Effects of gibberellic acid on metabolism starch-sucrose during banana ripening (Musa acuminta var. Nanicão)

Author(s)

Maria Rosecler Miranda Rossetto

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ)
• Defense date: 2001-06-01

Examining board members

Beatriz Rosana Cordenunsi; Giuseppina Pace Pereira Lima; João Roberto Oliveira do Nascimento

• Advisor: Beatriz Rosana Cordenunsi

Abstract

The ripening is an exclusive stage of fruit development, that involves a serie of metabolic transformation from different energy source. It is mediated by a dynamic enzymatic complex, resulting in formation/degradation of different coumpouds that will render fruit acceptable for the consumption. Depending on the type of fruit, this energy source can be in the form of organic acid, sucrose of the plant or starch. Banana (Musa acuminata) is a climateric fruit that uses starch as main carbon source, which is reduced during banana ripening of levels that vary from 12 to 20% to less than 1 %. Concomitant to the this degradation, the levels of sucrose can reach up to 15%, depending of the cultivar. The gibberellic acid, GA3-mediated is a plant growth regulation of the giberellins family, that has been studied in cereals because of their enhancing effect of gene expression of αamylase. In fruits, it is responsible for keeping the texture firm and the soluble solid levels, and delaying the ripening. The influence of the GA3 in the starch-sucrose metabolism in banana slices, were observed. That the phytohormone did not modify the respiratory peak nor the synthesis of ethylene. However, it delayed the starch degradation and the soluble sugars accumulation for about three days. This delay was followed by decrease and/or delay in the activity of the enzymes related to starch degradation: the α and β-amylases; and sucrose synthesis the sucrose phosphate synthase (SPS). However, was not observed a difference in the increase of gene expression of SPS and phosphorilase (AU)