Fig. 2

Effects of ultraviolet-B (UVB) and photosynthetically active radiation (PAR) on photosystem II (PS II) fluorescence parameters in Ulva prolifera on the 1st day and the 4th day. SHAM-1d and SHAM-4d show the changes of the SHAM group on the 1st day and the 4.^th day, respectively. A The maximum PSII quantum yield (Fv/Fm); B the effective PSII quantum yield (Y(II)); C the regulated non-photochemical quantum yield (Y(NPQ)); D the non-regulated non-photochemical quantum yield (Y(NO)); E images of the maximum PSII quantum yield (Fv/Fm); F images of the effective PSII quantum yield (Y(II)); G images of the regulated non-photochemical quantum yield (Y(NPQ)); H images of the non-regulated non-photochemical quantum yield (Y(NO)). The bar chart in the picture shows the relative percentage values of Fv/ Fm, Y(II), Y(NPQ), and Y(NO). All data are the mean values (± SD) from three biological replicates. Groups with different lowercase letters are significantly different (P < 0.05)