Effects of Light Environment During Culture on UV‐lnduced Cyclobutyl Pyrimidine Dimers and Their Photorepair in Rice (Oryza sativa L.)

Abstract

Abstract— We examined the effects of a light environment during culture of rice plants (Oryza sativa) on the steady‐state cyclobutyl pyrimidine dimer (CPD) level, CPD induction by challenge UVB exposure and the ability to photorepair CPD. The steady‐state CPD level in plants grown under visible radiation with supplemental UVB radiation in a growth chamber was several times higher than in plants grown without supplemental UVB radiation, whereas in outdoor‐grown plants, it was not enhanced by supplemental UVB radiation. The susceptibility to CPD induction by challenge UVB exposure was highest in dark‐grown plants and decreased with increasing irradiance of visible radiation at low and high levels and outdoors. Chronic UVB radiation reduced the susceptibility to UV‐induced CPD in plants grown both indoors and outdoors. There was a significant negative correlation between CPD levels induced by challenge UVB exposure and the content of UV‐absorbing compounds. The UV‐induced CPD could be reduced by subsequent blue radiation in all samples except in dark‐grown seedlings. The higher the irradiance of visible radiation in the culture, the greater the ability to photorepair CPD. Chronic UVB radiation did not increase the ability to photorepair CPD.