Involvement of ethylene in chlorophyll degradation in peel of citrus fruits

The effect of ethylene on chlorophyll degradation in the peel of Robinson tangerine (X Citrus reticulata Blanco) and calamondin (X Citrofortunellamitis Blanco] Ingram and Moore) fruits was studied. The chlorophyll degrading system in the peel of these two citrus species was not self-sustaining but required ethylene to function. Chlorophyll degradation ceased immediately when fruit were removed from ethylene and held in ethylene-free air at 0.2 atmospheric pressure. However, at atmospheric pressure, chlorophyll degradation continued for 24 hours in the absence of exogenous ethylene. Although chlorophyllase levels were negatively correlated with chlorophyll content in the peel (r = −0.981; P < 0.01), the level of chlorophyllase activity did not change when fruit were removed from ethylene, even though chlorophyll degradation had stopped. From these observations, it was concluded that ethylene is necessary for chlorophyll degradation in the two species of citrus studied, but its primary role is not solely for the induction of chlorophyllase activity.