Photosynthetic Growth Research Articles

Influence of Magnesium on Photosynthetic Characteristics and Growth Effects of Sugarcane at Seedling Stage

In this study, the effects of different concentrations of magnesium on photosynthetic characteristics and growth of sugarcane cultivars Roc22 and YT00-236 at seedling stage were investigated by combined cultivation of sand culture with nutrient solution. The results showed that under the stress of low magnesium, the synthesis and photosynthesis of chlorophyll are blocked with significantly decreased biomass accumulation, increased root-shoot ratio and slowed growth rate. Appropriate treatment of magnesium (0.1mmol/L) can promote sugarcane photosynthesis with maximal biomass, significantly decreased root-shoot ratio and increased growth rate. Excess With excessive treatment of magnesium (1mmol/L), the photosynthetic rate is lower than the value under low magnesium stress; Once the overall growth of sugarcane is inhibited, however, the growth is better than low magnesium stress. It is found that the photosynthesis and growth effects of ROC22 are stronger than that of YT00-236. It is preliminarily deduced that ROC22 is a sensitive variety of magnesium.

Effect of temporally heterogeneous light on photosynthetic light use efficiency, plant acclimation and growth in Abatia parviflora.

Individual leaves have a unique instantaneous photosynthetic photon flux density (PPFD) at which net photosynthetic light use efficiency (ϵL, the ratio between net photosynthesis and PPFD) is maximised (PPFDϵmax). When PPFD is above or below PPFDϵmax, efficiency declines. Thus, we hypothesised that heterogeneous PPFD conditions should increase the amount of time leaves photosynthesise at a PPFD different than PPFDϵmax and result in reduced growth. To date, this prediction has not been rigorously tested. Here, we exposed seedlings of Abatia parviflora Ruiz & Pav to light regimes of equal total daily irradiance but with three different daily time courses of PPFD: constant PPFD (No_H), low heterogeneity (Low_H) and high heterogeneity (High_H). Mean ϵL, leaf daily photosynthesis and plant growth were all significantly higher in No_H and Low_H plants than in High_H plants, supporting our hypothesis. In addition, mean ϵL was positively related to final plant biomass. Unexpectedly, High_H plants had more etiolated stems and more horizontal leaves than No_H and Low_H plants, possibly due to exposure to low PPFD in the morning and afternoon. In conclusion, PPFD heterogeneity had an important effect on average ϵL, photosynthesis and growth, but also on allocation and plant morphology.

Effects of short light/dark cycles on photosynthetic pathway switching and growth of medicinal Dendrobium officinale in aeroponic cultivation

Effects of short light/dark cycles on photosynthetic pathway switching and growth of medicinal Dendrobium officinale in aeroponic cultivation

Spermidine enhanced resistance of Chlorella to high levels of CO2 and light intensity for improving photosynthetic growth rate.

In order to promote the photosynthetic growth rate of Chlorella in the presence of flue gas CO2 from coal-fired power plants, spermidine was first used to enhance cellular resistance to a high CO2 concentration (15%) and high light intensity (30 000 lux). It was found that low concentrations (100–300 μM) of spermidine significantly enhanced the photosynthetic growth rate of Chlorella. The accelerated cell division decreased the cell diameter from 3.64 μm to 2.71 μm and the fractal dimension from 1.60 to 1.49, and the activity of total superoxide dismutase (T-SOD) increased from 0.48 U mL−1 to 5.33 U mL−1. Expression levels of key enzymes of photosystems I and II, ATP synthase and transportase markedly increased, thereby enhancing the electron transport and energy supply that reduced oxidative damage. Finally, an enhanced cellular resistance to the high CO2 concentration and high light intensity increased the biomass yield from 0.11 g L−1 to 1.71 g L−1 (300 μM).

A semi-mechanistic model describing the influence of light and temperature on the respiration and photosynthetic growth of Chlorella vulgaris

The influence of light and temperature on microalgae kinetics has been assessed extensively and many models have been developed. However, limited attention has been paid to the influence of light and temperature on microalgae respiration and growth under conditions inducing (strong) photoinhibition and no clear consensus has been made on which model to use. Based on experimental data collected using a combined respirometer-titrimeter, a previously developed microalgae model (Decostere et al., 2016b) was first extended with a respiration process (r = rmin + δ μ). It was found that the dark respiration (rmin) was depending on both light and temperature and increased at conditions inducing photoinhibition and heat stress. Furthermore, out of five models describing the influence of light and temperature on the microalgae growth rate, the model of Dermoun et al. (1992) was determined to be the best suited model.

NanoSIMS single cell analyses reveal the contrasting nitrogen sources for small phytoplankton

Nitrogen (N) is a limiting nutrient in vast regions of the world’s oceans, yet the sources of N available to various phytoplankton groups remain poorly understood. In this study, we investigated inorganic carbon (C) fixation rates and nitrate (NO3−), ammonium (NH4+) and urea uptake rates at the single cell level in photosynthetic pico-eukaryotes (PPE) and the cyanobacteria Prochlorococcus and Synechococcus. To that end, we used dual 15N and 13C-labeled incubation assays coupled to flow cytometry cell sorting and nanoSIMS analysis on samples collected in the North Pacific Subtropical Gyre (NPSG) and in the California Current System (CCS). Based on these analyses, we found that photosynthetic growth rates (based on C fixation) of PPE were higher in the CCS than in the NSPG, while the opposite was observed for Prochlorococcus. Reduced forms of N (NH4+ and urea) accounted for the majority of N acquisition for all the groups studied. NO3− represented a reduced fraction of total N uptake in all groups but was higher in PPE (17.4 ± 11.2% on average) than in Prochlorococcus and Synechococcus (4.5 ± 6.5 and 2.9 ± 2.1% on average, respectively). This may in part explain the contrasting biogeography of these picoplankton groups. Moreover, single cell analyses reveal that cell-to-cell heterogeneity within picoplankton groups was significantly greater for NO3− uptake than for C fixation and NH4+ uptake. We hypothesize that cellular heterogeneity in NO3− uptake within groups facilitates adaptation to the fluctuating availability of NO3− in the environment.

Thylakoid membrane lipid sulfoquinovosyl-diacylglycerol (SQDG) is required for full functioning of photosystem II in Thermosynechococcus elongatus

Sulfoquinovosyl-diacylglycerol (SQDG) is one of the four lipids present in the thylakoid membranes. Depletion of SQDG causes different degrees of effects on photosynthetic growth and activities in different organisms. Four SQDG molecules bind to each monomer of photosystem II (PSII), but their role in PSII function has not been characterized in detail, and no PSII structure without SQDG has been reported. We analyzed the activities of PSII from an SQDG-deficient mutant of the cyanobacterium Thermosynechococcus elongatus by various spectroscopic methods, which showed that depletion of SQDG partially impaired the PSII activity by impairing secondary quinone (QB) exchange at the acceptor site. We further solved the crystal structure of the PSII dimer from the SQDG deletion mutant at 2.1 Å resolution and found that all of the four SQDG-binding sites were occupied by other lipids, most likely PG molecules. Replacement of SQDG at a site near the head of QB provides a possible explanation for the QB impairment. The replacement of two SQDGs located at the monomer-monomer interface by other lipids decreased the stability of the PSII dimer, resulting in an increase in the amount of PSII monomer in the mutant. The present results thus suggest that although SQDG binding in all of the PSII-binding sites is necessary to fully maintain the activity and stability of PSII, replacement of SQDG by other lipids can partially compensate for their functions.

Nature inspired fractal tree-like photobioreactor via 3D printing for CO2 capture by microaglae

Based on the bionic fractal theory, a fractal tree-like photobioreactor (PBR) with high surface area to volume ratio is designed on the basis of bifurcation tree algorithm and manufactured via 3D printing technology. Numerical simulation and experimental results show that the fractal structure has a good flow performance and can lead to secondary flow, which is beneficial to enhance the turbulence and produce smaller bubble sizes. Chlorella culture in the fractal tree-like PBR has a higher Fv/Fm (Chlorophyll fluorescence parameter), close to 0.767, and higher efficiency of photosynthetic growth as well as CO2 capture, compared with multitubular PBR and conventional acrylic column reactors. Therefore, the fractal tree-like PBR can improve the efficiency of light energy utilization and bioreaction. Combined with 3D printing technology, fractal PBR blazes a new trail for process intensification on the microalgae cultivation.

Energy shifts induce membrane sequestration of DraG in Rhodospirillum rubrum independent of the ammonium transporters and diazotrophic conditions.

ABSTRACTMetabolic regulation of Rhodospirillum rubrum nitrogenase is mediated at the post-translational level by the enzymes DraT and DraG when subjected to changes in nitrogen or energy status. DraT is activated during switch-off, while DraG is inactivated by reversible membrane association. We confirm here that the ammonium transporter, AmtB1, rather than its paralog AmtB2, is required for ammonium induced switch-off. Amongst several substitutions at the N100 position in DraG, only N100K failed to locate to the membrane following ammonium shock, suggesting loss of interaction through charge repulsion. When switch-off was induced by lowering energy levels, either by darkness during photosynthetic growth or oxygen depletion under respiratory conditions, reversible membrane sequestration of DraG was independent of AmtB proteins and occurred even under non-diazotrophic conditions. We propose that under these conditions, changes in redox status or possibly membrane potential induce interactions between DraG and another membrane protein in response to the energy status.

Light Effects on Photosynthetic Capacity and Growth of Papaya (Carica papaya L.): A Short Review

Light Effects on Photosynthetic Capacity and Growth of Papaya (Carica papaya L.): A Short Review

How do microalgae perceive light in a high-rate pond? Towards more realistic Lagrangian experiments.

Hydrodynamics in a high-rate production reactor for microalgae cultivation affects the light history perceived by cells. The interplay between cell movement and medium turbidity leads to a complex light pattern, whose forcing effects on photosynthesis and photoacclimation dynamics are non-trivial. Hydrodynamics of high density algal ponds mixed by a paddle wheel has been studied recently, although the focus has never been on describing its impact on photosynthetic growth efficiency. In this multidisciplinary downscaling study, we first reconstructed single cell trajectories in an open raceway using an original hydrodynamical model offering a powerful discretization of the Navier–Stokes equations tailored to systems with free surfaces. The trajectory of a particular cell was selected and the associated high-frequency light pattern was computed. This light pattern was then experimentally reproduced in an Arduino-driven computer controlled cultivation system with a low density Dunaliella salina culture. The effect on growth and pigment content was recorded for various frequencies of the light pattern, by setting different paddle wheel velocities. Results show that the frequency of this realistic signal plays a decisive role in the dynamics of photosynthesis, thus revealing an unexpected photosynthetic response compared to that recorded under the on/off signals usually used in the literature. Indeed, the light received by a single cell contains signals from low to high frequencies that nonlinearly interact with the photosynthesis process and differentially stimulate the various time scales associated with photoacclimation and energy dissipation. This study highlights the need for experiments with more realistic light stimuli to better understand microalgal growth at high cell densities. An experimental protocol is also proposed, with simple, yet more realistic, step functions for light fluctuations.

A Genome-Wide, Mapped Algal Mutant Library Enables High-Throughput Genetic Studies in a Photosynthetic Eukaryote

Photosynthetic organisms provide food and energy for nearly all life on Earth, yet half of their genes remain uncharacterized. Characterization of gene functions could be greatly accelerated by new genetic resources in unicellular model organisms. We have generated a genome-wide, indexed library of mapped insertion mutants for the unicellular alga Chlamydomonas reinhardtii, which includes disruptions in 83% of nuclear genes. The abundance of individual mutants can be tracked with unique DNA barcodes, allowing the library to be screened as a pool. We demonstrated the power of this platform by performing a genome-wide screen that identified 3,109 mutants with defects in photosynthetic growth. Multiple alleles allowed identification of 44 genes required for photosynthesis, 21 of which are novel. Characterization of one of these genes, CPL3, showed it is important for photosystem I activity. The availability of the 62,389 mutants in our library will accelerate characterization of gene functions in photosynthetic eukaryotes.

Bioavailability of Mineral-Bound Iron to a Snow Algal-Bacterial Coculture and Implications for Albedo-Altering Snow Algal Blooms.

Snow algae can form large-scale blooms across the snowpack surface and near-surface environments. These pigmented blooms can decrease snow albedo and increase local melt rates, and they may impact the global heat budget and water cycle. Yet, the underlying causes for the geospatial occurrence of these blooms remain unconstrained. One possible factor contributing to snow algal blooms is the presence of mineral dust as a micronutrient source. We investigated the bioavailability of iron (Fe)-bearing minerals, including forsterite (Fo90, Mg1.8Fe0.2SiO4), goethite, smectite, and pyrite as Fe sources for a Chloromonas brevispina-bacterial coculture through laboratory-based experimentation. Fo90 was capable of stimulating snow algal growth and increased the algal growth rate in otherwise Fe-depleted cocultures. Fo90-bearing systems also exhibited a decrease in the ratio of bacteria to algae compared to those of Fe-depleted conditions, suggesting a shift in microbial community structure. The C. brevispina coculture also increased the rate of Fo90 dissolution relative to that of an abiotic control. Analysis of 16S rRNA genes in the coculture identified Gammaproteobacteria, Betaproteobacteria, and Sphingobacteria, all of which are commonly found in snow and ice environments. Archaea were not detected. Collimonas and Pseudomonas, which are known to enhance mineral weathering rates, comprised two of the top eight (>1%) operational taxonomic units (OTUs). These data provide unequivocal evidence that mineral dust can support elevated snow algal growth under otherwise Fe-depleted growth conditions and that snow algal microbial communities can enhance mineral dissolution under these conditions.IMPORTANCE Fe, a key micronutrient for photosynthetic growth, is necessary to support the formation of high-density snow algal blooms. The laboratory experiments described herein allow for a systematic investigation of the interactions of snow algae, bacteria, and minerals and their ability to mobilize and uptake mineral-bound Fe. Results provide unequivocal and comprehensive evidence that mineral-bound Fe in Fe-bearing Fo90 was bioavailable to Chloromonas brevispina snow algae within an algal-bacterial coculture. This evidence includes (i) an observed increase in snow algal density and growth rate, (ii) decreased ratios of bacteria to algae in Fo90-containing cultures relative to those of cultures grown under similarly Fe-depleted conditions with no mineral-bound Fe present, and (iii) increased Fo90 dissolution rates in the presence of algal-bacterial cocultures relative to those of abiotic mineral controls. These results have important implications for the role of mineral dust in supplying micronutrients to the snow microbiome, which may help support dense snow algal blooms capable of lowering snow albedo and increasing snow melt rates on regional, and possibly global, scales.

Light-dependent kinetic model for microalgae experiencing photoacclimation, photodamage, and photodamage repair

Microalgae naturally are exposed to changing light conditions. While a higher light intensity can promote a faster growth rate, it also can cause photodamage that leads to a temporary or semi-permanent decline in growth rate. We developed a model of photosynthetic growth including photoacclimation, reversible photodamage to photosystem II (PSII), and more severe photodamage to photosystem I (PSI). Phototrophic biomass optimizes its photosynthetic machinery to the light intensity it is experiencing; this is captured in the model by photoacclimation, in which photodamage to PSII caused by absorbed light is balanced by repair. However, repair of PSII photodamage can be overwhelmed by increases of light outside the photoacclimated condition, and this leads to severe PSII photodamage that slows the cells' specific growth rate. Furthermore, very large increases in light intensity can lead to photodamage to PSI, which is semi-permanent in that it can take days to weeks to repair. Our model captures all these phenomena. Example model outputs demonstrate the importance of each phenomenon for increases and decreases in light intensity from the photoacclimated state.

Dynamical localization of a thylakoid membrane binding protein is required for acquisition of photosynthetic competency.

Vipp1 is highly conserved and essential for photosynthesis, but its function is unclear as it does not participate directly in light-dependent reactions. We analyzed Vipp1 localization in live cyanobacterial cells and show that Vipp1 is highly dynamic, continuously exchanging between a diffuse fraction that is uniformly distributed throughout the cell and a punctate fraction that is concentrated at high curvature regions of the thylakoid located at the cell periphery. Experimentally perturbing the spatial distribution of Vipp1 by relocalizing it to the nucleoid causes a severe growth defect during the transition from non-photosynthetic (dark) to photosynthetic (light) growth. However, the same perturbation of Vipp1 in dark alone or light alone growth conditions causes no growth or thylakoid morphology defects. We propose that the punctuated dynamics of Vipp1 at the cell periphery in regions of high thylakoid curvature enable acquisition of photosynthetic competency, perhaps by facilitating biogenesis of photosynthetic complexes involved in light-dependent reactions of photosynthesis.

Regulating photoprotection improves photosynthetic growth and biomass production in Q<sub>C</sub>-site mutant cells of the cyanobacterium Synechocystis sp. PCC 6803

We characterized the photosynthetic growth of wild-type (WT) and QC-site mutant cells of the cyanobacterium Synechocystis sp. PCC 6803 grown in a photobioreactor under medium-intensity [~70 μmol(photon) m–2 s–1] and high-intensity [~200 μmol(photon) m–2 s–1] light conditions. Photosynthetic growth rate (the exponential phase) increased about 1.1–1.2 fold for the A16FJ, S28Aβ, and V32Fβ mutant compared with WT cells under medium-intensity light and about 1.2–1.3 fold under high-intensity light. Biomass production increased about 17–20% for A16FJ and S28Aβ mutant cells as compared with WT cells under medium-intensity light and about 14–17% for A16FJ and V32Fβ mutant cells under high-intensity light. The greater photosynthetic growth rate and biomass production of these QC-site mutant cells could be attributed to the increased photosynthesis efficiency and decreased dissipation of wasteful energy from phycobilisomes in mutants vs. WT cells. Our results support that manipulation of photoprotection may improve photosynthesis and biomass production of photosynthetic organisms.

CtrA Is Nonessential for Cell Cycle Regulation in <i>Rhodobacter sphaeroides</i>

The bacterial cell cycle consists of a series of genetically coordinated biochemical and biophysical events. In Caulobacter crescentus, CtrA is an essential cell cycle regulator that modulates many cell cycle processes. In the present study, the role of the CtrA was investigated in Rhodobacter sphaeroides 2.4.1 by employing genetic, molecular, and bioinformatic approaches. Examination of the ctrA-null mutant revealed that the loss of CtrA did not affect growth characteristics and cell morphology in R. sphaeroides when grown under aerobic or photosynthetic growth conditions but slower growth was noticed in the anaerobic-dark-DMSO condition. Phylogenetic analyses demonstrated that CtrA has diversified its role in major lineages of α-Proteobacteria and has possibly been involved in adaptation to variable lifestyles. Analysis of the CtrA binding sites in the R. sphaeroides genome suggests that CtrA may regulate 127 genes involving different cellular processes. Protein homology searches revealed that only a small number of ctrA-regulated genes are homologous across C. crescentus, R. capsulatus, and R. sphaeroides. Comparison of the functions of putative ctrA-regulated genes in C. crescentus, R. capsulatus, and R. sphaeroides revealed that all three species possessed broad pathway control across a variety of cluster of orthologous gene functions (COGs). However, interestingly, it seems that the essentiality of CtrA in C. crescentus may depend more on the selective control that it exerts on a few critical cell cycle genes and pathways that are not controlled by CtrA in a similar fashion in R. capsulatus and R. sphaeroides.

THE EFFECT OF ZINC ON THE GROWTH AND PHOTOSYNTHETIC APPARATUS OF WHEAT UNDER OPTIMAL AND HYPOTHERMIC CONDITIONS

The effect of zinc in a high concentration (1000 µM) on the growth and the photosynthetic apparatus of winter wheat plants ( Triticum aestivum L.) was investigated in the laboratory under optimal (22 ° C) and low (4 ° C) temperatures. It was shown that irrespective of the temperature, zinc in the stated concentration had a pronounced negative effect on the plants, causing a decrease in the content of the main photosynthetic pigments (chlorophylls and carotenoids) in the leaves, and a decline of the potential quantum efficiency of photosystem II. In addition, the exposure of the experimental plants to this metal caused a partial closure of stomata and a decrease of the stomatal pore size. These changes, along with other possible modifications and/or disruptions of physiological processes, inhibited the photosynthetic activity and growth of the plants. Where the temperature was optimal, however, the detrimental effect of zinc on the plants was attenuated toward the end of the experiment (3 days). Namely, the rate of photosynthesis, as well as the accumulation of shoot biomass reached a level typical of the control plants. Under hypothermic conditions, on the contrary, the inhibitory effect caused by the simultaneous action of these two stress factors, which was manifest in a number of the studied growth indices (shoot height and aboveground biomass) and the state of the photosynthetic apparatus (photosynthetic pigments content, rate of photosynthesis, leaf tissue water content) tended to build up. The approximately equal decrease in the values of the maximum quantum yield of the PS II photochemical activity ( F v / F m ) detected experimentally under temperature optimum and hypothermia is obviously connected with the weak dependence of light-dependent reactions on temperature.

Effect of coking wastewater on the growth and energy production of five wetland plant species

ABSTRACTIn order to investigate effect of coking wastewater (CW) on the growth and energy production of wetland plant species, cress (C), felon herb (FH), cockspur grass (CG), water shield (WS), and bracken fern (BF) were used to purify the CW. Results showed that high concentration of CW caused decreased photosynthetic rate, transpiration rate, and relative growth rate. C, WS, and BF showed higher adaptability than FH and CG. Below a CW concentration of 30%, growth of C, WS, and BF was less affected. Energy recovery of C, WS, and BF were more favorable when they grew in CW.

Differential physiological performance of two Eucalyptus species and one hybrid under different imposed water availability scenarios

Eucalyptus forest reproductive material responded differently to the imposed water scenarios through different water resistance mechanisms. Eucalyptus is amongst the most planted genera in the world. The focus of this study was to evaluate the ability of different forest reproductive material to withstand the occurrence of drought under different possible climate scenarios, both experienced by plants in the field: a long-term water deficit period (WS) and a short-term water deficit period followed by recovery, in comparison with a well-watered condition. The performance of two Eucalyptus species (Eucalyptus globulus and Eucalyptus nitens) and one hybrid (Eucalyptus globulus × Eucalyptus cypellocarpa), under such conditions, was assessed through several morphological and physiological traits. Under prolonged water stress, E. globulus, which experienced the lowest water potential values, suffered a decrease in CO2 assimilation rates as a result of stomatal limitations that, together with high oxidative damage, led to growth impairment. It also exhibited the slowest recovery from a short-term water stress period. The hybrid reacted to the prolonged water stress period through an active antioxidant system which allowed a higher photosynthetic assimilation rate and overall growth. Though it experienced a decrease in CO2 assimilation rate, due to non-stomatal limitations, E. nitens was able to maintain its growth under a prolonged water deficit period. Furthermore, under short-term drought stress followed by recovery, E. nitens was able to completely recover its gas-exchange parameters and increase overall growth production conferring a physiological advantage under the tested conditions. Our data demonstrate that, under the experimentally imposed water stress scenario, plants have different adaptive mechanisms to cope with continuous water deficit and recovery after a short-term stress situation.