Uv-induced Oxygen Free Radicals Production in Spinach Thylakoids

Besides being the ultimate driving force for photosynthesis and its important regulatory factor, solar light is also a major source of stress to photosynthetic organisms. The efficiency of the light induced damage increases with the wavelength decrease. Thus, from natural sunlight that reaches the Earth, the UV-A and UV-B (290–320 nm and 320 – 400 nm, respectively) spectral ranges have the highest damaging potential for photosynthetic organisms, mostly due to the UV-induced production of highly harmful reactive oxygen species (ROS) such as oxygen free radicals. The UV-induced oxygen free radicals production in aqueous suspensions of thylakoids (isolated photosynthetic organelles form spinach leaves), was investigated in this work by using the EPR-spin-trapping method. Two spin-traps, 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) and 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO), were used for the simultaneous detection of various free radicals, as a consequence of UV-A, -B and -C irradiation. Hydroxyl– and superoxide-anion–radicals make the majority of the created species.