The use of auxin-like compounds for promoting adventitious root formation in hardwood and softwood cuttings is one of the earliest and most successful practical applications of plant growth regulators.
The treatment of cuttings with preparations containing indolebutyric acid, alone or in combination with -naphthalene acetic acid, has been a routine procedure for many years for both professional plant propagators and home gardeners.
In the propagation of fruit plants by aseptic methods, synthetic cytokinins and auxins are essential components of culture media for axillary shoot proliferation and adventitious root formation, and micropropagation has also become a widely-used procedure in the horticultural industries.
Similarly, plant growth regulators are essential components of systems for plant regeneration in vitro by organogenesis and somatic embryogenesis, and the use of these compounds is fundamental to the application of biotechnology to the genetic improvement of fruit crops.
The importance of growth regulators in plant propagation is accepted by the general public, but use of growth regulators in fruit-crop production has become controversial.
Chemical crop protection and chemical aids to mechanization are of concern to consumers and to consumers' organizations in regard to residues, the wholesomeness of fresh foods, public health, and damage to the environment.
This concern is being expressed in many countries through increasingly stringent legislation on the use of chemicals in agriculture and horticulture.
There has also been a shift in consumer attitudes.
In California, for example, advertisements for fresh fruit often refer to the fact that growth regulators were not used in the growing of the crop.
These social pressures have led some to conclude that chemical controls in crop production, including growth regulators, will be greatly reduced, if not phased-out, and that major emphasis should now be given to fruit breeding and to increased use of genetic methods for crop protection and methods of management.
In future, use of growth regulators in the orchard or vineyard may well decline, but these compounds will remain as indispensible tools for plant propagation and for the genetic improvement of fruit crops by both conventional methods and biotechnology.
These views are well illustrated by recent research on (i) propagation of fruit crops and (ii) speeding the turnover of generations in fruit breeding by induction of precocious flowering in juvenile seedlings.