Hormone used for degreening of citrus fruits is

The hormone used for degreening of citrus fruits is Ethylene.
It accelerates fruit senescence and spoilage. Prolonged exposure of fruit to ethylene or its exposure to high doses during degreening induces physiological disorders and browning of the fruit peel.
Citrus fruits are exposed from 1 - 3 days (depending on the degree of greening) to an atmosphere containing ethylene (5 - 10 ppm) under controlled ventilation, 20 - 26°C and 90 - 95% RH. Conditions for degreening are specific to the production area.