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  • Author or Editor: Evangelos M. Sfakiotakis x
  • Journal of the American Society for Horticultural Science x
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Abstract

A method is described for the measurement of internal ethylene concentration in fruits on the tree. Ethylene levels in ‘Red Delicious’ fruits immediately after harvest were similar to those in fruits on the tree during development and ripening. The levels varied mostly between 0.02 to 0.15 ppm during the period from 83 to 140 days from bloom and sharply increased from 10 to 1000-fold within 5 days as autocatalytic ethylene production began. Ripening followed the upsurge in ethylene production. Isolating fruit from leaves by girdling plus defoliation of spur leaves hastened the increase in internal ethylene by approximately 1 month. Girdling or defoliating the spur did not markedly alter the onset of autocatalytic ethylene production compared to that observed by fruits on normal spurs. The data support the concept that fruits receive a ripening inhibitor from the leaves.

Open Access

Abstract

Ethylene and other olefinic compounds cause apples and other climacteric fruits to ripen. Propylene, which fruits do not produce, was employed to determine, 1) the stage of maturity apples must attain to autocatalytically produce ethylene, and 2) the effect of O2 tension on autocatalysis. ‘Red Delicious’ apples harvested at developmental stages representing 52, 58, 65, and 75% of maturity were gassed with propylene at concentrations of 0, 10, 50, 100, 500, and 1000 ppm for 1 week at 20°C. Propylene induced ethylene synthesis at all stages of maturity. Its ability to stimulate ethylene production, however, increased progressively with fruit maturation, although rate of production following treatment with 500 ppm propylene was constant. A shorter lag time to the onset of autocatalytic production was observed in more mature fruits which reflects a natural increase in sensitivity. Propylene administered at 6.5% O2 or less did not induce ethylene production, but an anaerobic atmosphere was necessary to completely inhibit ethylene synthesis in fruits once autocatalysis began.

Open Access