SodininkyStĖ ir darŽininkyStĖ 28(2)

necessary for their healthy development and for defense from adverse environmentalconditions (Gruenwald, 2009). In case of barley, as a major agricultural product, ithas been consumed as grains, but recently more attention is being paid to the youngleaves, due to their antioxidants (Lee et al., 2003), the most important of which areO-glycosyl isovitexin, superoxide dismutase, catalase, vitamin E, vitamin C and carotenoids(Paulickova et al., 2006). However, nutrient contents depend on barley variety(Ehrenbergerova et al., 2007), on where plants are grown, soil quality (Kulkarniet al., 2006), humidity, and especially lighting conditions (Wu et al., 2007). Light isone of the most important environmental factors, which acts on plants not only as thesole source of energy. Complex, multiple photoreception system (chlorophylls, carotenoids,phytochrome, cryptochrome, phototropins, and other) (Chen et al., 2004;Devlin et al., 2007) respond to light quantity and quality, duration, intermittence,and other parameters, thus determining plant morphogenetic changes, functioning ofthe photosynthetic apparatus, and process of metabolic reactions. Moreover, lightingconditions might evoke the photoxidative changes in plants, what lead in the alteredaction of antioxidant defense system: increased contents and activity of antioxidativeenzymes, carotenoid, tocopherol, flavonoid, ascorbate. Thus, in combination withother agrotechnical means, light, optimizing the irradiation conditions, or creatingthe mild photostress, might be effective means for phytochemical-rich vegetable cultivation.Solid-state lighting based on light-emitting diodes (LEDs) is one of the largestpotential advancements in horticultural lighting in the last decades (Morrow, 2008).Efficiency, longevity, and versatile application possibilities are the features of LEDswhich, when properly employed, are capable of providing performance well beyondany conventional lighting source (Bourget, 2008). This technology expanded the possibilitiesto analyze the effect of lighting parameters on physiological processes in plants.Therefore, the objective of our work was to evaluate the effect of light emitting diodeprovided lighting spectra on the antioxidative properties of young barley seedlings.Object, materials and conditions. Lighting experiments were performed at theLithuanian Institute of Horticulture in 2008, in the phytotron chambers, under controlledenvironmental conditions. The originally designed (Tamulaitis et al., 2005)light emitting diode based lighting units, consisting of red basal component (638nm, delivered by AlGaInP LEDs Luxeon TM type LXHL-MD1D, Lumileds Lighting,USA) and supplemental blue (455 nm, Luxeon TM type LXHL-LR5C, Lumileds Lighting,USA), red (669 nm, L670-66-60, Epitex, Japan), far red (735 nm, L735-05-AU,Epitex, Japan), LEDs were used. The LED combinations are presented in Table. TreatmentL1 contained the sole red light; treatment L2 contained red and blue LED’s;in the treatment L3, these two components were supplemented with 669 nm red lightand in treatment L4, the fourth, far red lighting component was added. Referenceplants were grown under high-pressure sodium lamps (Son-T Agro, Philips, USA).Photosynthetic photon flux density of about 200 µmol m -2 s -1 and 18 h photoperiodwas maintained in LED and reference lighting treatments.154