Factors Affecting Pigment Levels During Re-Greening of Valencia Orange

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Abstract
Seasonal changes in pigment levels were found to coincide with five colouring stages: green, colouring, orange, yellowing and re-greening. The changes in pigment levels mainly causing re-greening are a result of a reduction in carotenoids and an increase in chlorophyll levels after the carotenoids reach their maximum and the chlorophylls their minimum levels during the orange stage. More chlorophyll a than b occurs while the fruit is green, but it starts to fall below the chlorophyll b level during the colouring stage and thereafter. This happens in the re-greening cultivars of Citrus sinensis such as Valencia and Lane Late Navel oranges, but not in the non-re-greening cultivars such as Leng and Washington Navels. These changes in pigment levels appear to be related to increasing-light intensities during spring and summer and to hormonal control from seeds and/or the rootstock.

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