Spectral dependence of the inhibition of photosynthesis under simulated global radiation in the unicellular green alga Dunaliella salina

• Published in: Journal of photochemistry and photobiology. B, Biology Vol. 48; no. 2; pp. 166 - 173
• Main Authors: Ghetti, F., Herrmann, H., Häder, D.-P., Seidlitz, H.K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.1999
• Subjects: Biological weighting function; Dunaliella salina; Marine; Oxygen exchange; PAM fluorescence; PAR; Photosynthesis inhibition; Sun simulator; UV-A; UV-B; PAR; UV-B; Dunaliella salina; UV-A; Sun simulator; Oxygen exchange; Photosynthesis inhibition; Biological weighting function; PAM fluorescence
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/S1011-1344(99)00043-3

The inhibition of photosynthesis after exposure to simulated solar radiation has been investigated in the marine green alga Dunaliella salina by monitoring the chlorophyll fluorescence parameter, Δ F/F m′, and the maximum light utilization efficiency for oxygen production. 40 different irradiation regimes have been applied by combining two different levels of UV radiation with two different levels of photosynthetically active radiation (PAR), and by using 10 coloured glass filters with decreasing cut-off wavelengths ranging from 400 to 295 nm. After a 30 min exposure both Δ F/F m′ and the efficiency of oxygen production decrease under all irradiation conditions. Inhibition increases when the cut-off is shifted towards short wavelengths. The fit of the experimental data with an analytical model describing inhibition of photosynthesis as a function of a linear combination of the photon flux densities in the UV-B, UV-A and PAR allows the average weighting factors for inhibition of photosynthesis by the three spectral ranges (about 1.6, 1.9 × 10 −2 and 1.8 × 10 −4 (μmol m −2 s −1 −1 for UV-B, UV-A and PAR, respectively) to be calculated. The experimental data and the derived weighting factors are in agreement with previous results obtained under natural solar radiation. In addition, the data allow an estimation of a biological weighting function in the UV range to be made.