After the leaves fall, the vine does not present apparent vegetative activity, calling this phase dormancy or vegetative rest or winter rest. A stage triggered by the action of abscisic acid.
A classic division of the winter rest, attributed to R. Pouget, is based on five consecutive stages, from the formation of the bud, until its regrowth in the following vegetative cycle:
- 1st phase of pre-vegetative rest. It begins when the buds form on the shoot of the year, reaching a sufficient level of organogenesis so that they are apt to develop and allow the formation of a new shoot when conditions are favourable. Its duration is one week.
- 2nd phase of entry into vegetative rest. Duration of about two weeks, where the latent buds lose the possibility of sprouting quickly, due to the presence of abscisic acid, corresponding to the time of withering.
- 3rd phase of vegetative rest. It corresponds to a deep rest of the buds and lasts between one and two months, characterized at first by a long sprouting time, to later decrease due to increasing temperatures.
- 4th phase of rising of vegetative rest. It is a short period of one week that requires cold temperatures with daily averages of 10°C.
- 5th phase of post-vegetative rest and pre-sprouting. Its duration is 3 to 4 months, where the buds that suffered the action of low temperatures, acquire the ability to sprout quickly at all temperatures.
FACTORS
The factors that influence the lifting of the vegetative rest, and therefore the sprouting are the following:
physical factors.
- Drying of the wood. Being 35% the humidity limit, below which the tissues die.
- Temperature. In aerobic conditions, the temperature must be higher than 10°C, with a maximum limit of 40 to 50°C. However, in anaerobic conditions, when the shoots are submerged in water or in a nitrogen atmosphere, the temperature limits are are between 1 and 40 ºC.
- Photoperiod. The short days constitute a factor for the entry into vegetative rest, undoubtedly due to the formation of inhibitory substances, such as abscisic acid. Conversely, long days stimulate sprouting.
chemical factors.
The mechanism of entry and exit from vegetative rest is not well known, but it is accepted that it is due to the balance between growth-stimulating and inhibiting substances.
Biological factors.
From the studies by R. Pouget, it can be deduced that early budding vines have a less intense vegetative dormancy compared to later budding vines, since they require a shorter vegetative dormancy process, and have a faster rate of evolution. faster physiology. In addition, they are less sensitive to the retarding effect of low temperatures on the buds.
Early budding vines have a higher bud break speed than late bud break vines. These are characterized by a constant higher sprouting precocity. The values of this constant are all the greater as the vine sprouts early.
