Hormonal Control of Fruit Ripening

Ripening is the process by which physiologically mature fruits are transformed from a relatively unfavorable to a favorable condition with respect to texture, color, flavor, and aroma. In many fruits ripening occurs while the fruit is still attached to the parent plant, while in others such as the avocado, ripening takes place only following harvest. The complex physical and chemical changes of ripening have been studied extensively and techniques of handling and storage have evolved which can be satisfactorily applied to control the rate of ripening in the post-harvest period. While ripening normally occurs in fruit after growth ceases, it is a natural consequence of developmental changes during growth. This is evident from the fact that the time period from bloom to physiological maturity can be manipulated. A fruit is physiologically mature when the stage is set for ripening to ensue. The stage is set by the genetic makeup of the cultivar and the actors are the environmental conditions and chemical stimuli interacting during growth and development. Naturally occurring plant growth substances, their chemical analogs and antidotes, most certainly play a role in growth and development, and therefore must in some way influence the development of ripening capacity. However, the mechanism of their action has not been resolved, but this does not curtail speculation based on numerous observations which have been made. My purpose will be to briefly review the effects of certain plant growth substances on fruit ripening and suggest a possible role they may play in the process.