The initial respiratory rates at 20 centrigrade of detached
oranges (Valencia and navel), grapefruit, and lemons decreased
during ontogeny. Small attached oranges respired
at the same rate as detached fruits of the same weight, and
cutting the pedicel produced no shock or injury stimulus to
the respiratory rate. Small oranges and grapefruit (average
weight about 15 grams) showed pseudoclimacteric respiratory
patterns and produced ethylene. The height of the
respiratory rise and the amount of ethylene produced decreased
as the fruit increased in weight until the September
4th harvest, when the fruit weights were 120, 64, and 87
grams for grapefruit, Valencia, and navel oranges, respectively;
at that time no respiratory rise or ethylene production
was observed. The pattern for all subsequent harvest
revealed no postharvest rise in the respiratory rates. Lemon
fruit, in contrast, had a continuously decreasing respiratory
rate at all stages of ontogeny. Exposure to 20 microliters
of ethylene per liter induced an increase in the respiratory
rate of all varieties at every stage of ontogeny; this was
true also in young oranges and grapefruit following their
respiratory rise and decline.