Table I. Photosynthetic ETR from PSII versus photon absorption curve parameters and the fractional photon absorption (Abs; in percentage of total absorption) calculated for the upper cortex, medulla, and lower cortex under blue (425–475 nm), green (525–575 nm), red (615–665 nm), and white (400–700 nm) irradiance applied perpendicular to one side of the thallus surface of F. vesiculosusSlopes on the subsaturated part of the ETR versus light curve, maximum ETR values (ETR_{max}), and the light acclimation index Ek were estimated from curve fitting of the ETR versus photon absorption curves with an exponential function (Webb et al., 1974) using a nonlinear Levenberg-Marquardt fitting algorithm. The RGB values were calculated as average curves of blue, green, and red. Pairwise superscript letters indicate statistically significant differences (one-way ANOVA, *P* < 0.01; *n* = 5 for white and *n* = 4 for RGB).