Anthesis, pollination and fruitset in Pinot Noir

Aspects of pollination and resulting fruitset in Vitis vinifera cv. Pinot Noir were investigated in a cool climate wine area of Southern Tasmania (Australia). Changes in the appearance of the stigmatic surface and pollen grains were recorded using environmental scanning electron microscopy (ESEM). Flowers with the calyptra intact (before capfall), showed an apparently turgid stigmatic surface and pollen grains present on the surface were slender and elongated (L/D 35 μm/15 μm). Stigmas had a more flaccid appearance after capfall and pollen grains were more spherical and less elongated in shape (L/D 28 μm/20 μm). Pollen was visible on the stigma surface before capfall, indicating that anthesis occurred whilst the calyptra was in place. Pollen viability tests showed that the pollen was already viable at this stage, and it remained viable until after the flower had been open for several days. Fluorescence micrographs showed no evidence of pollen tube growth until after capfall. Flowers covered by waxed paper bags to eliminate external pollen and thus allow only self-pollination, gave a percentage fruitset equal to that of flowers where external pollen was not excluded. Results indicate that Pinot Noir can be self-pollinated, and that while anthesis commences prior to capfall, fertilisation does not proceed until after capfall.