Oxygen‐quenched chlorophyll a fluorescence and electron transport in barley during greening

Seedlings of barley (Hordeum vulgare L. cv. Conquest) were dark‐grown for 7 days and then transferred to light. The time courses of chlorophyll a fluorescence induction underwent changes during greening periods of from 3 to 48 h. Yields of variable fluorescence during greening correlated with electron transport capacity via photosystem II (PS II) except at the early stage from 3 to 6 h. The discrepancy may result from there being only a small amount of light harvesting complex associated with PSII for 3 to 6 h greening. Oxygen quenching effects were interpreted as indicating the development of the electron transport system and the organization of light harvesting complex associated with PSII. The most intensive O2 quenching of relative fluorescence is found during the early stage of greening when the ratio of the primary quinone electron acceptor (Q) to chlorophyll is high.