Abscisic Acid Improves Tomato Fruit Quality by Increasing Soluble Sugar Concentrations
Barickman, T. C., D. A. Kopsell, and C. E. Sams.  2016.  Journal of Plant Nutrition.

Abstract:
Abscisic acid (ABA) is crucial in fruit maturation and senescence and is considered as the other ripening control factor other than ethylene. Important components in ripening fruit are soluble sugars, which make the fruit sweeter and carotenoids, important flavor compounds in ripened fruit. The purpose of this study was to examine the effects of foliar ABA and calcium (Ca) fertilizer treatments (individually and in combination) on determinate beef-steak greenhouse tomato (Solanum lycopersicum) leaf chlorophylls and carotenoids, fruit carotenoids, and soluble sugar concentrations. Foliar spray treatment of 500 mg L-1 ABA increased zeaxanthin (ZEA) and -carotene (BC) in tomato leaf tissue. Increases in Ca fertilizer treatments significantly decreased tomato leaf violaxanthin (VIO), but no effect on other carotenoids. The application of 500 mg L-1 ABA foliar spray significantly increased glucose and fructose concentrations in tomato fruit tissue. Foliar application of ABA treatments can increase overall chlorophyll, carotenoid content, and fruit quality.