Relationship of Growth and Development to Changes in Sugars, Auxins, and Gibberellins in Fruit of Seeded and Seedless Varieties of Vitis Vinifera

Abstract

Measurements were made of growth and development of certain parts of the fruit and seed of 2-seeded and 3-seedless varieties of V. vinifera from anthesis to maturity. These were compared with changes in juice sugar and the auxin and gibberellin content of partially purified extracts of berries. The fruit of all varieties showed a double-sigmoid growth curve. The 1st growth cycle of seeded varieties was paralleled by a rise and fall in meristematic activity in the seeds and by auxin levels. In seedless berries, the rise and fall of auxin levels and "seed" meristematic activity was brief in comparison with their 1st growth cycle. Gibberellin activity was found in young berries of the 3 seedless varieties but not in seeded fruit of any age. This correlates with the known fact that seedless berries enlarge more than seeded berries after treatment with gibberellin or auxin or by girdling. Gibberellins may be important hormones in seedless berries. Mature stamens of all varieties showed gibberellin activity. The 2d growth cycle of all varieties could not be correlated with morphological, auxin or gibberellin changes; but it could be related to the influx of sugars into the berries and it is suggested that sugaring causes this growth osmotically. A 2d rise in auxin levels reached a peak at the beginning of the 2d growth cycle and of sugaring; this could not be explained, especially in seedless berries where there is not embryo growth. Trunk girdling of 2 seedless varieties caused no measurable change in auxin or gibberellin concentration expressed on dry weight, fresh weight or volume bases, but levels per berry increased because of the increase in berry volume after girdling.