Responses of superhigh-yield hybrid rice Liangyoupeijiu to enhancement of ultraviolet-B radiation

Effects of 111 days enhanced UV-B radiation on leaf pigments, grain quality, photosynthesis and growth were determined in Chinese superhigh-yield hybrid rice (Oryza sativa L.) Liangyoupeijiu (Peiai 64S × 9311). The chlorophyll concentrations of leaves under enhanced UV-B radiation were slightly reduced in the tillering stage, but recovered to levels equal to or above those of control in the later growth stages. Leaves treated with enhanced UV-B radiation for 99 days exhibited higher absorbance in the UV region than controls. Amylose concentration of UV-B treatment was significantly increased by 4.1%. Crude fat concentration, crude protein concentration and vitamin B1 showed no significant difference between control and treatment. The light-saturated photosynthetic activity of UV-B treated leaves normalized on fresh weight or chlorophyll concentration was, respectively, 45.2 and 35.3% higher than controls. Both indoor and field experiments indicated that UV-B treated leaves were more tolerant to photoinhibition, and its Do values tended to be higher than controls during the strong light period of midday. The D1 protein turnover played more important role in UV-B treated leaves against strong irradiance than in control leaves. Little difference was observed in the maximal PSII quantum efficiency of UV-B treated and control leaves during the process of leaf senescence. UV-B radiation reduced diseased grains per panicle and led to a higher seed setting rate. It may have a direct harmful effect on pathogens or reduced susceptibility of UV-B exposed plants to pathogens. Our results suggest that long-term exposure to enhanced UV-B radiation is unlikely to have detrimental effects on the photosynthetic capability of Liangyoupeijiu, and tends to inhibit its growth and biomass.