Sunlight

Question 1

What are the 4 key resources of the growing environment?

Answer 1

1. Sunlight
2. warmth
3. water
4. nutrients

Question 2

What is the main sources of both heat and sunlight?

Answer 2

solar radiation

Question 3

How much sunlight is needed for photosynthesis, at a minimum?

Answer 3

• full sunshine (intense sunlight, not blocked by cloud) is not required
• generally the amount of light becomes the only limiting factor to rate of photosynthesis if light levels drop below one third of full sunshine

Question 4

Name a weather condition that can slow photosynthesis (other than lack of sun or water stress)

Answer 4

Fog

Question 5

Name 6 positive effects that sunshine exposure has on grapes

Answer 5

1. enhances the development of anthocyanins (color pigments) in black grapes
2. reduces methoxypyrazines
3. promotes accumulation of tannins pre-veraison
4. promotes tannins’ polymerization after veraison (less bitterness)
5. promots favorable aroma precursors and compounds
6. increases the rate at which malic acid is used up in grape respiration (lower acidity levels)

Question 6

What negative effects does sunshine exposure have on grapes?

Answer 6

Can lead to sunburn on sun-exposed grapes, which has a negative effect on grape quality and yields

Question 7

Name 2 reasons sunshine in late spring and early summer is beneficial

Answer 7

1. associated with successful fruit set
2. the exposure of compound buds to sunshine promotes bud fruitfulness in next year’s growing season

Question 8

Which will receive more solar radiation per annum: regions at lower latitudes, or regions at higher latitudes?

Answer 8

lower latitudes

Question 9

Why do regions nearer to the equator receive more intense solar radiation than those nearer the poles?

Answer 9

• solar radiation is adsorbed and scattered as it travels through the 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
• radiation hits the earth at a low angle near the poles (due to curvature), so the radiation is spread over a larger area

Question 10

How does latitude affect hours of daylight?

Answer 10

• low latitude regions receive similar daylight hours (and hence heat and sunlight) throughout all seasons of the year
• high latitude regions have longer daylight hours in the summer and shorter daylight hours in the winter

Question 11

What is the target latitude range for grapes for wine production?

Answer 11

Between 30 and 50 latitude on each side of the equator

Question 12

What issues would regions closer than 30 to the equator run into?

Answer 12

• too hot during the day
• water stress
• sunburn

Question 13

What issues would regions farther than 50 to the equator run into?

Answer 13

• simply not warm enough during the growing season (despite long daylight hours) for enough sugar to accumulate in the grapes

Question 14

Give an example of a low latitude region whose altitude allows it to be successful in grape growing.

Answer 14

Salta Province in Argentina (3000m asl)

Question 15

Is sunshine more intense at high altitudes or low altitudes? Why?

Answer 15

• high altitudes
• because the solar radiation travels through less atmosphere before it reaches these sites

Question 16

Name 7 natural factors that affect temperature and sunlight

Answer 16

1. latitude
2. altitude
3. slopes/aspect
4. proximity to water
5. winds
6. characteristics of the soil
7. fogs, mists, clouds

Question 17

What is aspect?

Answer 17

The direction a particular slope faces

Question 18

Vineyards at what aspect receive the most solar radiation?

Answer 18

• vineyards that face the sun throughout most of the day (south-facing in northern hemi, north-facing in southern hemi)

Question 19

is the aspect and the steepness of the slope more important at higher or lower latitudes?

Answer 19

• higher
• slope increases the angle (nearer to perpendicular) at which solar radiation hits the earth, increasing intensity of heat and light

Question 20

Name two cool climate regions where slope is crucial.

Answer 20

Burgundy and Alsace Grand Cru (south-east facing)

Question 21

How might one limit the amount of heat and light in warm climates?

Answer 21

Planting on slopes that face away from the sun throughout most of the day

Question 22

Name 1 warm climate region where slope is crucial

Answer 22

Stellenbosch (south-facing slopes to retain acidity)

Question 23

What are the benefits of east-facing slopes?

Answer 23

• morning sunshine heats up the atmosphere when air and soil temps are at their lowest
• extends the hours of vine growth and grape ripening each day, especially in cool climates
• the grape canopy (dewy in the morning) dries out earlier, reducing the spread of fungal disease

Question 24

What is problematic about west-facing slopes?

Answer 24

• afternoon sun
• may become too hot, especially in warm climates
• increases risk of sunburn
• mitigate: in areas with coasts to the west )e.g. California and Western Australia), cool afternoon sea breezes

Question 25

Aside from proximity to sunlight, what 4 other benefits can slopes provide?

Answer 25

1. shallower, poorer soils
2. better drainage
3. shelter from winds and rains
4. protection from frost

Question 26

What are some of the problems with slopes?

Answer 26

• soil erosion
• inability to use machinery on steep slopes

Question 27

How can a large body of water impact nearby vineyards during the day?

Answer 27

During the day, the water and the air above a body of water remain relatively cool, and lowers the average temperature in the local area

Question 28

How can a large body of water impact nearby vineyards overnight?

Answer 28

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.

Question 29

Are large bodies of water beneficial in cool climates, warm climates, or both?