Characterization of a rice mutant having an increased susceptibility to light stress at high temperature

The effect of light irradiation at high temperature was investigated in a rice mutant, spl-2 , which is sensitive to solar radiation. Dead spots appeared on the mutant leaves when cultured at a high temperature (40°C) under strong white-light illumination (15 W m^?2). A similar damage was also observed in the wild-type leaves under the same conditions when the plants were preincubated in the dark for one day. Preillumination with weak light (6 W m^?2) lessened the irradiation-induced damage in the wild-type. These observations suggest that in rice plants the acclimatization to weak light has a protective effect against strong irradiation at high temperature, and the spl-2 locus participates in the mechanisms of the acclimatization. The action spectrum for the irradiation-induced damage at the high temperature (40°C) in the spl-2 leaves indicated that the maximum damage occurred at around 480 nm and, in a lesser extent, at around 680 nm. Activity of the O^?_2? and H₂O_2?scavenging enzymes in the spl?2 leaves were almost the same or somewhat higher than those in the wild-type after irradiation with strong white light (15 W m^?2) at 40°C, whereas the content of ascorbic acid in the spl?2 decreased significantly compared with the wild type.