자외선-B 스트레스에 대한 담배 잎의 광합성 능의 변화

Abstract

The effect of ultraviolet-B (UV-B) radiation on photosynthesis was studied by the simultaneous measurements of <TEX>$O_2$</TEX> evolution and chlorophyll (Chl) fluorescence in tobacco leaves. When the tobacco leaves were teated with UV-B (1 <TEX>$W{\cdot}m^{-2}$</TEX>), the maximal photosynthetic <TEX>$O_2$</TEX>, evolution (Pmax; 4.60 <TEX>${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$</TEX>) at 200 <TEX>${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$</TEX>) was decreased with increasing time of UV-B treatment showing 80% decline after 4 h treatment. Chl fluorescence parameters were also affected by ultraviolet-B. Fo was increased while both Fm and Fv were decreased, resulted in the decreased of photochemical efficiency of PSII (Fv/Fm). Non-radiative dissipation of absorbed light as heat as estimated as NPQ (Fm/Fm' - 1) was also decreased with increasing time of UV-B treatment while the extent of photochemical quenching (qP) was not changed. Thus, the ratio of (1-qP)/NPQ parameter was also increased with increasing time of UV-B treatment indicating PSII is under the threat of photoinhibition. The result indicate that UV-B primarily decreases the capacity to dissipate excitation energy by trans-thylakoid pH, which in turn inhibits PSII activity.