Berry formation occurs - fertilized ovules form seeds and wall of the ovary enlarges to form skin and pulp
When does flowering typically occur? What can cause it to happen earlier/later
Within eight weeks of budburst Warm temps (min 17C) are favored
Why is a long flowering period not desired?
When flowering takes weeks, grapes form at differnet time and ripen at different times (caused by low temps)
Typically what percentage of flowers become grapes?
Avg 30%
Ranges from 0-60% usually
What does successful fruit set need?
Pollen germination requires warm temps (26-32C)
Pollen tube growht is negatively affected by cold, rainy, and windy conditions - causes irregular fruit set
Hot, dry, windy conditions cause water stress and can also have a negative affect
What are the 2 common forms of irregular fruit set?
Coulure
Millerandage
Describe Coulure
Fruit set fails for a high proportion of flowers
Occurs when ovule fertilization is unsuccessful
Caused by: imbalance of carb levels, vigorous shoot growth diverting carbs from inflorescence (caused by fertile soils, heavy application of fertilizers, vigorous rootstocks, etc)
Describe Millerandage
A high proportion of grapes are seedless and are smaller in size ==> reduces volume of wine made
Seedless grapes can also stay small, green, unripe
Result from cold, wet, windy weather at fruit set
Grape Development
Months
Needs
Adverse Conditions
June - October
Mild water stress, Sunlight, Warmth
Too much water and nutrients, excessive shading, very cold or hot conditions
Four stages of grape development
Early Grape Growth
Veraison
Ripening
Extra Ripening
What happens during the early grape growth stage?
Hard green grapes grow in size, tartaric and malic acids accumulate
Aroma compunds/precursors develop (ie. Methoxypyrazines)
Tannins accumulate (very bitter at this time) (Sunshine promotes tannin accumulation)
Shoot growth still continues but more slowly now
Sugar levels are low
Water flow into the grape is high
What can slow down and what can speed up hte early grape growth stage?
Slow down: too much water and nitrogen
Because these encourage shoot growth over grape ripening so ripening is delayed and tehre may not be sufficient time before harvest must happen
Speed up: Mild water stress
Can lead to smaller grapes, reducing juice yield but greater skin to pulp ratio (can be a pro ie in high quality reds)
What mainly transports water to the grapes during early grape growth?
The xylem - type of transport tissue that transfers water and some nutrients from the roots to the other parts of the vne
Describe what happens during Veraison
Grape growht slows down for a few days (lag phase)
Grape cell walls become more stretchy and supple, green colored chlorophyll in the skin sells break down
Black varieties become red due to synthesis of anthocyanins
Describe what happens during ripening
Most important stage for determing grape quality
Cells in grape expand rapidly
Sugar and water accumulate - sugar accumulates very quickly at first (photosynthesis v imp)
Acid levels fall (tartaric & malic)- acid amount does not change but becomes diluted as sugar & water accumuate
Tannins, anthocyanins, aromas develop :
Methoxypyrazine levels fall
Terpenes increase
Tannins polymerize and become less bitter
Shoot growth has substantially slowed down
Why is sugar accumulation within the grape during ripening correlated to rate of grape transpiration?
During ripening, water and sugar soln are transported to the grape by the phloem that transfers it directly from the leaves
So when water leaves the grapes, it is actively replaced by this sugary solution
Why does malic acid concentration decrease more than tartaric’s during ripening?
At this stage, malic acid is metabolized during respiration, not sugar. Respiration rate is faster in warm temps (cool night tiems mean less malic acid loss)
What is length of ripening stage dependent on:
Grape variety
Climatic Conditions
Vine/Vineyard management
Time of Harvest
Describe Extra-Ripening
No more water nad sugar are imported into the grape by the phloem but grape transpiration still happens ==> grapes shrivel
Sugars concentrate
Extra-ripe aromas develop
What factors determine ripeness?
Level of Sugar
Level of Acidity
Profile of the aromas/flavors
Tannin Ripeness
What happens to the vine after harvest and as it enters its dormancy period?
Shoots lignify into canes
Roots, trunks, permanent wood store carbohydrates
