Effects of Light and Temperature on PSII Heterogeneity
It is generally accepted that nearly 30% of PSII (PSIIβ) is located in non-appressed thylakoid regions where it is associated with smaller light-harvesting chl a/b antenna (LHCII) than the bulk of PSII (PSIIα) in grana partitions (1). In addition to this antenna size heterogeneity there are PSII populations differing from each others in the properties of the reducing side. PSII-QB-reducing centers are connected to the plastoquinone pool functioning in vivo in electron transfer from water to NADP. PSII-QB-nonreducing centers are inefficient in this respect due to impaired electron transfer from QA to QB. It has been suggested that in mature spinach leaves the PSIIβ and PSII-QB-nonreducing constitute one and the same pool of PSII centers but under light of present knowledge, however, this generalization is not always valid (1).
KeywordsHigh Light Freeze Fracture Plastoquinone Pool PSII Center Freeze Fracture Replica
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