Carotenoids and Environmental Stress in Plants: Significance of Carotenoid-Mediated Modulation of Membrane Physical Properties (original) (raw)

Carotenoids were intensively studied during recent 30 years and many functions and associations of these pigments were documented. Among the first studied were the antenna and photoprotective functions of carotenoids in photosynthesis. Under low light conditions, carotenoids may act as energetic antennae, harvesting light at the wavelengths not absorbed by chlorophylls and transferring electron excitation states towards photochemical reaction centers. In this way, they widen the range of light used in photosynthesis. On the other hand, it has been shown that in excess of light carotenoids play an important role in photoprotection [1-4]. Carotenoid pigments also have ecological significance. Making flowers and fruits colored, they play an important role in ecosystems, attracting pollen-dispersing insects and fruit-eating animals. Carotenoids are also important for animals. Although these organisms are not able to synthesize carotenoids, they receive them in a food and incorporate into their own tissues. In humans, carotenoids normally occur in several types of tissues, e.g., muscles, liver, eye, blood and adipose tissue. Currently, about 25 carotenoids and their metabolites have been found in serum [5, 6]. There is increasing evidence that carotenoids are important constituents of human diet. In recent years, many papers about the effect of dietary carotenoids on human health have been published. They reduce risk of chronic diseases such as breast, prostate and other cancers [7-9], coronary heart disease [7, 10], age-related macular degeneration and other eye diseases [7]. They also have a stimulating effect on the immune system and cell-cell interactions such as gap junction communication [11-13]. Molecular mechanisms responsible for carotenoid functioning are largely unknown, however, their antioxidative action and modulatory effect on membrane physical properties are probably involved [14-19].