LONG-TERM ACCLIMATIZATION OF SCENEDESMUS-BICELLULARIS TO HIGH-FREQUENCY INTERMITTENT LIGHTING (100 HZ) .1. GROWTH, PHOTOSYNTHESIS AND PHOTOSYSTEM-II ACTIVITY

Responses of the green microalga, Scenedesmus bicellularis to high-fre quency intermittent lighting (IL, 100 Hz) were assessed after a 4 week acclimatization. Effects of IL on growth, photosynthesis and photosys tem II (PSII) activity were studied at limiting and saturating irradia nces, and compared to those of continuous light (CL) of the same insta ntaneous and daily irradiances. Even after a 4 week acclimatization pe riod, the photosynthetic capacity (P-max), the photosynthetic efficien cy (alpha) and the photosynthetic activity at growth irradiance, eithe r expressed on a per cell or a chlorophyll a basis, showed little diff erence, neither did the index of light adaptation (I-k) or PSII activi ty. In contrast, growth was lower under IL at saturating irradiance. R esults are discussed considering the non-linearity of the relationship between growth or photosynthesis and irradiance.