Definition - What does Stigma mean?
Stigma is the term in botany for the part of the grape vine that catches the pollen and helps it germinate. In the context of a grape vine, the stigma is the sticky tip of the pistil. It works with the style and/or ovary to create seeds and berries on the vine. Part of the female reproduction system, stigmas are found only on female or hermaphroditic vines.
WineFrog explains Stigma
Stigmas are a vital part of the reproductive process for grapes. Its sticky nature on the grape vine ensures that pollen is trapped on the tip of the pistil. Once there, the stigma sifts out pollen from other plants (one reason why we don’t see cross pollination more often in nature), then rehydrates the pollen and encourages it to germinate, moving it down the pollen tube and into the ovary of the flower.
The success of the stigma is one of the factors that determines if the berries of a vine are big or small. Each ovary contains up to four embryo sacs. Fertilized embryo sacs create seeds; the more seeds a berry has, the bigger it is.
Stigmas are found only on female or hermaphroditic vines (also called “perfect vines”). To find the stigma on a budding vine, look for a vase-shaped bud that is attached to the vine by a thick stem. The stigma will be the sticky tip of the bud.