A comparison of UV-B induced stress responses in three barley cultivars

Abstract

In order to investigate the role of potential genotype differences in three economically important barley cultivars, experiments were carried out to determine the influence of supplemental ultra-violet-B (UV-B, 280 320 nm) radiation on reactive oxygen species (ROS), antioxidant activity and photosynthesis. Greenhouse-grown barley (hordeum vulgare L.) culitvars ‘Cork’, ‘Prestige” and ‘Golden Promise’ showed different responses to supplemental 280-320nm (UV-B) representing 100,138 and 2378% levels of ambient biologically active UV-B radiation, respectively. Among the three cultures studied, cv. Golden Promise was the most tolerant to UV-B, cv. Prestige was slightly more sensitive than cv. Cork. A comparison with the other two cultivars showed that under supplemental UV-B, Golden Promise leaves (i) retained a higher quantum yield of photosynthesis under photosynthetically active radiation (PAR, 400-700nm) corresponding to growth conditions; (ii) had the smallest decrease in both electron transport arte and non-photochemical quenching under high PAR; (iii) contained less oxidized ascorbate [measured as dehydroascorbate or electron paramagnetic resonance (EPR) detectable mondehydoascorbate radicals] than either Cork or Prestige. Under the highest UV-B level applied, Golden Promise leaves maintained the same activity of both mondehydroascorbate-reductase (MDAR) and ascorbate-preoxidase (APX) enzymes, as untreated controls, while MDAR markedly decreased in the other two cultivars and APX slightly increased in cv. Prestige. These features together with the observation of directly EPR-trappable free radicals and the light dependant accumulation of mondehydoascorbate radicals in Cork and Prestige but not in Golden Promise leaves under High UV-B suggest that Golden Promise plants suffered less oxidative stress than other cultivars.