The Influence of Temperature on Regreening and Carotenoid Content of the ‘Valencia’ Orange Rind1

Abstract

Abstract ‘Frost Valencia’ [Citrus sinensis (L.) Osbeck] budded to trifoliate orange rootstock [Poncirus trifoliata (L.) Raf. 1, with orange-colored fruit, were subjected to 4 temperature regimes consisting of 2 day-night shoot environments and 2 constant soil temperatures in 2 glasshouses. In the cool shoot environment (20×15°C, day×night air temperature), carotenoid content of fruit increased substantially, whereas, in the warm glasshouses (30×15°), carotenoid content either changed little (apical and equatorial regions) or decreased slightly (basal region). Chlorophyll content of fruit increased to detectable levels only in the warm glasshouse. Soil temperatures of 15 and 25° had little or no influence on carotenoid or chlorophyll content of fruit in either glasshouse. Thus, regreening occurred only in the warm shoot environment and at both root temperatures. These temperature effects did not appear to operate through a redistribution of nitrogen to the rind.