The flower bud of the cultivated grapevine is a hermaphrodite flower, i.e. it contains the male and female sexual organs united in a single flower bud. The male sexual organs are the pollen-producing stamens or stamens (stamens, Mz. Stamina), which consist of the stem-shaped filament and the yellowish anthers at the tip. The entirety of all stamens of a flower is the androecium. An anthers contains four pollen sacs in which the pollen grains are formed with the haploid (n=19) male gametes (fertilisation hormones). In the vine flower, five of these free-standing stamens surround the female sexual organ, the ovary, in a circular pattern. The ovary consists of two fused together carpels, which contain two compartments with ovules inside. This is why the grapevine is one of the flowering plants with angiosperms
The ovary merges at its tip into the stylus, which ends in the scar (stigma). The disc-shaped stigma is a spongy tissue that secretes sticky secretions. At the base of the stamens and the ovary there are five nectar glands (honey glands) which fuse together to form a ring (discus or calyx). Five weakly developed sepals and five green petals, which have grown together to form a cap, cover the stamens and ovary in the form of an inverted calyx. This yellowish-green petal (cap, cap, perianthium) is shed at the beginning of flowering, after which pollination by pollen and subsequent fertilisation can take place.
It is largely irrelevant to the fruit set and berry development whether the seed is Selbstungself-pollinated or cross-pollinated. For example, even if a Riesling scar was pollinated by a Silvaner seed, a Riesling grape will develop. The natural crossing of two grape varieties that occurred in this case is therefore only potentially present in the embryo of the grape seed and would only become effective when this seed is sown and germinates to form a seedling. Two to three days pass between pollination of the scar and fertilisation of the egg, depending on the temperature. The pollen begins to germinate on the scar, the pollen tube grows through the stylus, penetrates to the maternal egg in the ovary and fertilises it.
From this fertilised egg cell (zygote), four to five and, more rarely, even six genetically different grape seeds are later produced in the grapevine by meiosis (reduction division and recombination division). The genetic difference of the nuclei results from a new composition of the parental chromosomes. Therefore, different grape varieties can develop from the individual nuclei of a berry. The stalk of the flower bud is lignified and becomes the berry stalk which carries the individual grape berry. See also under Flowering or a list of relevant keywords under Grapevine.