INDUCTION OF ETHYLENE PRODUCTION AND LIGNIN FORMATION IN WOUNDED MESOCARP TISSUE OF CUCURBITA MAXIMA

The ethylene production rate markedly increased in the wounded mesocarp tissue of winter squash (Cucurbita maxima) fruit. 1-Amino-cyclopropane-1-carboxylic acid (ACC) synthase activity was rapidly induced in mesocarp tissue in response to wounding, followed by increases in ACC level and in the rate of ethylene production.
Ethylene-forming enzyme (EFE) activity was also rapidly induced in response to wounding, almost in parallel with the rate of ethylene production.
In vitro EFE preparation showed a Km value of 0.168 mM. The enzyme required ascorbate and Fe²⁺ as cofactors for its high activity.

The activities of phenylalanine ammonia-lyase (PAL) and peroxidase (POD) rapidly increased after wounding, which may be associated with lignin formation in the wounded tissue.
Lignified cells were found to be localized within a couple of cell layers from the cut surface, especially in the first cell layer.
It was shown with 2, 5-norbornadiene, an inhibitor of ethylene action that the increases in PAL and POD activities and lignin formation is considered to be a defense mechanism of the wounded tissue forming physical barriers against microbial penetration.

Physiological Basis of Postharvest Technologies

H. Hyodo, C. Hashimoto, S. Morozumi, M. Ukai, C. Yamada

https://doi.org/10.17660/ActaHortic.1993.343.59