Excitation Energy Distribution in an Organism with a Chl A/C/Carotenoid Light Harvesting Complex

Abstract

Photosynthetic organisms have the capacity to regulate the distribution of excitation energy between PS2 and PS1 via a mechanism termed the light state transition (4, 11). It has been argued that this phenomenon serves to maintain equal turnover of PS2 and PS1 ensuring efficient linear electron transport. To date, state transitions have been described in organisms that use either a Chi a/b LHC or a phycobilisome as light harvesting antenna and models have been proposed to describe the state transition with regards to the particular type of antenna complex employed (see 1, 2, 7 and 13). However, not all photosynthetic algae use these types of light harvesting complex. A Chl a, Chi c and carotenoid antenna complex is used by the various members of the Chromophyta. These algae are taxanomically diverse (Bacillariophyta, Dinoflagellata, Chrysophyta, Phaeophyta, Prymnesiophyta) and contribute a major fraction to the primary productivity of the oceans. However, surprisingly few studies have been concerned with the details of photosynthesis in these organisms (for review see 10).