Abstract
Abstract Models describing the relationship between effective quantum efficiency of PS II (ΦPSII) and irradiance (I) are routinely used to determine how irradiance influences effective quantum efficiency and photosynthetic electron transport rate (ETR). However, with no single model one can accurately describe the relationship between ΦPSII and I, and explain the interdependence between ΦPSII and biophysical properties of photosynthetic pigments, especially in plants growing under low level irradiances. Basing on the mechanistic model of photosynthetic electron transport rate we have developed the model of the relationship between ΦPSII and I. The new model reveals that ΦPSII increases with photochemistry (kP) and heat dissipation (kD). Furthermore, the values of key parameters calculated using the new model were compared with the values calculated with two other empirical models. The new model was perfectly fitted to the light-response curves of ΦPSII. The key calculated photosynthetic parameters: maximum ΦPSII, maximum ETR and their corresponding saturation irradiance were close to the measured values. In addition, our model associates ΦPSII with intrinsic features of photosynthetic pigments. We concluded that ΦPSII decreased with increasing I due to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.
Highlight A model of the relationship between effective quantum efficiency of PS II (ΦPSII) and irradiance (I) has been developed. Using this new model it was found that ΦPSII decreased with increasing I due to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.
- ETR
- Electron transport rate
- ETRmax
- Maximum electron transport rate
- F
- Steady-state fluorescence
- Fm′
- Maximum fluorescence in the light
- Fv
- Variable fluorescence yield of the dark-adapted leaf
- gi
- Degeneration of energy level of photosynthetic pigment molecules in the ground state i
- gk
- Degeneration of energy level of photosynthetic pigment molecules in the excited state k
- I
- Irradiance
- NPQ
- Non-photochemical quenching
- N0
- Total light-harvesting pigment molecules
- PARsat
- Saturation irradiance corresponding to ETRmax
- kP
- Rate of photochemical reaction
- kD
- Rate of non-radiative heat dissipation
- PS II
- Photosystem II
- ae
- Initial slope of light-response curve of electron transport rate
- α′
- Fraction of light absorbed by PS II
- β′
- Leaf absorptance
- ξ1
- Probability of photochemistry
- ξ2
- Probability of non-radiative heat dissipation
- ξ3
- Probability of fluorescence
- σik
- Eigen-absorption cross-section of photosynthetic pigment from ground state i to excited state k due to light illumination
- Effective optical absorption cross-section of photosynthetic pigment molecule from ground state i to excited state k due to light illumination
- φ
- Exciton-use efficiency in PS II
- τ
- Average lifetime of the photosynthetic pigment molecules in the lowest excited state
- ΣPSII
- Effective quantum efficiency of PS II