The Growing Environment Flashcards
Explain the effects of temperature during vine growth, grape formation and ripening?
Temperature has a huge influence on vine growth and/or grape ripening in all parts of the vine growth cycle. A summary is provided below:
Cold Temperatures ensure dormancy.
Temperatures above 10°C stimulate bud
What is the optimal temperature for winter dormancy?
Cold temperatures (under 10°C / 50°F) in the winter ensure the dormancy of the vine, however, extreme temperatures (around -20°C / -4°F) can cause winter freeze and damage the vine.
What temperature stimulates budburst?
Temperatures above 10°C (50°F) stimulate budburst, and budburst is often more successful and uniform if there is a significant rise in temperature at this point. Warm soil temperatures can also promote budburst. Cold temperatures that bring frost can be very harmful for buds and new growth and can reduce yields substantially.
What’s the optimal temperature range for photosynthesis?
As the new shoots grow and leaves develop, the vine begins to use photosynthesis to create sugar for energy. The optimum temperature range for this approximately 18–33°C (64–91°F), and hence temperature is not usually a limiting factor at this time.
What temperature promotes successful uniform flowering and fruit set?
Warm temperatures promote successful, uniform flowering (optimum above 17°C / 63°F) and fruit set (optimum range 26–32°C / 79–90°F), whereas cold, damp conditions can cause problems for flowering and fruit set and therefore reductions in yield and potentially quality of the grapes and wine.
What temperature promotes bud fruitfulness?
Warm temperatures at this time also promote increased bud fruitfulness (above (under 25°C / 77°F is best) in the next year, and therefore affects yields in the next growing season.
What influence does temperature have on the various aspects of grape ripening?
Sugar accumulation in the grapes in generally faster at warm temperatures due both optimum rates of photosynthesis producing sugars and because increased grape transpiration promotes the movement of sugar into the grape.
Malic acid degradation is also increased at warm temperatures. Mean temperatures above 21°C (70°F) in the final month of ripening can lead to a rapid loss of acidity, whereas mean temperatures below 15°C (59°F) can reduce acid loss to a point that acidity levels in the must are too high.
The effect of temperature on the formation of aroma precursors and aroma compounds is very complex; generally riper aroma/flavours are associated with grapes grown in warmer climates.
Cool conditions may hinder the breakdown of methoxypyrazines, which can give herbaceous aromas.
In black grapes, anthocyanin synthesis (and therefore the development of colour) is optimum at 15–25°C (59–77°F). (Tannin synthesis possibly follows the same pattern, but more research is needed.)
How does extreme heat affect the grape ripening?
Extreme heat, especially when paired with dry conditions, can cause photosynthesis to slow or stop, slowing vine growth and grape ripening. This is due to the heat sensitivity of enzymes that catalyse photosynthesis.
In addition, water stress, which is typical in many hot regions, can also cause photosynthesis to slow down or stop due to the shutting of stomata to prevent water loss. The closed stomata limit intake of carbon dioxide, which is needed for photosynthesis.
Explain the effects of sunlight on vine growth, grape formation and ripening?
The vine needs sunlight for photosynthesis, which is needed for vine growth and grape berry formation and ripening.
However, full sunshine (intense sunlight, not
blocked by cloud) is not required, and generally amount of light only becomes the limiting factor to rate of photosynthesis if light levels drop below one third of full sunshine. Hence, fog can slow photosynthesis but an average cloudy day will not.
Grape exposure to sunshine has a number of effects, including enhancing the development of anthocyanins (colour pigments) in black grapes and the reduction of methoxypyrazines.
Sunshine on the grapes leads to greater accumulation of tannins pre-véraison and promotes tannins polymerisation after véraison, and therefore less bitterness.
It is also associated with increased levels of some favourable aroma precursors and aroma compounds (such as terpenes which are responsible for many of the fruity and floral aromas in wines, such as the grapey aromas found in Muscat).
Sunshine also warms the grapes and because of this increases the rate at which malic acid is used up in grape respiration, leading to lower acidity levels.
Prolonged periods of sunshine and hot temperatures can lead to sunburn on sun-exposed grapes, which has a negative effect on grape quality and yields.
Sunshine in late spring / early summer is also associated with successful fruit set and the exposure of compound buds to sunshine promotes bud fruitfulness in next year’s growing season.
List some of the natural factors that effect temperature and sunlight?
Latitude Altitude Slopes and aspect Proximity to water Winds Characteristic of the soil Mist, fog and clouds
Explain the effects of latitude?
All other factors being equal, regions at lower latitudes (nearer the Equator, e.g. Mendoza, South Africa, New South Wales) will receive more solar radiation per annum than regions at higher latitudes (nearer the Poles, e.g. northern France and Germany).
Regions nearer the Equator receive more intense solar radiation than those nearer the poles. Solar radiation is adsorbed (held by water droplets, dust and ozone) and scattered as it travels through the Earth’s atmosphere, decreasing its intensity.
The curvature of the Earth means that nearer the poles solar radiation must travel through a larger section of atmosphere to reach the Earth’s surface. It also means that the radiation hits the Earth at a low angle, so the radiation is spread over a larger area (it is more diffuse).
The number of hours of solar radiation through different times in the year is also determined by latitude.
It is generally said that grapes for wine production can grow between 30° and 50° latitude on each side of the Equator.
Explain the effects of altitude?
Temperature falls by approximately 0.6°C (1.1°F) over every 100 m increase in altitude. High-altitude sites can therefore be
favourable in areas of low latitude that would otherwise be too hot. There are vineyards in Salta (a low latitude region) planted at up to approximately 3000 m above sea level, and here grapes may struggle to ripen sufficiently every year. By comparison, many of the best vineyard sites in high latitude areas, such as Burgundy and Loire Valley, are at relatively low altitudes, as otherwise temperatures would be too low for sufficient ripening.
Sunshine is more intense at high altitudes than low altitudes because the solar radiation travels through less atmosphere before it reaches these sites. Ultraviolet radiation (radiation with a lower wavelength than visible sunlight) is also greater at higher altitudes. Both of these factors are thought to promote anthocyanin and tannin synthesis.
High-altitude sites often have a high diurnal range (the difference between day and night temperatures). The ground absorbs energy from solar radiation during the day and releases energy into the atmosphere during the night. At lower altitudes the air in the atmosphere (particularly the water vapour) absorbs some of this energy, meaning some heat is retained at night. At high altitudes the air is thinner and holds less moisture and therefore heat rapidly escapes, leading to relatively cool night-time temperatures. In warm climates, high diurnal range can be beneficial for the retention of acidity during grape ripening. For more information see Diurnal Range below.
Explain the effects and benefits of slopes and aspects?
Vineyards planted on slopes will face a particular direction. This is called aspect. Vineyards that face the sun throughout most of the day (south-facing in the northern hemisphere and north-facing in the southern hemisphere) will receive more solar radiation than those facing the opposite direction.
The importance of aspect and the steepness of the slope increases at high latitudes. This is because solar radiation hits the Earth at a low angle at high latitudes. In the context of the vine growth cycle, the angle is lowest in the spring and autumn (compared to the summer).
Extra warmth and light during spring and autumn extend the viable growing season for vines grown on slopes that face towards the sun.
In warm climates, it may be desirable to limit the amount of heat and light.
Slopes can provide additional benefits, including shallower, poorer soils and better drainage. Slopes can also provide shelter from winds and rain, and protection from frosts (air movement down the slope prevents frosts from forming). However, soil erosion and inability to use machinery on steep slopes can be problematic.
Explain the effects on vineyards that have proximity to water?
Large bodies of water, such as lakes and seas, can have a significant impact on nearby vineyards. This is because water heats up and cools down more slowly than dry land. During the day, the water and the air above a body of water remains relatively cool, and lowers the average temperature in the local area. Air directly above dry land heats up more quickly than that above the water, and this warm air rises. Cool air from above the water is drawn to the land to replace the warm air as it rises, resulting in cool, humid afternoon breezes.
The opposite happens at night. The water retains the warmth gained during the day, whereas, without solar radiation, the land loses heat relatively quickly. The warmth of the body of water keeps the local area warmer. The same effect can be experienced over the year, with large bodies of water giving cooler summers and milder winters.
The movement of air also helps to protect against winter freeze which could damage or even kill the vines and spring frosts that could reduce yields.
Vineyard areas in coastal regions can also experience ocean currents, which can have a marked influence on temperatures. A very good example is Bordeaux’s warmer growing climate due to the Gulf Stream.
Vineyards located in very close proximity to large bodies of water can benefit from radiation reflected from the water surface. The amount of radiation reflected depends on the angle at which the solar radiation hits the water and is greatest at high latitudes.
Then there is El Nino und La Nina a climatic cycle in the Pacific Ocean that has a significant effect on weather patterns. El Niño starts when warm water in the western Pacific Ocean moves eastwards along the Equator towards the Caribbean.
La Niña is caused when the eastern Pacific Ocean is cooler than average. It tends to result in cooler, wetter conditions in the Pacific Northwest, but warmer, drier conditions in California and South America. La Niña also causes wetter and cooler conditions in Australia.
Explain the effects of winds?
Winds and breezes can have a warming or cooling influence in many wine regions. Areas near to a body of water may experience cool breezes during the day, moderating the diurnal range of such regions.
Valleys that face the coast or other areas of low land (e.g. the Petaluma Gap in California) can mean that winds are felt even relatively far inland. Valleys can also lead to stronger winds as the moving air is funnelled. Winds that have travelled over hot land masses can bring warm air that heats the vineyard area, e.g. the Zonda in Mendoza.
As well as influencing temperature, winds and breezes reduce the occurrence of humid, stagnant air in the vine canopy that encourages the development of fungal diseases.
Strong winds can cause damage to vines and vineyard trellising, resulting in lower yields and higher equipment and labour costs. Rows of trees can be planted at the edges of vineyards to act as windbreaks; however, care must be taken as they can compete with the nearest vines for water and nutrients.
Explain the characteristics of soil?
Soil can also have an important effect on temperature. The drainage of the soil, its structure and colour all influence the warmth of the soil and the air above the soil.
Soils that drain freely, for example sandy or stony soils, warm up more quickly in the spring than damp soils. Rising soil temperature encourages the breakdown of starch in the roots, which stimulates budburst and shoot growth. Therefore, it is desirable for cool-climate vineyard areas to have free-draining soils to promote early budburst, and hence potentially a longer growing season within which to get the grapes ripe.
However, early budburst does increase the risk of harmful spring frosts damaging young buds and shoots. Warm soils also encourage root growth, which means the vine can absorb more water and nutrients.
The colour of the soil is also important. Light-coloured soils, such as those rich in chalk (e.g. as found in Sancerre and Champagne), reflect some energy from solar radiation. Extra light energy into the lower parts of the canopy that may receive less sunlight from above can be beneficial to increase photosynthesis and grape ripening in cool and cloudy climates or where late-ripening grapes are used.
However, in warm climates this may increase temperatures in the warmest parts of the day. Dark-coloured soils, such as some of those from volcanic origin (e.g. as found in Etna), absorb more energy and re-radiate most of it when temperatures are cooler, for example at night. This can be useful, especially in cool climates or for late-ripening grapes, allowing the development of colour and degradation of acid to continue during the night.
Stony soils, especially if the underlying soil is slightly damp, are also very effective at absorbing heat and releasing it at night. This is because stone and water are good conductors compared to air.
Explain the effects of mist, fog and clouds?
A number of vineyard areas are prone to mist. Mists are formed by tiny drops of water collecting in the air just above an area of ground or water. They are usually formed when warm air is rapidly cooled, causing water vapour in the air to condense. This may occur, for example, at night when warm air over a body of water meets cooler conditions above the land. Dense mist is called fog.
Whereas mist and fog occur at ground level, clouds usually form higher in the sky. Depending on the density of the mist, fog or amount of cloud cover, sunlight can be limited to the extent that photosynthesis is reduced.
As mists and fogs are made up from water droplets and occur at ground level they can also increase humidity in the vineyard and therefore the occurrence of fungal disease or, in areas with dry, sunny afternoons, noble rot.
What is diurnal range?
The diurnal range of a region or vineyard site is the average difference between day-time and night-time temperatures. Regions with continental climates or at high altitude tend to have higher diurnal ranges (larger difference between day and night temperatures), whereas regions near a large body of water tend to have lower diurnal ranges (smaller difference between day and night temperatures).
There are some schools of thought that suggest constant temperatures are more favourable for producing quality grapes. There are others that believe that a significant difference in night time temperatures is beneficial.
In warm or hot climates, such as those found in Mendoza or Ribera del Duero, a large diurnal range is often thought to be favourable. In these climates, a relatively cool period during the night can slow the respiration of malic acid and be beneficial for the formation of anthocyanins (day-time temperatures are too hot).
In cool and moderate climates, such as Mornington Peninsula or Mosel, a low diurnal range may be favourable so that night-time temperatures still allow ripening (e.g. acid degradation, anthocyanin synthesis) to continue, which may be needed for grapes to ripen sufficiently.
It is also thought that night-time temperatures can have some influence on aroma compounds. For example, warmer night temperatures are associated with a greater breakdown of methoxypyrazines, which may be important in cool climates, and cooler temperatures are associated with a greater retention of some other compounds, such as rotundone.
Explain the effects of water on the vine?
The vine needs water to survive and adequate water availability is vital for healthy vine growth and grape ripening. Generally, the vine needs a minimum of 500 mm of rainfall per year in cool climates and at least 750 mm in warm regions.
The vine needs water for turgidity (so that it doesn’t wilt), photosynthesis and regulating its temperature.
Water also acts as a solvent for nutrients in the soil, which is important for their uptake by the vine, and is the medium in which all of the vine’s biochemical and physiological mechanisms take place. Either too little or too much water can have a negative influence.
Water vapour diffuses out of the stomata (tiny pores) on the underside of vine leaves. The loss of water from the cells in the leaf causes water to be pulled upwards from the soil, through the roots and the above-ground parts of the vine. This is called transpiration.
Open stomata allow the free exchange of water vapour out of the vine, and also let carbon dioxide and oxygen diffuse in and out of the leaves. If the vine has sufficient water, it can keep its stomata open all day. A lack of water causes the vine to partially close its stomata. This can help conserve water, but also reduces or even stops photosynthesis due to lack of carbon dioxide entering the leaves.
A plentiful supply of water in the spring encourages the growth of lots of leaves and hence the establishment of a large leaf surface area to support the growth of the vine and ripening of grapes.
However, if water is too easily available into late spring and early summer, vegetative growth (growth of shoots and leaves) is promoted and prolonged into the period of grape ripening, which acts as a competitive source for the vine’s sugars, delaying and compromising ripening. It is therefore thought that mild water stress before véraison is beneficial as it inhibits further vegetative growth.
