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
