Importance Of Photosynthesis Research Articles

Research Progress in Improving Photosynthetic Efficiency.

Photosynthesis is the largest mass- and energy-conversion process on Earth, and it is the material basis for almost all biological activities. The efficiency of converting absorbed light energy into energy substances during photosynthesis is very low compared to theoretical values. Based on the importance of photosynthesis, this article summarizes the latest progress in improving photosynthesis efficiency from various perspectives. The main way to improve photosynthetic efficiency is to optimize the light reactions, including increasing light absorption and conversion, accelerating the recovery of non-photochemical quenching, modifying enzymes in the Calvin cycle, introducing carbon concentration mechanisms into C3 plants, rebuilding the photorespiration pathway, de novo synthesis, and changing stomatal conductance. These developments indicate that there is significant room for improvement in photosynthesis, providing support for improving crop yields and mitigating changes in climate conditions.

Hybrid Vigour and Hybrid Mimics in Japonica Rice

In crop improvement programs, hybrid vigour (heterosis) is an important breeding strategy but the molecular mechanisms of hybrid vigour are still unclear. Grain yield declines after F1 generation due to phenotypic segregation. We found that, at the early seedling stage in hybrids derived from the temperate japonica rice varieties ‘Doongara’ and ‘Reiziq’, hybrid vigour was approximately 40% greater than in the better parents. Inbred high-yielding lines (Hybrid Mimics) were developed from the ‘Doongara’ × ‘Reiziq’ F1 by selfing and recurrent selection for F1-like plants in the F2 through to the F5 generation. Grain yields are stable over subsequent generations in the Hybrid Mimic lines. The importance of photosynthesis in early seedling development was demonstrated. Photosynthesis-related genes were expressed in the hybrid earlier than in the parents; physiological evidence using gas exchange indicated the early commencement of photosynthesis. Dark germination experiments supported the requirement for photosynthesis for early vigour in hybrids.

Leaf cell-specific and single-cell transcriptional profiling reveals a role for the palisade layer in UV light protection.

Like other complex multicellular organisms, plants are composed of different cell types with specialized shapes and functions. For example, most laminar leaves consist of multiple photosynthetic cell types. These cell types include the palisade mesophyll, which typically forms one or more cell layers on the adaxial side of the leaf. Despite their importance for photosynthesis, we know little about how palisade cells differ at the molecular level from other photosynthetic cell types. To this end, we have used a combination of cell-specific profiling using fluorescence-activated cell sorting and single-cell RNA-sequencing methods to generate a transcriptional blueprint of the palisade mesophyll in Arabidopsis thaliana leaves. We find that despite their unique morphology, palisade cells are otherwise transcriptionally similar to other photosynthetic cell types. Nevertheless, we show that some genes in the phenylpropanoid biosynthesis pathway have both palisade-enriched expression and are light-regulated. Phenylpropanoid gene activity in the palisade was required for production of the ultraviolet (UV)-B protectant sinapoylmalate, which may protect the palisade and/or other leaf cells against damaging UV light. These findings improve our understanding of how different photosynthetic cell types in the leaf can function uniquely to optimize leaf performance, despite their transcriptional similarities.

Wheat susceptibility to blast is enhanced by a photosynthetic inhibitor

AbstractConsidering blast, caused by Pyricularia oryzae, as a critical threat to wheat yield and the importance of photosynthesis as the source of energy used by plants to activate their mechanisms of defence to counteract pathogen infections, this study aimed to investigate whether wheat plants compromised in their photosynthetic process by using an inhibitor of photosynthesis could become more susceptible to blast. Plants from cultivars BRS 220 (moderately resistant) and BRS Guamirim (susceptible) were non‐sprayed (‐DCMU plants) or sprayed (+DCMU plants) with a solution (10 μM) of 3‐([3,4‐dichlorophenyl]‐1,1‐dimethylurea) (DCMU) at 24 hr before inoculation with P. oryzae. Blast progressed much faster on the leaves of +DCMU plants from cultivars BRS 220 and BRS Guamirim in comparison with ‐DCMU plants of these cultivars. Increased susceptibility of plants from the two cultivars to blast caused by DCMU was associated with its negative effect on the photosynthetic apparatus, decreasing phenylalanine ammonia‐lyase activity and reducing the concentration of total soluble phenolics. Chitinase activity for the infected plants from the two cultivars was lower compared with non‐inoculated ‐DCMU plants but was greater for inoculated +DCMU plants. Distinctly, β‐1,3‐glucanases activity was kept stable for inoculated +DCMU plants. In conclusion, manipulation of the photosynthetic process of wheat plants by using DCMU allowed to understand their response to P. oryzae infection at the physiological level and reinforced the concept that photosynthesis was important for wheat resistance to blast.

Mitochondrial Iron Transporters (MIT1 and MIT2) Are Essential for Iron Homeostasis and Embryogenesis in Arabidopsis thaliana.

Iron (Fe) is an essential nutrient for virtually all organisms, where it functions in critical electron transfer processes, like those involved in respiration. Photosynthetic organisms have special requirements for Fe due to its importance in photosynthesis. While the importance of Fe for mitochondria- and chloroplast-localized processes is clear, our understanding of the molecular mechanisms that underlie the trafficking of Fe to these compartments is not complete. Here, we describe the Arabidopsis mitochondrial iron transporters, MIT1 and MIT2, that belong to the mitochondrial carrier family (MCF) of transport proteins. MIT1 and MIT2 display considerable homology with known mitochondrial Fe transporters of other organisms. Expression of MIT1 or MIT2 rescues the phenotype of the yeast mrs3mrs4 mutant, which is defective in mitochondrial iron transport. Although the Arabidopsis mit1 and mit2 single mutants do not show any significant visible phenotypes, the double mutant mit1mit2 displays embryo lethality. Analysis of a mit1 −− /mit2 + − line revealed that MIT1 and MIT2 are essential for iron acquisition by mitochondria and proper mitochondrial function. In addition, loss of MIT function results in mislocalization of Fe, which in turn causes upregulation of the root high affinity Fe uptake pathway. Thus, MIT1 and MIT2 are required for the maintenance of both mitochondrial and whole plant Fe homeostasis, which, in turn, is important for the proper growth and development of the plant.

Reduced expression of the rate-limiting carbon fixation enzyme RuBisCO in the benthic foraminifer Baculogypsina sphaerulata holobiont in response to heat shock

Baculogypsina sphaerulata (Parker and Jones, 1860) is a common large benthic foraminifer (LBF) and is an important calcifier in coral reef ecosystems. As there are concerns that global increasing temperatures may compromise the survival of this species, which forms a symbiotic relationship with the diatom Nitzschia sp., we investigated the response of the B. sphaerulata holobiont from the intertidal algal flats of Xiao Liu Chiu Island, Taiwan to heat shock. B. sphaerulata specimens were incubated at 26 (ambient), 28, 30, 32, or 34°C for 5h designed to simulate short pulses of elevated temperature that occur in situ from subaerial exposure at low tide. To assess the molecular-level response, we measured the expression of the ribulose 1-5-bisphosphate carboxylase/oxygenase (RuBisCO) protein in the diatom symbiont. There was a significant decrease in expression of this rate-limiting carbon fixation enzyme in B. sphaerulata holobionts incubated at 34°C/8°C above ambient (~50% decline relative to controls), but expression was resilient to levels of warming up to 6°C above ambient. This suggests that exposure to high temperatures occasionally experienced in nature may diminish the capacity for carbon fixation of the diatom symbiont. Given the importance of photosynthesis and carbon fixation in these marine calcifiers, these data suggest that climate-driven ocean warming may exert deleterious effects on the B. sphaerulata holobiont.

FtsH proteases located in the plant chloroplast

FtsHs are a well-characterized family of membrane bound proteases containing an AAA (ATPase associated with various cellular activities) and a Zn(2+) metalloprotease domain. FtsH proteases are found in eubacteria, animals and plants and are known to have a crucial role in housekeeping proteolysis of membrane proteins. In Arabidopsis thaliana, 12 FtsH family members are present (FtsH 1-12) and their subcellular localization is restricted to mitochondria and chloroplasts. In addition, five genes coding for proteins homologous to FtsH (FtsHi 1-5) have been detected in the genome, lacking the conserved zinc-binding motif HEXXH, which presumably renders them inactive for proteolysis. These inactive FtsHs as well as nine of the active FtsHs are thought to be localized in the chloroplast. In this article, we shortly summarize the recent findings on plastidic FtsH proteases in text and figures. We will mainly focus on FtsH 1, 2, 5 and 8 localized in the thylakoid membrane and known for their importance in photosynthesis.

Piecing together the puzzle of parasitic plant plastome evolution

The importance of photosynthesis as a mode of energy production has put plastid genomes of plants under a constant purifying selection. This has shaped the characteristic features of plastid genomes across the entire spectrum of photosynthetic plants and has led to a highly uniform and conserved plastid genome with respect to structure, size, gene order, intron and editing site positions and coding capacity. Parasitic species that have dropped photosynthesis as the main energy provider share striking deviations from the plastid genome norm: multiple rearrangements within the circular chromosome, pseudogenization and gene deletions, promoter losses, intron losses as well as the extensive loss of mRNA editing competence have been reported. The collective loss of larger sets of functionally related genes like those for the plastid NADH-dehydrogenase complex and concomitant losses of RNA polymerase genes together with their target promoters point to "domino effects" where an initial loss might have triggered others. An example, which will be discussed in more detail, is the concomitant loss of the intron maturase gene matK and all introns that are supposedly subject to MatK-dependent splicing in two Cuscuta species.

Discrete Cyclic Porphyrin Arrays as Artificial Light-Harvesting Antenna

The importance of photosynthesis has driven researchers to seek ways to mimic its fundamental features in simplified systems. The absorption of a photon by light-harvesting (antenna) complexes made up of a large number of protein-embedded pigments initiates photosynthesis. Subsequently the many pigments within the antenna system shuttle that photon via an efficient excitation energy transfer (EET) until it encounters a reaction center. Since the 1995 discovery of the circularly arranged chromophoric assemblies in the crystal structure of light-harvesting antenna complex LH2 of purple bacteria Rps. Acidophila, many designs of light-harvesting antenna systems have focused on cyclic porphyrin wheels that allow for efficient EET. In this Account, we review recent research in our laboratories in the synthesis of covalently and noncovalently linked discrete cyclic porphyrin arrays as models of the photosynthetic light-harvesting antenna complexes. On the basis of the silver(I)-promoted oxidative coupling strategy, we have prepared a series of extremely long yet discrete meso-meso-linked porphyrin arrays and covalently linked large porphyrin rings. We examined the photophysical properties of these molecules using steady-state absorption, fluorescence, fluorescence lifetime, fluorescence anisotropy decay, and transient absorption measurements. Both the pump-power dependence on the femtosecond transient absorption and the transient absorption anisotropy decay profiles are directly related to the EET processes within the porphyrin rings. Within these structures, the exciton-exciton annihilation time and the polarization anisotropy rise time are well-described in terms of the Forster-type incoherent energy hopping model. In noncoordinating solvents such as CHCl(3), meso-pyridine-appended zinc(II) porphyrins and their meso-meso-linked dimers spontaneously assemble to form tetrameric porphyrin squares and porphyrin boxes, respectively. In the latter case, we have demonstrated the rigorous homochiral self-sorting process and efficient EET along these cyclic porphyrin arrays. The meso-cinchomeronimide appended zinc(II) porphyrin forms a cyclic trimer. We have also shown that the corresponding meso-meso-linked diporphyrins undergo high-fidelity self-sorting assembling to form discrete cyclic trimer, tetramer, and pentamer with large association constants through perfect discrimination of enantiomeric and conformational differences of the meso-cinchomeronimide substituents. Collectively, these studies of covalently and noncovalently linked discrete cyclic porphyrin arrays aid in the understanding of the structural requirements for such very fast EET in natural light-harvesting complexes.

The development of biochemistry and molecular biology in China

The development of biochemistry and molecular biology in China

Cyanobacteria associated with hot spring travertines

Cyanobacteria are the major oxygenic photosynthetic microorganisms of hot spring travertines. This review describes the known cyanobacterium flora of travertine-depositing waters > 37 °C. The communities develop either upon (epilithon) or within (endolithon) the travertine surface, where they may influence the travertine fabric by providing nucleation sites for calcium carbonate. Mat photosynthesis locally increases the amount of travertine deposited, but the importance of photosynthesis in travertine deposition is rarely significant because the main loss of CO2is by atmospheric evasion of the hot, CO2-rich waters. The Oscillatoriales are the most important group of cyanobacteria in terms of their biomass, but the taxonomy of the order is in a state of chaos. Molecular methods will ultimately disclose the true affinities of the organisms but, at present, the use of form-taxa based upon morphological characters provides a practical alternative. Identification of fossilized cyanobacteria is problematic since few of the key characters survive as fossils. The known cyanobacterium flora is tabulated and an analytical key provided to identify the form-taxa of hot spring travertines.

Wood preservation, it's a gas

CO2 receives such bad press in the context of global warming that it's sometimes hard to imagine it can actually be useful. Aside from its importance in photosynthesis, workers at CSIRO Forestry and Forest Products (Australia) aim to patent their use of ‘supercritical’ CO2 as a delivery system for preservatives into wood. Supercritical CO2 combines a liquid's capacity to dissolve materials with a gas’ ability to penetrate the micropores of timber, particularly in otherwise difficult woods. Unfortunately, upon reversion to the gaseous state, the CO2 goes back into the atmosphere. (http://www.csiro.au/page.asp?type=mediaRelease&id=Prsupercritical)

Factors affecting fruit and seed production in Dactylorhiza maculata (Orchidaceae)

It has been argued that some of resources needed for fruit and seed production in terrestrial orchids originate from storage in underground biomass. Resources for female reproductive traits may also originate from current photosynthesis. Orchid mycorrhiza may also influence fruit and seed production. The extent to which current photosynthetic activity and nutrient uptake via mycorrhizal fungi affect fruit and seed production has only rarely been studied experimentally. This paper examines the importance of photosynthesis and mycorrhiza for fruit and seed production, leaf area and plant status in the next season for Dactylorhiza maculata (L.) Soo in two populations. Plants were hand-pollinated in two populations to assure successful fertilization. Photosynthesis in the main leaves and in the green parts of inflorescence was prevented and/or mycorrhizal function inhibited by applying thiabendazole to plants. None of the treatments affected relative capsule production, but all treatments resulted in significant decreases in capsule dry weight and the number of seeds produced. The fact that seed production remained high in spite of the experimental treatments indicates that resources stored in the underground corms were used in fruit development and seed production. Inhibition of photosynthesis decreased leaf area in the year following treatments, while the other treatments had no effect on subsequent growth.

The relative importance of photosynthesis and respiration in determining plant growth rate

The underlying physiological and biomass allocation parameters associated with differences in (RGR) among plant species characteristic of contrasting habitats have been well characterised. When grown at a single temperature under controlled environment conditions, plant species characteristic of unfavourable habitats exhibit lower RGR values than species from favourable environments. Slow growing species also exhibit lower rates of photosynthesis and respiration per unit plant mass. We examine the impact of different growth temperatures on photosynthesis and respiration and how this affects the RGR of some fast and slow growing species. Photosynthesis and respiration are both temperature sensitive in short-term experiments. Continued exposure to contrasting temperatures can, however, result in acclimation of respiration and photosynthesis. We examine the impact of different growth temperatures on photosynthesis and respiration and how this affects the RGR of a range of fast and slow growing species. Measurements of leaf level photosynthesis, leaf respiration (dark and light) and root respiration were made on 16 plant species that differed in RGR. Plants were grown hydroponically at 18, 23 and 28oC and measurements were made at the respective growth temperature. Photosynthesis and root respiration achieved homeostasis when plants were grown at the three temperatures. Leaf respiration however increased with temperature. There was a negative correlation between RGR and the percentage of daily photosynthesis respired, this relationship was maintained at all temperatures. RGR was reduced at 28oC due to a lack of acclimation of leaf respiration, which lead to an increase in ratio of respiration to photosynthesis. The importance of respiration and photosynthesis on ultimate growth rate will be discussed.

INFLUENCE OF PHOSPHORUS APPLICATION TO FLOODWATER ON OXYGEN CONCENTRATIONS AND SURVIVAL OF RICE DURING COMPLETE SUBMERGENCE

Low concentrations of phosphorous were added to the floodwater of submerged rice in an attempt to regulate algal growth, so as to increase floodwater O2 concentration and plant survival during submergence for up to 12 days. Increasing the phosphorus concentration of the floodwater by 1 ppm increased algal growth by at least 4-fold based on chlorophyll concentrations, and increased floodwater O2 concentrations to over twice air saturation. However, additions of phosphorus reduced rice plant survival during submergence by up to 35%. The adverse effects of a high phosphorus concentration in the floodwater were mainly attributed to competition between the algae and the submerged rice for CO2 and, perhaps, light. The importance of photosynthesis during the submergence of rice was supported by the results of experiments in which floodwater CO2 concentration was manipulated by altering pH. The survival of an intolerant rice cultivar during submergence increased from 0 to 17 and 62% at pH 8, 7 and 5 respectively, while floodwater CO2 concentrations at these pHs would have increased from 0.02 to 0.3 and 1.0 mol m−3 respectively. The results were used to question the importance of floodwater O2 concentrations above anoxia for submergence tolerance of rice.

Graft-transmissibility of resistance to cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae), in six highly antibiotic cowpea varieties

AbstractThe use of six cowpea varieties highly resistant to Aphis craccivora Koch in grafts (as resistant scion and rootstock) with the susceptible variety Prima indicated the presence of a graft-transmissible chemical involved in the resistance. Wrapping the resistant part in light-proof foil indicated that photosynthesis is involved in the production of the chemical. In a third test, intergrafting is involved in the production of the chemical. In a third test, intergrafting the resistant part with and without leaves confirmed the importance of photosynthesis in the transfer of resistance. Finally, covering the resistance intergrafts with foil showed that the accumulation of the chemical in the stem before the foil was applied was the major source of the graft-transmissible resistance.

Infection of Synechococcus cedrorum by the cyanophage AS-1M : III. Cellular metabolism and phage development

The importance of photosynthesis in the growth of cyanophage AS-1M in the unicellular blue-green alga Synechococcus cedrorum was determined. CO 2 fixation and O 2 evolution continued at high levels throughout the latent period, but decreased rapidly immediately prior to lysis. Growth of AS-1M in the dark resulted in a total cessation of phage development. Similar results were obtained when photosynthesis was perturbed by DCMU, CCCP, valinomycin, nigericin, or lack of CO 2. Supplementation by 1% glucose in the dark or in the light (+10 −5 M DCMU) restored phage development to about 10% of the control level. These results are interpreted to mean that cyanophage replication normally derives all of its energy and carbon from photosynthesis. However, infected cells do have a limited heterotrophic capacity.

Assimilation et translocation du 14CO2 chez le froment (Triticum aestivum L.) en fonction de la densité et de la structure du couvert aérien

Distributions of assimilates at different times after assimilation of 14CO2 shortly after ear emergence of semidwarf spring wheat differing in leaf angle and row width were similar. The differences in leaf angle were obtained with a normal droopy cultivar and a mutant derived from it and characterized by erect upper leaves. Shortly after emergence, flag leaf laminae and spikes (especially glumes, paleas and lemmas) were the main photosynthesizing parts. Their position in the upper levels accounted for the little effect of canopy architecture on their relative importance for photosynthesis. Leaf sheaths and particularly flag leaf sheaths photo-synthesized as much as about one third of their corresponding lamina. Most of the residual radioactivity at maturity was in the grains.

The path of carbon in photosynthesis of the lipids

The rates of C 11 incorporation into lipids and their components during steady-state photosynthesis in C 11O 2 by Chlorella pyrenoidosa reveal the metabolic importance of the galaclolipids and phosphatidyl glycerol. The most, rapidly labeled of the water-soluble deacylation products were galactosyl glycerol, digalactosyl glycerol, diglycerophosphate, sulfoglycosyl glycerol, and glycerophosphorylinositol. Labeling of the triglycerides proceeded more slowly than that of any of the surfactant lipids. Acid hydrolysis of the labeled galactolipids demonstrated active exchange of the galactose moieties with the intermediates of hexose photosynthesis and relatively slower labeling of the associated glycerol or fatty acids. However, the fatty acids of phosphatidylglycerol and the galactosyl diglycerides were more rapidly labeled than any other esterified fatty acids. Periodate oxidation of diglycerophosphate from phosphatidylglycerol indicated uniform labeling before 5 min. of steady-state photosynthesis. Possible metabolic sequences in the biosynthesis of the galactolipids and the phosphatides are discussed. The remarkable metabolic activity and high concentrations of phosphatidyl glycerol and the galactolipids in Chlorella attest to their importance in photosynthesis.

Oxidation-reduction reactions in the photosynthetic bacterium Chromatium. II. Dependence of light reactions on intensity of irradiation and quantum efficiency of cytochrome oxidation

The intensity dependences of light-induced reactions in Chromatium have been determined spectrophotometrically. The intensities of near-infrared irradiation required for half-maximum oxidation of the various cytochrome species are in the proportion 1:500:~4000 for C 423.5, C 426, and the combination of C 422 and C 430. The quantum requirement for intracellular cytochrome 423.5 oxidation has been determined by measuring the initial rate of absorbancy change (423 mμ) in anaerobic bacteria upon irradiation with monochromatic yellow light (589 mμ) of known quantum intensity. This requirement is 2 quanta per electron at both 11 and 29 °C. A hypothetical structure for the cytochrome system in Chromatium consists of three distinct electron-transfer pathways. The pathway including C 423.5 is of primary importance in photosynthesis.