Abstract
Diatoms are important phototrophs in the worlds’ oceans contributing approximately 40% of the global primary photosynthetic production. This is partially explained by their capacity to exploit environments with variable light conditions, but there is limited knowledge on how diatoms cope with changes in the spectral composition and intensity of light. In this study, the influence of light quality and high irradiance on photosynthesis in the centric diatom Coscinodiscus granii was investigated with microscopic imaging and variable chlorophyll fluorescence techniques. Determination of the wavelength-dependent functional absorption cross-section of photosystem (PS) II revealed that absorption of blue light (BL) and red light (RL) was 2.3-fold and 0.8-fold that of white light (WL), respectively. Hence, BL was more efficiently converted into photo-chemical energy. Excessive energy from BL was dissipated via non-photochemical quenching (NPQ) mechanisms, while RL apparently induced only negligible NPQ even at high irradiance. A dose dependent increase of cells exhibiting an altered chloroplast distribution was observed after exposure to high levels of BL and WL, but not RL. However, no effective quantum yield of PSII was measured in the majority of cells with an altered chloroplast distribution, and positive Sytox green® death staining confirmed that most of these cells were dead. We conclude that although Coscinodiscus granii can sustain high irradiance it does not perform chloroplast high-light avoidance movements for photo-protection.
Highlights
Diatoms are responsible for about 40% of the primary production in marine ecosystems and account for up to 20% of global carbon fixation (Nelson and Brzezinski, 1997; Geider et al, 2001)
Sigma(II)λ was 2.3 ± 0.4 fold higher in blue light than in white light, while Sigma(II)λ was 0.9 ± 0.2 fold lower in red light than in white light (Table 1)
Parameters of rapid light curves derived from chlorophyll fluorescence analysis revealed significantly higher alpha in blue light (BL) (0.44 ± 0.19 μmol e− μmol−1 photons) compared to red light (RL) (0.08 ± 0.02; p = 0.006) and white light (WL) (0.06 ± 0.01; p = 0.03; Table 1)
Summary
Diatoms are responsible for about 40% of the primary production in marine ecosystems and account for up to 20% of global carbon fixation (Nelson and Brzezinski, 1997; Geider et al, 2001). The evolutionary success and high productivity of diatoms (Boyd et al, 2000; Thomas and Dieckmann, 2002; Mock and Valentin, 2004) seem to be closely related to their ability to adapt to environmental fluctuations such as changes in irradiance and spectral composition of the light field (Depauw et al, 2012). The in situ solar irradiance in aquatic systems can be affected on different time scales by various factors such as vertical mixing, wave focusing, and varying cloud cover. Vertical shifts in the water column change the blue light (BL) to red light (RL) ratio, where RL is more strongly absorbed by seawater, while BL penetrates deeper into the water column in The frustule exhibits special optical properties and this has led to speculations that the frustule nanostructure could affect the photobiology of diatoms (Sumper and Brunner, 2006; De Stefano et al, 2007; Parker and Townley, 2007; Su et al, 2015) and potentially modulate their photosynthetic efficiency
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
