berry-development-process-i-ii
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  • 1. PHASE 1 ENVIRONMENTAL IMPACTS ON BERRY DEVELOPMENT PROCESSES A minimum amount of light is required for enzyme induction to drive the processes in Phase 1, however, low temperatures slow down enzyme activity and thus can prolong this phase. Excess water or nitrogen availability can also result in an extended Phase 1 influencing the activity of enzymes and hormones, especially in relation to cell-division in the developing pulp and skin, which governs the eventual size and juice content of berries. Conversely, low water levels can shorten this cell division phase in berries. In this instance, abscisic acid (ABA) is produced in roots when vines experience water stress after flowering, shortening the cell-division process and resulting in smaller berries.Viticulturists exploit this process as a quality management tool by the application of partial rootzone drying (PRD) and regulated deficit irrigation (RDI). KEY GRAPE QUALITY DEVELOPMENTS DURING THIS PHASE Some of the traits that are crucial for many wine styles develop very early during this phase. • Important acids accumulate, eg. tartaric and malic acid. These act as chemical stores of energy and may also be involved in defence of the berry against being eaten before the seed is fully developed. • The amount of tartaric acid remains constant during ripening but the concentration decreases as the berry increases in volume. • Malic acid is used as an energy source for berry metabolic processes. • Minerals are imported into berries with sugar, as are nitrogenous compounds.The import of nitrogen peaks after berry set. In unripe fruit, ammonium represents more than half of the total nitrogen. • Phenolic molecules are made from fruit set onwards, while the most important period for phenolic development is 2-3 weeks before veraison: • Many aroma characteristics develop during this early phase of berry development, such as the ‘grassy’ methoxypyrazines which contribute to the capsicum flavour in some wines. UNDERSTANDING GRAPEVINE GROWTH NUMBER 4: Viti-Noteswww.crcv.com.au 2005 The berry development process - Phases 1 and 2 Current Vitinote titles in this Understanding grapevine growth series include: 1. Dormancy and budburst 2. Spring shoot and root growth 3. Flowering 4. The berry development process – Phases 1 and 2 5. The berry development process – Phase 3 6. Defining berry ripeness 7. Site factors influencing berry ripening processes and rates of ripening THE FIRST STAGE OF BERRY DEVELOPMENT STARTS SOON AFTER FERTILIZATION OF THE FLOWER, AND IS CHARACTERIZED BY STRONG GROWTH OF THE SEED AND BERRY. AT THIS POINT, THE FINAL NUMBER OF CELLS IN THE BERRY IS DETERMINED AND ACIDS ARE ACCUMULATED
  • 2. THE CRC for Viticulture is a joint venture between the following core participants, working with a wide range of supporting partners. www.crcv.com.au • Similarly to acids, these may help defend the berry against herbivores. The role of this aroma in repulsing animal predators generally disappears as the berry matures, but it may be a desirable fruit characteristic in some varieties, eg. Sauvignon Blanc. • These compounds can be retained in fruits due to cloudy conditions, shaded fruit, and no water stress. PHASE 2 During Phase 2 the berry itself exhibits slow growth as energy is being diverted to development of the seeds. This is vital in biological and viticultural terms as the hormone abscisic acid (ABA) which eventually triggers berry ripening is formed in the seed. ABA is synthesized in the seed itself and incorporated into the embryo where it inhibits the germination of the seedling at this time. Late in Phase 2, ABA is exported into the fruit from the seed, where it initiates the ripening of berries. Lignification of the seed begins at the end of this stage. Phase 2 lasts between 7 and 40 days and depends on variety and temperature. It is the most temperature-sensitive stage, being delayed by daytime temperatures below 18°C or above 35°C, or night time temperatures below 13°C or above 30°C. These temperatures affect the activity of the vast number of enzymes active in differentiating and growing the seeds in the developing berry. Colour development is also delayed when vines experience high temperatures during this phase. Berries that contain an immature seed do not naturally accumulateABA and do not undergo veraison.The start of veraison can be artificially postponed by the application of cytokinin mimics orABA antagonists like salicylic acid. FURTHER INFORMATION Product or service information is provided to inform the viticulture industry about available resources,and should not be interpreted as an endorsement. USEFUL REFERENCES: • Biology of the grapevine, 1992 by MG Mullins, A Bouquet and E Williams published by Cambridge University Press. • Soil, irrigation and nutrition, Grape Production Series No. 2, 2003 edited by P Nicholas. • Viticulture and Environment, 1992 by J Gladstones. • Viticulture, 1992 by BG Coombe and PR Dry. Information in this Vitinote has been adapted from the CRCV Winegrape quality management: Research to Practice® workshop manual. The Viticulture Research to Practice® workshops are training programs whose delivery can be fine-tuned to suit each region. • Enquiries to Peter Mansfield at Winetac on (08) 8373 7090 or visit www.crcv.com.au for more information. Visit the web site at www.crcv.com.au/viticare/vitinotes/ for updates and more Vitinote titles. ©2005 Cooperative Research Centre for Viticulture THIS IS ALSO KNOWN AS THE ‘LAG’ PHASE AS THE BERRY ITSELF GROWS ONLY SLOWLY. DURING THIS PERIOD THE EMBRYO WITHIN THE SEED MATURES AND THE SEED COAT LIGNIFIES. TOWARDS THE END OF THIS PHASE AS VERAISON (PHASE 3) APPROACHES, COLOUR CHANGES OCCUR IN THE BERRY