Is the Measure of PSII Quantum Yield by Means of in-vivo Chl a-fluorescence really a direct Measure of Phytoplankton Primary Production?

Wilhelm, Christian; Bida, J.; Domin, A.; Lohr, Martin

doi:10.1007/978-94-009-0173-5_1100

Cited by 3 publications

(4 citation statements)

References 9 publications

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“…The turbidostat cultures of P. tricornutum were exposed to a minimum of 6 cycles of 6 h high light with a PPFD of 700 lmol m )2 s )1 (provided by 500-W quartz halogen lamps) followed by 18 h low light, to allow acclimation (see Wilhelm et al 1995a) before the experiments started. For each experiment 150 ml was transferred from the turbidostat vessel into a separate vessel and further incubated in the temperature controlled water bath under aeration.…”

Section: Methodsmentioning

confidence: 99%

Xanthophyll synthesis in diatoms: quantification of putative intermediates and comparison of pigment conversion kinetics with rate constants derived from a model

Lohr

Wilhelm

2001

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140

100

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Recently, we reported the presence of the violaxanthin-antheraxanthin-zeaxanthin cycle in diatoms, and showed that violaxanthin is the putative precursor of both diadinoxanthin and fucoxanthin in the diatom Phaeodactylum tricornutum Bohlin (M. Lohr and C. Wilhelm, 1999, Proc. Natl. Acad. Sci. USA 96: 8784-8789). In the present study, two possible intermediates in the synthesis of violaxanthin from beta-carotene were identified in P. tricornutum, namely beta-cryptoxanthin and beta-cryptoxanthin epoxide. In low light, the latter pigment prevails, but in high light beta-cryptoxanthin accumulates, probably as the result of an increased activity of the xantophyll-cycle de-epoxidase. The apparent kinetics of several xanthophyll conversion steps were determined for P. tricornutum and Cyclotella meneghiniana Kuitzing. The experimentally determined conversion rates were used to evaluate the hypothetical pathway of xanthophyll synthesis in diatoms. For this purpose a mathematical model was developed which allows the calculation of theoretical rates of pigment conversion for microalgae under steady-state growth conditions. A comparison between measured and calculated conversion rates agreed well with the proposal of a sequential synthesis of fucoxanthin via violaxanthin and diadinoxanthin. The postulation of zeaxanthin as an obligatory intermediate in the synthesis of violaxanthin, however, resulted in large discrepancies between the measured and calculated rates of its epoxidation. Instead of zeaxanthin, beta-cryptoxanthin epoxide may be involved in the biosynthesis of violaxanthin in diatoms.

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Section: Methodsmentioning

confidence: 99%

Xanthophyll synthesis in diatoms: quantification of putative intermediates and comparison of pigment conversion kinetics with rate constants derived from a model

Lohr

Wilhelm

2001

Planta

140

100

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“…Most experiments were performed with the diatom P. tricornutum, axenic strain 1090-1a of the Sammlung von Algenkulturen (SAG, Göttin-gen, Germany) (29), grown aseptically in a turbidostat as described previously (30). Continuous illumination with LL had a photon flux density (PFD) of 40 mol photons m Ϫ2 ⅐s…”

Section: Methodsmentioning

confidence: 99%

“…(HL1) or with 1,000 mol m Ϫ2 ⅐s Ϫ1 (HL2), followed by 18-h LL, to allow acclimation before the experiments started (30). For each experiment, 150 ml was transferred from the turbidostat vessel into a separate vessel and further incubated in the temperature-controlled water bath under aeration.…”

mentioning

confidence: 99%

Algae displaying the diadinoxanthin cycle also possess the violaxanthin cycle

Lohr

Wilhelm²

1999

Proc. Natl. Acad. Sci. U.S.A.

274

229

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According to general agreement, all photosynthetic organisms using xanthophyll cycling for photoprotection contain either the violaxanthin (Vx) cycle or the diadinoxanthin (Ddx) cycle instead. Here, we report the temporal accumulation of substantial amounts of pigments of the Vx cycle under prolonged high-light stress in several microalgae thought to possess only the Ddx cycle. In the diatom Phaeodactylum tricornutum, used as a model organism, these pigments also participate in xanthophyll cycling, and their accumulation depends on de novo synthesis of carotenoids and on deepoxidase activity. Furthermore, our data strongly suggest a biosynthetic sequence from Vx via Ddx to fucoxanthin in P. tricornutum. This gives experimental support to the long-stated hypothesis that Vx is a common precursor of all carotenoids with an allenic or acetylenic group, including the main light-harvesting carotenoids in most chlorophyll a͞c-containing algae. Thus, another important function for xanthophyll cycling may be to optimize the biosynthesis of light-harvesting xanthophylls under f luctuating light conditions.Fluctuating light intensities pose a serious problem to all photosynthetic organisms: in low light (LL), it is highly desirable to collect photons as efficiently as possible, but when light intensities become supersaturating for photosynthesis, there must be ways to protect the organism from potential damage by excess energy absorption. Carotenoids fulfill important functions in both situations, in light harvesting as well as in photoprotection (for reviews, see refs. 1-3).Within the last decade (4, 5), it has been recognized that in higher plants, the reversible conversion of the xanthophylls violaxanthin (Vx), antheraxanthin (Ax), and zeaxanthin (Zx; see Fig. 1) in the so-called xanthophyll cycle (6, 7) is intimately related to the ability of the plants to regulate the dissipation of surplus absorbed light energy on a short-term time scale. Zx, which is formed from Vx by enzymatic deepoxidation when the pH in the thylakoids drops below a critical level (8), is thought to enhance thermal dissipation, and two main mechanisms have been proposed (9-12). Recently the isolation of mutants defective in synthesis or cycling of xanthophylls has offered new possibilities for studying the influence of different carotenoids on energy dissipation in vivo (13,14).In several algal groups such as the diatoms, the dinophytes, and the haptophytes, which together are largely responsible for oceanic primary production (15), the Vx cycle is replaced by a xanthophyll-cycle alternating diadinoxanthin (Ddx) with diatoxanthin (Dtx) (16). This cycle comprises a single deepoxidation step, because only one of the ionon rings of Ddx carries an epoxide group. Epoxidation of the second ionon ring by the respective xanthophyll-cycle epoxidase does not occur, probably because of steric constraints caused by the acetylenic bond at C-7Ј (Fig. 1). As is the case with Zx, the formation of Dtx correlates with a higher ability for nonradiative relax...

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“…Induction of different light adaptation states was achieved by illumination at 10 lmol m )2 s )1 in batch cultures (low light, LLstate; 10 : 14 h L/D-cycle) and at 200 lmol m )2 s )1 in turbidostat cultures (medium light, ML-state; continuous light) for 10 and 5 days, respectively. The tubidostat system was performed as described in Wilhelm et al (1995a).…”

Section: Algal Materials and Growthmentioning

confidence: 99%

Estimation of chlorophyll content and daily primary production of the major algal groups by means of multiwavelength-excitation PAM chlorophyll fluorometry: performance and methodological limits

et al. 2005

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The performance and methodological limits of the Phyto-PAM chlorophyll fluorometer were investigated with laboratory grown algae cultures and natural phytoplankton from the rivers Saar and Saale. The Phyto-PAM is a 4-wavelength chlorophyll fluorometer with the functional combination of chlorophyll (Chl) estimation and assessment of photosynthetic activity, both differentiated into the main algal groups. The reliability of fluorescence-based Chl estimation strongly depends on the group specific calibration of the instrument and the resulting chlorophyll/fluorescence (Chl/F) ratios in reference algal cultures. A very high reliability of the Chl estimation was obtained in the case of constant Chl/F-ratios. Algae grown at different light intensities showed marked differences in Chl/F-ratios, reflecting differences in pigment composition and Chl a specific absorption (a*). When the Phyto-PAM was calibrated with laboratory grown diatoms, the Chl a in river grown diatoms was underestimated, due a lower content of accessory pigments and stronger pigment packaging. While this aspect presently limits the application of PAM fluorometry in limnology, this limitation may be overcome by future technical progress in the detection of dynamic changes in Chl/F-ratio via fluorescence-based measurements of the functional PS II absorption cross-section. Practically identical Chl/F-ratios were found for the diatom-dominated waters of the rivers Saar and Saale, suggesting that the same instrument calibration parameters may be applied for hydrographically similar surface waters. For this particular case, despite of the present methodological limitations, the potential of PAM fluorometry in limnology could be demonstrated. Light response curves were measured to estimate primary production with a spectrally resolved model in daily courses at two sampling sites. Fluorescence based primary production was closely correlated with measured oxygen evolution rates until midday. In the afternoon, at the water surface the fluorescence approach gave higher rates than the measured oxygen evolution. Possible explanations for the observed differences are discussed.

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Is the Measure of PSII Quantum Yield by Means of in-vivo Chl a-fluorescence really a direct Measure of Phytoplankton Primary Production?

Cited by 3 publications

References 9 publications

Xanthophyll synthesis in diatoms: quantification of putative intermediates and comparison of pigment conversion kinetics with rate constants derived from a model

Xanthophyll synthesis in diatoms: quantification of putative intermediates and comparison of pigment conversion kinetics with rate constants derived from a model

Algae displaying the diadinoxanthin cycle also possess the violaxanthin cycle

Estimation of chlorophyll content and daily primary production of the major algal groups by means of multiwavelength-excitation PAM chlorophyll fluorometry: performance and methodological limits

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