Effects of light quality on growth, biochemical composition and photo synthetic production in Cyclotella caspia Grunow and Tetraselmis gracilis (Kylin) Butcher

The effects of light quality on growth, biochemical composition and photosynthetic production in Cyclotella caspia Grunow and Tetraselmis gracilis (Kylin) Butcher were evaluated under controlled laboratory conditions. Cyclotella caspia had the highest values for maximum growth rate in blue-green light, whereas T. gracilis grew faster in red light. The highest cellular contents of chlorophylls a, (c₁ + c₂)] and carotenoids of C. caspia were found respectively in red and blue-green light, while protein content did not change in response to spectral quality. Tetraselmis gracilis cells were more stimulated to synthesize pigments and protein when incubated in white light. For both species, pigment ratios showed intermediate values in white regime. The maximum values for photosynthetic rates were obtained in blue-green and red regimes in C. caspia and in red light in T. gracilis. The chromatic adaptive mechanisms shown for both species are compared and discussed in light of recent works presented for different phytoplankters, with emphasis on ecophysiological responses obtained in distinct spectral regimes.