Conforming to the quencher theory published as early as 1963 (Duysens and Sweers, 1963), and considered as a dogma by the majority of the researchers, the chlorophyll a fluorescence induction in viva is attributed to the photoreduction of a fluorescence quencher, the bound quinone Q_A, to its nonquenching form, Q_A^-_· With our actual knowledge about the PSII center, another component, the primary acceptor pheophytine Pheo, can also be included in the biochemical modeling of this phenomenon. A theoretical discussion based on numerical simulation and fitting of the experimental data, shows three possible approaches of the fluorescence signal, all being derived from the same reaction scheme of the electron transfer around PSII. The fluorescence rise in two of these models was based on the conventional assumption, that the presence of Q_A^- determines the high fluorescence state. However, in the second model, the contribution to the fluorescence yield of the centers which have both Pheo and Q_A reduced has been considered higher (Vredenberg, 2000). The third model is based solely on the photochemical charge separation in the reaction center complex where P₆₈₀Pheo^- forms have a high fluorescence yield and P₆₈₀⁺Pheo^- create a dip (Strasser and Stirbet, 2000 and 2001).