Reversible lowering of modulated chlorophyll fluorescence after saturating flashes inHaematococcus lacustris(Volvocales) at room temperature

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Abstract
During modulated Chl fluorescence kinetics in zoospores of the green algaHaemutococcus lacustrisRostafinski, sudden reversible drops in fluorescence intensity immediately following each saturating light flash occur. In order to characterize the cause of these low‐waves several treatments were applied to modify their expression: (I) inhibition of non‐photochemical quenching by application of uncouplers: (2) application of effectors to the photosynthetic electron transport system: (3) brief chilling treatment and UV‐B irradiation. The results indicate that the phenomenon is not related to oscillations of the trans‐thylakoid pH gradient. The reversible short‐term decrease in fluorescence after a saturating light pulse seems to originate from an imbalance between charge separation capacity of the photosystems and the electron buffering capacity of the intersystem electron transport pool.