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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 I. pumila could act as a light attenuator, protecting its chloroplasts from excess high-energy quanta that would otherwise be intercepted by the chlorophylls.
Magnitude and variation in leaf plasticity were quantified in two Iris pumila (L.) populations from habitats of contrasting light conditions (open dune vs wood understorey) at three light intensities (high – 110, medium – 65, and low – 29 μmol m⁻² s⁻¹). Siblings developed from hand-pollinated seeds from 13 and 15 clonal genotypes in an open and a shaded population, respectively, raised in a growth-room were scored for morphological (leaf number, leaf area, specific leaf area), anatomical (stomatal density, leaf thickness, vascular bundle number, sclerenchyma and cuticle widths) and biochemical (chlorophyll content, chlorophyll a:b ratio) traits. Morphological traits in general and SLA (projected leaf area per unit leaf dry mass) in particular were more sensitive to variation in light conditions than any other examined leaf attribute, indicating their key importance for maximizimg light-energy interception at low irradiance. Regardless of the population origin, the average plasticity (percentage trait change between two successive treatments) of morphological traits declined with decreasing irradiance, opposite to anatomical traits, particularly leaf thickness, which increased parallel to light intensity decrease. Mean plasticity variation (across-family CV) changed with light level, ranking in the following order morphological
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