Anthocyanins are one of the most widespread classes of pigments in higher plants. They are important secondary metabolites produced through the flavonoid biosynthetic pathway in various plant organs (WinkelShirley, 2001). The anthocyanin biosynthetic pathway is controlled by environmental factors (light and temperature) and internal factors: plant hormones, other secondary metabolites and nutrients (Mol et al., 1996). Light acts as an essential stimulus and as a factor modulating the intensity of the pigment by affecting the regulatory and structural genes of anthocyanin biosynthesis. Although photoinduction of anthocyanin has been extensively studied in a variety of plants, the photoreceptors responsible have not been clearly defined (Sheoran et al., 2006). Anthocyanin synthesis involves many steps, from the primary precursor (phenylalanine) to the final products – glycosides of anthocyanidines. Phenylalanine ammonia-lyase (PAL) is the first enzyme to catalyze the elimination of NH3 from L-phenylalanine to give trans-cinnamate (Hanson and Havir, 1981). Trans-cinnamate can be a precursor of other secondary plant metabolites besides anthocyanins: phenolic acids, flavonols, lignins, proanthocyanidines, stilbenes, etc. PAL activity has been reported to positively correlate with anthocyanin synthesis in grapes (Kataoka et al., 1983), strawberries (Given et al., 1988) and apples (Tan, 1979), but its role in regulating anthocyanin formation remains unclear. According to Wang et al. (2000), PAL is not the only factor regulating anthocyanin accumulation in apple fruit; they found that anthocyanin accumulation decreased when apples ripened, even though PAL activity was relatively high. Anthocyanins play an important role in attracting insects or animals for pollination and seed dispersal. They also play a role as anti-oxidants and in protecting DNA and the photosynthetic apparatus from high radiation fluxes (Gould, 2004). Other possible functions of anthocyanins, such as protecting against cold stress or providing drought resistance, are likely to be associated with activities restricted to particular classes of plants (Chalker-Scott, 1999).