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In the present study, xanthophyll composition of eight parasitic Cuscuta species under different light conditions was investigated. Neoxanthin was not detected in four of the eight species examined, while in others it occurred at the level of several percent of total xanthophylls. In C. gronovii and C. lupuliformis it was additionally found that the neoxanthin content was considerably stimulated by strong light. In dark-adapted plants, lutein epoxide level amounted to 10-22% of total xanthophylls in only three species, the highest being for C. lupuliformis, while in others it was below 3%, indicating that the lutein epoxide cycle is limited to only certain Cuscuta species. The obtained data also indicate that the presence of the lutein epoxide cycle and of neoxanthin is independent and variable among the Cuscuta species. The xanthophyll cycle carotenoids violaxanthin, antheraxanthin and zeaxanthin were identified in all the examined species and occurred at the level found in other higher plants. The xanthophyll and lutein epoxide cycle pigments showed typical response to high light stress. The obtained results also suggest that the ability of higher plants to synthesize lutein epoxide probably does not depend on the substrate specificity of zeaxanthin epoxidase but on the availability of lutein for the enzyme.
Carotenoids (neoxanthin, violaxanthin, lutein and β-carotene) present in plant cell play a role in photoprotection. Industrial pollution causes oxidative stress in plants, while carotenoids react with free radicals and dissipate the excess of excitation energy. In this way carotenoids prevent the negative influence of free radicals on metabolism and can even restore some of the damages. This is confirmed by results of our analysis of the level of xanthophylls in 16 and 17-year-old trees of Scots pine (Pinus sylvestris L.). Developed from seed collected in north-eastern, the trees grow in a relatively unpolluted control site, and in a polluted site located 2 km for away from the Phosphorus Fertilizer Works. In the polluted site the environment is contaminated with SO2, NOx and F, Al, F, Pb, Cu. The needles analysed in this study were visually undamaged. Material was collected in experimental plot from 6 trees in October'98 and April'99, between 12.00 and 13.00 hours, at full sunlight. The pigments were analysed quantitatively and qualitatively by thin-layer chromatography. The paper presents results of content and distribution of neoxanthin, violaxanthin, lutein and β-carotene of Scots pine needles from a healthy control tree and a stressed tree. Marked differences in pigment levels depended on the stage of needle development and level of pollution.
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