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Involvement Of Polyamines In The Development And Ripening Of Avocado Fruits
Published 1986 · Biology
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Summary Polyamine metabolism was studied in avocado fruits, which are known to be typical climacteric fruits. An extract from the fruit mesocarp and the seed coat showed arginine decarboxylase (ADC) activity throughout the period of fruit growth, maturation and ripening, whereas no ornithine decarboxylase could be detected. The specific activity of ADC was 27-fold higher in the extract from the seed coat than in that from the mesocarp. During fruit maturation the seed coat shrivels and ADC activity in the whole fruit was reduced by 25-fold. The levels of putrescine and spermidine in the fruit declined during the course of fruit growth. 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 inhibiting both the activity of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and the conversion of ACC into ethylene. In view of the above, a possible involvement of polyamines in fruit ripening is discussed.