Abstract:As an economically important alga growing in the intertidal zone, Pyropia yezoensis has the unique characteristics of adapting to high ultraviolet radiation in the open air and to desiccation conditions. In this experiment, light without UV-B radiation was used as a control, and low UV-B radiation of 0.5 W/m2 and high UV-B radiation of 2 W/m2 were used to detect changes in chlorophyll fluorescence photosynthetic parameters, multi-spectral fluorescence parameters, and tyrosinase activity in response to UV-B ultraviolet radiation in the gametophytes of P. yezoensis. The results showed that the chlorophyll fluorescence photosynthetic parameters (QY_max, NPQ_Lss, qP_Lss, Rfd_Lss) of P. yezoensis under UV-B radiation displayed a gradient decline with irradiation time, and the values of photosynthetic parameters were lower at high radiation intensity (2 W/m2) than at low radiation intensity (0.5 W/m2). The early stress parameters of F440/F690 and F440/F740, which are positively related to secondary metabolites such as phenol or aldehyde concentration, showed that the group under conditions of 2 W/m2 entered a forced state earlier than the group under 0.5 W/m2. Secondary metabolites such as phenol or aldehyde showed concentration declines. F690/F740, which is negatively correlated with chlorophyll concentration, indicated that the chlorophyll concentration under 0.5 W/m2 irradiation was higher than that under no UV-B irradiation, but was lower than the maximum value in the rising period of 2 W/m2 irradiation. The chlorophyll concentration increased initially and then decreased rapidly after 4 h under 2 W/m2, indicating that the chlorophyll concentration is less sensitive to UV-B radiation under low radiation intensity, whereas it is more sensitive under high radiation intensity. The results showed that the tyrosinase activity was significantly higher in P. yezoensis gametophytes irradiated with UV-B than in the control group and that the enzyme activity under 2 W/m2 UV-B was higher than that under 0.5 W/m2 UV-B.
