There are three types of parthenocarpy:
Pollination can cause stigma by pollen or there is a grain attitude with the stimulating effect of forming grass pipe. Here, integuments are in normal structure. However, before the grass tube reaches the ovary, the embryo sac degenerates during flowering and fertilization cannot occur. There is absolutely a need for dusting. Due to the defective formation of the embryo sac, seedless grain attitude without fertilization is called stimulative parthenocarpy. It is seen in black corent grape variety.
A second form of mun in vines is vegetative parthenocarpy. In this event seen in white and red Corinthian grape varieties, the shape of the seed drafts is completely distorted and only the outer integuments have developed. Internal integuments are found as a bulging lump of meristematic tissue in the basal part of nuclear tissue. Nucellus shows an extreme development. There is no embryo sac. The occurrence of grain attitude when dusting is prevented by castration in these varieties shows that, unlike stimulative parthenocarpia, the stimulating effect of pollen powders is not required.
It is the occurrence of seedless fruit due to the absence of impegnation although the seed drafts are in normal structure. It is the condition seen in parthenocarp fruits that occurs in morphological hermaphrodite flowers. In case of pollination and fertilization, they form fruit with seeds and normal size.Although the third form of parthenocarpy, “Facultative parthenocarpy“, has a normal embryo sac, it is found in some grape varieties with abnormal flower structures and low pollen dust germination. When there is no good pollinator variety or even if it is a suitable pollinator, when the weather conditions are not suitable for pollination and fertilization, small grains with or without seeds can be formed on the same cluster.