Section in annual growth cycle of the grapevine after this fruit set (see also under BBCH Code ). It is the start of ripening of the berries. This begins in the northern hemisphere, depending on the grape variety and weather conditions, from the end of July / beginning of August, in the southern hemisphere in January. At this point, the still green and hard berries have reached about half their final size. With the start of ripening, they gradually change into a softer, plastic state.
From a certain degree of softness, the color change takes place, at which the berries start to become light (berry brightening) or change color. The poison green colour the berries change to white-green in the white wine varieties, White, yellow, yellow green, gray, pink, red or purple, for the red varieties in blue, purple or black, However, this does not happen with all berries at the same time, but affects those that are part of the blossom were fertilized first and most exposed to the sun and heat.
The color formation in the red wine varieties is favored above all by a high light intensity. With the change in color, the sugar content in the berries also begins to increase rapidly, with the berry sugar mainly from the assimilating ones Scroll comes from, but can also be mobilized from wood reserves if there is a lack of leaves, then at the expense of good maturity. The maturation-related conversion of the malic acid in sugar molecules also leads to acid degradation and sugar accumulation in the berries. With increasing sugar concentration, the total acidity in the berries steadily decreases, whereby the content of tartaric acid remains roughly the same. The decrease in concentration initially results from the increase in the volume of the berries, because with increasing sugar concentration the increases osmotic Pressure inside the berry so that water over it Xylem (Xylem) passively flows into the berries.
The berries increase in volume until the final volume is reached and the berry skin is so tight that the xylem connection is interrupted and no further water can flow in. Without this blockage of the water flow, the sugar molecules that are still embedded in the conductive tissue (phloem) would increase the osmotic pressure in the berry so much that the berries would inevitably burst. The final volume of the berries is reached after about three to four weeks, after which only sugar is stored until fully ripe. In this late ripening period, the grape-specific ones are the main ones flavorings trained in the berries. This comes with the relatively new term Engustment circumscribed. The one for the vintage optimal state or time in the vegetation cycle is considered physiological maturity designated. Since this does not happen at the same time for all the grapes in the vineyard, a selective harvest with several passes may be carried out.
The begins at the same time as the Véraison phase drove maturity, that is the young shoot of the vines. Adequate water supply during the growing season is crucial for the formation of excess sugar in the leaves, its storage in the berries and for good ripening of wood. A lack of water is indicated by premature yellowing of the lower leaves and can temporarily bring the entire metabolism to a standstill. at water stress (Drought stress) the vine has to keep the locking cells of the leaves as closed as possible in order to lose as little tissue water as possible and to avoid world death.
With closed lock cells, however, carbon dioxide can no longer be absorbed, which is the cause of sugar production photosynthesis necessary is. The Yellowing phenomena on dry-stressed plants can be interpreted as hunger symptoms, because without carbon dioxide absorption and assimilation, the plant cannot maintain its metabolism in the long term. Such drought stress phases always have a negative impact on the balance of substance and sugar production and thus also the quality of the harvested produce. The conclusion of the véraison or the next point in the cycle is considered maturation Designated (maturity).