ISHS Acta Horticulturae 343: Physiological Basis of Postharvest Technologies
INDUCTION OF ETHYLENE PRODUCTION AND LIGNIN FORMATION IN WOUNDED MESOCARP TISSUE OF CUCURBITA MAXIMA |
| Authors: | H. Hyodo, C. Hashimoto, S. Morozumi, M. Ukai, C. Yamada |
| Abstract:
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. | |
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