Anomalies in the kinetics of photosynthetic oxygen emission in sequences of flashes revealed by matrix analysis. Effects of carbonyl cyanide m-chlorophenylhydrazone and variation in time parameters

The model of Kok et al. (Kok, B., Forbush, B. and McGloin, M. (1970) Photochem. Photobiol. 11, 457–475) is considered the best kinetic explanation of the damped oscillations of O₂ evolution induced in higher plants by a sequence of brief saturating flashes. Matrix analysis applied to this model shows that the parameters involved (distribution of S states at zero time, probabilities of transition between states induced by a flash) cannot be completely known from the O₂ yield sequence, Y_n. However, four quantities, with limited content of information, are readily derived from data, without additional assumptions. They are σ₁, σ₂ and σ₃, three quasi-symmetrical functions of the transition coefficients, and $\text{Y}$, a weighed average of four consecutive Y_n values. The extent of misses and double hits and their variations can be qualitatively ascertained by inspection of the relative values of σ₁, σ₂ and σ₃. In a regular sequence (strictly obeying Kok's model), all four quantities should be constant along the time axis.It is shown that actual sequences are seldom regular, in particular in the following conditions: (1) variable flashing frequency, (2) addition of carbonylcyanide m-chlorophenylhydrazone, (3) incomplete deactivation, (4) change of flashing frequency at steady state.In order to account for these anomalies, it is proposed to modify Kok's model by introducing, in parallel to the four state storage entity (S states), a side carrier C, which can reversibly exchange a positive charge with it. In the new model, the transition coefficients are essentially time varying, thus producing a nonregular behaviour of Y_n sequences.