POLYAMINE INVOLVEMENT IN THE DEVELOPMENT AND RIPENING OF AVOCADO FRUIT

An extract from avocado fruit mesocarp and seed coat showed arginine decarboxylase (ADC) activity throughout the period of fruit growth, development and ripening, whereas no ornithine decarboxylase could be detected.
Kinetics studies of ADC activity showed similar Km for arginine in young fruitlets and mature fruits, whereas Vmax was 23-fold higher in young fruitlets.
The high activity of ADC found in fruitlets is restricted to the seed coat, a tissue which is active in fruitlets but shrivels in the mature fruit.
The level of putrescine and spermidine in the fruit declined during the course of fruit development and ripening.
This decrease was moderate during the period of fruit development until maturation.
However, a sharp decline in these polyamines was recorded in fruits undergoing ripening after harvest.
Spermine content did not change during development but decreased rapidly during ripening.
Addition of putrescine or spermine to avocado fruit tissue inhibited the biosynthesis of the ripening hormone ethylene by both inhibiting the activity of 1-amino cyclopropane carboxylic acid (ACC) synthase and by inhibiting the conversion of ACC to ethylene.
In view of the above, the involvement of polyamines in fruit ripening is discussed.

V International Symposium on Growth Regulators in Fruit Production

A. Apelbaum

https://doi.org/10.17660/ActaHortic.1986.179.131