Abstract:Bangia fuscopurpurea, with high nutritional value, is a cultivated seaweed species in China. Against the backdrop of current climate change, investigating the response of B. fuscopurpurea to different temperatures, particularly high temperatures, is significant for guiding the breeding of heat-tolerant varieties and promoting the sustainable and healthy development of the industry. This study elucidates the photosynthetic and antioxidative physiological responses of B. fuscopurpurea to different temperatures (5, 10, 15, 20, and 25 ℃) by examining parameters such as the maximum fluorescence yield of photosystemⅡ(Fv/Fm), maximum relative electron transport rate (rETRmax), malondialdehyde (MDA) content, soluble protein (SP) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, ascorbate peroxidase (APX) activity, and glutathione reductase (GR) activity. The results revealed the following: (1) Overall, Fv/Fm and rETRmax of B. fuscopurpurea exhibit a trend of initially increasing and then decreasing with temperature elevation. Throughout the cultivation period, B. fuscopurpurea maintained relatively high levels of Fv/Fm and rETRmax at 15 ℃; however, within the first three days, the Fv/Fm and rETRmax values at 20 and 25 ℃ were significantly lower compared to those of other temperature groups, but by day 5, they rose to levels comparable to those of the 15 ℃ group and significantly higher than those of the 5 and 10 ℃ group. (2) The MDA content initially decreased and then increased with temperature elevation, with the MDA content at 15 ℃ being significantly lower than that of the other groups. During the early period (6 h), the MDA content was higher at low temperatures (5 and 10 ℃). However, with prolonged treatment time (five days), the MDA content significantly increased in the high-temperature groups (20 and 25 ℃). (3) The SP content was highest at 15 and 20 ℃, with no significant difference between the high (25 ℃) and low (5 and 10 ℃) temperature groups. (4) SOD, APX, GR, and CAT activities were generally significantly higher at low and high temperatures, particularly on day 5, compared with the 15 and 20 ℃ group. With prolonged cultivation time (five days), GR activity significantly increased in the 25 and 10 ℃ groups, while CAT activity significantly increased in the 5 and 10 ℃ group. These results suggest that 15 ℃ is more suitable for the growth of B. fuscopurpurea, although it also exhibits strong adaptability to high temperatures (20 and 25 ℃). During temperature stress acclimation, antioxidative enzymes play a positive role.
