Carotenoids in Plants: Functional Diversity of

Structure and Occurrence

Carotenoids comprise tetraterpenoids (C₄₀) that, by the majority, are synthetized by photosynthetic organisms. In plants, they are localized in most types of plastids, which also represent their major site of biosynthesis. A few fungal species have been identified to be able to synthetize carotenoids de novo too. More than 700 compounds are known to belong to this class of lipids; β-carotene is one of the most prominent. Usually, carotenoids contain no oxygen. If that is the case, they are classified as xanthophylls, which are covered in a separate chapter (see Xanthophylls in Plants). The introduction of oxygen facilitates a specific chemistry that is focussed on in this chapter. Generally, carotenoids are considered to represent essential components of the photosynthetic apparatus. They are assumed to function as antioxidants, hormone precursors, and colorants. As diet constituent, carotenoids can contribute to the pigmentation of birds, e.g., the yellow and...