Vine Reproduction Describe grapevine reproductive morphology and grapevine varietal differences Range: inflorescence primordial, buds, flowers, berries, clusters Describe the 18-month reproductive cycle of a grapevine tcreagh@eit.ac.nz

Inflorescence initiation The potential yield of a vine is determined approximately 16 months before harvest

Inflorescence initiation Inflorescence initiation starts in the buds as they develop and continue to develop for 8-12 weeks Therefore the basal buds have potentially the most time to develop

Inflorescence initiation Inflorescence primordia and tendril primordia develop from the same initial structures, called anlagen, which are undifferentiated tissue Environmental conditions and the interaction of hormones determines whether the anlagen will develop into inflorescence primordia or tendril primordia

Inflorescence initiation Inflorescence initiation occurs at about the same time as flowering Therefore conditions at flowering also affect inflorescence initiation In good conditions vines usually form two inflorescence primordia, but may form up to four

Inflorescence initiation Inflorescence initiation is favoured by: Warm conditions

Inflorescence initiation Light Increased light to buds and leaves increases fruitfulness

(Source: winker, et al, (1974))

Inflorescence initiation Optimum nutrient levels Nitrogen, potassium and phosphorous deficiencies all affect fruitfulness

Inflorescence initiation Carbohydrate levels High vigour or drought can reduce the carbohydrate levels reducing inflorescence initiation

Inflorescence initiation The location of the bud Generally the primary bud has larger and more inflorescence primordia as it is the most well developed Buds located at nodes 4-10 potentially tend to have more inflorescence due mainly to the temperatures and time of development

Figure 5.2: fruitfulness along a cane

Inflorescence initiation These factors have implications for pruning For example, particularly in cooler climates cane pruning is favoured to achieve maximum fruitful buds

Inflorescence initiation Where low crops are desired, for example in premium cabernet sauvignon spur pruning may be favoured Canes that have grown in sunlight are generally selected, as they have many potentially fruitful buds

Flowering and Fertilisation Figure 5.3: bloom sequence of grape flower: (a) calyptra attached, (b) calyptra separating, (c) open flower (after Babo and mach, 1909) (Source: weaver, 1976)

Flowering and Fertilisation Figure 5.4: flower types: (a) hermaphrodite, (b) female, (c) male (After Babo and mach, 1909) (Source: weaver, 1976)

Flowering and Fertilisation V. Vinifera varieties generally have perfect or hermaphrodite flowers These flowers have functional pistil and stamens so they are capable of self pollination

Flowering and Fertilisation flower development As buds swell in the spring the inflorescence primordia which developed the year before, begin to differentiate into flowers Flowering usually occurs 6-10 weeks after the beginning of shoot growth The flower is fully developed when the pollen is mature in the anthers. 

Flowering and Fertilisation Pollination and fertilisation Definitions: Pollination: The transfer of pollen from the anther to the stigma

Flowering and Fertilisation The union of male nuclei from the pollen to the female nuclei in the ovary 

Flowering and Fertilisation The first visual indication that pollination is occurring is when Capfall occurs The pollen is released from the mature anthers this is termed cap fall and flowering is generally determined as when 80% cap fall occurs

Flowering and Fertilisation The pollen falls onto the stigma, then develops a tube which grows down the style to the ovary for fertilisation to take place Fertilisation occurs 2-3 days after pollination

Flowering and Fertilisation The embryo and berry development begin The embryo forms the seeds and the ovary becomes the berry

Flowering and Fertilisation Fruit set Fruit set is the transformation of flowers to fruit Up to 70-80% of the flowers may fail to set The size of the berry is largely determined by the number of seeds it contains

Flowering and Fertilisation The more seeds the larger the fruit A berry may contain up to four seeds, although two or less is usual in the wine grape varieties Berries with pistils that have not been fertilised will abscise from the cluster This is termed shatter

Flowering and Fertilisation The timing and the duration of flowering are influenced by: Climate influences In warm climates, flowering will begin when the mean daily temperature reaches 20oC In cool climates, flowering can last several weeks, and increasing day length is thought to stimulate flowering

Flowering and Fertilisation Warm, sunny, dry conditions favour pollen dispersal Cold, wet days prevent cap fall reducing the level of fertilization The growth of the pollen tube is also temperature sensitive Pollen tube growth is slowed in cooler weather, leading to a reduction in fertilization

The changes in berry development The green stage (Stage I). This is a period of rapid cell division leading to increased berry size. The berry remains hard and green tcreagh@eit.ac.nz

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The resting stage (Stage II) is a period of slow physical growth, but is the time seed development occurs. tcreagh@eit.ac.nz

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The ripening stage (Stage III) The beginning of the ripening period is signalled by veraison. The berry begins to soften and the colour of the berry changes due to colour pigment synthesis denoting the start of ripening. tcreagh@eit.ac.nz

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The ripening stage (Stage III) It is characterised by increasing berry size, but, sugar begins to increase (increasing Brix), acids decrease, and colour and flavour develop. The berries become softer to touch and translucent in appearance. tcreagh@eit.ac.nz

Acids The rate of decline of malic acid may depend on: Temperature In hot climates, malic acid is metabolised more rapidly than in cool climates As a rough rule of thumb, reaction rates for many reactions double or triple for every 10 degrees tcreagh@eit.ac.nz

Acids Cultivar Some varieties, eg Cabernet franc, Chenin blanc, Syrah and Pinot noir, have proportionally higher malic acid Riesling, Semillon, merlot, Grenache have higher tartaric acid content tcreagh@eit.ac.nz

Acids The total amount of tartaric acid in the berry reduces slowly as the berry ripens However, tartaric acid levels decline compared to berry volume due to a dilution effect of increased in sugars and fluid in the cells tcreagh@eit.ac.nz

Potassium Potassium (K+) increases after veraison in the skin although the mechanism of uptake is not well understood Potassium uptake increases the pH tcreagh@eit.ac.nz

Phenolic Compounds Phenolic compounds give colour, flavour, aroma and aging properties to wines, especially red wines Phenolics are found in the seeds and skin, but are generally extracted from the skin during wine making Anthocyanins are the specific phenols that produce colour in the berry skin tcreagh@eit.ac.nz

Phenolic Compounds Phenols are thought to be produced in the berry itself They are not transported from other parts of the vine tcreagh@eit.ac.nz

Phenolic Compounds Anthocyanin synthesis depends on Temperature Sugar accumulation Hereditary factors tcreagh@eit.ac.nz

Nitrogen Compounds During ripening the total nitrogen content of the berry increases due to an increase in ammonia cations, amino acids and proteins tcreagh@eit.ac.nz

Aromatic Compounds Aroma compounds develop late in berry development and many are found close to the skin Ripeness and sun exposure have effects on these compounds tcreagh@eit.ac.nz

Cultural and Climatic Influences on Berry Maturation Yield Achieving a balance between yield, quality and vine health is essential Yields have been increased by using: Improved clonal material Disease free material Fertilisation, irrigation and pest control However, increasing yield can reduce the vines ability to mature the fruit tcreagh@eit.ac.nz

Yield Overcropping Delays fruit maturity Retains acidity Retards anthocyanin synthesis Reduces sugar accumulation and flavour development Suppresses subsequent yields May shorten vine life tcreagh@eit.ac.nz

Yield Achieving an ideal yield depends on The variety Soil characteristics Weather The desired end product tcreagh@eit.ac.nz

Yield Undercropping Will not necessarily improve vine quality either It can result in: tcreagh@eit.ac.nz

Yield Prolonged shoot growth and leaf production Increased shading Depressed fruit acidity Unbalanced berry nitrogen and inorganic nutrient concentration Reduced yield can also lead to larger berries tcreagh@eit.ac.nz

Sunlight The proportion of far red light increases within the canopy Increased proportions of far red is thought to: Delay anthocyanin synthesis & decrease sugar concentration Increase ammonia and nitrate content in fruit Increase the total acidity tcreagh@eit.ac.nz

Sunlight Sunlight increases anthocyanin synthesis Shaded fruit may have higher titratable acidity and concentrations of tartaric and malic acids and a lower pH However, less pigmented varieties such as Pinot noir, require more direct exposure than more pigmented varieties tcreagh@eit.ac.nz

Sunlight This may be a reflection of potassium accumulation and lower pH Magnesium and potassium can also be increased by shading Berry size increases with shading Grape aroma is also enhanced with increasing sunlight tcreagh@eit.ac.nz

Temperature Sunlight directly and indirectly increases berry temperatures Darker coloured fruit has increased temperatures, and tightly clustered fruit will have increased temperature tcreagh@eit.ac.nz

The Effect of Climatic and Viticultural Variable on Berry Temperature Effect on Berry Temperature Sunlight Intensity Berry temperature increases with increasing sunlight intensity. Wind speed Berry temperature more closely approaches air temperature with high wind speed. Fruit exposure Berry temperature is increased with exposure to sunlight and decreased with exposure to clear skies at night. Cluster compactness Berry temperature increases with more compact clusters, less wind penetration. Temperature is more rapidly conducted berry to berry across tight clusters. Berry size Large berries are heated in sunlight more than small ones. Berry colour Dark berries are heated in sunlight more than white ones. Sugar content Immature berries will be heated more in sunlight than mature. tcreagh@eit.ac.nz

Temperature Increased berry temperature increases tcreagh@eit.ac.nz

Temperature Malic acid metabolism Anthocyanin synthesis Sugar accumulation Amino acid content Potassium accumulation Improved aromas tcreagh@eit.ac.nz

Temperature However this is varietal dependent and also dependent on the temperature and duration of temperature tcreagh@eit.ac.nz

Temperature Increased temperature decreases: Flavour and aroma Fruit development if high temperatures occur after pollination, reducing berry size due to vine stress tcreagh@eit.ac.nz

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Nutrients Nitrogen directly affects canopy growth and shading This impacts indirectly on fruit quality Low soil nitrogen may increase anthocyanin synthesis High potassium levels can reduce berry pH, lowering fruit colour and colour stability in red wines tcreagh@eit.ac.nz

Water Water affects the vine vigour A balance should be achieved to ensure fruit matures Excess water leads to canopy shading which indirectly affects ripening Excess water can also lead to a dilution effect in the berry, and in some varieties berry splitting occurs, resulting in quality loss tcreagh@eit.ac.nz