Collective Calculation of Actual Values of Non-Photochemical Quenching from Their Apparent Values after Chloroplast Movement and Photoinhibition

Abstract

Chlorophyll fluorescence parameters such as Fv / Fm , NPQ and ΦII (YII) are widely used to estimate the fitness and photosynthetic activity of plant leaves and non-photochemical dissipation of excessive excitation energy in photosystem II. The effect of chloroplast movement on these fluorescence parameters reduces the accuracy of estimations of the size of de-excitation processes, but there is no method to calculate correct parameters from altered (fluctuated) parameters. Chloroplast movement was recently identified as the “middle” kinetic component of NPQ . In this paper, we devised a complex but reasonable mathematical method to remove the effect of chloroplast movement on fluorescence parameters, based on our previously reported fluorescence theory. The fraction of “ S fluctuation” (designated as σ) was estimated from fluorescence observations and used to calculate the non-fluctuated Fs and F ′ m . fluorescence yields. From the σ values, the fractional change of light absorbance by a leaf caused by chloroplast movement was estimated at 70% - 100%, which varied according to the experimental conditions and plant species. The effect of photoinhibition on fluorescence parameters was also examined in this paper. The photochemical and non-photochemical de-excitation sizes during photoinhibition (measured by the parameters qPI and qSlow ) changed on a single regression line. Using this correlation, qPI and qSlow can be predicted from Fv / Fm , and the non-fluctuated Fm and Fo values can be estimated from the fluctuated <i> F ″ m</i> and <i> F ″ o</i> values.