Photosynthetic Production Research Articles

Adaptive Strategies Employed by Clonal Plants in Heterogeneous Patches

Heterogeneity is widespread in natural environments; as a result, connected clonal ramets often live in areas characterized by patches of different resources. Specifically, clonal plants are frequently affected by conditions of heterogeneous water stress. This raises the question of how clonal plants grow and reproduce in areas with patches of different resources. In this study, we investigated the adaptation mechanisms of clonal plants under heterogeneous environmental conditions. On the one hand, we bore in mind that phenotypic plasticity is abundantly exhibited in clonal plants. Clonal plants respond to water stress mainly through regulation of the size of individuals, the allocation of population biomass, and the number of daughter plants, as well as the extension ability and branching intensity of clonal organs, which directly affect reproduction and population stability in clonal plants. On the other hand, we also considered the physiological integration in clonal plants which has been shown in many studies. Ramets of clonal plants normally stay connected to each other through horizontal connectors (stolons or rhizomes). Communicated substances and resources such as water, mineral nutrition, photosynthetic products, and secondary metabolites are translocated between ramets; by such means, the plant relieves stress caused by heterogeneous patches. In this study, we sought to obtain scientific references to improve our understanding of how clonal plants in natural environments acclimate to stresses caused by soil heterogeneity.

Improving the predictions of leaf photosynthesis during and after short-term heat stress with current rice models.

In response to increasing global warming, extreme heat stress significantly alters photosynthetic production. While numerous studies have investigated the temperature effects on photosynthesis, factors like vapour pressure deficit (VPD), leaf nitrogen, and feedback of sink limitation during and after extreme heat stress remain underexplored. This study assessed photosynthesis calculations in seven rice growth models using observed maximum photosynthetic rate (Pmax ) during and after short-term extreme heat stress in multi-year environment-controlled experiments. Biochemical models (FvCB-type) outperformed light response curve-based models (LRC-type) when incorporating observed leaf nitrogen, photosynthetically active radiation, temperatures, and intercellular CO2 concentration (Ci ) as inputs. Prediction uncertainty during heat stress treatment primarily resulted from variation in temperatures and Ci . Improving FVPD (the slope for the linear effect of VPD on Ci /Ca ) to be temperature-dependent, rather than constant as in original models, significantly improved Ci prediction accuracy under heat stress. Leaf nitrogen response functions led to model variation in leaf photosynthesis predictions after heat stress, which was mitigated by calibrated nitrogen response functions based on active photosynthetic nitrogen. Additionally, accounting for observed differences in carbohydrate accumulation between panicles and stems during grain filling improved the feedback of sink limitation, reducing Ci overestimation under heat stress treatments.

Accelerating effects of growing-season warming on tree seasonal activities are progressively disappearing

The phenological changes induced by climate warming have profound effects on water, energy, and carbon cycling in forest ecosystems. In addition to pre-season warming, growing-season warming may drive tree phenology by altering photosynthetic carbon uptake. It has been reported that the effect of pre-season warming on tree phenology is decreasing. However, temporal change in the effect of growing-season warming on tree phenology is not yet clear. Combining long-term ground observations and remote-sensing data, here we show that spring and autumn phenology were advanced by growing-season warming, while the accelerating effects of growing-season warming on tree phenology were progressively disappearing, manifesting as phenological events converted from being advanced to being delayed, in the temperate deciduous broadleaved forests across the Northern Hemisphere between 1983 and 2014. We further observed that the effect of growing-season warming on photosynthetic productivity showed a synchronized decline over the same period. The responses of phenology and photosynthetic productivity had a strong linear relationship with each other, and both showed significant negative correlations with the elevated temperature and vapor pressure deficit during the growing season. These findings indicate that warming-induced water stress may drive the observed decline in the responses of tree phenology to growing-season warming by decelerating photosynthetic productivity. Our results not only demonstrate a close link between photosynthetic carbon uptake and tree seasonal activities but also provide a physiological perspective of the nonlinear phenological responses to climate warming.

Efficient semi-artificial photosynthesis of ethylene by a self-assembled InP-Cyanobacterial biohybrid system.

Biomaufacturing of ethylene is particularly important for modern society. Cyanobacterial cells are able to photosynthesize various valuable chemicals, a promising platform for next-generation biomanufacturing, and semiconductor-cyanobacterial hybrid system are capable of enhancing the solar-to-chemical conversion efficiency. Herein, the native ethylene-producing capability of a filamentous cyanobacterium Nostoc sphaeroides is confirmed experimentally. The self-assembly characteristic of N. sphaeroides is exploited to facilitate its interaction with InP nanomaterial, and the resulted biohybrid system gave rise to further elevated photosynthetic ethylene production. Based on chlorophyll fluorescence measurement and metabolic analysis, the InP nanomaterial augmented photosystem I activity and enhanced ethylene production metabolism of biohybrid cells is confirmed, the mechanism underlying material-cell energy transduction, as well as nanomaterial-modulated photosynthetic light and dark reactions are established. This work not only demonstrated the potential application of semiconductor-N. sphaeroides biohybrid system as a good platform for sustainable ethylene production, but also provided important reference for future studies to construct and optimize nano-cell biohybrid systems for efficient solar-driven valuable chemical production.

A Broad Light‐Harvesting Conjugated Oligoelectrolyte Enables Photocatalytic Nitrogen Fixation in a Bacterial Biohybrid

AbstractWe report a rationally designed membrane‐intercalating conjugated oligoelectrolyte (COE), namely COE‐IC, which endows aerobic N2‐fixing bacteria Azotobacter vinelandii with a light‐harvesting ability that enables photosynthetic ammonia production. COE‐IC possesses an acceptor‐donor‐acceptor (A‐D‐A) type conjugated core, which promotes visible light absorption with a high molar extinction coefficient. Furthermore, COE‐IC spontaneously associates with A. vinelandii to form a biohybrid in which the COE is intercalated within the lipid bilayer membrane. In the presence of L‐ascorbate as a sacrificial electron donor, the resulting COE‐IC/A. vinelandii biohybrid showed a 2.4‐fold increase in light‐driven ammonia production, as compared to the control. Photoinduced enhancement of bacterial biomass and production of L‐amino acids is also observed. Introduction of isotopically enriched 15N2 atmosphere led to the enrichment of 15N‐containing intracellular metabolites, consistent with the products being generated from atmospheric N2.

A Broad Light-Harvesting Conjugated Oligoelectrolyte Enables Photocatalytic Nitrogen Fixation in a Bacterial Biohybrid.

We report a rationally designed membrane-intercalating conjugated oligoelectrolyte (COE), namely COE-IC, which endows aerobic N2 -fixing bacteria Azotobacter vinelandii with a light-harvesting ability that enables photosynthetic ammonia production. COE-IC possesses an acceptor-donor-acceptor (A-D-A) type conjugated core, which promotes visible light absorption with a high molar extinction coefficient. Furthermore, COE-IC spontaneously associates with A. vinelandii to form a biohybrid in which the COE is intercalated within the lipid bilayer membrane. In the presence of L-ascorbate as a sacrificial electron donor, the resulting COE-IC/A. vinelandii biohybrid showed a 2.4-fold increase in light-driven ammonia production, as compared to the control. Photoinduced enhancement of bacterial biomass and production of L-amino acids is also observed. Introduction of isotopically enriched 15 N2 atmosphere led to the enrichment of 15 N-containing intracellular metabolites, consistent with the products being generated from atmospheric N2 .

The influence of agricultural practices on photosynthetic activity and productivity of a new variety of cannabis in the Middle Volga region

Relevance. In 2023, a new variety of single-domed drug-free cannabis, Lyudmila, of the fibrous direction of use, passed the State Examination and was approved for accreditation for admis-sion to use on the territory of the Russian Federation. In this regard, research on the development of elements of cultivation technology in specific soil and climatic conditions is of scientific and practical interest.Methods. The scientific experiment is based on methodological guidelines for registration tests offungicides in agriculture and methodological guidelines for conducting field and vegetation tests with cannabis. Indicators of photosynthetic activity of plants in crops were determined by the method of A.A. Nichiporovich. Mathematical processing of experimental data was carried out by the method of dispersion analysis according to B.A. Dospekhov.Results. Foliar top dressing contributed to an increase in the assimilation surface of the leaves in the variants with the treatment of plants for vegetation with preparations: Izagri Phosphorus — from 111.0 to 155.7 thousand m2/ha, Izagri Vita — from 112.2 to 139.7 thousand m2/ha, Humate +7 — from 135.9 to 148.4 thousand m2/ha (with 101.1–114.3 thousand m2/ha under control). The high yield of stems was obtained when sowing with a seeding rate of 3 million germinating seeds per hectare — 15.67 t/ha, with a decrease in the seeding rate to 2.5 and 2.0 million germinating seeds per hectare, the yield of stems decreased to 14.48–12.98 t/ha. Foliar treatments are effective, the yield of stems on the treated variants is higher than the control by 0.36–0.9 t/ha. The highest seed yield was obtained when sowing with a seeding rate of 2.5 million germinating seeds per hectare, on average 0.98 t/ha.

First Report of Myrtle Rust Caused by Austropuccinia psidii in Campomanesia guazumifolia (Camb.) Berg in Brazil.

Campomanesia guazumifolia is a Brazilian fruit tree that has ecological importance and the potential to be explored by the food and medical industries (Lima et al., 2011). In February 2019, in the experimental orchard at the Universidade Tecnológica Federal do Paraná, Dois Vizinhos city, Paraná State - Brazil, disease symptoms were observed on leaves, stems, and fruits of 22 C. guazumifolia trees. Yellow uredinia were observed on upper side of the leaves, stems, and flowers, which resembled typical uredinia of Myrtaceae rust. The pustules occurred mainly on young shoots, and on flowers, they infected their sepals. Over time, tissues colonized by the pathogen exhibited deformations and mummification occurred in infected fruits. In the orchard, the fungus affected 80% yield. Twenty diseased plant parts (from each of the eleven trees) were collected at different positions in the orchard. One strain were selected as a representative for morphological characterization, multilocus phylogenetic analysis, and pathogenicity tests. The structures observed were epiphyllous uredinia (leaves), united in small groups with hyaline and obovoid or obpyriform urediniospores, which presented echinulate ornaments, germinated pores in the subequatorial and inordinate positions (Cummins; Hiratsuka, 2003) (n = 30, 14.84 x 21.12 μm). The morphology of uredinia and urediniospores was similar to the morphological characteristics of the genus Austropuccinia previously described in Young (2019). For molecular identification, genomic DNA was extracted and the internal transcribed spacer (ITS) region (White et al. 1990), β-tubulin (TUB2) and translation elongation factor 1-alpha (TEF) (Machado et al. 2012) were amplified by PCR, and sequenced. Bayesian inference was used to reconstruct a phylogenetic tree, using MrBayes v. 3.2.1 (Ronquist et al., 2012). The multilocus phylogenetic analysis clearly distinguished the isolate APCG001 as Austropuccinia psidii separating it from all other species. The sequences were deposited in GenBank (accessions nos. ITS: ON003418, TUB2: ON568196, and TEF: ON437601). For pathogenicity tests, four healthy branches (20 leaves each) were sprayed with 2.5 mL of (APCG001) uredospore suspension (105 mL-1) and covered with a plastic bag in the orchard. The air temperature ranged from 16ºC to 25ºC. Sterile distilled water was used as a control. Three replications (pathogen and control) were performed on different trees. After 6 days, symptoms of rust appeared on the plants. Control branches did not show fungal growth. The inoculation test was repeated again, confirming the initial results. This is the first report of infection by A. psidii in C. guazumifolia trees in Brazil, causing rust, necrosis, and early senescence in fruits, leaves, and stems. Myrtaceae rust reduces the C. guazumifolia leaf area, affecting photosynthetic production and reducing fruit quality.

Impact of technological practices on the photosynthetic productivity of spring barley in Northern Forest-Steppe conditions

Aim. To determine the features of the formation of the photosynthetic apparatus in spring barley plants depending on the influence of individual elements of cultivation technology and to identify the most effective combinations for maximizing the genetic potential of the crop under the conditions of the northern part of the Right-Bank Forest-Steppe of Ukraine. Methods. During the research, a field study method, visual observation, weighing, the «cutting» method, calculations, and statistical analysis were applied. Results. The research conducted during 2018–2020 has shown that the fertilization system, the use of growth stimulants, and the preceding crop significantly influence the photosynthetic activity of spring barley plants at different stages of organogenesis. The leaf surface index values increased and reached their maximum at the VII and IX stages of organogenesis, after which they gradually decreased. The maximum leaf surface area of 5.03 to 5.24 m2/m2 was achieved in crops with the application of N60P80K80+N60(IV) in the presence of the preceding crop’s by-product. The photosynthetic potential of crops during the period from the II to XI stages of organogenesis was at the level of 1.02–2.42 million m2/ha·day when grown after soybeans and 0.92–2.39 million m2/ha·day when grown after corn for grain. The period from the IV to VIІІ stages of plant organogenesis was characterized by the most active accumulation of dry matter and the most significant influence of all studied agronomic practices on the formation of this indicator. Conclusions. Optimal indicators of photosynthetic activity of spring barley crops (leaf area index of 4.65 m²/m² at the VIII stage of organogenesis, net photosynthesis productivity of 6.71 g/m² per day, dry matter accumulation of 9.51 t/ha at the XI stage of organogenesis) are ensured by the cultivation technology that involves the application of mineral fertilizers at a rate of N45P90K90+N45(IV) against the background of the predecessor’s (corn for grain) byproduct and the use of growth stimulants for pre-sowing seed treatment and foliar application at the IV stage of organogenesis. Such parameters of plant photosynthetic apparatus operation contribute to obtaining a barley grain yield at the level of 4.88–5.27 t/ha.

Microalgae-material hybrid for enhanced photosynthetic energy conversion: a promising path towards carbon neutrality.

Photosynthetic energy conversion for high-energy chemicals generation is one of the most viable solutions in the quest for sustainable energy towards carbon neutrality. Microalgae are fascinating photosynthetic organisms, which can directly convert solar energy into chemical energy and electrical energy. However, microalgal photosynthetic energy has not yet been applied on a large scale due to the limitation of their own characteristics. Researchers have been inspired to couple microalgae with synthetic materials via biomimetic assembly and the resulting microalgae-material hybrids have become more robust and even perform new functions. In the past decade, great progress has been made in microalgae-material hybrids, such as photosynthetic carbon dioxide fixation, photosynthetic hydrogen production, photoelectrochemical energy conversion and even biochemical energy conversion for biomedical therapy. The microalgae-material hybrid offers opportunities to promote artificially enhanced photosynthesis research and synchronously inspires investigation of biotic-abiotic interface manipulation. This review summarizes current construction methods of microalgae-material hybrids and highlights their implication in energy and health. Moreover, we discuss the current problems and future challenges for microalgae-material hybrids and the outlook for their development and applications. This review will provide inspiration for the rational design of the microalgae-based semi-natural biohybrid and further promote the disciplinary fusion of material science and biological science.

Himalayan magnesite records abrupt cyanobacterial growth that plausibly triggered the Neoproterozoic Oxygenation Event

The widespread glaciation (∼750–580 Ma) of the late Neoproterozoic Snowball Earth and the subsequent (∼630–551 Ma) oxygenation of the oceans and atmosphere were critical factors in microbial evolution and the following ∼540–520 Ma explosion of complex life forms in the Cambrian. However, the underlying mechanisms that link these processes are still unclear due to poorly preserved fossil records and the tectonic destruction of the paleo-oceans, limiting our understanding of the Neoproterozoic Earth, a key time when unicellular life evolved into complex forms. Droplets of Neoproterozoic oceanwater and freshwater trapped in Himalayan crystalline magnesite (MgCO3) show that sedimentary basins were deprived of calcium for an extended period during the Snowball Earth glaciation, probably due to low riverine input of the dissolved products of weathering. Protracted precipitation of calcite-dolomite in a closed basin, now exposed in Kumaun Himalayas, Uttarakhand (India), decreased the Ca/Mg ratio in the seawater. This fall in the Ca/Mg ratio—initiated magnesite precipitation and increased the basin's oligotrophy (nutrition deficiency). The slow-growing photosynthetic cyanobacterial stromatolites could thrive in such oligotrophic conditions. The same is reflected in the field, i.e., the appearance of stromatolites towards the end of dolomite formation and their population expansion in the overlying magnesite beds. Continued magnesite precipitation in a closed basin, driven by positive feedback, resulted in high photosynthetic oxygen production, conceivably triggering the Neoproterozoic Oxygenation Event and stimulating Cambrian Explosion.

Influence of mineral components on photosynthetic activity and productivity of cucumber plants “Monsoon F1”

In the conditions of the greenhouse of I.A.Bunin YSU, the influence of water-soluble multicomponent micronutrients - Green Lift, Nutrivant Plus - was studied Melon, Vitanol Micro on the physiological development of cucumber plants “Monsoon F1”. It was established that multicomponent micro fertilizers affect plant growth. The high efficiency of non-root fertilizing on growth processes in variants with the use of Green Lift was revealed. The smallest result was obtained between control and application Vitanol. The highest effect on the photosynthetic potential of plants from the applied fertilizers was obtained in the variant with the use of Vitanol.

Microalga-bacteria interaction mitigates adverse effects on microalga produced by ZnO nanoparticles

Zinc oxide nanoparticles (ZnO NPs) used in myriad industries have become an emerging contaminant in various environments. Interactions of microalgae and bacteria, in suspension systems and immobilized, have been proposed for several biotechnology applications, such as wastewater treatment. However, the presence of NPs can affect the performance of these microorganisms during nutrient removal. This study assessed the effect of metal NPs on microalgae˗bacteria interaction, immobilized or in suspension. The effect of two concentrations of ZnO NPs (0.1 and 0.5 ppm) on the growth and photosynthetic pigments of the microalga Chlorella sorokiniana cultured in suspension or immobilized in alginate beads, alone or in the presence of the microalgae growth-promoting bacterium Azospirillum brasilense, was evaluated, and the effect of these NPs on indole-3-acetic acid (IAA) production by A. brasilense was also tested. The presence of ZnO NPs affected the growth of both microorganisms when cultured alone in suspension, and the IAA production by A. brasilense was reduced by 98 %. Nevertheless, when the two microorganisms were co-cultured in suspension, the negative effect of 0.1 ppm of ZnO NPs in C. sorokiniana was mitigated by A. brasilense, indicating a positive interaction between the two microorganisms. Furthermore, adding synthetic IAA enhances microalgae growth and photosynthetic pigment production regardless of NP concentration. On the other hand, immobilization of the cells produces a dose-response effect in the microorganisms, regardless of the partnerʼs presence. The results showed the positive effect of A. brasilense on stress mitigation of C. sorokiniana when 0.1 ppm of ZnO NPs are present and similar to the effect produced by synthetic IAA when the microorganisms are present in a suspension system. On the other hand, the immobilization of cells in alginate beads represents a physical barrier that acts as protection against the stress produced by ZnO NPs.

PHOTOSYNTHETIC ACTIVITY, PRODUCTIVITY, AND NUTRITIONAL VALUE OF MOWING AND GRAZING PHYTOCENOSES DEPENDING ON THE SPECIES COMPOSITION OF GRASSES

Studies of the photosynthetic activity of perennial grass mixtures allow for describing the peculiarities of the formation of perennial grass species forage productivity in the dry steppe zone. The study aimed to evaluate the cumulative effect of perennial cereal and legume grasses as part of complex grass mixtures on photosynthetic activity, productivity, and nutritional value of mowing and grazing phytocenoses. Adapting multicomponent grass created from various species of perennial grasses to the continental climate of the steppe zone of Northern Kazakhstan commenced, capable of resisting biotic and abiotic stresses due to biological characteristics and positively influencing other species in the phytocenoses. The study determined photosynthetic activity, the yield of green and dry masses, dry matter content, crude protein, metabolizable energy of natural pasture, single-species sowing of awnless brome, and multicomponent grass mixtures. The communal herbage obtained as a result of the study contained a large amount of crude protein (20.6%–24.7%), crude fat (2.0%–4.2%), crude fiber (18.0%–22.7%), crude ash (7.1%–7.7%), and nitrogen-free extractive substances (35.0%– 44.1%). The results further enunciated that the perennial grass herbage in question had an average photosynthetic potential of 1,450,330 m2×day ha-1 in single-species awnless brome crops, while in grass mixtures the said potential was higher, ranging from 1,510,250 to 1,815,250 m2×day ha-1. The authors concluded that it was necessary to create mowing and grazing fields composed of productive and stable perennial grass mixtures on degraded pasture lands to increase available forage for farm animals and improve the system's resistance to adverse conditions.

Smart utilization of betaine lipids in the giant clam Tridacna crocea

The giant clam Tridacna crocea thrives in poorly nourished coral reef water by forming a holobiont with zooxanthellae and utilizing photosynthetic products of the symbiont. However, detailed metabolic crosstalk between clams and symbionts is elusive. Here, we discovered that the nonphosphorous microalgal betaine lipid DGCC (diacylglycerylcarboxy-hydroxymethylcholine) and its deacylated derivative GCC are present in all tissues and organs, including algae-free sperm and eggs, and are metabolized. Colocalization of DGCC and PC (phosphatidylcholine) evidenced by MS imaging suggested that DGCC functions as a PC substitute. The high content of GCC in digestive diverticula (DD) suggests that the algal DGCC was digested in DD for further utilization. Lipidomics analysis showing the organ-specific distribution pattern of DGCC species suggests active utilization of DGCC as membrane lipids in the clam. Thus, the utilization of zooxanthellal DGCC in animal cells is a unique evolutionary outcome in phosphorous-deficient coral reef waters.

18 O enrichment of sucrose and photosynthetic and nonphotosynthetic leaf water in a C3 grass-atmospheric drivers and physiological relations.

The 18 O enrichment (Δ18 O) of leaf water affects the Δ18 O of photosynthetic products such as sucrose, generating an isotopic archive of plant function and past climate. However, uncertainty remains as to whether leaf water compartmentation between photosynthetic and nonphotosynthetic tissue affects the relationship between Δ18 O of bulk leaf water (Δ18 OLW ) and leaf sucrose (Δ18 OSucrose ). We grew Lolium perenne (a C3 grass) in mesocosm-scale, replicated experiments with daytime relative humidity (50% or 75%) and CO2 level (200, 400 or 800 μmol mol-1 ) as factors, and determined Δ18 OLW , Δ18 OSucrose and morphophysiological leaf parameters, including transpiration (Eleaf ), stomatal conductance (gs ) and mesophyll conductance to CO2 (gm ). The Δ18 O of photosynthetic medium water (Δ18 OSSW ) was estimated from Δ18 OSucrose and the equilibrium fractionation between water and carbonyl groups (εbio ). Δ18 OSSW was well predicted by theoretical estimates of leaf water at the evaporative site (Δ18 Oe ) with adjustments that correlated with gas exchange parameters (gs or total conductance to CO2 ). Isotopic mass balance and published work indicated that nonphotosynthetic tissue water was a large fraction (~0.53) of bulk leaf water. Δ18 OLW was a poor proxy for Δ18 OSucrose , mainly due to opposite Δ18 O responses of nonphotosynthetic tissue water (Δ18 Onon-SSW ) relative to Δ18 OSSW , driven by atmospheric conditions.

COMPARISON OF GROWTH AND YIELD OF SOYBEAN (Glycine max L) WITH VARIATION OF BIOFERTILIZER DOSAGE IN THE RAINY SEASON

The purpose of this research was to evaluate the influence of soybean cultivar combinations and biofertilizer dosages on the growth and yield of soybean plants during the rainy season. The analysis results indicated that these combinations did not have a significant effect on the growth and yield of the plants. The variations among treatments were predominantly influenced by the choice of cultivar. The use of biofertilizers enhanced nutrient availability for the plants but did not consistently yield significant results. Rainy season and other environmental factors also affected plant growth. Cultivar variations and genetic factors played a role in yield variations as well. The use of biofertilizers provided benefits for soil structure and microbial activity. In terms of pod and seed quantities, the Deja 2 cultivar with biofertilizer dosages of 0 g/kg and 10 g/kg demonstrated the highest yields. There were no significant differences in root dry weight across all treatments, while the highest shoot dry weight was observed in the Grobogan cultivar with a biofertilizer dosage of 0 g/kg. In terms of weight per 100 seeds, the Grobogan cultivar with biofertilizer dosages of 0 g/kg, 5 g/kg, 10 g/kg, and 15 g/kg exhibited the highest weights. This research indicates that genetic factors, environment, and biofertilizer dosages play a role in the growth and yield of soybean plants. In terms of the number of soybean plant branches, some treatments showed the best results, but the impact of biofertilizer dosages was not significantly observed. Regarding root dry weight, there were no significant differences among the treatments, possibly due to suboptimal translocation of photosynthetic products to the roots resulting from high rainfall. However, shoot dry weight tended to increase in treatments with high rainfall conditions. The parameters of pod fill count and seed count per plant were also influenced by the combination of cultivars and biofertilizer dosages. Some treatments exhibited higher yields, particularly in the combination of the Deja 2 cultivar with a biofertilizer dosage of 0 g/kg.

Is chloroplast size optimal for photosynthetic efficiency?

Improving photosynthetic efficiency has recently emerged as a promising way to increase crop production in a sustainable manner. While chloroplast size may affect photosynthetic efficiency in several ways, we aimed to explore whether chloroplast size manipulation can be a viable approach to improving photosynthetic performance. Several tobacco (Nicotiana tabacum) lines with contrasting chloroplast sizes were generated via manipulation of chloroplast division genes to assess photosynthetic performance under steady-state and fluctuating light. A selection of lines was included in a field trial to explore productivity. Lines with enlarged chloroplasts underperformed in most of the measured traits. Lines with smaller and more numerous chloroplasts showed a similar efficiency compared with wild-type (WT) tobacco. Chloroplast size only weakly affected light absorptance and light profiles within the leaf. Increasing chloroplast size decreased mesophyll conductance (gm ) but decreased chloroplast size did not increase gm . Increasing chloroplast size reduced chloroplast movements and enhanced non-photochemical quenching. The chloroplast smaller than WT appeared to be no better than WT for photosynthetic efficiency and productivity under field conditions. The results indicate that chloroplast size manipulations are therefore unlikely to lead to higher photosynthetic efficiency or growth.

Partial inhibition of the inter-photosystem electron transfer at cytochrome b6f complex promotes periodic surges of hydrogen evolution in Chlamydomonas reinhardtii

Periodic surges of H2 evolution were observed in the wild-type strain CC-5325 of the green unicellular alga Chlamydomonas reinhardtii in the presence of the electron transport inhibitors dibromo-6-isopropyl-3-methyl-1,4-benzoquinone (DBMIB, 3.5 μM) and 2,4-dinitrophenylether and iodonitrothymol (DNP-INT, 0.6 μM). Addition of DBMIB partly inhibited the electron transfer from Cytochrome b6f complex to Photosystem I, over-reduced the plastoquinone pool, gradually inhibited photosystem II and created anoxic conditions in cells. During 30 days of anaerobic incubation, continues H2 photoproduction with a minimum rate of 1 ml/L of culture per day was accompanied with additional outbursts of H2 evolution. The first noticeable peak of H2 evolution was observed on day 6 of incubation, with maximum rate of 23 ml of H2 per L of culture per day. It was repeated on day 9 and day 22 with the 2 and 4 times lower rates respectively. Addition of DNP-NT showed similar effect by inducing the H2 photoproduction for 15 days, albeit at much lower rates. Contribution of the direct and indirect pathways to the H2 production is shown by fluorescence, thermoluminescence and electron paramagnetic resonance spectroscopy. It is proposed that photosynthetic electron transport in combination with photorespiration, chlororespiration and starch accumulation can switch on and off between photosynthetic, H2 producing and survival modes of cell metabolism. Controlled switching between these modes could potentially maintain the long lasting photosynthetic H2 production in the wild-type of Chlamydomonas.

Antenna Modification in a Fast-Growing Cyanobacterium Synechococcus elongatus UTEX 2973 Leads to Improved Efficiency and Carbon-Neutral Productivity.

Our planet is sustained by sunlight, the primary energy source made accessible to all life forms by photoautotrophs. Photoautotrophs are equipped with light-harvesting complexes (LHCs) that enable efficient capture of solar energy, particularly when light is limiting. However, under high light, LHCs can harvest photons in excess of the utilization capacity of cells, causing photodamage. This damaging effect is most evident when there is a disparity between the amount of light harvested and carbon available. Cells strive to circumvent this problem by dynamically adjusting the antenna structure in response to the changing light signals, a process known to be energetically expensive. Much emphasis has been laid on elucidating the relationship between antenna size and photosynthetic efficiency and identifying strategies to synthetically modify antennae for optimal light capture. Our study is an effort in this direction and investigates the possibility of modifying phycobilisomes, the LHCs present in cyanobacteria, the simplest of photoautotrophs. We systematically truncate the phycobilisomes of Synechococcus elongatus UTEX 2973, a widely studied, fast-growing model cyanobacterium and demonstrate that partial truncation of its antenna can lead to a growth advantage of up to 36% compared to the wild type and an increase in sucrose titer of up to 22%. In contrast, targeted deletion of the linker protein which connects the first phycocyanin rod to the core proved detrimental, indicating that the core alone is not enough, and it is essential to maintain a minimal rod-core structure for efficient light harvest and strain fitness. IMPORTANCE Light energy is essential for the existence of life on this planet, and only photosynthetic organisms, equipped with light-harvesting antenna protein complexes, can capture this energy, making it readily accessible to all other life forms. However, these light-harvesting antennae are not designed to function optimally under extreme high light, a condition which can cause photodamage and significantly reduce photosynthetic productivity. In this study, we attempt to assess the optimal antenna structure for a fast-growing, high-light tolerant photosynthetic microbe with the goal of improving its productivity. Our findings provide concrete evidence that although the antenna complex is essential, antenna modification is a viable strategy to maximize strain performance under controlled growth conditions. This understanding can also be translated into identifying avenues to improve light harvesting efficiency in higher photoautotrophs.