光照对柑橘果皮类胡萝卜素和色泽形成的影响

以“红柿柑”为试材,在柑橘果实膨大末期通过套袋遮光处理以抑制果皮光合作用,研究光照对果皮糖、叶绿素、类胡萝卜素及果实外观色泽的影响。结果表明,遮光后果皮叶绿素含量迅速下降引起果实转色提早,但各种类胡萝卜素含量及总量并未提高,而是显著下降;至果实成熟时由于遮光与光照处理的果皮叶绿素均消失,遮光果实类胡萝卜素含量低颜色变淡,与光照处理相比,遮光前期果皮糖含量下降不大,而后期下降明显;若在后期去袋照光,果皮糖含量上升,与此相应,类胡萝卜素,尤其是β-隐黄质的积累增加,颜色加深,表明光对果皮类胡萝卜素合成尤其是β-隐黄质的积累有促进作用,其原因是光以环境信号的方式影响果皮的类胡萝卜素形成。

Effects of light on carotenoid biosynthesis and color formation of citrus fruit peel

The effects of shading fruit with opaque paper bag at the late stage of fruit enlargement on the contents of chlorophyll, carotenoid and in "Hongshigan" citrus (C. reticulata x C. sinensis) fruit peel and its color were examined. The results showed that after shading, the chlorophyll content in peel decreased quickly, which resulted in its earlier color shifting. In contrast, the contents of total carotenoids and each carotenoid component did not increase, but decreased significantly. At the stage of fruit riping, both chlorophyll in shaded and unshaded fruit disappeared, and the shaded fruit, owing to its lower level of carotenoids, had a lighter color than the unshaded fruit. The sugar content in peel of shaded fruit did not differ obviously from that of unshaded fruit at the earlier stage, but dropped markedly at the late stage of shading. Removing the enclosing paper bag from shaded fruit at the late stage of shading resulted in the increase of sugar, and correspondingly in the increase of carotenoid, especially of beta-cryptoxanthin accumulation with consequent darkening of fruit color. These results stressed the effect of light on stimulating carotenoid synthesis, especially the accumulation of beta-cryptoxanthin in citrus fruit peel. The light is the enviromental signal essential for carotenoid synthesis in citrus fruit during certain stage of fruit development.