In a grape cluster, individual berries enter the ripening phase at different times, leading to the uneven ripening pattern observed during véraison. Seeds are known to influence the growth of berries during berry formation but little is known about how seeds impact the ripening process. In Pinot noir, the size of the seed inside the berry, relative to the weight of the berry, influences when berries enter the ripening phase. This is associated with the differences in volume of auxin levels (a plant growth regulator). Berries with a higher ratio of seed-to-berry weight have higher auxin rates, which delays the berry's ripening. Conversely, berries with a lower ratio between seed-to-berry weight tend to ripen earlier. These differences in the berry auxin levels and seed-to-berry weight ratios may explain why berries enter the ripening at different times and the uneven ripening pattern of a grape cluster at véraison.
