The Vine Growth Cycle Flashcards
Explain the nature of the vine?
A vine left to grow without human intervention has different aims. In the wild, vines are woodland climbers. They grow quickly, clinging to trees for support and when they reach sunlight at the top of the woodland canopy, they flower and produce fruit.
The key purpose of the grapes is to attract birds and other animals, which eat them and disseminate the seeds. These grapes may be palatable for the birds, but they would not be suitable for producing wine.
Given their natural habitat in woodland locations, with high competition from other plants, vines are able to survive on limited natural resources. However, the vine does require access to adequate water, sunlight and warmth for photosynthesis. (Carbon dioxide is also required for photosynthesis. It becomes the limiting factor for photosynthesis if the vine has sufficient water, temperature, sunlight and nitrogen, but is outside the control of the grape grower.)
Warmth is also needed for other essential reactions such as respiration, the process in which energy is released from food substances, in this case, sugar. Nutrients are also important for cell structure and function and therefore vine growth and reproduction.
Explain dormancy?
November–March in the Northern Hemisphere, May–September in the Southern Hemisphere.
What the vine needs during this stage: - Temperatures below 10°C (50°) Adverse conditions: - Extremely cold temperatures - Unusually mild temperatures
Winter dormancy typically starts with leaf fall in the autumn and ends with budburst in the spring. Without leaves, the vine cannot photosynthesise. Therefore, until it has grown new leaves, the vine supports its growth by using stores of carbohydrates, mostly starch, accumulated during the previous growing season in the roots, trunk and branches.
Extreme lows in temperature, such as those found in the winter in Canada, New York State and China, can be harmful to the vine even when it is dormant. Vines can be severely damaged or killed by temperatures below −15°C (5°F). Temperatures below −25°C (−13°F) will kill most V. vinifera.
Explain budburst? And the effects of air temperature, soil temperature, grape variety and human factors?
March–April in the Northern Hemisphere, September–October in the Southern Hemisphere.
Budburst, also called budbreak, marks the end of winter dormancy. In this process, buds swell and open, and green shoots start to emerge. The timing of budburst depends on a number of factors.
What the vine needs during this stage: - Average air and soil temperatures above 10°C (50oF) Adverse conditions: - Frost - Cold soils
AIR TEMPERATURE
Compound buds form in the previous growing season.
Regions that have marked differences in temperature between the various seasons (for example, continental climates) can be advantageous for successful budburst.
In regions where there is often less contrast between winter and spring temperatures (for example, maritime climates), budburst can be less synchronised.
Furthermore, problems can occur when a few unusually mild winter days cause early budburst; any cold days and frosts that follow can potentially harm the newly burst buds, leading to lower yields.
SOIL TEMPERATURE
Higher soil temperatures around the roots encourage earlier budburst. Dry, free-draining soils, such as sandy soils, tend to warm up more quickly than water-storing soils, such as clay-rich soils, and therefore can be advantageous in cool climates where an early start to the growing season improves the chance of ripening.
GRAPE VARIETY
The average temperature required for budburst depends on the grape variety.
Grape varieties that require relatively low temperatures at budburst are referred to as ‘early budding’.
Grape varieties that require higher temperatures are referred to as ‘late budding’.
Because the buds of late-budding varieties need higher temperatures to burst, they are less at risk of spring frosts. (Please note that time of budding is not always linked to time of ripening and hence a grape variety that is early budding is not necessarily also early ripening.
HUMAN FACTORS
Some viticultural practices can also advance or delay budburst. For example, carrying out winter pruning late in the dormant period can postpone budburst, and this technique can be used in areas where spring frost is a known problem.
Name early budding and early ripening grape varieties?
Chardonnay Pinot Noir Zinfandel Cabernet Franc Pinot Gris Merlot?
Name early budding but late ripening grape varieties?
Chenin Blanc Grenache Sangiovese Gewurztraminer Malbec Muscat Nebbiolo Viognier
Name late budding but early ripening grape varieties?
Sauvignon Blanc
Syrah
Tempranillo
Riesling
Name late budding and late ripening grape varieties?
Cabernet Sauvignon
Carmenere
Semillon
Explain shoot and leaf growth? Also breakdown what nutrients the vine needs?
March–July in the Northern Hemisphere, September–January in the Southern Hemisphere
What the vine needs during this stage: - Stored Carbohydrates - Warmth, sunlight, nutrients and water Adverse conditions: - Low carbohydrate levels (caused by conditions in the previous growing season) - Water stress
Carbohydrates stored in the roots, trunk and branches of the vine support the initial shoot growth.
As leaves develop and mature, they provide energy for further growth via photosynthesis, and therefore need adequate warmth and sunlight for this to take place. Most of the vine’s energy is directed towards shoot growth until flowering starts.
As the vine grows, so does the vine’s need for nutrients (principally nitrogen, potassium and phosphorus). It is important that vines do not suffer from water stress in this time as this can limit photosynthesis and shoot growth. Nutrient uptake through the roots is also impaired in very dry soils.
Explain flowering and fruit set?
May–June in the Northern Hemisphere, November–December in the Southern
What the vine needs during this stage:
- Warm temperatures (minimum 17°C/63oF)
- Sunlight, warmth, water and nutrients for bud fruitfulness in the next growing season Adverse conditions:
- Rainy
- Cloudy
- Windy
- Cold temperatures
New buds develop at the base of the leaf stalks (petioles) on the new growing shoots. Prompt buds will burst within the growing season producing new shoots called lateral shoots. Compound buds will remain dormant until the following spring and provide the shoots for next year.
The yield and quality of grapes in the current growing season are strongly influenced by the processes of flowering and fruit set. Flowering describes the opening of the individual flowers within an inflorescence.
Within this process, the pollen-laden stamens (consisting of an anther and filament) are exposed. The pollen grains are shed and land on the moistened stigma surface, a process called pollination. Here, they germinate, with each pollen grain producing a pollen tube. These pollen tubes penetrate the stigma and then the ovule (the female reproductive cells) in the ovary. The pollen tube delivers the sperm cells, which fertilise the eggs in the ovule. This leads to the formation of a grape berry. The fertilised ovules form seeds, with up to four per grape.
Fruit set is the term used to describe this transition from flower to grape. Research has shown that cultivated varieties of vines are normally self-pollinating.
Typically, 30 per cent of flowers will become grapes, but this can range from zero to 60 per cent. Pollen germination requires warm temperatures (optimal at 26–32°C / 79–90°F).
What is coulure? And which grape varieties are naturally more susceptible?
A condition of the grape bunch in which fruit set has failed for a high proportion of flowers. This occurs when ovule fertilisation is unsuccessful, and therefore no grape develops. Some coulure is normal; however, excessive coulure can reduce yield dramatically.
Coulure is caused by an imbalance in carbohydrate levels. This can result from low rates of photosynthesis, which may be caused by cold, cloudy conditions or hot, arid conditions with high water stress (the vine stops photosynthesis to retain water). It can also result from vigorous shoot growth diverting carbohydrates from the inflorescence. Very fertile soils, heavy application of fertilisers and vigorous rootstocks can all cause strong shoot growth and therefore lead to coulure.
Some grape varieties are also naturally more susceptible to coulure than others; Grenache Cabernet Sauvignon Merlot Malbec
What is millerandage? And which grape varieties are naturally more susceptible?
A condition of the grape bunch in which there is a high proportion of seedless grapes. The seedless grapes can still ripen normally, but are smaller than grapes with seeds. Millerandage may therefore reduce the volume of wine that can be produced. Some seedless grapes stay small, green and unripe, which can be negative for wine quality. Millerandage can result from cold, wet, windy weather at pollination and fruit set.
Some varieties are more susceptible than others:
Chardonnay
Merlot
Explain grape development and its 4 stages?
June–October in the Northern Hemisphere, December–April in the Southern Hemisphere
What the vine needs during this stage: - Sunlight - Warmth - Mild water stress Adverse conditions: - Too much water and nutrients - Excessive shading of grapes - Very cold or very hot conditions throughout the day and night
Stage 1: Early Grape Growth
This stage starts soon after fruit set. Hard green grapes start to grow in size, and tartaric and malic acids accumulate. Some aroma compounds and aroma precursors (compounds with no aroma that will become aroma comounds during the fermentation process) also devlop, such as methoxypyrazines.
Sunshine on the grapes promotes tannin accumuldation. Sugar levels are low and water flows into the grape, transported by the xylem.
Stage 2: Veraison
Grape growth slows down for a few days (often called the lag phase). The grape cell walls become more stretchy and supple, green-coloured chlorophyll in skin cells is broken down and grapes of black varieties start to become red in colour due to the synthesis of compounds called anthocyanins.
Stage 3: Ripening
This is arguably the most important vine process in determining final grape quality. Shoot growth should have slowed down substantially by this time. During this stage, the cells in the grape expand rapidly, sugar and water accumulate and acid levels fall. Tannins, colour and a number of aroma precursors and aroma compounds develop. Harvest usually marks the end of this stage.
Sugar accumulation is very rapid at the start of the ripening stage and then slows towards the end. Sugar is produced in the vines’ leaves by photosynthesis. Photosynthesis can take place at a maximum rate at temperatures between 18–33°C.
During this stage of ripening, water flow via the xylem slows down and a sugar solution (a mixture of mainly sugar and water) is transported by the phloem into the grape.
The total amount of tartaric acid in the grape generally does not change; however, its concentration falls during ripening due to dilution, as sugar and water accumulate in the grape.
Mean temperatures above 21°C (70°F) in the final month of ripening can lead to a rapid loss of acidity (and a rise in pH).
During ripening, methoxypyrazine levels fall, but cool temperatures and limited sunlight (e.g. due to excessive shading of bunches) can hinder this decrease and the resulting wines may show particularly herbaceous aromas/flavours.
Other aroma compounds and aroma precursors increase during the ripening stage (e.g. terpenes, which give floral and citrus aromas such as the grapey aromas found in Muscat).
Stage 4: Extra-Ripening
If the grapes are left on the vine, they start to shrivel. No more sugar or water are imported to the grape by the phloem at this stage, but water loss in the grape through grape transpiration means that sugars are concentrated. Extra-ripe aromas can also develop in this stage. This may be desirable in some styles of wine, but not in others.
Grape shrivelling is most likely in hot, sunny, dry climates. In addition, some grape varieties are more susceptible than others (e.g. Syrah is particularly susceptible). The capacity to leave grapes on the vine also depends on weather conditions and disease pressure.
What are anthocyanins?
Anthocyanins are the most important natural colourants in wine grapes. Anthocyanins are a group of naturally occurring phenolic-compounds that are responsible for the red, purple and blue colours found in many fruits, vegetables and wine grapes.
On what factors does the length of the grape ripening stage depend on?
Grape variety – Some grape varieties naturally ripen earlier than others.
Climatic conditions – Sugar ripening is quickest in warm, dry conditions. However, very hot or dry conditions can cause the vine to shut down, which inhibits grape formation and ripening.
Management of the vine and vineyard – Heavy crop loads, excessive shading within the vine canopy and shoots that are still actively growing can all slow down ripening.
Time of harvest – Harvest depends on human factors (desired wine style, logistics) or natural factors (weather such as rain, onset of disease).
What is considered as optimal ripeness and how do you define ripeness?
The main aim of the grape grower or wine producer is to get the grapes ripe for the style of wine being made. What is determined as ‘ripe’ may depend on a number of parameters.
Optimal ripeness is the time at which the combination of the sugar, tannin and aroma ripeness is at its most favorable.
