Flash-induced oxygen yield sequences during the life cycle of Chlorella.

(i) The pattern of O2 flash yields in the first 4 hours of the life cycle cannot be described by the simple Kok model without additional assumptions. (ii) The miss coefficient α in the mature cells in significantly higher than that in the autospores, its change occurring at the expense of the single-hit coefficient β. Computer simulation yielded α values of 0.29 and 0.23 and β values of 0.66 and 0.72 in the light and dark, respectively. (iii) The onset of light at the beginning of the cycle drastically changes the equilibrium distribution of the S states in the dark; the ratio S0/S1 increases from 30/70 to 50/50 in 1 h, and is restored not earlier than in the 6th hour. (iv) In the presence of 1 mmol/l p-benzoquinone, the alga shows pronounced and long-lasting oscillations in the O2 yield sequences, independently of the time of the life cycle. This means that the O2-evolving system itself is always present and equally efficient throughout the life cycle. Limits imposed on its activity (mainly in the first 4 hours) are clearly of an external nature. The redox potential of the inner thylakoid space is presumably involved.