Effects of Growth Regulators on Fruit Set and Growth of the Acerola (Malpighia glabra L.)

Abstract

The low natural fruit set of acerola in Hawaii, attributed to absence of pollen transferring agents, indicated the feasibility of growth regulator application to induce fruit set. Among the several growth regulators tried initially, 4-chlorophenoxyacetic acid (PCA) and indolebutyric acid ( IBA) were found to be effective in promoting fruit set, the f rmer being more efficient over a wider range of concentration. PCA exhibited some phytotoxic effects in the nature of leaf curling, yellowing, and even death of young vegetative tips. Phytotoxic effects were reduced in severity with decrease in concentration. lBA at 100 ppm effected approximately 60 percent fruit set without any apparent phytotoxic effects. Under field conditions the satisfactory fruit set and lack of phytotoxic effects with IBA at 100 ppm make this a highly desirable compound, but the wide use of it may be prohibited by its high cost. On the other hand, PCA at 50 ppm can induce as much fruit set as lBA at 100 ppm, and phytotoxic effects are mild with early recovery. Furthermore, the very low cost of this material makes its use economically feasible.