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Plastids prepared from dark‐grown spruce seedlings showed a negligible activity of photosystem II, and no fluorescence variation was observed during actinic illumination. The photosystem II reaction centre, however, was present in primary thylakoids. Exposure of such seedlings to continuous light induced the development of photosystem II activity via three stages (rapid, lagged and gradual), and the variable fluorescence appeared. The rapid development of photosystem II may be attributed to the activation of the oxygen‐evolving system, possibly the manganese‐catalyzing site, and the lagged and gradual developments may be closely related to the formation of thylakoid membranes and their assembly to grana.

Abstract The reaction of singlet oxygen with 1,3-diphenylisobenzofuran was investigated in aqueous micellar solutions of sodium dodecyl sulfate and dodecyl trimethylammonium chloride using pyrene as photosensitizer. Singlet oxygen, produced by the photosensitization of pyrene bound to micelles, oxidized efficiently 1,3-diphenylisobenzofuran bound to micelles. The quantum yield for singlet oxygen production and the rate constant for furan oxidation were determined by the kinetic analysis for the oxidation reaction of furan. Quenching of singlet oxygen by sodium azide competed with the furan oxidation, and its rate constant was also determined. Results obtained were compared with those in methanolic solutions. The quantum yield for singlet oxygen production and the rate constant for furan oxidation were much higher in micellar solutions than those in methanolic solutions. Empty micelles wxas found to act as a considerably strong scavenger for singlet oxygen. The penetration probability of singlet oxygen from aqueous phase into the interior of micelles which bound furan was also estimated

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