A comparison of photosynthesis measurements by o2 evolution,14C assimilation, and variable chlorophyll fuorescence during light acclimatization of the diatom Coscinodiscus granii

Abstract

Photosynthetic rates of the large centric diatom Coscinodiscus granii were measured by means of multicolor variable chlorophyll fuorescence imaging, single cell14C assimilation, and optical O2 sensor measurements during light acclimatization of cultures grown at fve different irradiances: 50, 150, 235, 332, and 450 µmol photons m-2 s-1. Photo-acclimatization was evident from changes of cellular chlorophyll a content, growth rates, and light response curves. Each of the applied methods evaluates different parts and reactions in the photosynthetic apparatus, which makes a direct quantitative comparison of rates diffcult, although a different degree of correlation were found between all three methods. However, when used in combination, they provide information about the internal relationship of photosynthetic pathways as well as the variation in photosynthetic capacity between individual cells within a single algal culture.