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The influence of different dosages of UV-B radiation on spinach antioxidant phytochemical constituents was studied. Spinach (Spinacia oleracea L.) cv. 'Andromeda H' and 'Matador' were the objects of this study. Experiment was conducted in closed growth chambers of controlled environment at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. Plants were placed in different growth chambers at 18/13 °C day/night temperature and 12 h photoperiod. High-pressure sodium lamps (SON-T Agro, Philips) were used for illumination (150 µmol m-2 s-1). UV-B radiation (290-320 nm) was provided by UV-B fluorescent tubes (TL 40W/12 RS UV-B Medical, Philips). Spinach plants were exposed to 0 kJm-2 day-1, 2 kJm-2 day-1, 4 kJm-2 day-1 and 6 kJm-2 day-1 UV-B for 3 days. The results of investigation showed that more intense (6 kJ) UV-B radiation reduced the ascorbic acid amount in the investigated species spinach leaves. The lowest DPPH radical immobilization ability of both species spinaches is determined when they are affected by the UV-B. The amount of phenolic compounds in spinaches depended on their species and UV-B dose. Spinaches of both species exposed to 4 kJ UV-B radiation have accumulated a larger amount of anthocyanins. "Matador" spinaches affected by UV-B radiation, accumulated the significantly lower amount of total tocopherols. [ABSTRACT FROM AUTHOR]

The influence of substrate moisture and different dosages of UV-B radiation on spinach antioxidant phytochemical constituents was studied. Spinach (Spinacia oleracea L.) cv. 'Andromeda H' and 'Matador' were the objects of this study. Experiment was conducted in closed growth chambers of controlled environment at the Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry. Plants were placed in different growth chambers at 18/13°C day/night temperature and 12 h photoperiod. High-pressure sodium lamps (SON-T Agro, Philips) were used for illumination (150 µmol m-2 s-1). Spinacia oleracea plants after 21 days for germination were grown in normal (~40%) and drought (<10%) substrate. After 7 days substrate moisture influence plants were exposed to 0 kJm-2 day-1, 1 kJm-2 day-1 and 2 kJm-2 day-1, UV-B for 1 day. Analyses were made after 8-days of substrate moisture and UV-B radiation exposure. UV-B radiation (290-320 nm) was provided by UV-B fluorescent tubes (TL 40W/12 RS UV-B Medical, Philips). Different combinations of investigated factors had a significant influence on changes of spinach physiological indices. The lack of substrate moisture reduced the leaf area, fresh and dry biomass accumulation in the investigated species spinach, but under drought conditions increased accumulation of chlorophylls a, b and carotenoids. Spinaches of both species exposed to drought conditions and UV-B radiation have accumulated a larger amount of phenolic compounds and ascorbic acid, depended on their species and UV-B dose. [ABSTRACT FROM AUTHOR]