EFFECTS OF UV-B RADIATION ON REPRODUCTION AND GERMINATION OF THE INTERTIDAL GREEN ALGA, ULVA PERTUSA KJELLMAN
한태준; 공정애; 한영석; 강성호; Donat Hader
In macroalgae, UV-B radiation affects severely photosynthesis, growth, pigmentation and enzyme activity. However, little is known about the effects of UV-B radiation on reproduction and germination although these processes are clearly of importance affecting the population recruitment. We have conducted investigations into UV-B effects on Ulva pertusa which is a common fast growing macroalga of the intertidal zone on most coasts of Korea where its population is often exposed to highirradiances of solar radiation and must possess efficient mechanisms to prevent or counteract the harmful effects of solar radiation. There was a significantly lower incidence of reproduction and germination in UV-irradiated samples with the degree of reduction being greater in those exposed to higher UV doses. When plants were incubated under different irradiances of PAR immediately after UV exposures percentage inhibition of sporulation was lesser at higher irradiances. After exposure to moderate levels of UV-B irradiation, subsequent exposure to visible light caused differential germination being significantly higher at higher photon irradiances and in blue light compared to white and red light. The action spectrum for photoreactivation of germination in UV-B irradiated U. pertusa spores shows a major peak at 435 nmwith a smaller peak at 385 nm. After 2 h exposure to December sunlight, there was complete inhibition of germination in PAR + UV-A + UV-B in contrast to 100% germination in PAR or PAR + UV-A. In addition to mat-forming characteristics which would act as a selective UV-B filter under the canopy, lightdriven repair of reproduction and germination following UV-B exposure could explain successfulcontinuation of U. pertusa in intertidal settings possibly affected by intense solar UV-B radiation.