ABSTRACT
Grapevines provide an outstanding example of the effectiveness of plant growth regulating chemicals (PGRC) as modifiers of the agronomic characteristics of crop plants. This is a reputation which has arisen through the importance in viticulture of cultivated forms of grapevine which bear seedless fruit: fruit which often have an inherent capacity to respond to supplementary levels of PGRCs, especially auxins, gibberellins and cytokinins. The place of cytokinins in viticulture is indeed uncertain and utilization for enhancement of numbers of flowers set either directly by application at bloom or indirectly, through improved flower development, by application before bloom will probably depend on improved technology of application or development of improved analogues. The aspects of plant development which are most open to control are those of fruit set, growth, and development. However, even in these aspects of viticulture, plant growth regulators have not been a universal panacea and have sometimes created new problems.
