Effect of Sunny and Half-shaded Sites on the Growth of Plants and Anthocyanin Pigments Content in Leaves of Heuchera L. ‘Mysteria’ and ‘Peppermint Spice’ Cultivars

Two cultivars of Heuchera L. - ‘Mysteria’ and ‘Peppermint Spice’ were grown in a collection at a sunny site and a slightly shaded one. The access of sunlight was limited by shade nets, which were stretched on wooden scaffolding over the plants. The dynamics of growth of the plants in the sunny and half-shaded sites was assessed in the growth periods, in two consecutive years. After the second year, the content of anthocyanins in the leaves of different physiological maturity (young, mature and fully mature) was measured. Apart from August, during the whole growth period both cultivars formed more leaves during the first year of cultivation. Both the ‘Mysteria’ and ‘Peppermint Spice’ cultivars formed more leaves at the sunny site. The research showed that the highest content of anthocyanins in the Heuchera ‘Mysteria’ and ‘Peppermint Spice’ cultivars growing at the sunny and half-shaded sites was found in young leaves, whereas the lowest content was noted in fully mature leaves. The highest content of anthocyanins in both Heuchera cultivars was found at the initial growth period, i.e. between May and July, when the light intensity was the greatest, regardless of the place of cultivation. At the end of the growth period, the biosynthesis of anthocyanins decreased significantly. Anthocyanins accumulated in the vacuole are able to play a role as the screening pigments under intensive PAR and UV-B radiation.