Photosynthesis Research

Current research articles.


The journal Photosynthesis Research is an international journal dealing with both basic and applied aspects of photosynthesis. The journal publishes research at all levels of plant organization: molecular, subcellular, cellular, whole plant, canopy, ecosystem and global.

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Photosynthesis Research - Abstracts



Evolution of the acceptor side of photosystem I: ferredoxin, flavodoxin, and ferredoxin-NADP + oxidoreductase

Abstract

The development of oxygenic photosynthesis by primordial cyanobacteria ~2.7 billion years ago led to major changes in the components and organization of photosynthetic electron transport to cope with the challenges of an oxygen-enriched atmosphere. We review herein, following the seminal contributions as reported by Jaganathan et al. (Functional genomics and evolution of photosynthetic systems, vol 33, advances in photosynthesis and respiration, Springer, Dordrecht, 2012), how these changes affected carriers and enzymes at the acceptor side of photosystem I (PSI): the electron shuttle ferredoxin (Fd), its isofunctional counterpart flavodoxin (Fld), their redox partner ferredoxin-NADP+ reductase (FNR), and the primary PSI acceptors F x and F A/F B. Protection of the [4Fe–4S] centers of these proteins from oxidative damage was achieved by strengthening binding between the F A/F B polypeptide and the reaction center core containing F x, therefore impairing O2 access to the clusters. Immobilization of F A/F B in the PSI complex led in turn to the recruitment of new soluble electron shuttles. This function was fulfilled by oxygen-insensitive [2Fe–2S] Fd, in which the reactive sulfide atoms of the cluster are shielded from solvent by the polypeptide backbone, and in some algae and cyanobacteria by Fld, which employs a flavin as prosthetic group and is tolerant to oxidants and iron limitation. Tight membrane binding of FNR allowed solid-state electron transfer from PSI bridged by Fd/Fld. Fine tuning of FNR catalytic mechanism led to formidable increases in turnover rates compared with FNRs acting in heterotrophic pathways, favoring Fd/Fld reduction instead of oxygen reduction.


Datum: 01.12.2017


Association of Ferredoxin:NADP + oxidoreductase with the photosynthetic apparatus modulates electron transfer in Chlamydomonas reinhardtii

Abstract

Ferredoxins (FDX) and the FDX:NADP+ oxidoreductase (FNR) represent a key junction of electron transport downstream of photosystem I (PSI). Dynamic recruitment of FNR to the thylakoid membrane has been considered as a potential mechanism to define the fate of photosynthetically derived electrons. In this study, we investigated the functional importance of the association of FNR with the photosynthetic apparatus in Chlamydomonas reinhardtii. In vitro assays based on NADP+ photoreduction measurements as well as NMR chemical shift perturbation analyses showed that FNR preferentially interacts with FDX1 compared to FDX2. Notably, binding of FNR to a PSI supercomplex further enhanced this preference for FDX1 over FDX2, suggesting that FNR is potentially capable of channelling electrons towards distinct routes. NADP+ photoreduction assays and immunoblotting revealed that the association of FNR with the thylakoid membrane including the PSI supercomplex is impaired in the absence of Proton Gradient Regulation 5 (PGR5) and/or Proton Gradient Regulation 5-Like photosynthetic phenotype 1 (PGRL1), implying that both proteins, directly or indirectly, contribute to the recruitment of FNR to the thylakoid membrane. As assessed via in vivo absorption spectroscopy and immunoblotting, PSI was the primary target of photodamage in response to high-light stress in the absence of PGR5 and/or PGRL1. Anoxia preserved the activity of PSI, pointing to enhanced electron donation to O2 as the source of the observed PSI inactivation and degradation. These findings establish another perspective on PGR5/PGRL1 knockout-related phenotypes and potentially interconnect FNR with the regulation of photosynthetic electron transport and PSI photoprotection in C. reinhardtii.


Datum: 01.12.2017


Identification of the ferredoxin interaction sites on ferredoxin-dependent glutamate synthase from Synechocystis sp. PCC 6803

Abstract

Based on in silico docking methods, five amino acids in glutamate synthase (Gln-467, His-1144, Asn-1147, Arg-1162, and Trp-676) likely constitute key binding residues in the interface of a glutamate synthase:ferredoxin complex. Although all interfacial mutants studied showed the ability to form a complex under low ionic strength, these docking mutations showed significantly less ferredoxin-dependent activities, while still retaining enzymatic activity. Furthermore, isothermal titration calorimetry showed a possible 1:2 molar ratio between the wild-type glutamate synthase and ferredoxin. However, each of our interfacial mutants showed only a 1:1 complex with ferredoxin, suggesting that the mutations directly affect the glutamate synthase:ferredoxin heterodimer interface.


Datum: 01.12.2017


Photosynthetic fuel for heterologous enzymes: the role of electron carrier proteins

Abstract

Plants, cyanobacteria, and algae generate a surplus of redox power through photosynthesis, which makes them attractive for biotechnological exploitations. While central metabolism consumes most of the energy, pathways introduced through metabolic engineering can also tap into this source of reducing power. Recent work on the metabolic engineering of photosynthetic organisms has shown that the electron carriers such as ferredoxin and flavodoxin can be used to couple heterologous enzymes to photosynthetic reducing power. Because these proteins have a plethora of interaction partners and rely on electrostatically steered complex formation, they form productive electron transfer complexes with non-native enzymes. A handful of examples demonstrate channeling of photosynthetic electrons to drive the activity of heterologous enzymes, and these focus mainly on hydrogenases and cytochrome P450s. However, competition from native pathways and inefficient electron transfer rates present major obstacles, which limit the productivity of heterologous reactions coupled to photosynthesis. We discuss specific approaches to address these bottlenecks and ensure high productivity of such enzymes in a photosynthetic context.


Datum: 01.12.2017


Gallium ferredoxin as a tool to study the effects of ferredoxin binding to photosystem I without ferredoxin reduction

Abstract

Reduction of ferredoxin by photosystem I (PSI) involves the [4Fe–4S] clusters FA and FB harbored by PsaC, with FB being the direct electron transfer partner of ferredoxin (Fd). Binding of the redox-inactive gallium ferredoxin to PSI was investigated by flash-absorption spectroscopy, studying both the P700+ decay and the reduction of the native iron Fd in the presence of FdGa. FdGa binding resulted in a faster recombination between P700+ and (FA, FB), a slower electron escape from (FA, FB) to exogenous acceptors, and a decreased amount of intracomplex FdFe reduction, in accordance with competitive binding between FdFe and FdGa. [FdGa] titrations of these effects revealed that the dissociation constant for the PSI:FdGa complex is different whether (FA, FB) is oxidized or singly reduced. This difference in binding, together with the increase in the recombination rate, could both be attributed to a c. −30 mV shift of the midpoint potential of (FA, FB), considered as a single electron acceptor, due to FdGa binding. This effect of FdGa binding, which can be extrapolated to FdFe because of the highly similar structure and the identical charge of the two Fds, should help irreversibility of electron transfer within the PSI:Fd complex. The effect of Fd binding on the individual midpoint potentials of FA and FB is also discussed with respect to the possible consequences on intra-PSI electron transfer and on the escape process.


Datum: 01.12.2017


Structural basis for the isotype-specific interactions of ferredoxin and ferredoxin: NADP + oxidoreductase: an evolutionary switch between photosynthetic and heterotrophic assimilation

Abstract

In higher plants, ferredoxin (Fd) and ferredoxin-NADP+ reductase (FNR) are each present as distinct isoproteins of photosynthetic type (leaf type) and non-photosynthetic type (root type). Root-type Fd and FNR are considered to facilitate the electron transfer from NADPH to Fd in the direction opposite to that occurring in the photosynthetic processes. We previously reported the crystal structure of the electron transfer complex between maize leaf FNR and Fd (leaf FNR:Fd complex), providing insights into the molecular interactions of the two proteins. Here we show the 2.49 Å crystal structure of the maize root FNR:Fd complex, which reveals that the orientation of FNR and Fd remarkably varies from that of the leaf FNR:Fd complex, giving a structural basis for reversing the redox path. Root FNR was previously shown to interact preferentially with root Fd over leaf Fd, while leaf FNR retains similar affinity for these two types of Fds. The structural basis for such differential interaction was investigated using site-directed mutagenesis of the isotype-specific amino acid residues on the interface of Fd and FNR, based on the crystal structures of the FNR:Fd complexes from maize leaves and roots. Kinetic and physical binding analyses of the resulting mutants lead to the conclusion that the rearrangement of the charged amino acid residues on the Fd-binding surface of FNR confers isotype-specific interaction with Fd, which brings about the evolutional switch between photosynthetic and heterotrophic redox cascades.


Datum: 01.12.2017


Evolution of Chlamydomonas reinhardtii ferredoxins and their interactions with [FeFe]-hydrogenases

Abstract

Ferredoxins are soluble iron sulphur proteins which function as electron donors in a number of metabolic pathways in a broad range of organisms. In photosynthetic organisms, PETF, or ferredoxin 1 (FDX1), is the most studied ferredoxin due to its essential role in photosynthesis, where it transfers electrons from photosystem I to ferredoxin-NADP+ oxidoreductase. However, PETF can also transfer electrons to a large number of other proteins. One important PETF electron acceptor found in green microalgae is the biologically and biotechnologically important [FeFe]-hydrogenase HYDA, which catalyses the production of molecular hydrogen (H2) from protons and electrons. The interaction between PETF and HYDA is of considerable interest, as PETF is the primary electron donor to HYDA and electron supply is one of the main limiting factors for H2 production on a commercial scale. Although there is no three dimensional structure of the PETF–HYDA complex available, protein variants, nuclear magnetic resonance titration studies, molecular dynamics and modelling have provided considerable insight into the residues essential for forming and maintaining the interaction. In this review, we discuss the most recent findings with regard to ferredoxin-HYDA interactions and the evolution of the various Chlamydomonas reinhardtii ferredoxin isoforms. Finally, we provide an outlook on new PETF-based biotechnological approaches for improved H2 production efficiencies.


Datum: 01.12.2017


Preface: ferredoxin


Datum: 01.12.2017


Redox changes of ferredoxin, P700, and plastocyanin measured simultaneously in intact leaves

Abstract

Properties and performance of the recently introduced Dual/KLAS-NIR spectrophotometer for simultaneous measurements of ferredoxin (Fd), P700, and plastocyanin (PC) redox changes, together with whole leaf chlorophyll a (Chl) fluorescence (emission >760, 540 nm excitation) are outlined. Spectral information on in vivo Fd, P700, and PC in the near-infrared region (NIR, 780–1000 nm) is presented, on which the new approach is based. Examples of application focus on dark–light and light–dark transitions, where maximal redox changes of Fd occur. After dark-adaptation, Fd reduction induced by moderate light parallels the Kautsky effect of Chl fluorescence induction. Both signals are affected analogously by removal of O2. A rapid type of Fd reoxidation, observed after a short pulse of light before light activation of linear electron transport (LET), is more pronounced in C4 compared to C3 leaves and interpreted to reflect cyclic PS I (CET). Light activation of LET, as assessed via the rate of Fd reoxidation after short light pulses, occurs at very low intensities and is slowly reversed (half-time ca. 20 min). Illumination with strong far-red light (FR, 740 nm) reveals two fractions of PS I, PS I (LET), and PS I (CET), differing in the rates of Fd reoxidation upon FR-off and the apparent equilibrium constants between P700 and PC. Parallel information on oxidation of Fd and reduction of P700 plus PC proves essential for identification of CET. Comparison of maize (C4) with sunflower and ivy (C3) responses leads to the conclusion that segregation of two types of PS I may not only exist in C4 (mesophyll and bundle sheath cells), but also in C3 photosynthesis (grana margins plus end membranes and stroma lamellae).


Datum: 01.12.2017


Interaction and electron transfer between ferredoxin–NADP + oxidoreductase and its partners: structural, functional, and physiological implications

Abstract

Ferredoxin–NADP+ reductase (FNR) catalyzes the last step of linear electron transfer in photosynthetic light reactions. The FAD cofactor of FNR accepts two electrons from two independent reduced ferredoxin molecules (Fd) in two sequential steps, first producing neutral semiquinone and then the fully anionic reduced, or hydroquinone, form of the enzyme (FNRhq). FNRhq transfers then both electrons in a single hydride transfer step to NADP+. We are presenting the recent progress in studies focusing on Fd:FNR interaction and subsequent electron transfer processes as well as on interaction of FNR with NADP+/H followed by hydride transfer, both from the structural and functional point of views. We also present the current knowledge about the physiological role(s) of various FNR isoforms present in the chloroplasts of higher plants and the functional impact of subchloroplastic location of FNR. Moreover, open questions and current challenges about the structure, function, and physiology of FNR are discussed.


Datum: 01.12.2017


Anatomical and diffusional determinants inside leaves explain the difference in photosynthetic capacity between Cypripedium and Paphiopedilum , Orchidaceae

Abstract

Comparing with other angiosperms, most members within the family Orchidaceae have lower photosynthetic capacities. However, the underlying mechanisms remain unclear. Cypripedium and Paphiopedilum are closely related phylogenetically in Orchidaceae, but their photosynthetic performances are different. We explored the roles of internal anatomy and diffusional conductance in determining photosynthesis in three Cypripedium and three Paphiopedilum species, and quantitatively analyzed their diffusional and biochemical limitations to photosynthesis. Paphiopedilum species showed lower light-saturated photosynthetic rate (A N), stomatal conductance (g s), and mesophyll conductance (g m) than Cypripedium species. A N was positively correlated with g s and g m. And yet, in both species A N was more strongly limited by g m than by biochemical factors or g s. The greater g s of Cypripedium was mainly affected by larger stomatal apparatus area and smaller pore depth, while the less g m of Paphiopedilum was determined by the reduced surface area of mesophyll cells and chloroplasts exposed to intercellular airspace per unit of leaf area, and much thicker cell wall thickness. These results suggest that leaf anatomical structure is the key factor affecting g m, which is largely responsible for the difference in photosynthetic capacity between those two genera. Our findings provide new insight into the photosynthetic physiology and functional diversification of orchids.


Datum: 20.11.2017


Mechanisms of drought-induced dissipation of excitation energy in sun- and shade-adapted drought-tolerant mosses studied by fluorescence yield change and global and target analysis of fluorescence decay kinetics

Abstract

Some mosses stay green and survive long even under desiccation. Dissipation mechanisms of excess excitation energy were studied in two drought-tolerant moss species adapted to contrasting niches: shade-adapted Rhytidiadelphus squarrosus and sun-adapted Rhytidium rugosum in the same family. (1) Under wet conditions, a light-induced nonphotochemical quenching (NPQ) mechanism decreased the yield of photosystem II (PSII) fluorescence in both species. The NPQ extent saturated at a lower illumination intensity in R. squarrosus, suggesting a larger PSII antenna size. (2) Desiccation reduced the fluorescence intensities giving significantly lower F 0 levels and shortened the overall fluorescence lifetimes in both R. squarrosus and R. rugosum, at room temperature. (3) At 77 K, desiccation strongly reduced the PSII fluorescence intensity. This reduction was smaller in R. squarrosus than in R. rugosum. (4) Global and target analysis indicated two different mechanisms of energy dissipation in PSII under desiccation: the energy dissipation to a desiccation-formed strong fluorescence quencher in the PSII core in sun-adapted R. rugosum (type-A quenching) and (5) the moderate energy dissipation in the light-harvesting complex/PSII in shade-adapted R. squarrosus (type-B quenching). The two mechanisms are consistent with the different ecological niches of the two mosses.


Datum: 18.11.2017


Novel quantitative insights into carbon sources for synthesis of poly hydroxybutyrate in Synechocystis PCC 6803

Abstract

Many freshwater cyanobacteria accumulate polyhydroxybutyrate (PHB) under nitrogen or phosphorus deprivation. While prior literature has shed lights on transcriptomic and metabolomic changes in the model cyanobacterium Synechocystis PCC 6803 cells, the quantitative contributions of the newly fixed carbon following nitrogen deprivation or the externally added acetate to PHB synthesis are not clear. Similarly, it is not clear how photomixotrophy affects precursor contributions. In this study, we show that (i) the pre-growth mode (photoautotrophic or photomixotrophic), while significantly impacting glycogen levels, does not have any significant effect on PHB levels, (ii) the carbon fixed following nitrogen deprivation contributes 26% of C for PHB synthesis in photoautotrophically pre-grown cells and its contribution to the PHB synthesis goes down with the addition of acetate at the resuspension phase or with photomixotrophic pre-growth, (iii) the acetate added at the start of nitrogen deprivation, doubles the intracellular PHB levels and contributes 44–48% to PHB synthesis and this value is not greatly affected by how the cells were pre-grown. Indirectly, the labeling studies also show that the intracellular C recycling is the most important source of precursors for PHB synthesis, contributing about 74–87% of the C for PHB synthesis in the absence of acetate. The addition of acetate significantly reduces its contribution. In photoautotrophic pre-growth followed by acetate addition under nitrogen starvation, the contribution of intracellular C reduces to about 34%. Thus, our study provides several novel quantitative insights on how prior nutritional status affects the precursor contributions for PHB synthesis.


Datum: 09.11.2017


Salt stress effects on the photosynthetic electron transport chain in two chickpea lines differing in their salt stress tolerance

Abstract

The main objective of this study was to evaluate the effects of salt stress on the photosynthetic electron transport chain using two chickpea lines (Cicer arietinum L.) differing in their salt stress tolerance at the germination stage (AKN 87 and AKN 290). Two weeks after sowing, seedlings were exposed to salt stress for 2 weeks and irrigated with 200 ml of 200 mM NaCl every 2 days. The polyphasic OJIP fluorescence transient and the 820-nm transmission kinetics (photosystem I) were used to evaluate the effects of salt stress on the functionality of the photosynthetic electron transport chain. It was observed that a signature for salt stress was a combination of a higher J step (VJ), a smaller IP amplitude, and little or no effect on the primary quantum yield of PSII (φPo). We observed for AKN 290 a shorter leaf life cycle, which may represent a mechanism to cope with salt stress. For severely salt-stressed leaves, an inhibition of electron flow between the PQ pool and P700 was found. The data also suggest that the properties of electron flow beyond PSI are affected by salt stress.


Datum: 09.11.2017


Red shift in the spectrum of a chlorophyll species is essential for the drought-induced dissipation of excess light energy in a poikilohydric moss, Bryum argenteum

Abstract

Some mosses are extremely tolerant of drought stress. Their high drought tolerance relies on their ability to effectively dissipate absorbed light energy to heat under dry conditions. The energy dissipation mechanism in a drought-tolerant moss, Bryum argenteum, has been investigated using low-temperature picosecond time-resolved fluorescence spectroscopy. The results are compared between moss thalli samples harvested in Antarctica and in Japan. Both samples show almost the same quenching properties, suggesting an identical drought tolerance mechanism for the same species with two completely different habitats. A global target analysis was applied to a large set of data on the fluorescence-quenching dynamics for the 430-nm (chlorophyll-a selective) and 460-nm (chlorophyll-b and carotenoid selective) excitations in the temperature region from 5 to 77 K. This analysis strongly suggested that the quencher is formed in the major peripheral antenna of photosystem II, whose emission spectrum is significantly broadened and red-shifted in its quenched form. Two emission components at around 717 and 725 nm were assigned to photosystem I (PS I). The former component at around 717 nm is mildly quenched and probably bound to the PS I core complex, while the latter at around 725 nm is probably bound to the light-harvesting complex. The dehydration treatment caused a blue shift of the PS I emission peak via reduction of the exciton energy flow to the pigment responsible for the 725 nm band.


Datum: 09.11.2017


C-terminal residues of ferredoxin-NAD(P) + reductase from Chlorobaculum tepidum are responsible for reaction dynamics in the hydride transfer and redox equilibria with NADP + /NADPH

Abstract

Ferredoxin-NAD(P)+ reductase ([EC 1.18.1.2], [EC 1.18.1.3]) from Chlorobaculum tepidum (CtFNR) is structurally homologous to the bacterial NADPH-thioredoxin reductase (TrxR), but possesses a unique C-terminal extension relative to TrxR that interacts with the isoalloxazine ring moiety of the flavin adenine dinucleotide prosthetic group. In this study, we introduce truncations to the C-terminal residues to examine their role in the reactions of CtFNR with NADP+ and NADPH by spectroscopic and kinetic analyses. The truncation of the residues from Tyr326 to Glu360 (the whole C-terminal extension region), from Phe337 to Glu360 (omitting Phe337 on the re-face of the isoalloxazine ring) and from Ser338 to Glu360 (leaving Phe337 intact) resulted in a blue-shift of the flavin absorption bands. The truncations caused a slight increase in the dissociation constant toward NADP+ and a slight decrease in the Michaelis constant toward NADPH in steady-state assays. Pre-steady-state studies of the redox reaction with NADPH demonstrated that deletions of Tyr326–Glu360 decreased the hydride transfer rate, and the amount of reduced enzyme increased at equilibrium relative to wild-type CtFNR. In contrast, the deletions of Phe337–Glu360 and Ser338–Glu360 resulted in only slight changes in the reaction kinetics and redox equilibrium. These results suggest that the C-terminal region of CtFNR is responsible for the formation and stability of charge-transfer complexes, leading to changes in redox properties and reactivity toward NADP+/NADPH.


Datum: 08.11.2017


Crystal structure of Psb27 from Arabidopsis thaliana determined at a resolution of 1.85 Å

Abstract

Proper biogenesis and maintenance of photosynthetic thylakoid membrane complexes are essential for the photosynthetic light reactions. A thylakoid lumenal protein, Psb27, plays a vital role in assembly or/and maintenance of photosystem II (PSII). In cyanobacteria, it is a small lipoprotein docked to the lumenal side of PSII, and functions in the assembly of the Mn4Ca cluster and in the PSII repair cycle. However, Psb27 from Arabidopsis thaliana is not a lipoprotein, and it is involved in PSII repair and acclimation to fluctuating light stress, suggesting a functional divergence between Arabidopsis Psb27 and cyanobacterial Psb27s. To gain a better understanding of Psb27 from higher plants, we determined the crystal structure of Arabidopsis Psb27 by X-ray crystallography at a resolution of 1.85 Å. The structure of Arabidopsis Psb27 is a four-helix bundle, similar to its orthologues from cyanobacteria. However, there are several structural differences between Arabidopsis Psb27 and cyanobacterial Psb27s concerning the overall molecular shape, the N- and C-terminal structures, and the surface charge. These differences suggest that Psb27 from higher plants and cyanobacteria may function differently.


Datum: 02.11.2017


Christoph Beck (1941–2017): a Chlamydomonas biologist


Datum: 01.11.2017


Redox potentials of ubiquinone, menaquinone, phylloquinone, and plastoquinone in aqueous solution

Abstract

Quinones serve as redox active cofactors in bacterial photosynthetic reaction centers: photosystem I, photosystem II, cytochrome bc 1, and cytochrome b 6 f. In particular, ubiquinone is ubiquitous in animals and most bacteria and plays a key role in several cellular processes, e.g., mitochondrial electron transport. Their experimentally measured redox potential values for one-electron reduction E m(Q/Q·−) were already reported in dimethylformamide (DMF) versus saturated calomel electrode but not in water versus normal hydrogen electrode (NHE). We calculated E m(Q/Q·−) of 1,4-quinones using a quantum chemical approach. The calculated energy differences of reduction of Q to Q·− in DMF and water for 1,4-quinone derivatives correlated highly with the experimentally measured E m(Q/Q·−) in DMF and water, respectively. E m(Q/Q·−) were calculated to be −163 mV for ubiquinone, −260 mV for menaquinone and phylloquinone, and −154 mV for plastoquinone in water versus NHE.


Datum: 01.11.2017


Acclimation of Swedish and Italian ecotypes of Arabidopsis thaliana to light intensity

Abstract

This study addressed whether ecotypes of Arabidopsis thaliana from Sweden and Italy exhibited differences in foliar acclimation to high versus low growth light intensity, and compared CO2 uptake under growth conditions with light- and CO2-saturated intrinsic photosynthetic capacity and leaf morphological and vascular features. Differential responses between ecotypes occurred mainly at the scale of leaf architecture, with thicker leaves with higher intrinsic photosynthetic capacities and chlorophyll contents per leaf area, but no difference in photosynthetic capacity on a chlorophyll basis, in high light-grown leaves of the Swedish versus the Italian ecotype. Greater intrinsic photosynthetic capacity per leaf area in the Swedish ecotype was accompanied by a greater capacity of vascular infrastructure for sugar and water transport, but this was not associated with greater CO2 uptake rates under growth conditions. The Swedish ecotype with its thick leaves is thus constructed for high intrinsic photosynthetic and vascular flux capacity even under growth chamber conditions that may not permit full utilization of this potential. Conversely, the Swedish ecotype was less tolerant of low growth light intensity than the Italian ecotype, with smaller rosette areas and lesser aboveground biomass accumulation in low light-grown plants. Foliar vein density and stomatal density were both enhanced by high growth light intensity with no significant difference between ecotypes, and the ratio of water to sugar conduits was also similar between the two ecotypes during light acclimation. These findings add to the understanding of the foliar vasculature’s role in plant photosynthetic acclimation and adaptation.


Datum: 01.11.2017






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