THE SIGNIFICANCE OF INTRACELLULAR SELF-SHADING ON THE BIOOPTICAL PROPERTIES OF BROWN,RED, AND GREEN MACROALGAE1

The spectral light absorption and fluorescence excitation spectra from thalli (in vivo) and thylakoid micelles (no intracellular self-shading) from the macroalgae Laminaria digitata (L.) Edmonson, Palmaria palmata (L.) Kuntze, and Ulva sp. were examined. In all the examined species, the intracellular self-shading (i.e. the package effect) was highly significant to the extent that absorption peaks related to individual pigments were significantly suppressed. Thus, for studies related to taxonomy and physiology, “unpacked”spectra may be more informative. Thylakoid micelle preparations offer opportunities to examine more closely species-specific differences in the packaging effect, light harvesting and utilization, and pigmentation. As well, the thylakoid micelles, when analyzed with biochemical assays or fluoromtry, may provide insight into components of the photosynthetic machinery that are specific to different classes of mncroalgne. We present the Chl a-specific absorption coefficients and the corresponding fluorescence excitation spectra of macroalgal thylakoid micelles for the three species.