Timing of application and growth regulator interaction effects on fruit growth of two species of actinidia

Fruit growth of most, if not all, species appears to depend on a triple interaction between auxins, gibberellins and cytokinins, although the limiting hormone may vary between species or cultivars. The response of Actinidia deliciosa (green kiwifruit) and Actinidia chinensis (gold kiwifruit) to the natural plant extract (Benefit®), the synthetic auxin, 1-naphthalene acetic acid (NAA) and the cytokininlike compound CPPU depended on time of application and concentration. A strong hormonal interaction was found between NAA and CPPU. However results differed significantly between the two Actinidia species. These results are discussed in terms of periods of cell division and cell expansion during fruit growth and additive and synergistic interactions between growth regulators.