Development of the Two Heterogeneous Photosystem II Units in Etiolated Bean Leaves
AUTOR(ES)
Melis, Anastasios
RESUMO
The development of the photosystem II units in relation to the heterogeneity of their photochemical centers was studied in etiolated bean leaves (Phaseolus vulgaris var. red kidney) greened under continuous or intermittent light. The study was done in order to see whether grana are the loci of the units with the efficient photosystem II activity (α units), while the stroma thylakoids are the loci of the units with the less efficient photosystem II activity (β units), as it has been proposed. In addition, the interrelations between α and β centers have been investigated. It was found that the α and the β centers of photosystem II were present in the first photosynthetic membranes irrespective of the mode of greening of the leaves. The magnitude of their respective photochemical rate constants, K′α and Kβ, increased with time in continuous light and it reached the steady-state values of the mature chloroplasts within 16 hours, while in intermittent light it remained smaller. The differentiation of the system II units in α and β centers containing units is more evident under conditions of intermittent illumination, i.e. when the rate of chlorophyll biosynthesis is the limiting step for chloroplast development.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=542525Documentos Relacionados
- Development of the Primary Photochemical Apparatus of Photosynthesis during Greening of Etiolated Bean Leaves 1
- Greening of Etiolated Bean Leaves in Far Red Light
- Development of Photosystem I and Photosystem II Activities in Leaves of Light-grown Maize (Zea mays) 1
- Induction of Porphyrin Synthesis in Etiolated Bean Leaves by Chelators of Iron 12
- Development of Photosystem II Activity in Chlamydomonas reinhardi Mutants: Insertion of Photosystem II Units into Inactive Preexisting Membranes versus Continuous Formation of New Photosynthetic Membranes 1