Abscisic Acid Metabolism during Fruit Development and Maturation of Mangosteens

Abstract

Endogenous abscisic acid (ABA), its 2-trans isomer (trans-ABA), phaseic acid (PA), and dihydrophaseic acid (DPA) concentrations were quantified in the peel, aril, and seed of mangosteen (Garcinia mangostana L.). Changes in carbon dioxide (CO2) and ethylene (C2H4) production and 1-aminocyclopropane-1-carboxylic acid (ACC) concentration in the peel and aril were also examined. ACC concentration and CO2 and C2H4 production were high at the beginning of fruit development and gradually decreased toward harvest, which confirms that mangosteen is a nonclimacteric fruit. In the peel and aril, the increase in ABA concentration preceded the decrease in peel firmness and coloring of the peel. This suggests that ABA may induce the maturation of mangosteens. The state of ABA metabolism varied with the part of fruit. In the peel, PA and DPA were not considered to be predominant metabolites of ABA because their concentrations were low compared to ABA throughout fruit development. In contrast, in the aril and seed, it is possible that the PA-DPA pathway may be a main pathway of ABA metabolism because the concentrations of DPA in the aril and of PA in the seed directly coincided with the concentrations of ABA. The differences in the ABA metabolites between aril and seed may be caused by the rate of ABA metabolism. The concentrations of ABA and its metabolite in the seed decreased toward harvest.