Sequence of Chloroplast Degreening in Calamondin Fruit as Influenced by Ethylene and AgNO(3).
C(2)H(4) disrupts the internal membranes of the chloroplast and induces an increase in chlorophyllase activity in degreening calamondin [x Citrofortunella mitis (Blanco) Ingram and Moore] fruit. Whether the loss of chlorophyll in the peel is causally related to breakdown of the chloroplast and/or chlorophyllase activity is not readily apparent. Chlorophyllase levels were inversely related to chlorophyll content, but electron micrographs also showed that internal membranes of the chloroplasts were disrupted simultaneously with the decrease in chlorophyll content. Silver, a potent inhibitor of C(2)H(4)-mediated effects, retarded the loss of chlorophyll in calamondin rind, reduced the C(2)H(4)-induced increase in chlorophyllase level, and prevented the disruption of the chloroplast membranes. The results do not permit the proposal of a mechanism of C(2)H(4) metabolism in the degreening of calamondin fruit.
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University of Florida, Institute of Food and Agricultural Sciences, Agricultural Research and Education Center, Lake Alfred, Florida 33850.