Electron transport capabilities of chloroplasts isolated from non-photosynthesizing leaves.

The photosynthetic inhibitor CMU was used to retard chlorophyll formation in illuminated dark grown pea (Pisum sativum L. var. Meteor) explants. Levels of chlorophyll were restored to those of the control plants by the addition of exogenous sucrose, but carbon dioxide uptake was absent. In vitro electron transport studies with chloroplasts isolated from these plants revealed a functional PS I and PMS catalysed cyclic photophosphorylation. PS II activity as measured by ferricyanide reduction was absent but was fully functional in the presence of silicomolybdate. The results showed that a functional PS II developed in the absence of a complete electron transport system and that cyclic phosphorylation could operate in vivo without PS II.