Duree de vie et rendement de fluorescence de la chlorophylle in vivo. Leur relation dans differents modeles d'unites photosynthetiques

Lifetime and yield of chlorophyll fluorescence in vivo: Their relationship in different models of photosynthetic units. We have used phase fluorimetry to measure the relation between fluorescence lifetime (τ) and yield (F{cyrillic}) of chlorophyll during the induction phase of photosynthesis in isolated chloroplasts and in vivo. This relationship is usually non-linear, curving slightly toward negative values of τ, and does not extrapolate to zero. In the discussion we examine the conditions which might give rise to curvature and a non-zero intercept. A model of connected photosynthetic units, characterized by an intersystem frequency of energy exchange, T, can account for the concavity of the experimental curves when 0.6 ≤ T ≤ 1 ns^-1. Two hypotheses are suggested to account for the non-zero intercept: the occurrence of sensitized fluorescence emission, or the existence in the initial fluorescence of a constant fraction independent of System II.