Effects of altered photic regimes on diel patterns of species-specific photosynthesis

Diel patterns of photosynthesis were measured for two polar diatoms (Coscinodiscus sp. and Porosira pseudodenticulata) collected in September 1985 from McMurdo Sound, Antarctica, and four temperate dinoflagellates (Gonyaulax hyalina, Gymnodinium splendens, Dinophysis caudata, and Glenodinium sp.) collected in July 1985 and January 1986 from the Southern California Bight, California, USA. For phytoplankton incubated under three combinations of photoperiod and irradiance, distinct diel patterns of light-saturated (P _max) and light-limited (P _L ) photosynthesis were found for (i) different species isolated from the same environment, and (ii) polar diatoms and temperate dinoflagellates. The time of day when the maximum rate of P _max occurred was influenced by both irradiance and daylength for the polar diatoms but not by daylength for three out of four temperate dinoflagellates. The range of values of the ratio of maximum to minimum rates of photosynthesis (P _max:P _min) was similar for polar diatoms and temperate dinoflagellates. The results of this study suggest that changes in irradiance or photoperiod could influence species-specific patterns of photosynthesis in nature. As a consequence, in light-limited environments differential reproductive success could result from these diel patterns, and ultimately be reflected in temporal and spatial differences in community structure.     

Inorganic layer compounds

Interactions of organic materials with solid surfaces can be successfully studied with inorganic layer crystals that take up organic compounds between the layers. The kind of information obtainable is illustrated by three selected examples. Investigations with long-chain compounds clarify the possible chain conformations in planar alkyl chain aggregates (mono- and bimolecular films). Studies with polyelectrolytes demonstrate the influence of the charge patterns on polymer adsorption and interactions with nucleotides present very specific adsorption phenomena.