All classes of plant growth regulators, including auxins, gibberellins, cytokinin, abscisic acid and ethylene markedly affect and interact every facets of grape life in different ways.
The roles and possible mode of actions that these substances with other chemicals play in induction of parthenocarpy, fruit set, ripening and coloration of grape fruit were discussed.
GA₃, streptomycin or 4-CPA induced formation of seedless berries in `Delaware´, `Muscat Bailey A´ and `Kyoho´ grape cultivars. The effects of induction of parthenocarpy by GA treatment was strikingly stabilized by combined application with BA, atlox BI or 4-CPA. Daminozide and ethephon effectively increased berry-set in `Kyoho´, ´Pione´ and `Concord´ grape cultivars. Growth regulators affect both ripeaing and coloration of grape fruit. Growth substances reacted in diverse ways to ripening of grape fruit, depending on the time of application. Auxin and ethylene applied during the sloR--growth phase delayed the onset of ripening. But ABA and ethylene applied after veraison enhanced ripening and anthocyanin development in grape berries.
To increase our knowledge of growth regulators for practical uses for viticulture, the following facts should be investigated: 1) Induction of parthenocarpy in major cultivars by streptomycin, 2; Production of large clusters and good sized berries with high quality, 3) Increase of berry-set while maintaining berry size of ´Muscat Bailey A´, ´Kyoho´ and `Pione´ in unfavorable circumstance and vine condition, 4) Stimulation or delay of ripening in fruit, 5) Promotion of coloration in fruit, 6) Development of chemical thinning method in berries, 7) Development of chemicals for prevention of be.-ry abscissions after harvest, 8) Effect of using mixtures of growth regulators on every facets in grape growing, and 9) Practical application of new growth regulator such as brassinolide for viticulture.
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