Influence of Chemical and Physical Factors on Long-Term Delayed Fluorescence in Dunaliella tertiolecta

Abstract

The long-term delayed fluorescence in the marine alga Dunaliella tertiolecta (Chlorophyta) was investigated for the influence of herbicide DCMU, reference toxicant 3,5-DCP, temperature, excitation light spectrum, and intensity. We observed a strong transient peak in otherwise monotonic decay kinetics, which was almost insensitive to illumination light spectra as opposed to Prorocentrum minimum, where the peak was induced only by far-red illumination. DCMU and 3,5-DCP influenced the DF kinetics of D. tertiolecta in a dose-dependent and qualitatively different way. We observed strong influence of temperature on the transient peak position (Q₁₀ = 2.6, E_a = 71.5 kJ/mol, which are in the expected range of plastoquinone-PSII reactions). At the lowest illumination intensity, the peak was less pronounced, whereas the decay kinetics of the DCMU-treated samples was unchanged. The approach and results presented in this study could be used in modeling, especially where systematic variations in external influences present a decision-point between different models.

Keywords:

• DCMU
• Delayed fluorescence
• Dunaliella
• Photosynthesis
• Phyto-plankton