Protective Function of Foliar Anthocyanins: in Situ Experiments on A Sun-Exposed Population of Iris Pumila L. (Iridaceae)
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Anthocyanins are a group of water-soluble flavonoids known for their protective role against photoinhibitory and photooxidative damage to leaf cells under environmental stress. The effects of variation in light quantity on rates of anthocyanin production in foliage of Iris pumila were evaluated spectrophotometrically in a field experimental setting accomplished by shielding one half of each examined plant with a 65% neutral-density shade, whereas the other half experienced full sunlight. In unshaded leaves, the average anthocyanin level increased by 55.3% compared to their shaded counterparts. Because there was no a significant difference in the average level of pheophytin (a breakdown product of chlorophyll) between unshaded and shaded leaves, the results suggested that the elevated anthocyanin concentrations in sun-exposed foliage of L pumila could act as a light attenuator, protecting its chloroplasts from excess high-energy quanta that would otherwise be intercepted by the chlorophylls.