Effect of ultraviolet radiation on accumulation and leakage of 86Rb+ in guard cells of Vicia faba

The effects of UV-C (254 nm), UV-A (365 nm) and broad-band UV (280–380 nm) on guard cells of Vicia faba L. cv. Long Pod were investigated in the presence of white light (450 μmol m^?2 s^?1). UV-C (7 μmol m^?2 s^?1) was found to cause leakage of ⁸⁶Rb⁺ from guard cells, while UV-A (0.3 μmol m^?2 s^?1) stimulated increased uptake in these cells. A relatively small stimulatory effect was observed by broad-band UV (3 μmol m^?2 s^?1) during the first 30 min of irradiation with an apparent equilibration of influx and efflux thereafter. Leakage of ⁸⁶Rb⁺ from guard cells continued despite the removal of UV-C and an increase in the amount of white light from 450 to 1500 μmol m^?2 s^?1, suggesting that membranes were irreversibly damaged. Irradiation of guard cells with UV-C for 30, 45 and 90 min indicated that these cells began to be affected already by 30 min UV-C irradiation.