AVOCADO FRUIT RIPENING AND ETHYLENE BIOSYNTHESIS

Avocado is a climacteric fruit which does not produce large amounts of ethylene on the tree and does not ripen until it is harvested.
Attached fruits contain trace amounts of ethylene and ACC (l-aminocyclopropane-l-carboxylic acid), have low ACC synthase activity, and contain some MACC (l-(malonylamino) cyclopropane – l – carboxylic acid). After harvest ACC synthase activity is increased, leading to ACC accumulation before the climacteric rise.
Ethylene can promote EFE activity (ethylene forming enzyme) which rapidly converts ACC to ethylene during the climacteric rise.

The limiting factor for ripening on the tree is the low level of the ACC, which itself is limited by low ACC synthase activity.
After infusion of ACC to attached fruits, the latter begin to produce much more ethylene and show a climacteric rise on the tree.
These fruits abscise at the climacteric peak and are ripe a day later.

The sequence of ethylene biosynthesis steps during avocado fruit ripening is discussed.

V International Symposium on Growth Regulators in Fruit Production

A. Blumenfeld, Y. Sitrit, J. Riov

https://doi.org/10.17660/ActaHortic.1986.179.132