Photosynthetic characteristics and physiological plasticity of an Aphanizomenon flos-aquae (Cyanobacteria, Nostocaceae) winter bloom in a deep oligo-mesotrophic lake (Lake Stechlin, Germany)
authors: Viktória Üveges, Kálmán Tapolczai, Lothar Krienitz & Judit Padisák
In winter of 2009/2010, Aphanizomenon
flos-aquae bloomed in the ice and snow covered oligomesotrophic Lake... more
In winter of 2009/2010, Aphanizomenon
flos-aquae bloomed in the ice and snow covered oligomesotrophic Lake Stechlin, Germany. The photosynthesis
of the natural population was measured at eight
temperatures in the range of 2–35C, at nine different
irradiance levels in the range of 0–1,320 lmol m-2 s-1
PAR at each applied temperature. The photoadaptation
parameter (Ik) and the maximum photosynthetic rate
(Pmax) correlated positively with the temperature
between 2 and 30C, and there was a remarkable drop
in both parameters at 35C. The low Ik at low
temperatures enabled the active photosynthesis of
overwintering populations at low irradiance levels
under ice and snow cover. The optimum of the
photosynthesis was above 20C at irradiances above
150 lmol m-2 s-1. At lower irradiance levels
(7.5–30 lmol m-2 s-1), the photosynthesis was the
most intensive in the temperature range of 2–5C. The
interaction between light and temperature allowed the
proliferation of A. flos-aquae in Lake Stechlin resulting
in winter water bloom in this oligo-mesotrophic lake.
The applied 2C is the lowest experimental temperature
ever in the photosynthesis/growth studies of A. flosaquae,
and the results of the P–I and P–T measurements
provide novel information about the tolerance and
physiological plasticity of this species.
Growth, biophysical parameters and anatomical aspects of young rubber tree plants inoculated with arbuscular mycorrhizal fungi Glomus clarum
Mycorrhizal fungi are beneficial when associated with plants because they favor growth and develop. Although... more Mycorrhizal fungi are beneficial when associated with plants because they favor growth and develop. Although infrequent, artificial inoculation of arbuscular mycorrhizal fungi (AMF) has become an alternative to reduce the use of fertilizers and pesticides in crops, as well as for the formation of seedlings, to obtain precocious and well fed rootstocks. The objective of the study was to evaluate the effect of inoculation of AMF Glomus clarum on growth and biophysical and anatomical characteristics of young rubber trees. The treatments consist of plants inoculated with the fungus Glomus clarum and fertilized with 50 ppm of phosphorus (mic+50P), non-inoculated plants fertilized with 50 ppm of phosphorus (s/mic+50P) and non-inoculated plants fertilized with 500 ppm of phosphorus (s/mic+500P). The mycorrhizal plants showed height and stem diameter, dry matter accumulation of the aerial part, stomatal density and leaf area similar to the plants s/mic+500P. Greater accumulation of dry matter in the roots, higher transpiration rate, less stomatal resistance and lower leaf temperature were reported for the mycorrhizal plants. The anatomical analyses of the roots showed alterations in the vascular tissue, with increase in the number of xylem poles in the mycorrhizal plant roots.
The major light-harvesting protein of Acaryochloris marina
Chen M, Quinnell RG, Larkum AWD. 2001. PS 2001 Proceedings 12th International Congress on Photosynthesis, CSIRO Publication, Melbourne, Australia, S31-008. pp 1-4.
The major light-harvesting protein complex containing chlorophyll d was isolated from Acaryochloris marina thylakoid... more The major light-harvesting protein complex containing chlorophyll d was isolated from Acaryochloris marina thylakoid membranes. Isolation was achieved by detergent solubilisation followed by separation on 6 - 40% sucrose gradients using ultracentrifugation. The best Chl d yield (70%) used 0.3% dodecyl maltoside, 0.15% octylglucoside, 0.05% zwittergent 3-14 with the detergent: total Chl d ratio around 10:1 (w/w). Characterisation of the light-harvesting pigment protein complex (lhc) involved non-denaturing and SDS-PAGE electrophoresis, absorbance and fluorescence spectroscopy. The main polypeptide in the lhc was shown to be ca 34 kDa and to contain Chl d and Chl a indicating that the Acaryochloris lhc is similar to that of prochlorophytes. The Chl a level varied with the culture conditions, which is consistent with previous findings.
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The Function of MgDVP in a Chlorophyll d-Containing Organism
Martin Schliep, Min Chen, Anthony Larkum and Rosanne Quinnell. In: Photosynthesis. Energy from the Sun. 2008, 17, 1125-1128,
DOI: 10.1007/978-1-4020-6709-9_246
The cyanobacterium Acaryochloris marina is an exceptional organism utilising chlorophyll d (Chl d) as its major... more The cyanobacterium Acaryochloris marina is an exceptional organism utilising chlorophyll d (Chl d) as its major photosynthetic pigment. Acaryochloris cells contain 90–99% Chl d with minor amounts of chlorophyll a and a chlorophyll c-like pigment. These unusual characteristics make it an excellent candidate to study various aspects of photosynthesis driven by Chl d. However, little is known about the pathway of Chl d biosynthesis. We specifically designed HPLC methods to analyse pigment compositions of Acaryochloris. This enabled us to detect intermediate products of the chlorophyll biosynthesis. We identified Mg-Protoporphyrin IX monomethyl ester (MgPMe) and Mg-2,4-divinyl pheoporphyrin (MgDVP) and the environmental factors influencing their concentration levels. HPLC-facilitated analysis of pigments from Acaryochloris cells cultured under various light quantities was performed; light stress conditions induced an increase in the ratio of MgDVP to Chl d. Pigment analysis of Acaryochloris cells grown under oxygen-stressed conditions demonstrated a decrease in MgDVP levels. We propose that the Chl d biosynthesis pathway favours an aerobic environment despite the fact that Acaryochloris cells can survive under anaerobic conditions.
Chlorophyll d as the major photopigment in Acaryochloris marina
Chen M, Quinnell R, Larkum A. Journal of Porphyrins and Phthalocyanines (JPP) Volume: 6, Issue: 12(2002) pp. 763-773
DOI: 10.1142/S1088424602000889
Chlorophyll (Chl) d is the major pigment in the photosystems (PS) and light-harvesting complex(es) of Acaryochloris... more Chlorophyll (Chl) d is the major pigment in the photosystems (PS) and light-harvesting complex(es) of Acaryochloris marina. Chl a is present in small and variable amounts in PSII and in the light-harvesting complex(es). Isolated PSII complex showed a major fluorescence emission peak at 725 nm and a smaller emission peak due to Chl d at 701 nm, while the PSI complex showed two pools of Chl d, one with emission at 730 nm and the other at 709 nm at 77 K. In PSI and PSII of classical cyanobacteria and of higher plants, where Chl a is the predominant pigment rather than Chl d, these differences are not as pronounced. Light energy absorbed by phycobiliproteins was also active in these Chl d emissions. The major light-harvesting pigment protein is similar to the prochlorophyte Chl-binding protein (pcb) and had a major emission peak at 711 nm. In Cyanobacteria an iron-stress induced Chl-binding protein (isiA) forms a polymeric ring around PSI, and so the effect(s) of iron stress on A. marina where investigated. No clear evidence could be deduced for the formation of an isiA protein under iron stress and no clear changes in the proportion of Chl d :Chl a could be discerned although phycobilins showed a decreased under iron-stress conditions. That Chl d replaces Chl a in all its functions in A. marina is clear; the advantage of this evolutionary development appears to be to enable A. marina to absorb far-red light which occurs in environments where red light is filtered out by other photosynthetic organisms.
Chromatic photoacclimation, photosynthetic electron transport and oxygen evolution in the Chlorophyll d-containing oxyphotobacterium Acaryochloris marina
Gloag RS*, Ritchie RJ, Chen M, Larkum AWD, Quinnell RG. 2007. Biochimica et Biophysica Acta-Bioenergetics. 1767: 127-135
*undergraduate student project
Changes in photosynthetic pigment ratios showed that the Chlorophyll d-dominated oxyphotobacterium Acaryochloris... more Changes in photosynthetic pigment ratios showed that the Chlorophyll d-dominated oxyphotobacterium Acaryochloris marina was able to photoacclimate to different light regimes. Chl d per cell were higher in cultures grown under low irradiance and red or green light compared to those found when grown under high white light, but phycocyanin/Chl d and carotenoid/Chl d indices under the corresponding conditions were lower. Chl a, considered an accessory pigment in this organism, decreased respective to Chl d in low irradiance and low intensity non-white light sources. Blue diode PAM (Pulse Amplitude Modulation) fluorometry was able to be used to measure photosynthesis in Acaryochloris. Light response curves for Acaryochloris were created using both PAM and O(2) electrode. A linear relationship was found between electron transport rate (ETR), measured using a PAM fluorometer, and oxygen evolution (net and gross photosynthesis). Gross photosynthesis and ETR were directly proportional to one another. The optimum light for white light (quartz halogen) was about 206+/-51 micromol m(-2) s(-1) (PAR) (Photosynthetically Active Radiation), whereas for red light (red diodes) the optimum light was lower (109+/-27 micromol m(-2) s(-1) (PAR)). The maximum mean gross photosynthetic rate of Acaryochloris was 73+/-7 micromol mg Chl d(-1) h(-1). The gross photosynthesis/respiration ratio (P(g)/R) of Acaryochloris under optimum conditions was about 4.02+/-1.69. The implications of our findings will be discussed in relation to how photosynthesis is regulated in Acaryochloris.
The major light-harvesting pigment protein of Acaryochloris marina
Chen M, Quinnell R, Larkum A. FEBS letters Volume 514, Issues 2-3, 13 March 2002, pp 149-152
The major light-harvesting protein complex containing chlorophyll (Chl) d was isolated from Acaryochloris marina... more The major light-harvesting protein complex containing chlorophyll (Chl) d was isolated from Acaryochloris marina thylakoid membranes. Isolation was achieved by detergent solubilisation followed by separation on 6–40% sucrose gradients using ultracentrifugation. The best Chl d yield (70%) used 0.3% dodecyl maltoside, 0.15% octyl glucoside, 0.05% zwittergent 3-14 with the detergent:total Chl d ratio around 10:1 (w/w). Characterisation of the light-harvesting pigment protein complex (lhc) involved non-denaturing electrophoresis, SDS–PAGE, absorbance and fluorescence spectroscopy. The main polypeptide in the lhc was shown to be ca. 34 kDa and to contain Chl d and Chl a, indicating that the Acaryochloris lhc is similar to that of prochlorophytes. The Chl a level varied with the culture conditions, which is consistent with previous findings.
Photosynthetic architecture differs in coastal and oceanic diatoms
Robert F. Strzepek & Paul J. Harrison
Diatoms are a key taxon of eukaryotic phytoplankton and a major contributor to global carbon fixation1. They are... more Diatoms are a key taxon of eukaryotic phytoplankton and a major contributor to global carbon fixation1. They are ubiquitous in the marine ecosystem despite marked gradients in environmental properties, such as dissolved iron concentrations, between coastal and oceanic waters. Previous studies have shown that offshore species of diatoms and other eukaryotic algae have evolved lower iron requirements to subsist in iron-poor oceanic waters, but the biochemical mechanisms responsible for their decreased iron demand are unknown2, 3. Here we show, using laboratory-cultured model species, a fundamental difference between a coastal and an oceanic diatom in their photosynthetic architecture. Specifically, the oceanic diatom had up to fivefold lower photosystem I and up to sevenfold lower cytochrome b 6 f complex concentrations than a coastal diatom. These changes to the photosynthetic apparatus markedly decrease the cellular iron requirements of the oceanic diatom but not its photosynthetic rates. However, oceanic diatoms might have also sacrificed their ability to acclimate to rapid fluctuations in light intensity—a characteristic of dynamic and turbid coastal waters. We suggest that diatoms, and probably other eukaryotic algal taxa, exploited this difference in the underwater light climate between oceanic and coastal waters, enabling them to decrease their iron requirements without compromising photosynthetic capacity. This adaptation probably facilitated the colonization of the open ocean by diatoms, and contributes to their persistence in this iron-impoverished environment.
Photosynthetic iron requirements of marine diatoms
PhD Thesis, University of British Columbia, 2003
Marine diatoms play a predominant role in the global carbon cycle but their growth is often limited by iron... more
Marine diatoms play a predominant role in the global carbon cycle but their growth is often limited by iron availability, especially in some oceanic regions. Diatoms from oceanic waters have lower iron requirements than coastal species, but the biochemical basis for this difference is unknown. The photosynthetic apparatus is a probable source of interspecific variability in iron requirements because it is both iron- rich and highly plastic, but it has not been examined in any oceanic diatom species.
I examined the phenotypic and genotypic variability in diatom iron requirements and measured for the first time the cellular concentrations of photosystems in a coastal and an oceanic diatom (Thalassiosira weissflogii and T. oceanica, respectively) acclimated to a range of irradiances and iron concentrations. Growth and photosynthetic rates, elemental composition, and photosynthetic pigments were measured. Photosynthetic electron transport chain complexes were quantified to construct a photosynthetic iron budget.
In iron-limited diatoms, nearly all the cellular iron was required for photosynthetic electron transport. Consequently, cellular and photosynthetic iron requirements co-varied with growth irradiance. Growth and photosynthetic measurements established that the increased iron requirement of low light acclimated cells did not appreciably heighten their susceptibility to iron limitation, or necessarily result in iron- light co-limitation, because the reduction in growth rate (Fe demand) at low light was greater than the increase in Fe requirements. The diatoms acquired comparatively more iron at low light by uncoupling rates of steady state iron uptake from growth and, in the
coastal diatom, by reducing cell volumes. Instead, diatoms were more iron-stressed growing near their maximum capacity under high irradiances.
The photosynthetic iron requirements of the oceanic diatom were substantially diminished: the cytochrome b6f complex and photosystem I, the most iron-rich complexes, were present at extraordinarily low concentrations compared to those found in coastal diatoms. The concentrations of these complexes were comparably low in Fe- replete cells, demonstrating that their abundance was not a consequence of iron deficiency. These results provide the first biochemical explanation for the low cellular iron requirements of an oceanic phytoplankton species.
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Photoprotection capacity differs among diatoms: Possible consequences on the spatial distribution of diatoms related to fluctuations in the underwater light climate
Johann Lavaud, Robert F. Strzepek, and Peter G. Kroth
In this study, we show a fundamental difference between diatom species from different marine habitats in their ability... more In this study, we show a fundamental difference between diatom species from different marine habitats in their ability to cope with changes in irradiance. Estuarine species show a higher and more flexible capacity for photoprotection than oceanic and coastal species, and when exposed to excess light, the impairment of their photosynthetic capacity because of photoinhibition was reduced. This resulted in maintenance of growth in a fluctuating light regime, conferring the estuarine species an adaptive advantage. The ability of diatoms, and to a larger extent other phytoplankton, to occupy a wide range of ecological niches depends critically on their capacity to exploit the differences in underwater light climate. These results might explain how diatoms adapt to the challenge of maintaining optimal photosynthetic production in turbulent waters, in which the rate of light change is high.
Martin StPaul N, J-M Limousin, J Rodriguez-Calcerrada, J Ruffault, S Rambal, MG Letts & L Misson. In press. Photosynthetic sensitivity to drought varies among populations of Quercus ilex along a rainfall gradient. Functional Plant Biology. 39(1):25-37
Drought frequency and intensity are expected to increase in the Mediterranean as a consequence of global climate... more Drought frequency and intensity are expected to increase in the Mediterranean as a consequence of global climate change. To understand how photosynthetic capacity responds to long-term water stress, we measured seasonal patterns of stomatal (SL), mesophyll (MCL) and biochemical limitations (BL) to net photosynthesis (Amax) in three Quercus ilex (L.) populations from sites differing in annual rainfall. In the absence of water stress, stomatal conductance (gs), maximum carboxylation capacity (Vcmax), photosynthetic electron transport rate (Jmax) and Amax were similar among populations. However, as leaf predawn water potential (Ψl,pd) declined, the population from the wettest site showed steeper declines in gs, Vcmax, Jmax and Amax than those from the drier sites. Consequently, SL, MCL and BL increased most steeply in response to decreasing Ψl,pd in the population from the wettest site. The higher sensitivity of Amax to drought was primarily the result of stronger stomatal regulation of water loss. Among-population differences were not observed when gs was used instead of Ψl,pd as a drought stress indicator. Given that higher growth rates, stature and leaf area index were observed at the wettest site, we speculate that hydraulic architecture may explain the greater drought sensitivity of this population. Collectively, these results highlight the importance of considering among-population differences in photosynthetic responses to seasonal drought in large scale process-based models of forest ecosystem function.
Letts, M.G., J. Rodriguez-Calcerrada, V. Rolo & S. Rambal. 2012. Long-term physiological and morphological acclimation by Buxus sempervirens L. to understory and canopy gap light intensities. Trees - Structure and Function. 26(2): 479-491
Physiological and morphological plasticity are essential for growth and reproduction in contrasting light... more Physiological and morphological plasticity are essential for growth and reproduction in contrasting light environments. In dry forest ecosystems, light generalists must also cope with the trade-offs involved in synchronous acclimation to light availability and drought. To understand how the broadleaf evergreen tree-shrub Buxus sempervirens L. (common box) inhabits both understory and successional terrain of Mediterranean forest, we measured photosynthesis–fluorescence light response, morphological traits and architectural characteristics across a light gradient. Our results show that B. sempervirens exhibits stress resistance syndrome, with little change in net photosynthesis rate across a light availability gradient, due to compensatory physiological and morphological acclimation. Light energy processing and dissipation potential were highest in leaves of well-illuminated plants, with higher electron transport rate, fraction of open photosystem II reaction centres, non-photochemical quenching, photorespiration and dark respiration. In contrast, traits reducing light capture efficiency were observed in high light shrubs, including higher leaf mass per unit area, leaf clumping, leaf inclination and branch inclination. We suggest that both physiological and morphological plasticity are required for B. sempervirens to survive across a light gradient in a dry forest ecosystem, while exhibiting homoeostasis in photosynthetic gas exchange. We further speculate that the low growth rate of B. sempervirens is effective in full sun only due to a lack of competition in low resource microsites.
Evolution and Functional Diversification of Fructose Bisphosphate Aldolase Genes in Photosynthetic Marine Diatoms
Diatoms and other chlorophyll-c containing, or chromalveolate, algae are among the most productive and diverse... more Diatoms and other chlorophyll-c containing, or chromalveolate, algae are among the most productive and diverse phytoplankton in the ocean. Evolutionarily, chlorophyll-c algae are linked through common, although not necessarily monophyletic, acquisition of plastid endosymbionts of red as well as most likely green algal origin. There is also strong evidence for a relatively high level of lineage-specific bacterial gene acquisition within chromalveolates. Therefore, analyses of gene content and derivation in chromalveolate taxa have indicated particularly diverse origins of their overall gene repertoire. As a single group of functionally related enzymes spanning two distinct gene families, fructose 1,6-bisphosphate aldolases (FBAs) illustrate the influence on core biochemical pathways of specific evolutionary associations among diatoms and other chromalveolates with various plastid-bearing and bacterial endosymbionts. Protein localization and activity, gene expression, and phylogenetic analyses indicate that the pennate diatom Phaeodactylum tricornutum contains five FBA genes with very little overall functional overlap. Three P. tricornutum FBAs, one class I and two class II, are plastid localized, and each appears to have a distinct evolutionary origin as well as function. Class I plastid FBA appears to have been acquired by chromalveolates from a red algal endosymbiont, whereas one copy of class II plastid FBA is likely to have originated from an ancient green algal endosymbiont. The other copy appears to be the result of a chromalveolate-specific gene duplication. Plastid FBA I and chromalveolate-specific class II plastid FBA are localized in the pyrenoid region of the chloroplast where they are associated with β-carbonic anhydrase, which is known to play a significant role in regulation of the diatom carbon concentrating mechanism. The two pyrenoid-associated FBAs are distinguished by contrasting gene expression profiles under nutrient limiting compared with optimal CO2 fixation conditions, suggestive of a distinct specialized function for each. Cytosolically localized FBAs in P. tricornutum likely play a role in glycolysis and cytoskeleton function and seem to have originated from the stramenopile host cell and from diatom-specific bacterial gene transfer, respectively.
Morphological and photosynthetic acclimation of Potamogeton perfoliatus to differenet environments of Lake Balaton
by Viktor Tóth
Co-authored with: Ágnes Vári, Szilveszter Lugosi
Comparative significance and synchronicity of morphological and photosynthetic adjustments of Potamogeton perfoliatus... more Comparative significance and synchronicity of morphological and photosynthetic adjustments of Potamogeton perfoliatus to shore-specific environments were examined on plants growing at the maximum depth of colonisation of the northern and southern shores of Lake Balaton. The shore-specific environments did not affect photophysiological parameters: the photosynthesis of plants on both shores was high, coupled with low respiration and compensation irradiances. In contrast, morphological and habitual differences between the shores were significant: plants of the shady, northern shore had lighter, but larger leaves, and longer internodes concentrated in the apex of the plants. Thus, photophysiological variability of Potamogeton does not follow its morphological differentiation.
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