Transcript VEN124 Section I

Lecture 2:
Grape Composition and Ripening:
Viticulture from the Plant’s Perspective
Reading Assignment:
Text, Chapter 2, p. 13-52
Characteristics of Plants
• Stuck where they are: use chemical
strategies to deal with problems
– Nutrient limitation
– Competition
– Excess/shortage of water
– Extremes of temperature
– Disease/Pest pressure
– Lack of light
Characteristics of Plants
• Prioritize nutrient use for survival
• Role of fruit:
– Dispersal of seed
– Fruit is attractive to mobile agents that will
disperse seed (animals; insects; birds)
– Seed itself designed to “taste bad” so it will
not be consumed
Characteristics of Grapevines
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•
Grown in a wide variety of soils/climates
Persist in nutrient deficient soils
Crop set happens in previous season
Dormant buds developmentally
programmed in prior season
• Extensive root structure: can represent
up to 90% of the mass of the vine
Factors Impacting Grapevine
Performance
• Soil
• Topography/Location: hillside, valley
floor
• Disease/Pest pressure: impacts
composition of fruit
Factors Impacting Grapevine
Performance
• Climate
– Temperature
– Sunshine
– Humidity
– Rainfall
– Evaporation
– Wind
– Water availability
Factors Impacting Grapevine
Performance
• Microclimate
– Climate of individual vines: heating of
vineyard floor
– Climate of individual clusters:
• Shading effects
• Humidity retention
Factors Impacting Grapevine
Performance
• The Human Element
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Irrigation practices
Use of fertilizers
Timing of treatments
Canopy management
Trellising system
Use of rootstocks
Pruning practices
Cluster manipulation: leaf removal, dropping of
fruit
Berry Structure
• Skin: 3 layers
– Epidermis
– Hypodermis
– Outer mesocarp
• Fleshy mesocarp
• Brush and center septum
• Vascular system
– Ovular
– Ventral
– Dorsal
• Seeds
AJEV (1987) 38(2): 120-7
Berry Development: Maturation of
Fruit Follows Maturation of Seed
1. Flowering/Fertilization
2. Green Berry Stage
Cell division occurs
Acids accumulate
3. Veraison
Color changes occur
4. Ripening
Berry swells and softens
Sugars Water Acids
Factors Affecting Berry Development
and Maturation
• Climate: Warmer: mature faster, less acidity,
less color, higher pH, fewer late berry
characters
• Variety: Mature at different rates
• Disease/Pest pressure: alters composition of
fruit, alters timing of development
• “Balance” of vine: carbohydrate demands of
vine versus fruit versus level of
photosynthesis
Berry Composition at Harvest
Sugar
Organic Acids
Amino Acids
Phenolics
Volatiles
Water
g/L
200
10
5
2-5
trace
800
SUGARS (hexoses):
glucose
fructose
sucrose
Sucrose is the circulating product of
photosynthesis cleaved to produce
glucose and fructose in berry
SUGARS (pentoses):
arabinose
xylose
Not metabolized by yeast
Sucrose
glucose + fructose
Allows for accumulation of
sugar in berry
ORGANIC ACIDS:
malate
tartrate
MALATE:
COOH
HOCH
CH2
COOH
From the TCA cycle
Cytoplasmic
Used for energy
generation
TARTRATE:
COOH
HOCH
HCOH
COOH
Accumulates in vacuole
From ascorbic acid and
5-ketoglutarate
Amino Acids:
glutamate
glutamine
arginine
alanine
proline
Typically comprise 90% of all amino
acids
Amino Acids:
High -Amino Butryic Acid (GABA)
indicates fruit was held at a high
temperature post-harvest
Phenolics:
Large Variety
Found as tartaric acid esters
Caftaric Acid Most Prevalent
HO
HO
CH=CH-CO-Tartate
Volatile Compounds:
terpenes
esters
Sulfur-Containing Compounds
glutathione (glu-cys-gly)
cysteine
methionine
AJEV (1987) 38(2):120-7
Location of Compounds in Berry
Sucrose
Glucose
Location of Compounds in Berry
Malate
Tartrate
Location of Compounds in Berry
Phenols
Phenolic
compounds
Location of Compounds in Berry
Potassium
Location of Compounds in Berry
Inorganic
anions