FROST DAMAGE AND CARBOHYDRATE METABOLISM IN CITRUS FRUIT

FALCONE FERREYRA, M. LORENA; GARRÁN, SERGIO M.; ANDERSON, CATALINA M.; VÁZQUEZ, DANIEL E.; IGLESIAS, A. A; PODESTÁ, FLORENCIO E.

Bariloche, Río Negro

Congreso; XXXIX Reunión anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB); 2003

Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB)

Freezing temperatures can cause severe damage and economic loses to the citrus industry by reducing yield and by afecting the external and internal parameters of fruit quality. The activities and levels of the enzymes involved in the carbohydrate metabolism of fruit from orange trees (Citrus sinensis L., cv. Valencia late) exposed to different temperatures were analized. The aim of the work was to find biological markers to develop an early diagnostic technique for frozen fruits. The enzymatic activity measurements (in terms of U/mg and U/g FW) showed a significative and moderate increase in frozen fruits compared to control in pyrophosphate-dependent phosphofructokinase (1.85-fold), Ala amino transferase (1.6-fold), phosphoenolpyruvate carboxylase (1.75-fold) and pyruvate kinase (1.75-fold). A more pronounced rise was observed in lactic and alcohol dehydrogenase activities (4.4 and 4.7-fold, respectively). In contrast, only NADP-malic enzyme diminished (40%). These results were consistent with the profile in the immunoreactive proteins levels. Another important feature to emphasize was the marked decrease in total soluble protein in frozen fruits. These studies suggest that freezing temperatures induce the activation of the glycolytic and fermentative metabolisms.