EPR spectroscopy
Two types of paramagnetic centers: transition metal ions and stable organic radicals were found in seedlings and flag leaves of both barley genotypes.
EPR spectra, recorded in the range of 400 mT, showed the presence of signals with intensities that depended on the genotype of barley, the stage of plant development and, first of all, on the condition of the plant growth (Fig. 4). In the spectra of control seedlings of both genotypes, the main signal with g = 2.00 was split to six lines (hyperfine structure HFS), equally separated by the distance of 9.2 mT. These lines overlapped on a broader signal with g also equal 2.00, more noticeable in the spectrum of Maresi. These signals were more intensive in the spectrum of control seedlings of the sensitive genotype than in tolerant one. Between the third and the fourth line of the hyperfine structure, a narrow signal with g = 2.00 (signal R), also more intensive in the spectrum of sensitive cultivar, was visible. Two strong signals at g = 2.35–2.37 and at g = 2.15–2.20 (overlapping the one of HFS lines) could be distinguished in the spectrum of seedling of the tolerant genotype, whereas only