Photosynthesis In Higher Plants Research Articles

Photosynthetic activity of crops and sequestration of atmospheric carbon by meadow clover and spring wheat in crop rotation

The purpose of the research is to estimate the intensity of absorption of light energy by crop rotation crops during the growing season and determine the amount of atmospheric carbon absorbed during photosynthesis. In a long-term stationary experiment, the absorption of photosynthetically active radiation (FAR) by crops of meadow clover for 2 years of use and spring wheat in variants without fertilizers and when applying N60P60K60 was studied. Chlorophyll A, chlorophyll B and carotene, which serve as photoreceptors-pigments of photosynthesis in higher plants, were used to assess the intensity of absorption of light energy. The most active period of absorption of HEADLIGHTS by meadow clover leaves was noted from the stalking phase to flowering, the amount of chlorophyll A and B in the leaves was 11.08…14.32 mg/g dry weight, carotene – 2.2…3.3 mg/g dry weight. During photosynthesis, the carbon content in clover leaves varied in the range of 40.4…45.5 %. The content of the main products of photosynthesis, sugars, decreased from 9.8 % in the stalking phase to 3.4 % during seed formation. The most intensive process of photosynthesis of spring wheat took place during the period from the tillering phase to the beginning of maturation, the chlorophyll content was 9.14…11.90 mg/g dry weight, carotene was 2.5…4.3 times lower. Most sugars were noted at the beginning of entering the tube: without fertilizers – 15.3 %, when applying NPK of 60 kg d. v./ ha – 17.2 %. The amount of carbon absorbed by meadow clover crops during photosynthesis during the growing season, depending on the experimental options, was 2.26…2.42 t/ha (8.09…8.66 t/ha CO2), spring wheat – 1.49…1.93 t/ha (5.33…6.90 t/ha CO2).

Greening of barley seedlings under changed gravity conditions

Plants possess sensitive mechanisms for detecting gravitational changes, and altered gravity conditions can affect metabolic processes, including photosynthesis. Photosynthesis in higher plants occurs in chloroplasts, where pigment-binding proteins play a crucial role in capturing and transferring light energy. Microgravity's impact on the photosynthetic apparatus has been studied in space-flight experiments, but results have been contradictory. This study investigates the influence of clinorotation on barley seedlings' photosynthetic apparatus during greening. The study examines pigment biosynthesis, chloroplast membrane formation, and photochemical characteristics. Results show that clinorotation affects pigment accumulation, and the differences are more pronounced in the early stages of greening, highlighting the importance of gravity in plant photosynthesis.

Laboratory Simulation of Photosynthesis in a Wide Range of Electromagnetic and Radiation Environment Parameters

The problem of studying the limits of stability and mechanisms of adaptation of living systems to environmental parameters that vary over a wide range is briefly analyzed. The main attention is focused on the analysis of the electromagnetic environment and background radiation. These factors vary relatively little on the modern Earth, which leads to their insufficient knowledge. At the same time, they present serious challenges for future space missions. One of the main methods for studying the influence of such factors on living organisms is laboratory simulation. Previous experiments have demonstrated the need to develop a new laboratory setup, the requirements for the parameters of which are presented in this paper. In general, the setup will have a high potential for solving the problems of modeling the effect of astro-geophysical factors on the physiological state of living organisms and, in particular, the activity of photosynthesis in higher plants. The implementation of the proposed program of laboratory simulation experiments will allow us to advance in understanding the problems of life evolution, the mechanisms of the possible influence of solar activity on the biosphere, and studies of the role of the biosphere in global climate changes of planets at various time horizons.

Correlating Coffea canephora 3D architecture to plant photosynthesis at a daily scale and vegetative biomass allocation.

Coffea canephora (C. canephora) has two botanical varieties, Robusta and Conilon. Intraspecific variability was hypothesized and projected for the selection of C. canephora plants able to maintain production in the context of global climate changes. For that, architectural, C-assimilation and biomass analyses were performed on 17-month-old Robusta (clones 'A1' and '3V') and Conilon (clones '14' and '19') varieties grown in non-limiting soil, water and mineral nutrient conditions. Nondestructive coffee plant architecture coding, reconstruction and plant photosynthesis estimations were performed using a functional-structural plant modeling platform OpenAlea. 3D reconstructions and inclusion of parameters calculated and estimated from light response curves, such as dark respiration (Rd), maximum rate of carboxylation of RuBisCO and photosynthetic electron transport allowed the estimation of instantaneous and daily plant photosynthesis. The virtual orchard leaf area index was low, and light was not a limiting factor in early C. canephora development stages. Under such conditions, Robusta assimilated more CO2 at the plant and orchard scale and produced higher total biomass than Conilon. Lower plant daily photosynthesis and total biomass were correlated to higher Rd in Conilon than in Robusta. Among the architectural traits, leaf inclination, size and allometry were most highly correlated with plant assimilation and biomass. Relative allocation in leaf biomass was higher in '19' Conilon than in young Robusta plants, indicating intraspecific biomass partitioning. Similarly, variation in relative distribution of the root biomass and the root volume reflected clonal variation in soil occupation, indicating intraspecific variability in space occupation competitiveness. Coffea canephora denoted high root allocation in both Conilon and Robusta clones. However, relevant differences at subspecific levels were found, indicating the high potential of C. canephora to cope with drought events, which are expected to occur more frequently in the future, because of climate changes. The methodology developed here has the potential to be used for other crops and tree species. Highlights Functional-structural plant model was used to estimate photosynthesis on a plant and daily scales in Coffea canephora (C. canephora). Among the architectural traits, leaf shape and inclination had the most impact on photosynthesis and biomass. Under non-limiting conditions, Robusta had higher plant photosynthesis and biomass than Conilon. A higher leaf biomass allocation in Conilon clone '19' than in Robusta suggested variety-specific partitioning. Variation in the relative distribution of the root biomass indicated C. canephora intraspecific soil occupation variability.

A chloroplast-localized pentatricopeptide repeat protein involved in RNA editing and splicing and its effects on chloroplast development in rice

BackgroundThe chloroplast is the organelle responsible for photosynthesis in higher plants. The generation of functional chloroplasts depends on the precise coordination of gene expression in the nucleus and chloroplasts and is essential for the development of plants. However, little is known about nuclear-plastid regulatory mechanisms at the early stage of chloroplast generation in rice.ResultsIn this study, we identified a rice (Oryza sativa) mutant that exhibited albino and seedling-lethal phenotypes and named it ssa1(seedling stage albino1). Transmission electron microscopy (TEM) analysis indicated that the chloroplasts of ssa1 did not have organized thylakoid lamellae and that the chloroplast structure was destroyed. Genetic analysis revealed that the albino phenotypes of ssa1 were controlled by a pair of recessive nuclear genes. Map-based cloning experiments found that SSA1 encoded a pentapeptide repeat (PPR) protein that was allelic to OSOTP51,which was previously reported to participate in Photosystem I (PSI) assembly. The albino phenotype was reversed to the wild type (WT) phenotype when the normal SSA1 sequence was expressed in ssa1 under the drive of the actin promoter. Knockout experiments further created mutants ssa1–2/1–9, which had a phenotype similar to that of ssa1. SSA1 consisted of 7 pentatricopeptide repeat domains and two C-terminal LAGLIDADG tandem sequence motifs and was located in the chloroplast. GUS staining and qRT–PCR analysis showed that SSA1 was mainly expressed in young leaves and stems. In the ssa1 mutants, plastid genes transcribed by plastid-encoded RNA polymerase decreased, while those transcribed by nuclear-encoded RNA polymerase increased at the mRNA level. Loss-of-function SSA1 destroys RNA editing of ndhB-737 and intron splicing of atpF and ycf3–2 in the plastid genome. Yeast two-hybrid and BiFC assays revealed that SSA1 physically interacted with two new RNA editing partners, OsMORF8 and OsTRXz, which have potential functions in RNA editing and chloroplast biogenesis.ConclusionsRice SSA1 encodes a pentatricopeptide repeat protein, which is targeted to the chloroplast. SSA1 regulates early chloroplast development and plays a critical role in RNA editing and intron splicing in rice. These data will facilitate efforts to further elucidate the molecular mechanism of chloroplast biogenesis.

Energy transfer in photosynthesis mediated by resonant confinement of exciton-polariton

The ultra efficiency of energy transfer in photosynthesis has important biological significance. The underlying mechanism of energy transfer has never stopped being explored. Possible roles of quantum mechanics behind the natural phenomenon lead to many explorations in the field. Yet conventional mechanisms based on Förster resonance energy transfer or localized quantum coherence effects face certain challenges in explaining the unusual efficiency. We hereby bring up the attention of the dual properties of wave and particle of quantum mechanics into this context. In a previous research, we attributed the success of a similar efficiency in an artificial photosynthesis experiment to a mechanism mediated by resonant confinement of exciton-polariton. This paper extends the work to biological photosynthesis in higher plants and green sulfur bacteria. We explore specifically whether the exciton-polaritons of light-harvesting pigments, constrained by the optical cavity resonance, can act as intermediate states to mediate energy transfer. Namely, the pigments give a full play to their dual roles, receiving sunlight in the form of particle-like excitons, and rapidly transferring them to the reaction centers in the form of wave-like polaritons for maximal energy utilization. Taking realistic structure and data into account and based on approximate theoretical models, our quantitative estimate shows that such a mechanism is indeed capable of explaining at least partly the efficiency of photosynthesis. With comprehensive discussion, many deficits in the theoretical modeling can be reasonably reduced. Thus the conclusion may be further strengthened by realistic situations. Meanwhile, the underlying approach may also be extended to e.g. photovoltaic applications and neural signal transmissions, offering similar mechanisms for other energy transfer processes.

Putrescine regulates stomatal opening of cucumber leaves under salt stress via the H2O2-mediated signaling pathway

The stomatal aperture is imperative for photosynthesis in higher plants. The function of polyamines (PAs) in stomatal regulation under a stressful environment has not been fully determined. In this study, we demonstrated the mechanism by which putrescine (Put) regulates stomatal changes in cucumber leaves under salt stress. The results showed that foliar application of Put alleviated the decrease of stomatal aperture and photosynthesis caused by salt stress and promoted plant growth. Exogenous Put caused a significant increase in endogenous PAs and hydrogen peroxide (H2O2) levels by 105.43% and 27.97%, respectively, while decreased abscisic acid (ABA) content by 67.68% under salt stress. However, application of inhibitors of aminoguanidine hydrochloride (AG), 1, 8-diaminooctane (1, 8-DO), diphenyleneiodonium chloride (DPI) and salicylhydroxamic acid (SHAM) upregulated the 9-cis-cyclocarotenoid dioxygenase (NCED) gene and downregulated the reduced glutathione synthetase (GSHS) gene. These inhibitors also decreased the stomatal aperture, levels of H2O2 and reduced glutathione (GSH), but increased the ABA content under salt stress and Put treatment conditions. The order of influence is AG > 1, 8-DO > DPI > SHAM. However, Put-induced downregulation of ABA content and upregulation of GSH content under salt stress were effectively blocked by N, N′-dimethylthiourea (DMTU, H2O2 scavenger) and 1-chloro-2,4-dinitrobenzene (CDNB, GSH scavenger) treatments. Taken together, these results suggest that Put induced the formation of H2O2 signaling mediates the degradation of PAs by diamine oxidase (DAO), increasing GSH content and inhibiting the accumulation of ABA in leaves, thereby promoting stomatal opening in salt-stressed cucumber leaves.

Additive Production of a Material Based on an Acrylic Polymer with a Nanoscale Layer of Zno Nanorods Deposited Using a Direct Current Magnetron Discharge: Morphology, Photoconversion Properties, and Biosafety.

On the basis of a direct current magnetron, a technology has been developed for producing nanoscale-oriented nanorods from zinc oxide on an acrylic polymer. The technology makes it possible to achieve different filling of the surface with zinc oxide nanorods. The nanorods is partially fused into the polymer; the cross section of the nanorods is rather close to an elongated ellipse. It is shown that, with intense abrasion, no delamination of the nanorods from the acrylic polymer is observed. The zinc oxide nanorods abrades together with the acrylic polymer. Zinc oxide nanorods luminesces with the wavelength most preferable for the process of photosynthesis in higher plants. It was shown that plants grown under the obtained material grow faster and gain biomass faster than the control group. In addition, it was found that on surfaces containing zinc oxide nanorods, a more intense formation of such reactive oxygen species as hydrogen peroxide and hydroxyl radical is observed. Intensive formation of long-lived, active forms of the protein is observed on the zinc oxide coating. The formation of 8-oxoguanine in DNA in vitro on a zinc oxide coating was shown using ELISA method. It was found that the multiplication of microorganisms on the developed material is significantly hampered. At the same time, eukaryotic cells of animals grow and develop without hindrance. Thus, the material we have obtained can be used in photonics (photoconversion material for greenhouses, housings for LEDs), and it is also an affordable and non-toxic nanomaterial for creating antibacterial coatings.

Polymer-Modified Single-Walled Carbon Nanotubes Affect Photosystem II Photochemistry, Intersystem Electron Transport Carriers and Photosystem I End Acceptors in Pea Plants.

Single-walled carbon nanotubes (SWCNT) have recently been attracting the attention of plant biologists as a prospective tool for modulation of photosynthesis in higher plants. However, the exact mode of action of SWCNT on the photosynthetic electron transport chain remains unknown. In this work, we examined the effect of foliar application of polymer-grafted SWCNT on the donor side of photosystem II, the intersystem electron transfer chain and the acceptor side of photosystem I. Analysis of the induction curves of chlorophyll fluorescence via JIP test and construction of differential curves revealed that SWCNT concentrations up to 100 mg/L did not affect the photosynthetic electron transport chain. SWCNT concentration of 300 mg/L had no effect on the photosystem II donor side but provoked inactivation of photosystem II reaction centres and slowed down the reduction of the plastoquinone pool and the photosystem I end acceptors. Changes in the modulated reflection at 820 nm, too, indicated slower re-reduction of photosystem I reaction centres in SWCNT-treated leaves. We conclude that SWCNT are likely to be able to divert electrons from the photosynthetic electron transport chain at the level of photosystem I end acceptors and plastoquinone pool in vivo. Further research is needed to unequivocally prove if the observed effects are due to specific interaction between SWCNT and the photosynthetic apparatus.

Plastid-Targeted Cyanobacterial Flavodiiron Proteins Maintain Carbohydrate Turnover and Enhance Drought Stress Tolerance in Barley.

Chloroplasts, the sites of photosynthesis in higher plants, have evolved several means to tolerate short episodes of drought stress through biosynthesis of diverse metabolites essential for plant function, but these become ineffective when the duration of the stress is prolonged. Cyanobacteria are the closest bacterial homologs of plastids with two photosystems to perform photosynthesis and to evolve oxygen as a byproduct. The presence of Flv genes encoding flavodiiron proteins has been shown to enhance stress tolerance in cyanobacteria. In an attempt to support the growth of plants exposed to drought, the Synechocystis genes Flv1 and Flv3 were expressed in barley with their products being targeted to the chloroplasts. The heterologous expression of both Flv1 and Flv3 accelerated days to heading, increased biomass, promoted the number of spikes and grains per plant, and improved the total grain weight per plant of transgenic lines exposed to drought. Improved growth correlated with enhanced availability of soluble sugars, a higher turnover of amino acids and the accumulation of lower levels of proline in the leaf. Flv1 and Flv3 maintained the energy status of the leaves in the stressed plants by converting sucrose to glucose and fructose, immediate precursors for energy production to support plant growth under drought. The results suggest that sugars and amino acids play a fundamental role in the maintenance of the energy status and metabolic activity to ensure growth and survival under stress conditions, that is, water limitation in this particular case. Engineering chloroplasts by Flv genes into the plant genome, therefore, has the potential to improve plant productivity wherever drought stress represents a significant production constraint.

Influence of trace elements, applied in classical and nano forms, on photosynthesis of higher plants in relation to enhancement of crop productivity

One of the main factors of increasing the productivity of agricultural plants is intensifying the activity of the photo- synthetic apparatus, since the productivity of crops depends on the ability to absorb solar radiation and convert it into the energy of chemical bonds for further use in metabolic processes. The amount of photosynthetically active radia- tion absorbed by crops, in its turn, depends on the area, duration, and activity of the assimilation surface functioning. The use of fertilizers, that contain trace elements, can further achieve both raising the yield of cultivated plants and environmental protection. In this regard, the state-of-the-art research on the infl uence of the main trace elements (iron, zinc, manganese, molybdenum, cobalt, selenium, boron, titanium) and one macroelement - magnesium - on photosynthetic characteristics of plants and crops is discussed. Based on the literature data and the results of our own research, we documented the effect of trace elements on leaves carbon dioxide exchange rates, the content of photo- synthetic pigments, the antioxidant enzymes activity, as well as the traits of the photosynthetic apparatus capacity. The infl uence of nanometals on the content and ratio of pigments, net CO 2 assimilation rate, and the photochemical activity of photosystems, including the effect of stress factors, is discussed. The specifi cities of the infl uence of nanometals are discussed and possible mechanisms of the effect of low concentrations of trace elements on plant metabolism are analyzed. It is shown that trace elements infl uence photosynthetic processes in plants and the systems of their antioxi- dant protection. The relevance of trace elements in the development of new strategies to elaborate the technologies of cultivating next-generation plants, including those that will be based on new physical and chemical properties of macro- and micronutrients in a nano form, is highlighted

Condensation of Rubisco into a proto-pyrenoid in higher plant chloroplasts

Photosynthetic CO2 fixation in plants is limited by the inefficiency of the CO2-assimilating enzyme Rubisco. In most eukaryotic algae, Rubisco aggregates within a microcompartment known as the pyrenoid, in association with a CO2-concentrating mechanism that improves photosynthetic operating efficiency under conditions of low inorganic carbon. Recent work has shown that the pyrenoid matrix is a phase-separated, liquid-like condensate. In the alga Chlamydomonas reinhardtii, condensation is mediated by two components: Rubisco and the linker protein EPYC1 (Essential Pyrenoid Component 1). Here, we show that expression of mature EPYC1 and a plant-algal hybrid Rubisco leads to spontaneous condensation of Rubisco into a single phase-separated compartment in Arabidopsis chloroplasts, with liquid-like properties similar to a pyrenoid matrix. This work represents a significant initial step towards enhancing photosynthesis in higher plants by introducing an algal CO2-concentrating mechanism, which is predicted to significantly increase the efficiency of photosynthetic CO2 uptake.

Editorial: Biographical Memoirs, Volume 69

Editorial: Biographical Memoirs, Volume 69

Chloroplast Transition Metal Regulation for Efficient Photosynthesis.

Plants require sunlight, water, CO2, and essential nutrients to drive photosynthesis and fulfill their life cycle. The photosynthetic apparatus resides in chloroplasts and fundamentally relies on transition metals as catalysts and cofactors. Accordingly, chloroplasts are particularly rich in iron (Fe), manganese (Mn), and copper (Cu). Owing to their redox properties, those metals need to be carefully balanced within the cell. However, the regulation of transition metal homeostasis in chloroplasts is poorly understood. With the availability of the arabidopsis genome information and membrane protein databases, a wider catalogue for searching chloroplast metal transporters has considerably advanced the study of transition metal regulation. This review provides an updated overview of the chloroplast transition metal requirements and the transporters involved for efficient photosynthesis in higher plants.

Zinc in Soil Environment for Plant Health and Management Strategy

Zinc is an essential element for photosynthesis and its deficiency may play a role in the reduction of activity of rubisco and hence decreased rate of photosynthesis in higher plants. Zinc deficiency sometimes resembles Fe/Mn deficiencies. Under severe zinc deficiency the shoot apices die ('die-back') as is widely distributed. Zinc toxicity leads to chlorosis in young leaves. Induced manganese deficiency might also be of importance as high zinc supply strongly decreases the manganese content of plants. Most preventing measures for zinc deficiency are selection of Zn efficient variety that is tolerant to high level of bicarbonate as well as low zinc in soil. Curative measure for correcting are application of 20-25 kg/ha ZnSo4 in acid soil, 22 kg Zn/ha initially followed by 5-10 kg Zn in the later years or 50% gypsum + 10 t GM + 22 kg Zn once in 2-3 years in sodic soils, 1.0-1.5 kg/ha Zn as foliar spray at tillering stage and 2 times latter is very helpful for correct this deficiency. Zinc is very tightly bound to phytic acid and the formation of protein-zinc-phytic acid complexes increases the resistance to hydrolysis that leads to decrease in bioavailability of Zn to human and animals. Enrichment of cereal grains with Zn through both genetic (e.g., breeding) and agronomic (e.g., application of Zn fertilizers) biofortification is a high priority area of research, and will contribute to minimizing Zn-deficiency-related health problems in human populations.

Is Nitrogen a Key Determinant of Water Transport and Photosynthesis in Higher Plants Upon Drought Stress?

Drought stress is a major global issue limiting agricultural productivity. Plants respond to drought stress through a series of physiological, cellular, and molecular changes for survival. The regulation of water transport and photosynthesis play crucial roles in improving plants’ drought tolerance. Nitrogen (N, ammonium and nitrate) is an essential macronutrient for plants, and it can affect many aspects of plant growth and metabolic pathways, including water relations and photosynthesis. This review focuses on how drought stress affects water transport and photosynthesis, including the regulation of hydraulic conductance, aquaporin expression, and photosynthesis. It also discusses the cross talk between N, water transport, and drought stress in higher plants.

LOW PHOTOSYNTHETIC EFFICIENCY 1 is required for light-regulated photosystem II biogenesis in Arabidopsis

Photosystem II (PSII), a multisubunit protein complex of the photosynthetic electron transport chain, functions as a water-plastoquinone oxidoreductase, which is vital to the initiation of photosynthesis and electron transport. Although the structure, composition, and function of PSII are well understood, the mechanism of PSII biogenesis remains largely elusive. Here, we identified a nuclear-encoded pentatricopeptide repeat (PPR) protein LOW PHOTOSYNTHETIC EFFICIENCY 1 (LPE1; encoded by At3g46610) in Arabidopsis, which plays a crucial role in PSII biogenesis. LPE1 is exclusively targeted to chloroplasts and directly binds to the 5' UTR of psbA mRNA which encodes the PSII reaction center protein D1. The loss of LPE1 results in less efficient loading of ribosome on the psbA mRNA and great synthesis defects in D1 protein. We further found that LPE1 interacts with a known regulator of psbA mRNA translation HIGH CHLOROPHYLL FLUORESCENCE 173 (HCF173) and facilitates the association of HCF173 with psbA mRNA. More interestingly, our results indicate that LPE1 associates with psbA mRNA in a light-dependent manner through a redox-based mechanism. This study enhances our understanding of the mechanism of light-regulated D1 synthesis, providing important insight into PSII biogenesis and the functional maintenance of efficient photosynthesis in higher plants.

Transcript profiling of sucrose synthase genes involved in sucrose metabolism among four carrot (Daucus carota L.) cultivars reveals distinct patterns

BackgroundCarrot which contains lots of nutrients has a large demand around the world. The soluble sugar content in fleshy root of carrot directly influences its taste and quality. Sucrose, as an important member of soluble sugar, is the main product of photosynthesis in higher plants and it plays pivotal roles in physiological processes including energy supply, signal transduction, transcriptional regulation, starch and cellulose synthesis, and stress tolerance. Sucrose synthase is a key enzyme involved in sucrose metabolism and is closely related to sucrose content. However, the molecular mechanism involved in sucrose metabolism in carrot has lagged behind.ResultsHere, carrot roots of five developmental stages from four carrot cultivars were collected, and the contents of soluble sugar and sucrose in different stages and cultivars were surveyed. Three DcSus genes (DcSus1, DcSus2, and DcSus3), with lengths of 2427 bp, 2454 bp and 2628 bp, respectively, were identified and cloned in carrot. Phylogenetic analysis from the deduced amino acid sequences suggested that three DcSus were clustered into three distinct groups (SUSI, II and III). Results of enzymatic profiles demonstrated that the DcSus activities showed decrease trends during taproot development. Correlation analysis indicated that the DcSus activity showed negative correlation with soluble sugar content and strong negative correlation with sucrose concentration. Quantitative real-time PCR analysis showed that the expression profiles of the DcSus genes are significantly different in carrot tissues (root, leaf blade, and petiole), and the expression levels of the DcSus genes in the leaf blade were much higher than that in the root and petiole. The expression profiles of DcSus genes showed strong negative correlation with both sucrose content and soluble sugar content.ConclusionsDuring carrot root development, the soluble sugar content and sucrose content showed increasing trends, while DcSus activities had persisting declinations, which may be due to the decreasing expression levels of genes encoding sucrose synthase. Our data demonstrate that synthesis of sucrose in carrot tissue is closely related with DcSus genes. The results from our study would not only provide effective insights of sucrose metabolism in carrot, but also are beneficial for biologists to improve carrot quality.

Zinc in plant-soil system and management strategy

Zinc is an essential element for photosynthesis and its deficiency may play a role in the reduction of activity of rubisco and hence decreased rate of photosynthesis in higher plants. Zinc deficiency sometimes resembles Fe/Mn deficiencies. Under severe zinc deficiency the shoot apices die ‘die-back ’as is widely distributed. Zinc toxicity leads to chlorosis in young leaves. Induced manganese deficiency might also be of importance as high zinc supply strongly decreases the manganese content of plants. Most preventing measures for zinc deficiency is selection of Zn efficient variety that is tolerant to high level of bicarbonate as well as low zinc in soil. Curative measure for correcting is application of 20–25 kg/ha ZnSO4 in acid soil is very helpful for correct this deficiency. Zinc is very tightly bound to phytic acid and the formation of protein-zinc-phytic acid complexes increases the resistance to hydrolysis that leads to decrease in bioavailability of Zn to human and animals. Enrichment of cereal grains with Zn through both genetic and agronomic biofortification is a high priority area of research, and will contribute to minimizing Zndeficiency-related health problems in human populations.

Application of a mathematical model of variation potential for analysis of its influence on photosynthesis in higher plants

Local injuries induce generation of variation potential (VP) in higher plants; VP propagates into intact parts of a plant and induces the photosynthesis inactivation, which is probably connected with a proton influx into the cells. The aim of this work was to theoretically investigate participation of the intra- and extracellular pH changes in this process using the VP mathematical model developed earlier. The VP model took into account main systems of ion transport in a cell and their regulation; concentrations of the potential-forming ions; buffering properties, and the involvement of a “wound substance” in a signal propagation. To describe the dependence of the photosynthetic parameters on the pH changes, experimentally obtained linear relations were used. The model was shown to give a good qualitative description of the photosynthetic response at a distance of 10 cm from the injury area and simulated a considerable attenuation of the response at a distance of 22 cm. Analysis of the dependence of the photosynthetic response parameters on the VP amplitude also showed a qualitative correspondence of the model with the experimental results. Thus, experimental photosynthetic response is described well by the VP model that presumes linear dependencies of the photosynthetic parameter changes on pH shifts. This theoretical result supports a hypothesis about a key role of pH shifts in the development of the photosynthetic response.