Viticulture Week 4 & 5

Front 1

* What is the effect of N on vines with low N status?

Back 1

• Will stimulate plant growth due to increasing nitrogen available for protein building

• Increasing leaf area

• Increase in chlorophyll formation

• Increase in carbon assimilation (more sugars)

• Growth of storage organs (trunk, roots, canes)

• Increased root growth increases uptake of other nutrients


• Increased nitrogen fertilization can increase yield and improve the grape composition, increasing wine quality

Front 2

* What is the effect of N on vines with normal N status?

Back 2

• Adding N does not increase growth.

• There will be a trend towards more balanced vine growth, leaf area/fruit weight ratios that are correct, and the production of ripe grapes

• Once maximum vine growth, yield and composition are attained then nitrogen status is said to be adequate

Front 3

* What cautions are there with respect to using N on vines with normal N status?

Back 3

– The results of a farming method that seeks maximum growth or maximum yield are unlikely to result in the optimal grape composition

– Yield and quality always exist on a spectrum, it is not solely in opposition‐ lowest yields don’t always mean best composition but the highest yields almost never yield good grapes

Front 4

* What are the plant assimilable forms of N?

Back 4

NO3- Nitrate
NH4- Ammonium

Front 5

* What is the role of water in plant growth?

Back 5

Essential in plant growth.

Reaction medium

Crucial for photosynthesis

Front 6

* Where do grape vines get their water from?

Back 6

Rain fall.

Irrigation.

Runoff (minor)

Front 7

* What is water lost to?

Back 7

Photosynthesis

Reactions requiring H2O

Evapotranspiration

Runoff

Soil Drainage

Soil Evaporation

Front 8

* What is transpiration?

Back 8

A process in which the water vapor escapes through the plant via its stomata and lenticels into its external environment (atmosphere).

Front 9

* Why does soil water capacity matter?

Back 9

Regardless of soil type, the local water capacity of the soil will determine how much water is available to the grape vine.

Front 10

* Where is the carbon in grapevines?

Back 10

Grape vines are almost completely made of Carbon compounds.

Front 11

* What process facilitates carbon assimilation?

Back 11

Photosynthesis.

Front 12

* What is vine balance?

Back 12

Even Carbon distribution.

Balanced root and shoot growth.

Fruit development does not deplete or negatively impact plant reserves.

Front 13

* Water, Nitrogen and Carbon balance are all achieved through _____________ .

Back 13

vineyard management

Front 14

* Why is thinning complicated?

Back 14

Thinning decisions are a complicated process because decisions are made based on growing conditions and fruit goals.

Front 15

* Why is exposed leaf area a useful way of thinking about canopies in terms of photosynthetic efficiency?

Back 15

10% or less of light passes through the leaf

High leaf numbers therefore retard ripening - lower layers of leaves are feeding off of the higher leaves.

Front 16

* What does light have to do with plant fertility?

Back 16

Higher levels of light are associated with higher levels of inflorescences.

Front 17

* What, beyond photosynthesis, does light impact in grape/vine growth?

Back 17

Bud fertility

Phenol synthesis

Fruit composition

Temperature

Front 18

* Studies have been done looking into the difference in impact of light and temperature, in general what did they say?

Back 18

In high light environments more color is associated with cooler temperatures.

In lower light environments warmer temperatures were associated with more color.

Excessive absolute fruit temperatures, rather than the differ- ence between fruit temperatures and ambient temperatures, re- duced anthocyanin concentrations in sun-exposed grape berries. East- and west-exposed clusters received the same total expo- sure to solar radiation on cloudless days and were heated to the same degree above ambient temperature at the time of maxi- mum sun exposure. The highest absolute fruit temperatures occurred in west-exposed fruit because ambient temperature typically increases throughout the day. In warm to hot viticultural regions, exposure of grapes to full sunlight on west- and south-facing canopies should be avoided unless some method is used for reducing fruit temperature. Complete fruit shading is not recommended because some sunlight is needed for maximum anthocyanin synthesis and for balancing the com- position of other fruit components. Partial shade might be pro- vided in vertical shoot positioned canopies by incomplete positioning of shoots on west- and south-facing canopies. Additionally, leaf stripping should be minimized unless there are multiple layers of leaves.

Front 19

What is the effect of N fertilization on vines with high N status?

Back 19

Crowded canopy increases disease pressure and non‐productive leaves

Reduces bud fertility (poor light)

Retards phenol synthesis (poor light)

Can promote green flavors (pyrazines) in some varities (poor light)

Excessive nitrogen levels can encourage vegetative growth and reduce carbohydrate storage‐ impacting the source‐sink balance

Poor grape color and sugars (vine growth - carbs going to amino acid and protein synthesis)