Chlorophyll Photosynthesis Research Articles

The influence of powdery mildew (Sawadaea bicornis (Wallr.) Miyabe) on chlorophyll fluorescence in Norway maple (Acer platanoides L.) seedlings

The article presents the results of research on impact of Sawadaea bicornis (Wallr.) Miyabe on the state of photosynthetic apparatus in Acer platanoides L. seedlings using a technique of chlorophyll fluorescence induction (ChlF) measurement, which at the present time can be implemented through the use of biosensors. The research was conducted in September 2022 in the territory of the Botanical Garden of Oles Honchar Dnipro National University. To diagnose a violation of the native chlorophyll photosynthesis in fresh leaves of A. platanoides, a portable fluorometer “Floratest” was used (selected spectral range for fluorescence intensity measurement was 670–800 nm). The research was carried out on fresh leaves of Norway maple seedlings both not unaffected and affected with powdery mildew. Analysis of the data obtained indicates a high sensitivity of the parameters of chlorophyll fluorescence induction to damage by the disease regardless of environmental conditions of local growth of A. platanoides seedlings. The high informativeness of induction changes in chlorophyll fluorescence in the structural organization of chloroplasts in Norway maple leaves determined by the parameters Fo, Fm, Fv, Fv/Fо, Fv/Fm, (Fm–Fst)/Fst, (Fp–Fо)/Fv was revealed. This study demonstrated the effectiveness of using the studied chlorophyll fluorescence parameters to detect severe stress in Norway maple seedlings caused by powdery mildew exposure when the fungus affects more than 50% of the leaf blade area. It is further necessary to conduct dynamic studies throughout the growing season to determine the effectiveness of using these parameters to detect mild stress in the early stages of infection. Therefore, our research showed that the method of induction of chlorophyll fluorescence using the “Floratest” device allows you to quickly determine the general condition of the plant by evaluating photosynthesis, which is the main life process. Analysis of chlorophyll fluorescence parameters is a powerful and effective tool for determining the effect of a parasitic fungus on a plant.

Nitrogen Supply of Crops and Type of Fertilization and Their Impact on the Soil Case Study of Apulia Region

Nitrogen (N) is one of the fundamental elements for plant development: it plays a very important role in biochemical processes, such as chlorophyll photosynthesis, the production of amino acids and proteins, but it is also the most critical element in fertilization. When nitrogen is administered to the soil, in its more complex forms, organic and ureic, it transforms into increasingly simple forms such as Ammonia (NH) and Nitric (NO3) and becomes assailable by plants. Due to its agronomic function, nitrogen represents an element that must be appropriately integrated into the crop cycle through careful fertilization and a careful balance between withdrawals, losses and contributions. The choice of the nitrogen fertilization strategy must obviously aim to guarantee the availability of the element to the crops in the phases in which they need it most, avoiding losses that can represent a threat to the environment or to the crop economic balance. This article has the main purpose of highlighting the impact of the main fertilizations used in the regional agricultural context, in relation to the concentration of nitrogen in its various forms which remains in the soil, thus becoming part of a potential environmental impact both of the matrix itself and of the aquifers. Below, through the analysis of the main crop types. The conclusion is the impact of the main crop type and them fertilization on the soil in particular for the nitrogen compounds.

Melatonin enhanced the heavy metal-stress tolerance of pepper by mitigating the oxidative damage and reducing the heavy metal accumulation

Heavy metals (HMs), like vanadium (V), chromium (Cr), cadmium (Cd), and nickel (Ni) toxicity due to anthropogenic, impair plant growth and yield, which is a challenging issue for agricultural production. Melatonin (ME) is a stress mitigating molecule, which alleviates HM-induced phytotoxicity, but the possible underlying mechanism of ME functions under HMs' phytotoxicity is still unclear. Current study uncovered key mechanisms for ME-mediated HMs-stress tolerance in pepper. HMs toxicity greatly reduced growth by impeding leaf photosynthesis, root architecture system, and nutrient uptake. Conversely, ME supplementation markedly enhanced growth attributes, mineral nutrient uptake, photosynthetic efficiency, as measured by chlorophyll content, gas exchange elements, chlorophyll photosynthesis genes' upregulation, and reduced HMs accumulation. ME treatment showed a significant decline in the leaf/root V, Cr, Ni, and Cd concentration which was about 38.1/33.2%, 38.5/25.9%, 34.8/24.9%, and 26.6/25.1%, respectively, when compared with respective HM treatment. Furthermore, ME remarkably reduced the ROS (reactive oxygen species) accumulation, and reinstated the integrity of cellular membrane via activating antioxidant enzymes (SOD, superoxide dismutase; CAT, catalase; APX, ascorbate peroxidase; GR, glutathione reductase; POD, peroxidase; GST, glutathione S-transferase; DHAR, dehydroascorbate reductase; MDHAR, monodehydroascorbate reductase) and as well as regulating ascorbate-glutathione (AsA-GSH) cycle. Importantly, oxidative damage showed efficient alleviations through upregulating the genes related to key defense such as SOD, CAT, POD, GR, GST, APX, GPX, DHAR, and MDHAR; along with the genes related to ME biosynthesis. ME supplementation also enhanced the level of proline and secondary metabolites, and their encoding genes expression, which may control excessive H2O2 (hydrogen peroxide) production. Finally, ME supplementation enhanced the HM stress tolerance of pepper seedlings.

Aboveground responses to belowground root damage detected by non-destructive sensing metrics in three tree species

Abstract Root systems form a significant part of tree biomass and function. Yet, roots are hidden from our eyes, making it difficult to track the belowground processes. By contrast, our capacity to detect aboveground changes in trees has been continuously improving using optical methods. Here, we tested two fundamental questions: (1) To what extent can we detect aboveground responses to mechanical damage of the root system? (2) To what extent are roots redundant? We applied three different non-destructive remote sensing means: (1) optical means to derive leaf greenness, (2) infrared means to detect the changes in leaf surface temperature and (3) spectral means to derive five vegetation indices (i.e. the photochemical reflectance index (PRI), the chlorophyll photosynthesis index (CIRed-edge), the anthocyanin reflectance index 1, the structure insensitive pigment index and the normalized difference water index (NDWI)). We recorded the above metrics for hours and days and up to a month following induced root damage in three key Mediterranean tree species: Aleppo pine (Pinus halepensis Mill.), Palestine oak (Quercus calliprinos Webb.) and Carob (Ceratonia siliqua L.). To induce root damage, we removed 25, 50 and 75 percent of the root system in each species and compared it with control saplings. Tree aboveground (canopy) responses to root damage increased over time and with damage level. Leaf warming (up to 3°C) and decreased PRI were the most significant and rapid responses, with temperature differences being visible as early as 2 days following root damage. NDWI and greenness were the least sensitive, with responses detectable only at 75 percent root damage and as late as 14 or 30 days following root damage. Responses varied vastly among species, with carob being the most sensitive and pine being the least. Changes in leaf temperature and PRI indicated that leaf transpiration and photosynthesis were impaired by root damage. Although trees build roots in excess, mechanical damage will eventually decrease transpiration and photosynthesis across tree species.

Pseudomonas koreensis culture filtrate alleviates tomato drought stress: modulation of antioxidant systems coupled with the porphyrin and chlorophyll–photosynthesis–fructose and mannose axis

Pseudomonas koreensis culture filtrate alleviates tomato drought stress: modulation of antioxidant systems coupled with the porphyrin and chlorophyll–photosynthesis–fructose and mannose axis

Winter wheat and soil total nitrogen integrated monitoring based on canopy hyperspectral feature selection and fusion

Nitrogen, as a key element for crop reproductive and nutritional growth, plays an important role in overall agricultural production. Hyperspectral remote sensing (RS) offers possibility for monitoring farm nitrogen content by its non-destructive and high throughput advantages. However, the integrated high-precision acquisition of nitrogen content in crops and soils is still a technical challenge that needs to be solved urgently. This study proposed a novel approach combining feature selection based on improved grey wolf optimizer (IGWO) and feature fusion with projected gradient nonnegative matrix factorization and matrix cross recombination (PNMF-MCR) to realize the integrated monitoring of total nitrogen (TN) content in winter wheat and soil based on crop canopy hyperspectral data. Therein, the IGWO originated from GWO, additionally considered a comprehensive feature selection criterion which are the relevance with TN, the representative ability of the entire spectra, and the redundancy of the selected wavebands. The selected TN sensitive wavebands are 487, 611, 706, 817, 920 nm for winter wheat and 478, 587, 699, 812, 892 nm for soil, which could effectively represent the TN information of full spectrum from the aspects of nitrogen metabolism enzymes, chlorophyll photosynthesis, and the structure of cellular arrangements within the leaf. To further integrate the TN sensitive spectral information of crop and soil, PNMF-MCR was firstly proposed to generate a feature matrix VF by fusing the winter wheat and soil TN sensitive wavelengths. The TN inversion results based on the fused feature matrix VF achieved a high accuracy for both winter wheat and soil simultaneously. On the ground-based RS platform, the R2 and RMSE of the validation dataset for winter wheat are 0.7920 and 0.1431 g/kg. The validation results for soil are 0.7928 and 0.0037 g/kg. On the Airborne-based RS platform, the R2 and RMSE of the validation dataset for winter wheat are 0.6934 and 0.1490 g/kg. The validation results for soil are 0.6988 and 0.0040 g/kg. To verify the proposed method, predictive performances for TN of winter wheat and soil were validated in different time, at different locations for different winter wheat varieties on different platforms (ground-based platform and airborne-based platform). All above validations demonstrated the good universality and predictive ability of proposed hybrid method, which provide a feasible solution for integrated monitoring of crop and soil.

Synthesis and Photophysics Characterization of Boronic Styril and Distyryl BODIPYs for Water-Based Dye-Sensitized Solar Cells.

In this study, two boronic acid BODIPYs are obtained through a microwave-assisted Knoevenagel reaction. The aim is to use them for the first time as dyes in a photosensitized solar cell (DSSC) to mimic chlorophyll photosynthesis, harvesting solar light and converting it into electricity. The microwave-assisted Knoevenagel reaction is a straightforward approach to extending the molecular conjugation of the dye and is applied for the first time to synthesize BODIPY’s boronic acid derivatives. These derivatives have proved to be very useful for covalent deposition on titania. This work studies the photo-physical and electrochemical properties. Moreover, the photovoltaic performances of these two new dyes as sensitizers for DSSC are discussed. Experimental data show that both dyes exhibit photosensitizing activities in acetonitrile and water. In particular, in all the experiments, distyryl BODIPY was more efficient than styryl BODIPY. In this study, demonstrating the use of a natural component as a water-based electrolyte for boronic BODIPY sensitizers, we open new possibilities for the development of water-based solar cells.

OXI1 and DAD Regulate Light-Induced Cell Death Antagonistically through Jasmonate and Salicylate Levels.

Singlet oxygen produced from triplet excited chlorophylls in photosynthesis is a signal molecule that can induce programmed cell death (PCD) through the action of the OXIDATIVE STRESS INDUCIBLE 1 (OXI1) kinase. Here, we identify two negative regulators of light-induced PCD that modulate OXI1 expression: DAD1 and DAD2, homologs of the human antiapoptotic protein DEFENDER AGAINST CELL DEATH. Overexpressing OXI1 in Arabidopsis (Arabidopsis thaliana) increased plant sensitivity to high light and induced early senescence of mature leaves. Both phenomena rely on a marked accumulation of jasmonate and salicylate. DAD1 or DAD2 overexpression decreased OXI1 expression, jasmonate levels, and sensitivity to photooxidative stress. Knock-out mutants of DAD1 or DAD2 exhibited the opposite responses. Exogenous applications of jasmonate upregulated salicylate biosynthesis genes and caused leaf damage in wild-type plants but not in the salicylate biosynthesis mutant Salicylic acid induction-deficient2, indicating that salicylate plays a crucial role in PCD downstream of jasmonate. Treating plants with salicylate upregulated the DAD genes and downregulated OXI1 We conclude that OXI1 and DAD are antagonistic regulators of cell death through modulating jasmonate and salicylate levels. High light-induced PCD thus results from a tight control of the relative activities of these regulating proteins, with DAD exerting a negative feedback control on OXI1 expression.

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

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

Action of N-Succinyl and N,O-Dicarboxymethyl Chitosan Derivatives on Chlorophyll Photosynthesis and Fluorescence in Drought-Sensitive Maize

Chitosan induces plant tolerance to various abiotic stresses, including water deficit. However, its use may be limited, due to its constitution and low solubility in water. Thus, chemical modifications were proposed in this study with the objective of potentializing its biological effects in maize plants. The derivatives were semi-synthesized (N-succinyl and N,O-dicarboxymethyl) and, together with chitosan, they were applied, via the leaf, in a drought-sensitive maize hybrid (BRS1030) under pre-flowering water deficit. The water deficit was maintained for 15 days and the analyses were performed at the beginning and end of stress, and also in rehydration. Leaf water potential, gas exchange, chlorophyll fluorescence, and content of chloroplastidic pigments were evaluated. The use of the derivatives modulated photosynthesis parameters, affecting the involved mechanisms, such as stomatal activity, water use efficiency and photosystem II activity. Chlorophyll fluorescence indicated that the antenna complex was damaged by the water deficit condition, with a decrease in the energy flux in the electron transport chain and in the photochemical phase of photosynthesis. However, the spraying of chitosan derivatives induced tolerance to water deficit, suggesting that chitosan derivatives are more bioavailable to plants. Water stress decreases pigment content, but both the application of chitosan and derivatives increased these contents. It is concluded that chitosan derivatives improved the photosynthetic parameters in maize susceptible to drought, inducing tolerance to this stress, and the possible reasons and consequences are discussed.

Improvement of Antioxidative Defense of Cells Exposed to Radio Frequencies by a Nanotechnology Device

Transfer of an electromagnetic activity from a complex biological system, to another complex system is present both in current life and in quantum physics studies. Chlorophyll photosynthesis, is a typical model of an interaction between electromagnetic fields, deriving from solar energy and elements of a biochemical nature, the chlorophyll, responsible for the energy production, as a process deriving from chemical transformation. The following report presents a series of evidences, collected by means of various experimental approaches, aimed at demonstrating that by inducing the electromagnetic activity of an active substance on an electric field in stationary conditions, a quantum variation of the electric field can be obtained. Such electric field, is transferred to a support of fluorescent nanocrystals called Quantum Dots, whose electronic structure is suitable to maintain the starting quantum characteristics stable. The application of patches containing the aforementioned nanocrystals, on two biological models: Saccharomyces cerevisiae colonies and Pisum sativum plants, exposed to the irradiation of specific routers, showed a protective activity of these patches, evidenced by a regular increase in antioxidative defense and cell proliferation. The results reported in this research suggest the possibility of application of patchs supporting fluorescent nanocrystals as an effective defense against the production of reactive oxygen species.

Carbon‐Dot/Natural‐Dye Sensitizer for TiO2 Solar Cells Prepared by a One‐Step Treatment of Celery Leaf Extract

AbstractAttempts have been made to create artificial photovoltaic (PV) devices that can harness sunlight in a clean and efficient way by mimicking natural photosynthesis processes. Inspired by the role of chlorophyll in photosynthesis, we introduced pheophytin‐ or pyropheophytin‐capped carbon dots (CDs) into the dye‐sensitized solar‐cell system. The CD hybrids were synthesized by means of a single‐step hydrothermal treatment of celery leaf extract. The effects of hydrothermal temperature on the physical properties of CDs and the survival rate of the natural dyes were studied. CDs heated at 120 °C (C‐120) display a relatively homogenous smaller particle size distribution and lower photoluminescence emission intensity relative to their counterparts obtained at higher temperatures. Heated at lower temperatures, the achieved CD hybrids contain a higher amount of surviving dye molecules which would be converted into pheophytins or pyropheophytins. The nanocrystalline TiO2 solar cells based on C‐120 gave the highest power conversion efficiency (PCE) of 0.48 % under AM 1.5G one full sun illumination, which can be compared favorably to the average value of 0.20 % normally reported for other biomass‐derived carbon‐dot‐sensitized devices. Besides functioning as a light sensitizer, C‐120 CDs with a lower amount of trap states can also work as an effective electron‐transfer intermediate to improve the interaction between the dye and TiO2 and suppress the photogenerated carrier recombination, thus improving solar‐cell performance.

ИНТЕНСИВНОСТЬ ФОТОСИНТЕЗА ХЛОРОФИЛЛСОДЕРЖАЩИХ ОРГАНОВ РАСТЕНИЙ У СТАРЫХ И НОВЫХ СОРТОВ ГОРОХА ПОСЕВНОГО

ИНТЕНСИВНОСТЬ ФОТОСИНТЕЗА ХЛОРОФИЛЛСОДЕРЖАЩИХ ОРГАНОВ РАСТЕНИЙ У СТАРЫХ И НОВЫХ СОРТОВ ГОРОХА ПОСЕВНОГО

Synthesis and characterization of chlorophyllaenol derivatives: Chlorophyllatert-butyldimethylsilyl-enol ether and 131-deoxo-131, 132-didehydro-chlorophylla

Using the sterically hindered base, 1,8-diazabicyclo[5.4.0]undec-7-ene, for enolization and tert-butyldimethylsilyl-trifluoromethanesulfonate for silylation, chlorophyll (Chl) [Formula: see text] produced after 15 min at 0 [Formula: see text]C in deaerated pyridine solution under argon, after work-up and chromatographic purification on a sucrose column, tert-butyldimethylsilyl-enol ether of Chl [Formula: see text] in a yield of 77%. The 131-deoxo-131,132-didehydro-chlorophyll [Formula: see text], was obtained in a yield of 23% through a reaction sequence, where Chl [Formula: see text] was first reduced with sodium borohydride to 13[Formula: see text]-hydroxy-Chl [Formula: see text], which via demetalation yielded 13[Formula: see text]-hydroxypheophytin [Formula: see text]. In the presence of the sterically hindered base, 1,8-bis(dimethylamino)naphthalene, trifluoroacetylimidazole dehydrated 13[Formula: see text]-hydroxypheophytin [Formula: see text] to 131-deoxo-131,132-didehydro-pheophytin [Formula: see text], which after metalation yielded 131-deoxo-131,132-didehydro-Chl [Formula: see text]. Using 1,8-bis(dimethylamino)naphthalene and trifluoroacetylimidazole, the straight conversion of 13[Formula: see text]-hydroxy-Chl [Formula: see text] to 131-deoxo-131,132-didehydro-Chl [Formula: see text] was found unsuccessful. The major products were characterized by electronic absorption spectra (UV-vis) and practically completely assigned1H and [Formula: see text]C NMR spectra. Some intermediates of the syntheses were also characterized by ESI-TOF mass spectra. Compared with Chl [Formula: see text], the macrocyclic ring-current in the synthesized Chl [Formula: see text] enol derivatives was found weakened by the expansion of the [Formula: see text]-system to include the isocyclic ring E. Nevertheless, these enol derivatives were still considered to be diamagnetic and aromatic. The possibility of the functional role of the enol derivatives of chlorophyll in photosynthesis is discussed.

A New Group of Eubacterial Light-Driven Proton Pumps Lacking the Carboxylic Proton Donor

One of the main functions of microbial rhodopsins is outward-directed light-driven proton transport across the plasma membrane, which can provide sources of energy alternative to respiration and chlorophyll photosynthesis. Proton-pumping rhodopsins are found in Archaea (Halobacteria), multiple groups of Bacteria, numerous fungi, and some microscopic algae. An overwhelming majority of these proton pumps share the common transport mechanism, in which a proton from the retinal Schiff base is first transferred to the primary proton acceptor (normally an Asp) on the extracellular side of retinal. Next, reprotonation of the Schiff base from the cytoplasmic side is mediated by a carboxylic proton donor (Asp or Glu), which is located on helix C and is usually hydrogen-bonded to Thr or Ser on helix B. The only notable exception from this trend was recently found in Exiguobacterium, where the carboxylic proton donor is replaced by Lys. Here we describe a new group of efficient proteobacterial retinal-binding light-driven proton pumps which lack the carboxylic proton donor on helix C (most often replaced by Gly) but possess a unique His residue on helix B. We characterize the group spectroscopically and propose that this histidine forms a proton-donating complex compensating for the loss of the carboxylic proton donor.

A new group of eubacterial light-driven retinal-binding proton pumps with an unusual cytoplasmic proton donor

One of the main functions of microbial rhodopsins is outward-directed light-driven proton transport across the plasma membrane, which can provide sources of energy alternative to respiration and chlorophyll photosynthesis. Proton-pumping rhodopsins are found in Archaea (Halobacteria), multiple groups of Bacteria, numerous fungi, and some microscopic algae. An overwhelming majority of these proton pumps share the common transport mechanism, in which a proton from the retinal Schiff base is first transferred to the primary proton acceptor (normally an Asp) on the extracellular side of retinal. Next, reprotonation of the Schiff base from the cytoplasmic side is mediated by a carboxylic proton donor (Asp or Glu), which is located on helix C and is usually hydrogen-bonded to Thr or Ser on helix B. The only notable exception from this trend was recently found in Exiguobacterium, where the carboxylic proton donor is replaced by Lys. Here we describe a new group of efficient proteobacterial retinal-binding light-driven proton pumps which lack the carboxylic proton donor on helix C (most often replaced by Gly) but possess a unique His residue on helix B. We characterize the group spectroscopically and propose that this histidine forms a proton-donating complex compensating for the loss of the carboxylic proton donor.

Novel chlorophylls and new directions in photosynthesis research.

Chlorophyll d and chlorophyll f are red-shifted chlorophylls, because their Qy absorption bands are significantly red-shifted compared with chlorophyll a. The red-shifted chlorophylls broaden the light absorption region further into far red light. The presence of red-shifted chlorophylls in photosynthetic systems has opened up new possibilities of research on photosystem energetics and challenged the unique status of chlorophyll a in oxygenic photosynthesis. In this review, we report on the chemistry and function of red-shifted chlorophylls in photosynthesis and summarise the unique adaptations that have allowed the proliferation of chlorophyll d- and chlorophyll f-containing organisms in diverse ecological niches around the world.

Relationships between gross primary production, green LAI, and canopy chlorophyll content in maize: Implications for remote sensing of primary production

Life on Earth depends on photosynthesis. Photosynthetic systems evolved early in Earth history, providing evidence for the significance of pigments in plant functions. Photosynthetic pigments fill multiple roles from increasing the range of energy captured for photosynthesis to protective functions. Given the importance of pigments to plant functioning, greater effort is needed to determine and quantify the relationship between gross primary production (GPP) and canopy chlorophyll (Chl) content, the main photosynthetic pigment, as well as its proxy, green leaf area index (GLAI), both used as quantitative measures of plant greenness. The objective of this study is to establish relationships for GPP vs. canopy Chl content and GPP vs. GLAI in maize. The main focus of the paper is to reveal fine details of the relationships and understand their features in different stages of maize development. Data on GPP, leaf Chl content and GLAI were collected across ten years (2001–2010) at three AmeriFlux sites in Nebraska over irrigated and rainfed maize. Relationships of GPP vs. total canopy Chl content and GPP vs. GLAI were established for vegetative, tasseling and reproductive stages. In each stage, relationships were close with determination coefficients above 0.9; however, the shapes and slopes of the relationships in vegetative stages were different from reproductive stages. This difference was more pronounced for the GPP vs. GLAI relationship. In part, this difference is due to different leaf Chl contents in vegetative and reproductive stages. Smaller but detectable differences in shape and slope were also found for the GPP vs. canopy Chl relationship. Despite the differences in relationships for vegetative and reproductive stages, for the entire growing season, green LAI (GLAI) explained 90% of GPP variation with a coefficient of variation (CV)=17%, while total canopy Chl content explained more than 92% of GPP variation with CV=15%. Quantitative characterization of relationships between GPP and such biophysical characteristics as GLAI and canopy Chl content underlines the role of chlorophyll in photosynthesis and has significant implications on remote sensing of primary production.

Effect of salinity on seed germination, ion content and photosynthesis of cotyledons in halophytes or xerophyte growing in Central Asia

Aims We investigated the impact of salinity on seed germination, chlorophyll content, chloroplast structure and photosynthesis of the green embryos in desiccated seeds of the xerophyte Haloxylon persicum, xero-halophyte Haloxylon ammodendron and euhalophyte Suaeda physophora. Methods Seeds of H. persicum, H. ammodendron and S. physophora were collected from natural environment in Fukang, Xinjiang province. Pretreatment with 700 mM NaCl was carried out to stimulate the natural ‘seed priming’; we analyzed the joint effect of salinity and different species on germination physiology and cotyledonal structure and photosynthetic function changes during germination and recovery stage. Important Findings We found that seeds did not suffer ion toxicity for the two halophytes H. ammodendron and S. physophora, as evidenced by the high final germination after ungerminated seeds pretreated with 700 mM NaCl were transferred to distilled water, but the final germination of the xerophyteH. persicum was significantly lower than that of control. The Na + concentration in embryos increased under salinity for all species, while K + concentration decreased by salinity only for H. persicum and H. ammodendron, i.e. the concentration of K + in embryos of H. persicum and H. ammodendron decreased by 36% and 46%, respectively. For all species, whether dry intact seeds or cotyledons of dry seeds imbibed in deionized water and NaCl solution, had high chlorophyll content. Treatment with NaCl also caused chloroplast thylakoids to swell and chlorophyll content to decrease in seeds of H. persicum, but no significant change was observed in the more salt-tolerant species S. physophora and H. ammodendron. Fluorescence measurement showed that 700 mM NaCl decreased the Fv/Fm ratio of cotyledons in seeds for all species, especially for H. persicum and H. ammodendron .P hotosynthetic oxygen releasing was detected from the seeds that were moistened with distilled water and 700 mM NaCl for 6 or 24 h and from the seeds that were initially moistened with 700 mM NaCl in darkness for 10 days, then transferred to distilled water for another 6 and 24 h. The results indicated that the chlorophyll in cotyledon of desiccated seed had photosynthetic function in early germination stage, even under high-saline condition. In addition, the photosynthesis of chlorophyll in the embryonic cotyledons of desiccated seeds during germination was similar to that in leaves of young seedlings for all species. In conclusion, the chloroplasts of the two halophytes were more salt resistant compared with the xerophyte H. persicum. The photosynthetic function of chlorophyll in cotyledons of mature seeds may be ecologically important for seedling development in early stage for plants growing in extremely saline or arid environments.

Leptosphaeria rhodopsin: Bacteriorhodopsin-like proton pump from a eukaryote

Bacteriorhodopsin-like proteins provide archaea and eubacteria with a unique bioenergetic pathway comprising light-driven transmembrane proton translocation by a single retinal-binding protein. Recently, homologous proteins were found to perform photosensory functions in lower eukaryotes, but no active ion transport by eukaryotic rhodopsins was detected. By demonstrating light-driven proton pumping in a fungal rhodopsin from Leptosphaeria maculans, we present a case of a retinal-based proton transporter from a eukaryote. This result implies that in addition to oxidative phosphorylation and chlorophyll photosynthesis, some lower eukaryotes may have retained the archaeal route of building an electrochemical transmembrane gradient of protons.