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blossom

fioritura (I)
flor (ES)
fleur (F)
flower (GB)
flor (PO)
bloem (N)
Blütezeit beim Rebstock (I)

The beginning of this section in the annual growth cycle the grapevine, is about six to eight weeks after expulsion, The exact time of the year-specific temperature development, the reached temperature sums depending on the respective location and the vine-specific growth under changing weather. Constantly warm temperatures with good ones water supply accelerate the speed of the shoot growth and thus the formation of the inflorescence (Latin inflorescence, depending on the country and region also bloom, umbel, dotzen or appearance) on the third to seventh drive node, Depending on the zonal climate, Microclimate and sun exposure will flower in the northern hemisphere from mid-May to late July (in Central Europe, according to the old winegrower rule, the start falls on June 24th = St. John's Day, plus or minus eight days), in the southern hemisphere from November to mid-December. In contrast to many other flowering plants, the single flowers of the vine are small, green-yellow and rather inconspicuous due to the lack of petals and petals. With the ripening of fruit, the individual berries of the grape,

Flowering begins

In the pre-flowering stage, the longitudinal axis of the inflorescence first stretches, then the lateral branches spread apart with the closed single flowers still close together. With increasing development, the individual flowers separate from the flower cluster, swell and change to green-yellowish just before the actual start of flowering. The beginning of flowering is set when, in dry, warm weather, the first petals (perianthium) that have grown together into a flower cap detach from the flower base. At lower humidity the flower caps are thrown off using a sophisticated jumping mechanism, so that the scars scented with honey are exposed and the stamens can spread out.

Flowering - before dropping the cap and full bloom with 50% of the flowers

The single flowers of the vine are common to most grape varieties hermaphroditic or bisexual. This means that in a single flower they contain both the stamens with the male gametes in the pollen grains (= pollen) as well as the ovaries with the female egg cells and the scar to be pollinated (see also in detail under flower bud ). The full bloom stage is reached when around half of the flower caps have been dropped. However, the individual flowers on the plants never bloom at the same time, but in a somewhat staggered sequence, just like the individual plants on the vine, depending on the time exposition (Sun exposure) and position on the fruit shoots do not start at the same time, but with a delay in flowering.

Drawing: vine bloom in three phases

Flowering

The total flowering period is usually around eight days, but can also take up to three weeks in poor, wet and cold weather. With increasing global warming or climate Change there is a trend towards earlier flowering dates with shorter flowering times. The number and size of the banknotes as well as the number of single flowers were created a year earlier when the winter bud was formed (see below initiation ). On a fruit shoot there are usually one to three (up to a maximum of five) inflorescences in the form of a so-called panicle (So actually the name grape is not correct for the inflorescence of the vine). After flowering, pollination and fertilization, the ovary develops into a berry and the appearance into a grape. each grape has about 150 berries on average. However, it depends on the fertilization success whether a berry actually ripens from the maternal tissue of the ovary. In bad weather, the process of pollination and the unfertilized flowers suffer Verrieseln (fall off).

female flowers

There are also varieties that are functional female Flowers in which the stamens have been reduced or are sterile at all. That is often with table grapes the case. But these are inevitably one pollination instructed why you earnings varies greatly depending on the flowering conditions and the success of fertilization. For seedless varieties like korinthiaki or Sultana the female genital organs are sterile. Without the seeds that stimulate fruit growth, the berries remain small and atrophy, but they are suitable for the production of seedless Dry berries. The growth of these seedless berries can be artificially determined by growth hormones ( gibberellins ) can be induced.

hermaphrodite

On the other hand, they are Wild vines (Vitis vinifera sylvestris) usually dioecious, which means that each vine carries either only male or only female sexual organs. Both organs are present as an attachment to the vine, but only one organ is functional, while the other is hormonally suppressed. In dioecious plants selfing (Self-fertilization) is not possible and the female plants can only be fertilized by cross-pollination with pollen from a male vine. The forced recombination of the genetic makeup of paternal and maternal plants preserves the genetic diversity in a wild population and thus facilitates adaptations to environmental changes ( heterozygosity = Divisiveness). In viticulture, however, this is not desirable because of the uncertain yields. However, many of the as documents varieties used hybrids of wild grapes and therefore dioecious. In the breeding varieties with male flowers are preferred by rootstocks, which cause less effort due to the lack of grapes.

Self-fertilization (self-fertilization)

A selfing (Self-fertilization) is usually avoided by nature, since only that pollination ensures the continued existence. In hermaphrodite flowers, the female scars are self-sterile due to chemical, physiological and mechanical mechanisms for their own male pollen. However, as mentioned, there are other mechanisms in nature. Because with the Wild vines self-fertilization is simply prevented by the dwelling or the separated sexes. In the case of crop plants, these self-sterility mechanisms have often been wholly or partly bred away. During fruit and seed formation, the grape skeleton, berry skin and berry flesh, as well as the seed shells with the supply tissue for the embryo from the mother vine are formed. Only the embryo in the grape seed is the result of sexual fertilization, the grape is not affected. Riesling remains Riesling, even when fertilized by Silvaner pollen.

natural crossings

All vine species with the same DNA structure can be crossed with each other. These are all European (Vitis vinifera), but also most American and Asian varieties. This means that most varieties can not only fertilize each other (which a priori does not mean reproduction), but can also be crossed and new varieties are created. When the seeds germinate, they would be so seedlings spontaneous crossbred two parent plants. A variety with a different mother places new properties are most likely to arise when one pollination by another variety. In this way, innumerable grape varieties have arisen naturally in thousands of years (see four examples in the picture). However, the genetic material of the mother and father plants are also recombined if fertilization takes place within two vines of the same variety. However, their genetic differences are small because the vines in the vineyard mostly Clones by vegetative propagation are.

natural crossings - Cabernet Sauvignon, Riesling, Tempranillo, Grüner Veltliner

fertilization

The cultivated vine is mostly self-pollinating, primarily within the hermaphrodite flower (autogam) or between two flowers of the same appearance, which is understood as self-fertilization in the narrower sense. Self-fertilization in a broader sense also applies between two flowers of the same vine (geitonogam). Hermaphrodite plants of a grape variety can not only be pollinated with the pollen grains of plants of the same variety, but also of other varieties and can therefore be successfully cross-pollinated (xenogam), without the development of the flower into a berry being impaired. However, the germination capacity of the self-fertilized seeds (vine seeds) can be impaired. As a rule, cross-fertilized varieties are more fertile and vital than those from self-fertilization. But this is irrelevant, because in winegrowing the grapes are not intended for pressing and their seeds are not intended for sowing. Any pollen is sufficient for berry training.

The wind is also involved to a certain extent in the pollen transmission, the seeds can fly several hundred meters. The insects attracted by the scent of flowers also transmit, for example bees the pollen grains from one flower to another. In principle, however, the cultivated vine does not have to be cross-fertilized and is therefore not dependent on the presence of fertilizing insects like many other plants and the dwelling wild vines. This is a great advantage and crucial for the security of earnings. No matter where the pollen grains come from the stamens on the sticky scar, they stick there (pollination), germinate and form a pollen tube that grows into the scar and the stylus around the (only) egg cell in the ovary to fertilize (fertilization). From this fertilized egg cell (zygote) later arise through the so-called meiosis (reduction division and recombination division) to five (rarely also six) genetically different grapevines in the berry. The genetic difference between the nuclei results from a new composition of the parent chromosomes.

open pollinated

In vines grown from vine seeds without human intervention, the paternal pollen donor is not known a priori. Such spontaneously created varieties are different from the conscious ones new breed by people with " bloomed open "(English" open pollinated ", abbreviation" OP "). The fertilization ultimately results in a single berry from each individual flower. This means that a bunch of grapes with, for example, 150 berries could (purely theoretically) have 150 different fathers (although a father is a foreign vine). In this case, each berry of this grape would have the same mother, but the grape 150 different fathers (pollen donors). The pollen can come from its own flower, from a flower from the same plant, from a flower from another plant from the same vine, from a neighboring plant of the same variety, or from vines of other types from neighboring vineyards.

The maternal tissue of the ovary then grows into a berry with five to six seeds. As mentioned above, these could grow out seedlings perform different types of game. From intersections between Cabernet Sauvignon x Bronner are 1983 in Freiburg three quite different grape varieties emerged ( baron. Cabernet carbon. Souvignier Gris ). The three underlying kernels could theoretically all come from the same berry. Bad weather such as cold, rain, wind or prevails during the vine bloom hail the fertilization process is impaired. Rain, wind and high air humidity hinder the pollen and flight, but also have the effect that the caps' jumping mechanism does not work or only works to a limited extent and that they are not blown off, but remain loosely on the scars and stick there. This means that pollination can no longer take place. The outgrowth of the pollen tubes is hindered by the cold. Therefore, all ovules are never fully fertilized.

However, since the embryo in the seed stimulates fruit formation, the under-fertilized berries remain smaller. The result is parthenocarpy (or stenospermocarpy = apparent virginity) or early Verrieseln (Fall off) the completely unfertilized flowers. The grape then shows less and petits Grapes on. However, this does not have to be a disadvantage because a reduced yield can increase the quality. Because the ingredients produced in the grapevine are now concentrated on a smaller number of berries, and this can result in more extract substances, higher sugar content and overall better wine quality. The berries reach pea size a few weeks after flowering. This is already part of the next development step, the fruit set,

Additional information

For the fertilization process, see also under flower bud and hermaphrodite flower, A list of keywords relevant to grape varieties can be found at grapevine contain. All tools, work and measures in the vineyard during the growth cycle can be found under the keyword Weingarten Care,

Graphics: taken from Bauer / Regner / Schildberger, viticulture,
ISBN: 978-3-70402284-4, Cadmos Verlag GmbH

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