THE EFFECT OF HIGH TEMPERATURE ON DEGREENING IN RIPENING BANANAS
Bananas of the Cavendish subgroup fail to degreen when ripened at the high temperatures of the tropics (>24°C), resulting in 'green-ripe' fruit. Previous work in our laboratories has revealed that this failure to degreen is not due to an inhibition by high temperature of either ethylene or carotenoid biosynthesis. The bananas remain green because of the retention of chlorophyll and associated thylakoid lamellae. Analysis of chlorophyll fluorescence induction curves reveals that ripening at high temperatures is accompanied by a rapid and complete loss of PS II dependent fluorescence. Thus the chlorophyll retained by 'green-ripe' bananas is not photosynthetically active. Banana thylakoid fragments possess a chlorophyll bleaching system which is dependent upon the presence of free fatty acids. As high temperature accelerates the rate at which the galactolipids and their fatty acid components are broken down during ripening, we discuss the possibility that bleaching in vivo at temperatures >24°C may be affected by the changing linolenic acid concentration.
Blackbourn, H., John, P. and Jeger, M. (1989). THE EFFECT OF HIGH TEMPERATURE ON DEGREENING IN RIPENING BANANAS. Acta Hortic. 258, 271-278