The influence of UV-B radiation on the superoxide dismutase of maize, potato, sorghum, and wheat leaves

The influence of UV-B radiation on superoxide dismutase (SOD, EC 1.15.1.1) with reference to the activity and types of isoenzymes was studied in leave s of C-3 plants (potato, Solanum tuberosum L. cv. Desiree, and wheat, Triti cum aestivum L. var. Almansor) and C-4 plants (maize, Zea mays L. var. LG12 , and sorghum, Sorghum Pr 8515 Pioneer). Plants were grown under controlled conditions in growth chambers with and without UV-B radiation. After 10 da ys of irradiation it was found that UV-B affected both the total activity o f SOD and the number and amount of isoforms in all plants. The total specif ic activity of SOD increased significantly in wheat, maize, and potato, whe reas a decline was induced in sorghum. Native gels revealed that UV-B cause d preferential changes of the SOD isoforms in all plants used. Inhibition s tudies with cyanide and hydrogen peroxide showed that, in maize, UV-B radia tion caused a large accumulation of one Mn-SOD and in contrast the level of the Cu,Zn-SOD isoforms decreased. In potato leaves, UV-E changed the patte rn of SOD isoenzymes causing the appearance of one isoform and the disappea rance of another. In wheat and sorghum the pattern of the isoenzymes was no t altered, only their relative amounts. The rise, in SOD activity in maize, potato, and wheat is possibly correlated with the tolerance of VV-E ascrib ed to these crops by different researchers and the sensitivity of sorghum t o UV-E is possibly associated with the decrease in SOD activity.