The hormesis effects of low-dose 60Co gamma irradiation on high-temperature tolerance in cultivated Sargassum horneri (Fucales, Phaeophyceae).

Radiation hormesis is a phenomenon in which low doses of ionizing radiation can have stimulatory effects on biological systems. The temperate brown alga Sargassum horneri was the subject of this study on the hormetic effects of low-dose 60Co gamma radiation on macroalgae incubated in vitro at high temperatures. Sargassum horneri embryos were irradiated with 15, 20, and 25 Gy 60Co radiation and then incubated in vitro at 18, 21, 24, 27, and 30 °C. The same radiation treatment was also applied to S. horneri embryos grown in situ in outdoor mass cultivation. Non-irradiated in vitro control cultures had optimal growth at 21 °C, but irradiated cultures had optimal growth at 27 °C and growth was significantly enhanced by 32% compared to the control cultures at 21 °C. In contrast, in situ cultures of S. horneri in outdoor 10-ton seawater tanks showed that irradiated thalli had less total biomass as compared to non-irradiated control thalli. While low doses of gamma radiation may induce high-temperature tolerance resulting in better growth rates under the highly controlled in vitro culture conditions, these effects were not clearly observed in the in situ outdoor mass-cultivation. [ABSTRACT FROM AUTHOR]