SodininkyStĖ ir darŽininkyStĖ 28(2)

Discussion. The determined antioxidant properties of barley green are of thesame level as of the other leafy vegetables and remarkably lower than the propertiesof wheatgrass (Urbonavičiūtė et al., 2008). However, it is inadmissible to make thejudgments about the benefits or harm of the barely bioactive compounds for humanhealth. In this study we exclusively present the light quality as the physiological toolto improve antioxidant properties of plant materials, were barleygrass was chosen aseasily cultivated phytochemical-rich object.Different Lithuanian barley varieties were distinguished for unequal metabolicsystem sensitivity to lighting quality. ‘Luokė’ barley is more sensitive to differentlight quality treatments than ‘Aura’. This could be related to overall properties of variety,as ‘Aura’ is declared to be more resistant to various leaf diseases (Leistrumaitė,Liatukas, 2006) and environmental conditions. The exact selection of the cultivarscan significantly modify nutrient profiles of the desired valuable substances in greenmass (Ehrenbergova et al., 2007), therefore the more light-sensitive varieties couldbe chosen for the higher antioxidant effect.Comparing LED treatments and high pressure sodium lamps, rich in red-orangewaves, LED treatments, except the lighting with sole red light (L1), are superior inenhancing the antioxidant potential of barley grass as compared to high pressure sodiumlamps. Red light possibly acts as photostressor for plants, thus the supplementation ofthe lighting spectra with the light components of different colors (though maintainingthe same lighting flux) has the more pronounced effect on the free radical scavengingactivity (Fig. 1), the contents of phenolic compounds (Fig. 2) and vitamin C (Fig. 3), asthese molecules participate in the redox signaling pathways in higher plant cells (Shaoet al., 2008). The most pronounced effect on the contents of antioxidant compoundswas observed, when the red light was supplemented with the blue light: the tendentiousincrease in the DPPH scavenging activity, contents of phenolic compounds and vitaminC were determined. In pea seedlings, red light had a significant effect on antioxidantactivity for human nutrition benefits, although blue light was not observed as the factor,affecting antioxidant activity (Wu, 2007). However, the necessity of the supplementalblue light for normal wheat photosynthesis, growth and yield when cultivated underred LED light was also reported (Goins et al., 1997). The inclusion of other spectralcomponents did not have such an effect. Moreover, the supplementation of lightingspectra with the red light of different wavelength than the basal red component didnot have any significant effect on metabolism. Far red light had the pronounced effectonly on the contents of vitamin C in plant material. It has been shown that increasingthe proportion of far-red (FR) radiation induces early leaf physiological senescencein certain plant species (Causin et al., 2006), what reveals by the photosynthesis inhibition,increased amount of ascorbate and phenols in leaves.Conclusion. High flux of sole red light acts as the photooxidative stressor forplants, thus it was expected to evoke the action of the defense systems and the higheraccumulation of antioxidative compounds. However, the supplementation of the redlight with other spectral components, such as blue, far red, acting on different photoreceptorsnormalized the metabolism and, as the result, remarkably higher contentsof vitamin C, phenolic compounds and higher antioxidant activity was determined.158