The flower bud of the cultivated grapevine is one hermaphrodite flower, that is, it contains the male and female genitalia united in a single flower bud. The male sexual organs are the pollen-producing stamens or stamens (Stamen, Mz. Stamina), which consist of the stalk-shaped filament and the yellowish anthers sitting on the tip. The totality of all stamens of a flower are the androecium. A dust bag contains four pollen sacs, in which the pollen grains are formed with the haploid (n = 19) male gametes (fertilization hormones). In the vine flower, five of these freestanding stamens surround the female sexual organ, the ovary, in a circle. This consists of two mutually grown carpels (carpels), which contain two compartments with ovules inside. Therefore, the grapevine is one of the bedecktsamigen flowering plants.
The ovary goes over at its tip in the style, which ends in the scar (stigma). The disc-shaped scar is a spongy tissue that separates sticky secretions. At the base of the stamen and the Fruchtknotens are five nectar glands (honey glands), which are fused into a ring (discus or calyx). Five weakly formed sepals and five green petals (petals) grown together to form a cap cover the stamens and the ovary in the form of an inverted calyx. This yellow-green perianth (cap, cap, perianthium) is at the beginning of the blossom then the pollination by the pollen and the subsequent fertilization can take place.
For the fruit set and berry development, it is largely irrelevant if the seed even- or pollinated has been. Even if, for example, a Riesling scar was pollinated by a Silvanersamen, a Riesling grape develops. The natural crossing of two grape varieties in this case is therefore only potentially present in the embryo of the grape seed and would only become one during seeding and germination of this kernel seedling be effective. Between pollination of the scar and fertilization of the egg pass two to three days depending on the temperature. The pollen begins to germinate on the scar, the pollen tube grows through the stylus, penetrates to the maternal oocyte in the ovary and fertilizes them.
From this fertilized egg cell (zygote) then arise later by meiosis (reduction division and recombination division) four to five and rarely even six genetically different seed pits in the grape. The genetic difference of the nuclei results from a new compilation of the parental chromosomes. Therefore, different grape varieties can emerge from the individual kernels of a berry. The stalk of the flower bud becomes woody and becomes the berry stalk, which carries the single grape berry. See also below blossom or a list of relevant keywords below grapevine,
Graphics: Taken from Bauer / Regner / Schildberger, viticulture,
ISBN: 978-3-70402284-4 Cadmos Verlag GmbH