Rapid delayed luminescence from chloroplasts: Kinetic analysis of components; The relationship to the O2 evolving system

Delayed luminescence from saturating flashes given to isolated chloroplasts was measured in the time range of 65–800 μsec with the following results:

1. 1. Three distinct components having decay half times of approx. 10, 35 and 200 μsec could be detected.

2. 2. The yields of both the 35- and 200-μsec delayed luminescence components oscillate with a period of four, in phase with oscillations of O₂ yield; no large oscillations of fluorescence paralleling those of luminescence or O₂ were observed.

3. 3. 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) abolished the 10- and 200-μsec components and the oscillatory behavior of the 35-μsec component.

4. 4. The 35- and 200-μsec components are not directly influenced by System I.

The DCMU isolated 35-μsec component showed the following properties:

1. 1. The decay is first order and the emission spectrum is essentially identical to that of chloroplast fluorescence;

2. 2. The yield saturates with a total emission of about 10^-4 quanta/trap.

3. 3. The temperature dependence indicates an activation energy of about 250 mV for the yield and 200 mV for the decay.

4. 4. Maximal emission was obtained when Q, the acceptor of System II, was oxidized prior to the flash.

The results are discussed in terms of possible mechanisms concerning the production and behavior of the luminescence.