The flower bud of the cultivated grapevine is one hermaphrodite flower, that is, it contains the male and female genital organs united in a single flower bud. The male sexual organs are the pollen-producing stamens or stamens (stamen, Mz. Stamina), which consist of the stem-shaped stamen (filament) and the yellowish anthers located at the tip (anthers). The entirety of all stamens of a flower are the androeceum. A dust bag contains four pollen bags in which the pollen grains are formed with the haploid (n = 19) male gametes (fertilization hormones). In the vine flower, five of these free-standing stamens surround the female reproductive organ, the ovary. This consists of two intermingled fruit leaves (carpels), which contain two compartments with ovules inside. That is why the grapevine is one of the covered velvety flowering plants.
The top of the ovary merges into the stylus, which ends in the stigma. The disc-shaped scar is a spongy tissue that deposits sticky secretions. At the base of the stamens and the ovary there are five nectar glands (honey glands) that have grown into a ring (disc or goblet). Five weakly developed sepals (sepals) and five green petals (petals) grown together into a cap cover the stamens and the ovaries in the form of an inverted chalice. This yellow-green flower cover (cap, cap, perianthium) is at the beginning of the blossom discarded, then pollination by the pollen and subsequent fertilization can take place.
For the fruit set and the berry development it is largely irrelevant whether the seed self- or pollinated has been. So even if, for example, a Riesling scar has been pollinated by a Silvaner seed, a Riesling wine grape develops. The natural crossing of two grape varieties in this case is only potentially present in the embryo of the grape seed and would only become one when this seed was sown and germinated seedling be effective. Depending on the temperature, two to three days pass between pollination of the scar and fertilization of the egg cell. The pollen begins to germinate on the scar, the pollen tube grows through the stylus, penetrates to the maternal egg in the ovary and fertilizes it.
From this fertilized egg cell (zygote), four to five, and rarely even six, genetically different grapevines in the grape berry later develop through meiosis (reduction division and recombination division). The genetic difference between the nuclei results from a new composition of the parent chromosomes. Therefore, different grape varieties can arise from the individual seeds of a berry. The stem of the flower bud becomes woody and becomes the berry stem that supports the individual grape. See also under blossom or a list of relevant keywords under grapevine,
Graphics: taken from Bauer / Regner / Schildberger, viticulture,
ISBN: 978-3-70402284-4 Cadmos Verlag GmbH