Insights into the consequences of grana stacking of thylakoid membranes invascular plants: a personal perspective

The striking structural architecture of thylakoid membranes of higher plant and some green algal chloroplasts that house the light harvesting and ener gy transducing functions of chloroplasts have evoked many hypotheses concer ning the significance of grana. The differentiation of the thylakoids into grana and stroma membrane regions is a morphological reflection of the non- random distribution of the photosystems II and I between appressed and non- appressed membrane domains, which became known as lateral heterogeneity. In this overview, the first section deals with changing concepts regarding th e distribution of the photosystems between stacked and unstacked thylakoid domains from a personal historical perspective. The remaining section descr ibes some functional implications of the lateral separation of most PSII co mplexes in appressed membrane regions of grana stacks from PSI complexes, A TP synthase and auxiliary proteins located in non-appressed membrane domain s.