The Structure and Biochemical Changes during Finger Drop in Ripening Bananas

摘要

Finger drop is a typical physiological disorder of some banana cultivars under certain conditions which individual fingers dislodged from the banana crown during ripening. 'Kluai Horn Thong' (Musa acuminata, AAA Group) exhibited 100% finger drop whenthey were fully ripe while 'Kluai Namwa' (Musa x paradisiaca, ABB Group) did not show finger drop at all upon fully ripening. Tissue at the pedicel adjacent to the rupture area of 'Kluai Horn Thong' at unripe stage was stained with ruthenium red much more dense than that at fully ripening stage, while 'Kluai Namwa' had no difference in staining with ruthenium red at both unripe and fully ripening stages. Polygalacturonase activity and water-soluble pectin content in the pedicel tissue adjacent to the rupture area of 'Kluai Horn Thong' were higher than that of 'Kluai Namwa'. The difference became greater when finger drop advanced. While alkaline soluble pectin content in the pedicel tissue adjacent to the rupture area of 'Kluai Namwa' was much higher constantly than that of 'Kluai Horn Thong' throughout the study period. Histochemical study in the pedicel adjacent to the rupture area at which finger drop occurred did not show an abscission zone in unripe and fully ripe bananas. It is concluded that finger drop in ripening banana resulted from a localized softening and weakening of tissue in the pedicel adjacent to the rupture area and finger drop does not require an abscission zone.