Experiments were performed in fruits of the following Citrus species: orange (Citrus sinensis cv. Navelina), Clementine (Citrus clementina cv. Clemenules), and Satsuma mandarin (Citrus unshiu cv. Owari), and red grapefruit (Citrus paradisi cv. Star Ruby). Trees of Navelina orange, Clementine mandarin and Star Ruby grape- fruit were growing in the Spanish Citrus Germplasm Bank (IVIA, Moncada, Valencia, Spain) and those of Satsuma mandarin in a com- mercial orchard located in Lliria (Valencia, Spain). Both orchards were subjected to standard agronomical practices, and soil con- ditions and temperature regimes were similar between the two locations. Mature-green fruits at the end of the cell-enlargement phase and before the initiation of natural degreening (latter July) were covered with black plastic bags,