Sargassum horneri and Ascophyllum nodosum extracts enhance thermal tolerance and antioxidant activity of Neopyropia yezoensis

Neopyropia yezoensis is an economically important red alga. As the water temperature rises due to global warming it is particularly important to develop economically valuable cultivars with thermal tolerance. Ascophyllum (Acadian Seaplants, LLC) Marine Plant Extract Powder (AMPEP) is a biostimulant for plant growth and enhances resistance to abiotic stresses. The purpose of this study was to determine the temperature tolerance and antioxidant activity when N. yezoensis was exposed to AMPEP and an extract from Sargassum horneri . Neopyropia yezoensis blades were exposed to 1 g L −1 of AMPEP and S. horneri extract (SHE) at 10 ℃ for 10 days. After the exposure, the blades were transferred to 500 mL flasks and cultivated with fresh medium for 15 days. We measured the specific growth rate (SGR), total protein, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). At 10 ℃, both the control and the samples exposed to SHE and AMPEP showed similar SGRs. At the sublethal temperature, 20 ℃, SGRs with SHE and AMPEP were significantly higher than control. The SGRs at 20 ℃ were even similar to the SGRs at the optimal temperature, 10 ℃. The protein contents at 20 ℃ with SHE and AMPEP showed no degradation despite temperature stress. SHE showed higher SOD and GPx activities than AMPEP at both optimal and sublethal temperatures. These results suggest the potential of S. horneri extract (SHE) as a new source of biostimulants enhancing thermal tolerance in N. yezoensis .