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Annual growth cycle of grapevines
The annual growth cycle of grapevines is the process that takes place in the vineyard each year, beginning with bud break in the spring and culminating in leaf fall in autumn followed by winter dormancy. From a winemaking perspective, each step in the process plays a vital role in the development of grapes with ideal characteristics for making wine. Viticulturalists and vineyard managers monitor the effect of climate, vine disease and pests in facilitating or impeding the vines progression from bud break, flowering, fruit set, veraison, harvesting, leaf fall and dormancy-reacting if need be with the use of viticultural practices like canopy management, irrigation, vine training and the use of agrochemicals. The stages of the annual growth cycle usually become observable within the first year of a vine's life. The amount of time spent at each stage of the growth cycle depends on a number of factors-most notably the type of climate (warm or cool) and the characteristics of the grape variety.〔J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pg 741-742 Oxford University Press 2006 ISBN 0-19-860990-6〕
==Bud break==
The grape starts its annual growth cycle in the spring with bud break. In the Northern Hemisphere, this stage begins around March while in the Southern Hemisphere it begins around September when daily temperatures begin to surpass 10 °C (50 °F). If the vine had been pruned during the winter, the start of this cycle is signaled by a "bleeding" of the vine. This bleeding occurs when the soil begins to warm and osmotic forces pushes water, containing a low concentration of organic acids, hormones, minerals and sugars, up from the root system of the vine and it is expelled from the cuts (or "wounds") left over from pruning the vine. During this period a single vine can "bleed" up to of water.〔J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pg 82 Oxford University Press 2006 ISBN 0-19-860990-6〕
Tiny buds on the vine start to swell and eventually shoots begin to grow from the buds. Buds are the small part of the vine that rest between the vine's stem and the petiole (leaf stem). Inside the buds contain usually three primordial shoots. These buds appear in the summer of previous growth cycle green and covered in scales. During winter dormancy they turn brown until the spring when the vine begins the process of bud break and the first sign of green in the vineyard emerges in the form of tiny shoots.〔J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pg 107 Oxford University Press 2006 ISBN 0-19-860990-6〕 The energy to facilitate this growth comes from reserves of carbohydrate stored in roots and wood of the vine from the last growth cycle. Eventually the shoots sprout tiny leaves that can begin the process of photosynthesis, producing the energy to accelerate growth. In warm climates, after about 4 weeks the growth of the shoots starts to rapidly accelerate with the shoots growing in length an average of 3 cm (1 in) a day.〔
In temperate climates, where temperatures can reach above 10 °C (50 °F) in mid-winter, some early budding varieties (such as Chardonnay) can be at risk of premature bud break. This is a potential viticultural hazard in places like the Margaret River region of Western Australia where warm currents from the Indian Ocean can coax Chardonnay vines to prematurely bud in the mid-winter month of July. After bud break, the young shoots are very vulnerable to frost damage with vineyard managers going to great lengths protect the fragile shoots should temperature dramatically drop below freezing. This can include setting up heaters or wind circulators in the vineyard to keep cold air from settling on the vines.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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