PHOTOACCLIMATION OF PHOTOSYNTHESIS IRRADIANCE RESPONSE CURVES AND PHOTOSYNTHETIC PIGMENTS IN MICROALGAE AND CYANOBACTERIA 1

The photosynthesis‐irradiance response (PE) curve, in which mass‐specific photosynthetic rates are plotted versus irradiance, is commonly used to characterize photoacclimation. The interpretation of PE curves depends critically on the currency in which mass is expressed. Normalizing the light‐limited rate to chl a yields the chl a ‐specific initial slope (α chl ). This is proportional to the light absorption coefficient (a chl ), the proportionality factor being the photon efficiency of photosynthesis (φ m ). Thus, α chl is the product of a chl and φ m . In microalgae α chl typically shows little (<20%) phenotypic variability because declines of φ m under conditions of high‐light stress are accompanied by…