State I/State II and Dark Adaptation in Green and Blue-green Algae

Abstract

Light driven changes in the distribution of excitation energy between photosystem I (PSI) and photosystem (PSII) were first reported by Bonaventura and Myers (1969) and Murata (1969). They showed that algal cells illuminated by light preferentially absorbed in PSI undergo a transition to a state (STATE I) characterised by a high efficiency of PSII processes. Conversely, cells illuminated by light preferentially absorbed by PSII undergo a transition to a state (STATE II) characterised by a high photo-efficiency of PSI photoprocesses. In the case of higher plants and green algae, these changes appear to be linked to the phosphorylation of LHC-II, the major chlorophyll protein complex of the PSII light-harvesting system (Allen et al, 1981). Analogous changes, however, are seen in blue-green (Duysens, Talens, 1969; Williams et al, 1981) and red algae (Murata 1969, Ried, Reinhardt 1977) that lack the LHC-II complex. The basis of these latter changes is not yet understood. In addition to these STATE I / STATE II linked changes, excitation energy distribution changes are also observed on dark adaptation of both green and blue-green algae. This paper is directed at gaining a better understanding of excitation energy, distribution changes both in DARK adapted algae and in systems lacking LHC-II.