Lecture 2: Grape Composition and Ripening: Viticulture from the Plant’s Perspective

Reading Assignment: Text, Chapter 2, p

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 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 –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 g/L Sugar200 Organic Acids 10 Amino Acids 5 Phenolics2-5 Volatilestrace Water800

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 From the TCA cycle HOCH Cytoplasmic CH 2 Used for energy generation COOH

TARTRATE: COOH Accumulates in vacuole HOCHFrom ascorbic acid and 5-ketoglutarate HCOH COOH

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 HOCH=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 MalateTartrate

Location of Compounds in Berry Phenols Phenolic compounds

Location of Compounds in Berry Potassium

Location of Compounds in Berry Inorganic anions