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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]

Homogenous germlings of the marine macroalga Ulva fasciata D. (synonym, Ulva lactuca L.) were used to study hormesis effects in macroalgae grown under a low dose of 60Co γ-ray radiation. The results of this study are the first to confirm the effects of macroalgal hormesis. Here it was demonstrated that growth of U. fasciata germlings was promoted substantially under 15 Gy of 60Co γ-ray radiation, with an average increase of algal biomass of 47.43%. The levels of polysaccharides and lipids varied among the tested material and showed no effects from the 60Co γ-ray radiation. However, the amount of protein was higher in the irradiated algae than in the control; the highest protein content of the irradiated algae was 3.958% (dry weight), in contrast to 2.318% in nonirradiated samples. This technique was applied to a field algal mass culture, which decreased the harvest time from 90 to 60 d. The mass culture approach may facilitate the production of macroalgae under unstable weather conditions such as typhoons in the summer or strong waves in the winter. The mass-cultured macroalgae could be used as a source of bioenergy through the fermentation of algal simple sugars that derived from polysaccharides to produce ethanol. [ABSTRACT FROM AUTHOR]

Germlings were grown from Monostroma latissimum Wittr. reproductive cells on nylon ropes. Holdfast threads and some uniseriate filaments were observed to have penetrated the fibers of the dispersed ropes. The algal filaments were easily isolated and prepared for cultivation, in comparison to the methods of enzymatically isolated algal protoplasts. Under low light (60-100 μmol photons · m−2 · s−1), the algal filaments grew to form a filamentous mass. When cultivated under stronger light (300-600 μmol photons · m−2 · s−1), they grew to initially form tubular thalli and then, when cultivated under light intensities >700 μmol photons · m−2 · s−1, formed foliaceous thalli. Consequently, the filaments were homogenized into small sections and then sewed on the nylon rope for algal mass cultivation. Under high-intensity natural light, they grew to form leafy thalli. [ABSTRACT FROM AUTHOR]

Homogenous germlings of the marine macroalga Ulva fasciata D. (synonym, Ulva lactuca L.) were used to study hormesis effects in macroalgae grown under a low dose of (60) Co γ-ray radiation. The results of this study are the first to confirm the effects of macroalgal hormesis. Here it was demonstrated that growth of U. fasciata germlings was promoted substantially under 15 Gy of (60) Co γ-ray radiation, with an average increase of algal biomass of 47.43%. The levels of polysaccharides and lipids varied among the tested material and showed no effects from the (60) Co γ-ray radiation. However, the amount of protein was higher in the irradiated algae than in the control; the highest protein content of the irradiated algae was 3.958% (dry weight), in contrast to 2.318% in nonirradiated samples. This technique was applied to a field algal mass culture, which decreased the harvest time from 90 to 60 d. The mass culture approach may facilitate the production of macroalgae under unstable weather conditions such as typhoons in the summer or strong waves in the winter. The mass-cultured macroalgae could be used as a source of bioenergy through the fermentation of algal simple sugars that derived from polysaccharides to produce ethanol., (© 2011 Phycological Society of America.)