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Non-photochemical quenching (NPQ) protects plants from photodamage caused by excess light energy. Substantial variation in NPQ has been reported among different genotypes of the same species. However, comparatively little is known about how environmental perturbations, including nutrient deficits, impact natural variation in NPQ kinetics. Here, we analyzed a natural variation in NPQ kinetics of a diversity panel of 225 maize (Zea mays L.) genotypes under nitrogen replete and nitrogen deficient field conditions. Individual maize genotypes from a diversity panel exhibited a range of changes in NPQ in response to low nitrogen. Replicated genotypes exhibited consistent responses across two field experiments conducted in different years. At the seedling and pre-flowering stages, a similar portion of the genotypes (∼33%) showed decrease, no-change or increase in NPQ under low nitrogen relative to control. Genotypes with increased NPQ under low nitrogen also showed greater reductions in dry biomass and photosynthesis than genotypes with stable NPQ when exposed to low nitrogen conditions. Maize genotypes where an increase in NPQ was observed under low nitrogen also exhibited a reduction in the ratio of chlorophyll a to chlorophyll b. Our results underline that since thermal dissipation of excess excitation energy measured via NPQ helps to balance the energy absorbed with energy utilized, the NPQ changes are the reflection of broader molecular and biochemical changes which occur under the stresses such as low soil fertility. Here, we have demonstrated that variation in NPQ kinetics resulted from genetic and environmental factors, are not independent of each other. Natural genetic variation controlling plastic responses of NPQ kinetics to environmental perturbation increases the likelihood it will be possible to optimize NPQ kinetics in crop plants for different environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

We discuss the role of epigenetic changes at the level of promoter methylation of the key enzymes of carbon metabolism in the regulation of respiration by light. While the direct regulation of enzymes via modulation of their activity and post-translational modifications is fast and readily reversible, the role of cytosine methylation is important for providing a prolonged response to environmental changes. In addition, adenine methylation can play a role in the regulation of transcription of genes. The mitochondrial and extramitochondrial forms of several enzymes participating in the tricarboxylic acid cycle and associated reactions are regulated via promoter methylation in opposite ways. The mitochondrial forms of citrate synthase, aconitase, fumarase, NAD-malate dehydrogenase are inhibited while the cytosolic forms of aconitase, fumarase, NAD-malate dehydrogenase, and the peroxisomal form of citrate synthase are activated. It is concluded that promoter methylation represents a universal mechanism of the regulation of activity of respiratory enzymes in plant cells by light. The role of the regulation of the mitochondrial and cytosolic forms of respiratory enzymes in the operation of malate and citrate valves and in controlling the redox state and balancing the energy level of photosynthesizing plant cells is discussed. [ABSTRACT FROM AUTHOR]

This study explores and compares the limits for photosynthesis in subzero temperatures of six Antarctic lichens: Sphaerophorus globosus, Caloplaca regalis , Umbilicaria antarctica , Pseudephebe minuscula , Parmelia saxatilis and Lecania brialmontii combining linear cooling and chlorophyll fluorescence methods. The results revealed triphasic S-curves in the temperature response of the maximum quantum yield (F V /F M) and effective quantum yield of photosystem II (Φ PSII) for all species. All investigated species showed a high level of cryoresistance with critical temperatures (T c) below −20 °C. However, record low T c temperatures have been discovered for L. brialmotii (−54 °C for F V /F M and −40 °C for Φ PSII) and C. regalis (−52 °C for F V /F M and −38 °C for Φ PSII). Additionally, the yield differentials (F V /F M − Φ PSII) in functions of temperature revealed one or two peaks, with the larger one occurring for temperatures below −20 °C for the above-mentioned species. Finally, Kautsky kinetics were measured and compared at different temperatures (20 °C, 10 °C, 0 °C and −10 °C and then −10 °C after 1 h of incubation). This research serves as a foundation for further developing investigations into the biophysical mechanisms by which photosynthesis is carried out at subzero temperatures. [Display omitted] • Antarctic lichens are cryo-resistant, their critical (cooling) temperature was found below -20°C. • Among 6 tested lichens, Lecania brialmontii showed highest frost-resistance. • Critical (cooling) temperature is lower for maximum quantum yield (F V /F M) than effective quantum yield of PSII (Φ PSII). • Differential between normalized F V /F M and Φ PSII is suggested as a new parameter for cold-resistance studies. [ABSTRACT FROM AUTHOR]

Five decades ago, the first report of a shift from C 3 to CAM (crassulacean acid metabolism) photosynthesis following the imposition of stress was published in this journal. The annual, Mesembryanthemum crystallinum (Aizoaceae), was shown to be a C 3 plant when grown under non-saline conditions, and a CAM plant when exposed to high soil salinity. This observation of environmentally triggered CAM eventually led to the introduction of the term facultative CAM, which categorises CAM that is induced or upregulated in response to water-deficit stress and is lost or downregulated when the stress is removed. Reversibility of C 3 –to–CAM shifts distinguishes stress-driven facultative-CAM responses from purely ontogenetic increases of CAM activity. We briefly review how the understanding of facultative CAM has developed, evaluate the current state of knowledge, and highlight questions of continuing interest. We demonstrate that the long-lived leaves of a perennial facultative-CAM arborescent species, Clusia pratensis , can repeatedly switch between C 3 and CAM in response to multiple wet–dry–wet cycles. Undoubtedly, this is a dedicated response to environment, independent of ontogeny. We highlight the potential for engineering facultative CAM into C 3 crops to provide a flexible capacity for drought tolerance. [ABSTRACT FROM AUTHOR]

Although significant efforts to produce carotenoid-enriched foods either by biotechnology or traditional breeding strategies have been carried out, our understanding of how changes in the carotenoid biosynthesis might affect overall plant performance remains limited. Here, we investigate how the metabolic machinery of well characterized tomato carotenoid mutant plants [namely crimson (old gold-og), Delta carotene (Del) and tangerine (t)] adjusts itself to varying carotenoid biosynthesis and whether these adjustments are supported by a reprogramming of photosynthetic and central metabolism in the source organs (leaves). We observed that mutations og , Del and t did not greatly affect vegetative growth, leaf anatomy and gas exchange parameters. However, an exquisite metabolic reprogramming was recorded on the leaves, with an increase in levels of amino acids and reduction of organic acids. Taken together, our results show that despite minor impacts on growth and gas exchange, carbon flux is extensively affected, leading to adjustments in tomato leaves metabolism to support changes in carotenoid biosynthesis on fruits (sinks). We discuss these data in the context of our current understanding of metabolic adjustments and carotenoid biosynthesis as well as regarding to improving human nutrition. [ABSTRACT FROM AUTHOR]

Contribution of inflorescences to seed filling have attracted great attention given the resilience of this photosynthetic organ to stressful conditions. However, studies have been almost exclusively focused to small grain cereals. In this study, we aimed to explore these responses in quinoa, as a climate resilient seed crop of elevated economic and nutritious potential. We compared the physiological and metabolic performance of panicles and leaves of two quinoa cultivars growing under contrasting salinity levels. Plant growth, photosynthetic and transpiratory gas exchange and chlorophyll fluorescence were monitored in inflorescences and leaves throughout the experiment. At flowering stage, young and mature leaves and panicles were sampled for key metabolic markers related to carbon, nitrogen and secondary metabolisms. When subjected to salt stress, panicles showed attenuated declines on photosynthesis, water use, pigments, amino acids, and protein levels as compared to leaves. In fact, the assimilation rates, together with a high hexose content evidenced an active photosynthetic role of the panicle under optimal and salt stress conditions. Moreover, we also found significant genotypic variability for physiological and metabolic traits of panicles and leaves, which emphasizes the study of genotype-dependent stress responses at the whole plant level. We conclude that quinoa panicles are less affected by salt stress than leaves, which encourages further research and exploitation of this organ for crop improvement and stress resilience considering the high natural diversity. • Quinoa panicles are net sources of photosynthetic C assimilation at flowering stage. • Panicles show stable physiological and metabolic responses to salt stress. • Sugar dynamics are cultivar- and organ-dependent under salt stress conditions. • High levels of hexoses might be associated with salt stress tolerance. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) is an important food and vegetable crop worldwide. In recent years, the arid environment resulting from climate change has caused a sharp decline in potato yield. To clarify the effect of drought priming at the seedling stage on the tolerance of potato plants to drought stress during tuber expansion, we conducted a pot experiment to investigate the physiological response of the plants generated from seed potatoes of the variety 'Favorita' to varied water supply conditions: normal water supply at the seedling stage (control), normal water supply at the seedling stage and drought stress at the mid-tuber-expansion stage (non-primed), and drought priming at the seedling stage plus drought stress at the mid-tuber-expansion stage (primed). Drought priming resulted in an increase in the number of small vascular bundles in potato plants compared to non-primed plants. It also altered the shape and density of stomata, enhancing water use efficiency and reducing whole-plant transpiration. The primed plants maintained the basal stem cambium for a longer time under drought stress, which gained an extended differentiation ability to generate a greater number of small vascular bundles compared to non-primed plants. Drought priming increased the amount and rate of dry matter translocation, and so reduced the adverse effects on tubers of potato under drought stress. Therefore, drought priming at the seedling stage improved the photosynthetic performance and yield, and probably enhanced the drought tolerance of potato. • Drought priming improved the photosynthetic performance and yield, and probably enhance the drought tolerance of potato. • Changed the shape and density of stomata, improved water use efficiency, and reduced whole-plant transpiration of potato. • Increased the number and area of small vascular bundles, and mitigated the negative effect of drought stress on tuber yield. [ABSTRACT FROM AUTHOR]

Sugar homeostasis is a critical feature of biological systems. In humans, raised and dysregulated blood sugar is a serious health issue. In plants, directed changes in sucrose homeostasis and allocation represent opportunities in crop improvement. Plant tissue sucrose varies more than blood glucose and is found at higher concentrations (cytosol and phloem ca. 100 mM v 3.9-6.9 mM for blood glucose). Tissue sucrose varies with developmental stage and environment, but cytosol and phloem exhibit tight sucrose control. Sucrose homeostasis is a consequence of the integration of photosynthesis, synthesis of storage end-products such as starch, transport of sucrose to sinks and sink metabolism. Trehalose 6-phosphate (T6P)-SnRK1 and TOR play central, still emerging roles in regulating and coordinating these processes. Overall, tissue sucrose levels are more strongly related to growth than to photosynthesis. As a key sucrose signal, T6P regulates sucrose levels, transport and metabolic pathways to coordinate source and sink at a whole plant level. Emerging evidence shows that T6P interacts with meristems. With careful targeting, T6P manipulation through exploiting natural variation, chemical intervention and genetic modification is delivering benefits for crop yields. Regulation of cereal grain set, filling and retention may be the most strategically important aspect of sucrose allocation and homeostasis for food security., Competing Interests: Declaration of competing interest MJP and CAG are founders and shareholders of spinout company SugaROx. Other than that, the authors have no competing financial interests or personal relationships that would influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

A plant's genome encodes enzymes, transporters and many other proteins which constitute metabolism. Interactions of plants with their environment shape their growth, development and resilience towards adverse conditions. Although genome sequencing technologies and applications have experienced triumphantly rapid development during the last decades, enabling nowadays a fast and cheap sequencing of full genomes, prediction of metabolic phenotypes from genotype × environment interactions remains, at best, very incomplete. The main reasons are a lack of understanding of how different levels of molecular organisation depend on each other, and how they are constituted and expressed within a setup of growth conditions. Phenotypic plasticity, e.g., of the genetic model plant Arabidopsis thaliana , has provided important insights into plant-environment interactions and the resulting genotype x phenotype relationships. Here, we summarize previous and current findings about plant development in a changing environment and how this might be shaped and reflected in metabolism and its regulation. We identify current challenges in the study of plant development and metabolic regulation and provide an outlook of how methodological workflows might support the application of findings made in model systems to crops and their cultivation. [ABSTRACT FROM AUTHOR]

Studying the effects of nitrogen limitation on carbon, nitrogen metabolism, and nutrient uptake of mung bean is a scientific issue. In this study, urea (CO(NH 2) 2 , 125 kg hm−2) was applied at the V2, V6, R1, R2, and R4 stages, respectively, to ensure sufficient N resources during the growth process of mung beans. This study found that nitrogen limitation inhibited mung bean photosynthesis and reduced photosynthetic efficiency, which was manifested by reducing Pn (net photosynthetic rate), Gs (stomatal conductance), Tr (transpiration rate), and Ci (intercellular carbon dioxide concentration). Second, nitrogen limitation reduced N metabolism-related enzyme activity, such as NR (nitrate reductase), GOGAT (glutamate synthase), and GDH (glutamate dehydrogenase), indicating that nitrogen limitation inhibited the process of nitrogen metabolism, reducing nitrogen assimilation. Meanwhile, topdressing N fertilizer can promote the P and K uptake, and improve the partial factor productivity of P and K, which suggests that nitrogen limitation reduced P and K use efficiency. In addition, this study found that Lvfeng5 responded more significantly to nitrogen fertilizers, and had higher nitrogen use efficiency or better adaptability compared with Lvfeng2. This study provided valuable insights into the physiological and metabolic responses of mung beans to nutrient deficiency. [ABSTRACT FROM AUTHOR]

Halophytes are potential future crops with a valuable nutritional profile. Produced in indoor farming, they are considered to contribute to sustainable and resilient food systems. Indoor farms operate using artificial light. In this context narrowband and low dose UVB radiation can be used to increase plant secondary metabolites, such as carotenoids, and provide an improved nutritional profile for a human diet. UVB radiation can cause eustress or distress in the plant depending on the lighting situation. The aim of this study was to identify the doses of UVB that lead to either eustress or distress and to analyze these responses in Salicornia europaea. Therefore, S. europaea plants were exposed to different UVB radiation levels, low, medium and high, and analyzed for reactive oxygen species (ROS), plant hormones, amino acids, and photosynthetic pigments. High UVB treatment was found to affect phenotype and growth, and the metabolite profile was affected in a UVB dose-dependent manner. Specifically, medium UVB radiation resulted in an increase in carotenoids, whereas high UVB resulted in a decrease. We also observed an altered oxidative stress status and increased SA and decreased ABA contents in response to UVB treatment. This was supported by the results of menadione treatment that induces oxidative stress in plants, which also indicated an altered oxidative stress status in combination with altered carotenoid content. Thus, we show that a moderate dose of UVB can increase the carotenoid content of S. europaea. Furthermore, the UVB stress-dependent response led to a better understanding of carotenoid accumulation upon UVB exposure, which can be used to improve lighting systems and in turn the nutritional profile of future crops in indoor farming., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Lead is a highly toxic metal. It impairs the metabolism of living organisms. Plants show different sensitivity to the action of this element. One of the plants with relatively high lead tolerance is Zea mays, where even in detached leaves treated with Pb 2+ ions, the photosynthesis rate remains very high compared to other plant species. This study set out to determine the mechanism responsible for the high resistance of maize photosynthetic tissue to the toxic effect of this metal. For this purpose, the cut leaves of Z. mays were incubated in Pb(NO 3 ) 2 solutions at different concentrations. Regions of lead accumulation in tissues and cells were located using histochemical methods and transmission electron microscopy. The experiments showed a diverse distribution of lead ions in the leaf blade of Z. mays. Most of the accumulated Pb 2+ ions were observed in the vascular bundle and the bundle sheath, while minimal traces of metal were transferred to the mesophyll. In Pisum sativum leaves, although Pb(NO 3 ) 2 concentration in the solution was two-fold lower, lead accumulated in all the leaf tissues - mainly in the vascular bundle, epidermis, sclerenchyma, and mesophyll. Thus, bundle sheath cells in maize leaves were able to inhibit the flow of Pb 2+ ions to the ground tissue. Therefore, the influence of the toxic metal on photosynthesis in mesophyll cells remained minimal. These experiments show that the structure of Z. mays leaf, with a layer of bundle sheath cells (characteristic of C 4 plants), contributes to the protecting photosynthetic tissue against the toxic effect of lead., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier GmbH.. All rights reserved.)

Graphene, one of the emerging carbon nanomaterials, has many advantages and applications. Salinity stress seriously affects ecology and agroforestry worldwide. The effects of graphene on alfalfa under salinity stress were investigated. The results indicated that graphene promoted alfalfa growth under non-salinity stress but caused some degree of damage to root cells and leaf parameters. Graphene used in salinity stress had a positive effect on growth parameters, chlorophyll, photosynthetic gas parameters, stomatal opening, ion balance, osmotic homeostasis, cell membrane integrity and antioxidant system, while it decreased Na + , lipid peroxidation and reactive oxygen species levels. Correlation analysis revealed that most of the parameters were significantly correlated; and principal component analysis indicated that the first two dimensions (78.1% and 4.1%) explained 82.2% of the total variability, and the majority of them exceeded the average contribution. Additionally, Gene Ontology functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes signaling pathway enrichment analysis showed that there were numerous differentially expressed genes and pathways to regulate alfalfa responding to salinity stress. Taken together, the findings reveal that graphene does not enter the plant, but improves the properties and adsorption of soil to enhance salt tolerance and seedling growth of alfalfa through morphological, physiological, biochemical, and transcriptomic aspects. Furthermore, this study provides a reference for the application of graphene to improve soil environment and agricultural production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

• Sodium arsenite was strongly efficient to inhibit grapevine trunk diseases foliar symptoms until 2003. • The use of sodium arsenite is banned and no efficient solutions are available. • Arsenic is translocated to leaves. • The leaf photosynthesis of sodium arsenite treated vine is firstly reduced and then stimulated. • The vine defense responses are also altered. Sodium arsenite (NaAsO 2) was especially used as a dormant spray to control grapevine trunk diseases (GTDs) in European vineyards until 2003 when it was banned. It was an efficient product but it was banned due to high risk for human health and the environment. Now, as one of the consequences with climatic changes, GTDs threaten the sustainability of vineyards since no similar and efficacious sprays are presently available to reduce the impact of GTDs. Research efforts were devoted to identify other active ingredients and biological control agents but they remained limited in term of efficacy. New solutions might follow from a better understanding of the modes of action of sodium arsenite which are currently lacking, specially its impact on grapevine physiology. For this study, grafted plants cv. Tempranillo were sprayed by sodium arsenite at the end of the winter. During the vegetative period, the impact on plant physiology was studied by measurement of the photosynthetic activity, the vine growth and development, and some defense responses. Our results showed that arsenic was translocated throughout the vine with an increasing gradient from the leaves to the root system, that photosynthesis was firstly reduced and then stimulated, and that plant tolerance responses were induced especially antioxidant system. The activation of grapevine defense responses by sodium arsenite could be a complementary action to fight fungal pathogens in addition to the fungicide effect. [ABSTRACT FROM AUTHOR]

Abstract Main conclusion Integrated proteome analyses revealed differentially accumulated proteins in the non-leaf green organs in wheat glume and awn that play important roles in photosynthesis and drought resistance. Two non-leaf green organs in wheat, glume and awn, have photosynthetic potential, contribute to grain yield, and also play roles in resistance to adverse conditions. We performed the first integrated proteome analysis of wheat glume and awn in response to water deficit. Water deficit caused a significant decrease in important agronomic traits and grain yield. A total of 120 and 77 differentially accumulated protein (DAP) spots, representing 100 and 67 unique proteins responsive to water deficit, were identified by two-dimensional difference gel electrophoresis (2D-DIGE) in glumes and awns, respectively, of the elite Chinese bread wheat cultivar Zhongmai 175. The DAPs of both organs showed similar functional classification and proportion and were mainly involved in photosynthesis, detoxification/defense, carbon/energy metabolism, and proteometabolism. Comparative proteome analyses revealed many more drought-responsive DAP spots in glumes than in awns, which indicate that glumes underwent more proteome changes in response to water deficit. The main DAPs involved in photosynthesis and carbon metabolism were significantly downregulated, whereas those related to detoxification/defense and energy metabolism were markedly upregulated under water deficit. The potential functions of the identified DAPs revealed an intricate interaction network that responds synergistically to drought stress during grain development. Our results from the proteome perspective illustrate the potential roles of wheat non-leaf green organs glume and awn in photosynthetic and defensive responses under drought stress. [ABSTRACT FROM AUTHOR]

Abstract Drought is known to limit carbon assimilation in plants. However, it has been debated whether photosynthesis is primarily inhibited by stomatal or non-stomatal factors. This research assessed the underlying limitations to photosynthesis in peanuts (Arachis hypogaea L.) grown under progressive drought. Specifically, field-grown peanut plants were exposed to either well-watered or drought-stressed conditions during flowering. Measurements included survey measurements of gas exchange, chlorophyll fluorescence, PSII thermotolerance, pigment content, and rapid A-C i response (RACiR) assessments. Drought significantly decreased stomatal conductance with consequent declines in photosynthesis (A N), actual quantum yield of PSII, and electron transport rate (ETR). Pigment contents were variable and depended on stress severity. Stomatal closure on stressed plants resulted in higher leaf temperatures, but F v /F m and PSII thermotolerance were only slightly affected by drought. A strong, hyperbolic relationship was observed between stomatal conductance, A N , and ETR. However, when RACiR analysis was conducted, drought significantly decreased A N at C i values comparable to drought-stressed plants, indicating non-stomatal limitations to A N. The maximum rate of carboxylation and maximum electron transport rate were severely limited by drought, and chloroplast CO 2 concentration (C C) declined substantially under drought along with a comparable increase in partitioning of electron flow to photorespiration. Thus, while stomatal conductance may be a viable reference indicator of water deficit stress in peanut, we conclude that declines in A N were largely due to non-stomatal (diffusional and metabolic) limitations. Additionally, this is the first study to apply the rapid A-C i response method to peanut, with comparable results to traditional A-C i methods. [ABSTRACT FROM AUTHOR]

Abstract Essential oils (EOs) have been extensively studied as valuable eco-friendly compounds with herbicidal activity for weed management. Phytotoxic potential of EOs, extracted from a wild population of Origanum vulgare ssp. hirtum (Link) Ietswaart, has been here evaluated on plant model Arabidopsis, through a physiological and metabolomic approach. The EOs composition was mainly characterized by monoterpenes and sesquiterpenes, with a strong abundance of two monoterpenic phenols, namely carvacrol and thymol, and the monoterpene o -cymene. The in vitro bioassay confirmed a strong phytotoxic effect of EOs on Arabidopsis rosettes, showing by both a strong growth reduction and highly chlorotic leaves. In well-developed seedlings, EOs firstly caused growth reduction and leaf chlorosis, together with a series of interconnected metabolic alterations: i) impairing the nitrogen assimilation into amino acids, which affects in particular the glutamine metabolism; and as consequence ii) excessive accumulation of toxic ammonia into the leaves, associated with oxidative stress and damage; iii) declining the efficiency of the photosynthetic apparatus, connected to the reduced CO 2 fixation and photooxidation protection; iv) impairing the photorespiratory pathway. Overall, the results highlights that EOs alters principally the ability of Arabidopsis seedlings to incorporate inorganic nitrogen into amino acids, principally glutamine, leading to a dramatic accumulation of ammonia in leaf cells. This primary effect induces, in turn, a cascade of reactions that limits the efficiency of PSII, inducing oxidative stress and finally causing a strong plant growth reduction, leaf necrosis and eventually plant death. These findings suggest that O. vulgare EOs might be proficiently exploited as a potential bioherbicide in an ecofriendly agriculture. Moreover, its multitarget activity could be advantageous in limiting weed resistance phenomenon. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Boron (B) toxicity frequently affects plant performances and productivity, especially in arid and semi-arid environments. In this experiment, loquat seedlings were subjected to 25 μM (control) or 400 μM B (B excess) to test the hypothesis that (i) B alters sugar/polyol metabolism in polyol-producing tree species as loquat and (ii) changes of leaf and stem anatomy assist young tissues against toxic effect of B. Gas exchange was monitored from the beginning of the experiment (FBE) till one week after the first visible symptoms of B toxicity appeared in the upper part of the stems (147 d FBE). At 147 FBE, plant biometric parameters and pattern of B accumulation, leaf and stem anatomy, chlorophyll a fluorescence kinetics as well as biochemical measurements were assessed in top (asymptomatic) leaves and upper stem bark. Boron accumulated principally (in the row) in top leaves > top bark > top wood in B-stressed plants, but no changes in allocation pattern were found between controls and B-stressed plants. Excess B promoted the increase in the spongy layer of top leaves and caused the development of cork and numerous collenchyma cells with increased cell wall thickness. This mechanism, which has never been described before, can be considered an attempt to store excessive B in tissues where B ions are less harmful. The accumulation of sorbitol (B-complexing polyol) in top leaves and stem bark can be considered as a further attempt to detoxify B excess. However, B toxicity drastically affects the photosynthetic rate of top leaves, mainly due to non-stomatal limitations, i.e., reduction of ambient CO 2 use efficiency and of photosystem II (PSII) efficiency, modification of the partitioning excess energy dissipation in PSII, thus leading to an increased level of lipid peroxidation. Our results suggest that changes in sugar metabolism associated with leaf and stem bark thickening partially assist (but not totally preserve) young tissues of loquat plants under B stress. [ABSTRACT FROM AUTHOR]

Abstract With unfavourable climate changes and an increasing global population, there is a great need for more productive and stress-tolerant crops. As traditional methods of crop improvement have probably reached their limits, a further increase in the productivity of crops is expected to be possible using genetic engineering. The number of potential genes and metabolic pathways, which when genetically modified could result in improved photosynthesis and biomass production, is multiple. Photosynthesis, as the only source of carbon required for the growth and development of plants, attracts much attention is this respect, especially the question concerning how to improve CO 2 fixation and limit photorespiration. The most promising direction for increasing CO 2 assimilation is implementating carbon concentrating mechanisms found in cyanobacteria and algae into crop plants, while hitherto performed experiments on improving the CO 2 fixation versus oxygenation reaction catalyzed by Rubisco are less encouraging. On the other hand, introducing the C 4 pathway into C 3 plants is a very difficult challenge. Among other points of interest for increased biomass production is engineering of metabolic regulation, certain proteins, nucleic acids or phytohormones. In this respect, enhanced sucrose synthesis, assimilate translocation to sink organs and starch synthesis is crucial, as is genetic engineering of the phytohormone metabolism. As abiotic stress tolerance is one of the key factors determining crop productivity, extensive studies are being undertaken to develop transgenic plants characterized by elevated stress resistance. This can be accomplished due to elevated synthesis of antioxidants, osmoprotectants and protective proteins. Among other promising targets for the genetic engineering of plants with elevated stress resistance are transcription factors that play a key role in abiotic stress responses of plants. In this review, most of the approaches to improving the productivity of plants that are potentially promising and have already been undertaken are described. In addition to this, the limitations faced, potential challenges and possibilities regarding future research are discussed. [ABSTRACT FROM AUTHOR]

Abstract In the Mediterranean region, grapevines usually deal with drought during their summer growth season. Concurrently, grapevines are hosts to a large number of viruses from which grapevine leafroll associated virus-3 is one of the most widespread and provokes considerable economic losses in many vineyards. However, information concerning grapevine metabolic responses to the combination of drought and viral infection is scarce. Gas-chromatography coupled to mass-spectrometry based metabolite profiling was used in combination with growth analysis, viral loads and gas exchange data to perform an integrative study of the effects of individual and combined stress in two Majorcan grapevine varieties at two experimental years. Metabolic responses of both varieties to the combination of water stress and virus infection were specific and not predicted from the sum of single stress responses. Correlations between respiration, biomass and key metabolites highlight specific adjustments of respiratory and amino acid metabolism possibly underlying the maintenance of carbon balance and growth in grapevines under stress combination. [ABSTRACT FROM AUTHOR]

Abstract The predicted accentuation of drought events highlights the importance of optimize plants capacity to tolerate drought, but also the capacity to recovery from it, especially in species, as olive tree (Olea europaea L.), that grows in particularly susceptible regions. Three different concentrations (10, 100 and 1000 μM) of salicylic acid (SA), a stress signaling phytohormone, was sprayed on 3-year-old potted olive trees subjected to three successive drought and rewatering events. Trees responses to SA application are concentration dependent, being 100 μM the most effective concentration to improve drought tolerance and recovery capacity. During drought events, this effectiveness was achieved by osmolytes accumulation, leaf water status maintenance, reduced photosynthetic systems drought-associated damages, and by optimizing shoot/root ratio. The better plant fitness during drought allowed a fast recovery of the physiological functions upon rewatering and reduced the necessity to invest in extra repair damages, allowing the regrowth. The intense abscisic acid (ABA) signal close to upper epidermis in stressed controls suggests a "memory" of the worst water status displayed by those plants. SA attenuated the limitation of total biomass accumulation imposed by drought, mainly in root system, increased water use efficiency and lead to a higher intense signal of indoleacetic acid (IAA) in leaves during recovery period. In summary, in a suitable concentration, SA demonstrate to be a promising tool to increase drought adaptability of olive trees. [ABSTRACT FROM AUTHOR]

The physiological and molecular responses to water stress are mediated by a range of mechanisms, many of which involve abscisic acid (ABA)-dependent signaling pathways. In addition, plants contain drought response genes that can be induced by ABA-independent routes, mediated by secondary messengers such as Ca 2+ , or regulated by epigenetic modifications. The complex processes involved in the response to water stress can be investigated using molecular techniques to evaluate the expression patterns of genes of interest and to infer the behavior of different genotypes and species. In the present study, we first analyzed the stability of a set of reference genes for normalization of the gene expression with real-time quantitative polymerase chain reaction (RT-qPCR), since there were no results related to the genotype used in this study. We verified that although there were some variations between algorithms used, the three most stable reference genes were SAND, PP2A-3 and EF-1α. The expressions of genes encoding for proteins associated with drought-tolerance responses, namely 9- cis -epoxycarotenoid dioxygenase 3 (EgrNCED3), pyrabactin resistance 1 (EgrPYR1), dehydration-responsive element-binding 2.5 (EgrDREB2.5) transcription factors, calcium-dependent protein kinase 26 (EgrCDPK26), methyl transferase 1 (EgrMET1) and deficient in DNA methylation 1 (EgrDDM1) protein, were determined by RT-qPCR in leaf samples from drought sensitive (VM05) and drought tolerant (VM01) clones of the hybrid Eucalyptus camaldulensis x Eucalyptus urophylla grown under water stress and irrigation conditions. When the two clones were maintained under conditions of water deficiency, VM01 exhibited higher expression levels of EgrNCED3 and EgrPYR1 genes than VM05 at all sampling times, implying that ABA biosynthesis and subsequent induction of the ABA-dependent cascade mediated by the PYR1-ABA receptor complex were enhanced in the tolerant clone. Under water-stress conditions, this clone also presented increased expression of the EgrDREB2.5 gene, representative of an ABA-independent cascade, and of the EgrCPK26 gene, related to stomatal opening and closure. On the other hand, the expression levels of EgrMET1 and EgrDDM1 genes in the sensitive clone were higher than in the tolerant clone under all conditions, showing a putative impact of epigenetic modifications on tolerance to water deficiency. The results obtained indicate that the superior ability of the VM01-tolerant clone to perceive water deficiency and activate drought-resistance genes is associated with the high expression levels of EgrNCED3, EgrPYR1 and EgrDREB2.5 under water-stress conditions. These findings will facilitate future research on the functional characterization of stress-related response genes, the identification of molecular markers, the evaluation of drought tolerance and genetic transformation in tree species. [ABSTRACT FROM AUTHOR]

Nitrogen is an essential macronutrient for plants and the common limiting factor for crop productivity worldwide. An effective approach to combat N deficiency and overuse is to understand the mechanism of low-nitrogen tolerance in plants and develop low-nitrogen-tolerant crop cultivars. Wild soybean has a high tolerance to poor environmental conditions, but, until now, no study has illustrated the mechanism of low-nitrogen tolerance at a metabolomic level. In this study, the photosynthetic characteristics and metabolomics of wild and cultivated soybean seedlings were analyzed, and the mechanism of wild soybean’s low-nitrogen tolerance was explained using a sand culture experiment. Wild soybean was less affected by low-nitrogen stress than cultivated soybean as assessed by plant growth parameters and photosynthesis. The root length of wild soybean increased, and a high root-shoot ratio was maintained under low-nitrogen stress. Carotenoids accumulated, which contributed to its higher low-nitrogen tolerance. A total of 48 and 60 differentially accumulated metabolites were identified in leaves and roots, respectively, between the low-nitrogen stress and control groups. The ability of wild soybean to tolerate low nitrogen also resulted from its capability to enhance the TCA cycle, synthesize key amino acids, accumulate metabolites, such as soluble sugars and organic acids, and synthesize favorable secondary metabolites under low-nitrogen stress. The current results reveal the mechanism underlying wild soybean’s high low-nitrogen tolerance and provide the methodology and theoretical basis for utilizing wild soybean, improving cultivated soybean, and studying the low-nitrogen tolerance of other plants. [ABSTRACT FROM AUTHOR]

Previous results have shown that hydrogen peroxide (H 2 O 2 ) is involved in abscisic acid (ABA)-induced adventitious root development under drought stress. In this study, a comparative proteomic analysis was conducted to explore the key proteins during ABA-H 2 O 2 -induced adventitious rooting in cucumber ( Cucumis sativus L.) under drought stress. The results revealed that 48 of 56 detected proteins spots were confidently matched to NCBI database entries. Among them, 10 protein spots were up-regulated while 4 protein spots were down-regulated under drought stress; 22 protein spots were up-regulated by ABA under drought stress; treatment with ABA plus H 2 O 2 scavenger catalase (CAT) up-regulated 6 protein spots and down-regulated 6 protein spots under drought stress. The identified proteins were divided into three categories: biological process, molecular function, and cellular component. According to their functions, the 48 identified proteins were grouped into 10 categories, including photosynthesis, stress response, protein folding, modification, and degradation, etc. According to subcellular localization, about 24 proteins (half of the total) were predicted to be localized in chloroplasts. ABA significantly up-regulated the expression of photosynthesis-related proteins (SBPase, OEE1), stress-defense-related proteins (2-Cys-Prx, HBP2), and folding-, modification-, and degradation-related proteins (TPal) under drought stress. However, the effects of ABA were inhibited by CAT. The proteins were further analyzed at the transcription level, and the expression of four of five genes (except 2-Cys-Prx ) was in accordance with the corresponding protein expression. The protein abundance changes of OEE1 and SBPase were also supported by western blot analysis. Therefore, H 2 O 2 may be involved in ABA-induced adventitious root development under drought stress by regulating photosynthesis-related proteins, stress defense-related proteins, and folding-, modification-, and degradation-related proteins. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max [L.] Merr.) at fluorescence stage frequently experiences drought stress. Although triadimefon has been observed to improve drought tolerance of plants, reports on its role in drought resistance on leaf photosynthesis and assimilate transport are limited. This study examined the effects of triadimefon on leaf photosynthesis and assimilate transport at fluorescence stage of soybean experiencing drought stress. Results showed that triadimefon application relieved the inhibitory effects of drought stress on photosynthesis and increased RuBPCase activity. Drought increased soluble sugar contents, yet reduced starch content in the leaves by heightening the activities of sucrose phosphate synthase (SPS), fructose-1,6-bisphosphatase (FBP), invertase (INV), and amylolytic enzyme, impeding the translocation of carbon assimilates to roots and reducing plant biomass. Nevertheless, triadimefon elevated starch content and minimized sucrose degradation by augmenting sucrose synthase (SS) activity and restraining the activities of SPS, FBP, INV, and amylolytic enzyme compared with drought alone, regulating the carbohydrate balance of drought-stressed plants. Therefore, triadimefon application could reduce the photosynthesis inhibition and regulate the carbohydrate balance of drought-stressed soybean plants to lessen the impacts of drought on soybean biomass. [ABSTRACT FROM AUTHOR]

We examined the patterns of photosynthetic O 2 evolution at 1 mM (optimal) and 10 mM (supra-optimal) bicarbonate in mesophyll protoplasts of Arabidopsis thaliana. The photosynthetic rate of protoplasts reached the maximum at an optimal concentration of 1 mM bicarbonate and got suppressed at supra-optimal levels of bicarbonate. We examined the basis of such photosynthesis inhibition by mesophyll protoplasts at supra-optimal bicarbonate. The wild-type protoplasts exposed to supra-optimal bicarbonate showed up signs of oxidative stress. Besides the wild-type, two mutants were used: nadp-mdh (deficient in chloroplastic NADP-MDH) and vtc1 (deficient in mitochondrial ascorbate biosynthesis). The protoplasts of the nadp-mdh mutant exhibited a higher photosynthetic rate and greater sensitivity to supra-optimal bicarbonate than the wild-type. The ascorbate-deficient vtc1 mutant had a low photosynthetic rate and no significant inhibition at high bicarbonate. The nadp-mdh mutants had elevated activities, protein, and transcript levels of key antioxidant enzymes. On the other hand, the antioxidant enzyme systems in vtc1 mutants were not much affected at supra-optimal bicarbonate. We propose that the inhibition of photosynthesis at supra-optimal bicarbonate depends on the redox state of mesophyll protoplasts. The robust antioxidant enzyme systems in protoplasts of nadp-mdh mutant might be priming the plants to sustain high photosynthesis at supra-optimal bicarbonate. [ABSTRACT FROM AUTHOR]

The carbon dioxide emitted by human accounts for only a small fraction of global photosynthesis consumption, half of which is due to microalgae. The high efficiency of algae photosynthesis is attributed to the pyrenoid-based CO 2 -concentrating mechanism (CCM). The formation of pyrenoid which has a variety of Rubisco-binding proteins mainly depends on liquid-liquid phase separation (LLPS) of Rubisco, a CO 2 fixing enzyme. At present, our understanding of pyrenoid at the molecular level mainly stems from studies of the model algae Chlamydomonas reinhardtii. In this article, we summarize the current research on the structure, assembly and application of Chlamydomonas reinhardtii pyrenoids, providing new ideas for improving crop photosynthetic performance and yield. [ABSTRACT FROM AUTHOR]

Iron (Fe) is an essential element for photosynthetic organisms, required for several vital biological functions. Photosynthesis, which takes place in the chloroplasts of higher plants, is the major Fe consumer. Although the components of the root Fe uptake system in dicotyledonous and monocotyledonous plants have been extensively studied, the Fe transport mechanisms of chloroplasts in these two groups of plants have received little attention. This review focuses on the comparative analysis of Fe transport processes in the evolutionary ancestors of chloroplasts (cyanobacteria) with the processes in embryophytes and green algae (Viridiplantae). The aim is to summarize how chloroplasts are integrated into cellular Fe homeostasis and how Fe transporters and Fe transport mechanisms have been modified by evolution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Miscanthus  ×  giganteus and Zea mays , closely-related C 4 grasses, originated from warm climates react differently to low temperature. To investigate the response to cold (12–14 °C) in these species, the photosynthetic and anatomical parameters as well as biochemical properties of the cell wall were studied. The research was performed using M. giganteus (MG) and two Z. mays lines differentiated for chilling-sensitivity: chilling-tolerant (Zm-T) and chilling-sensitive (Zm-S). The chilled plants of Zm-S line demonstrated strong inhibition of net CO 2 assimilation and a clear decrease in F’ v /F’ m , F v /F m and ɸ PSII, while in MG and Zm-T plants these parameters were almost unchanged. The anatomical studies revealed that MG plants had thinner leaves, epidermis and mesophyll cell layer as well as thicker cell walls in the comparison to both maize lines. Cold led to an increase in leaf thickness and mesophyll cell layer thickness in the Zm-T maize line, while the opposite response was observed in Zm-S. In turn, in chilled plants of MG and Zm-T lines, some anatomical parameters associated with bundle sheath cells were higher. In addition, Zm-S line showed the strong increase in the cell wall thickness at cold for mesophyll and bundle sheath cells. Chilling-treatment induced the changes in the cell wall biochemistry of tested species, mainly in the content of glucuronoarabinoxylan, uronic acid, β-glucan and phenolic compounds. This work presents a new approach in searching of mechanism(s) of tolerance/sensitivity to low temperature in two thermophilic plants: Miscanthus and maize. [ABSTRACT FROM AUTHOR]

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae . Its structure is similar to those of jasmonates (JAs), which play diverse roles in multiple plant biotic and abiotic defenses. However, the biological activity of COR is 1000 times greater than the activity of JA. In addition to being involved in the JA pathway, COR affects plant photosynthetic efficiency. In this study, we examined wheat blade pretreatment with COR. Blades treated with COR remained green longer than those of control plants under drought stress conditions, resulting in less yield loss with COR treatment. To investigate the mechanism of COR in drought resistance further, we employed two-dimensional gel electrophoresis technology and matrix-assisted laser desorption/ionization mass spectrometry to sequester and identify key proteins. Six COR-inducible proteins that are located in the chloroplast and involved directly in photosynthesis were found. The wheat homologue of protein gi|326509937 is degradation of periplasmic proteins 1 (DEGP1) in Arabidopsis , which is a response to photosystem II reparation, and was maintained at a low level with COR treatment. Finally, we measured levels of chlorophyll and photosynthetic performance to reveal the phenotypic effect of COR. Taken together, the results demonstrate that COR enhances drought tolerance by maintaining high photosynthetic performance. [ABSTRACT FROM AUTHOR]

Inhibition of photosynthesis is a central, primary response that is observed in both desiccation-tolerant and desiccation-sensitive plants affected by drought stress. Decreased photosynthesis during drought stress can either be due to the limitation of carbon dioxide entry through the stomata and the mesophyll cells, due to increased oxidative stress or due to decreased activity of photosynthetic enzymes. Although the photosynthetic rates decrease in both desiccation-tolerant and sensitive plants during drought, the remarkable difference lies in the complete recovery of photosynthesis after rehydration in desiccation-tolerant plants. Desiccation of sensitive plants leads to irreparable damages of the photosynthetic membranes, in contrast the photosynthetic apparatus is deactivated during desiccation in desiccation-tolerant plants. Desiccation-tolerant plants employ different strategies to protect and/or maintain the structural integrity of the photosynthetic apparatus to reactivate photosynthesis upon water availability. Two major mechanisms are distinguished. Homoiochlorophyllous desiccation-tolerant plants preserve chlorophyll and thylakoid membranes and require active protection mechanisms, while poikilochlorophyllous plants degrade chlorophyll in a regulated manner but then require de novo synthesis during rehydration. Desiccation-tolerant plants, particularly homoiochlorophyllous plants, employ conserved and novel antioxidant enzymes/metabolites to minimize the oxidative damage and to protect the photosynthetic machinery. De novo synthesized, stress-induced proteins in combination with antioxidants are localized in chloroplasts and are important components of the protective network. Genome sequence informations provide some clues on selection of genes involved in protecting photosynthetic structures; e.g. ELIP genes (early light inducible proteins) are enriched in the genomes and more abundantly expressed in homoiochlorophyllous desiccation-tolerant plants. This review focuses on the mechanisms that operate in the desiccation-tolerant plants to protect the photosynthetic apparatus during desiccation. [ABSTRACT FROM AUTHOR]

Vegetation is a highly dynamic component of the Earth surface and substantially alters the water cycle. Particularly the process of oxygenic plant photosynthesis determines vegetation connecting the water and carbon cycle and causing various interactions and feedbacks across Earth spheres. While vegetation impacts the water cycle, it reacts to changing water availability via functional, biochemical and structural responses. Unravelling the resulting complex feedbacks and interactions between the plant-water system and environmental change is essential for any modelling approaches and predictions, but still insufficiently understood due to currently missing observations. We hypothesize that an appropriate cross-scale monitoring of plant-water relations can be achieved by combined observational and modelling approaches. This paper reviews suitable remote sensing approaches to assess plant-water relations ranging from pure observational to combined observational-modelling approaches. We use a combined energy balance and radiative transfer model to assess the explanatory power of pure observational approaches focussing on plant parameters to estimate plant-water relations, followed by an outline for a more effective use of remote sensing by their integration into soil-plant-atmosphere continuum (SPAC) models. We apply a mechanistic model simulating water movement in the SPAC to reveal insight into the complexity of relations between soil, plant and atmospheric parameters, and thus plant-water relations. We conclude that future research should focus on strategies combining observations and mechanistic modelling to advance our knowledge on the interplay between the plant-water system and environmental change, e.g. through plant transpiration. [ABSTRACT FROM AUTHOR]

Since their discovery, twenty years ago, KT-HAK-KUP transporters have become a keystone to understand how alkali cation fluxes are controlled in major land-dwelling photosynthetic organisms. In this review we focus on their discovery, phylogeny, and functions, as well as the regulation of its canonical member, AtHAK5. We also address issues related to structure-function studies, and the technological possibilities opened up by recent findings. Available evidence suggests that this family of transporters underwent an early divergence into major groups following the conquest of land by embryophytes. KT-HAK-KUPs are necessary to accomplish several major developmental and growth processes, as well as to ensure plant responses to environmental injuries. Although the primary function of these transporters is to mediate potassium (K + ) fluxes, some of them can also mediate sodium (Na + ) and cesium (Cs + ) transport, and contribute to maintenance of K + (and Na + ) homeostasis in different plant tissues. In addition, there is evidence for a role of some members of this family in auxin movement and in adenylate cyclase activity. Recent research, focusing on the regulation of the canonical member of this family, AtHAK5, revealed the existence of a complex network that involves transcriptional and post-transcriptional phenomena which control the enhancement of AtHAK5-mediated K + uptake when Arabidopsis thaliana plants are faced with low K + supply. In spite of the formidable advances made since their discovery, important subjects remain to be elucidated to gain a more complete knowledge of the roles and regulation of KT-HAK-KUPs, as well as to improve their use for innovative procedures in crop breeding. [ABSTRACT FROM AUTHOR]

ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1) was first described as a protein involved in salicylic acid (SA)-, ethylene-, and reactive oxygen species (ROS)-dependent defense and acclimation responses. It is a molecular regulator of biotic and abiotic stress-induced programmed cell death. Its role is relatively well known in annual plants, such as Arabidopsis thaliana or Nicotiana benthamiana. However, little is known about its functions in woody plants. Therefore, in this study, we aimed to characterize the function of EDS1 in the Populus tremula L.  ×   P. tremuloides hybrid grown for several seasons in the natural environment. We used two transgenic lines, eds1–7 and eds1–12 , with decreased EDS1 expression levels in this study. The observed changes in physiological and biochemical parameters corresponded with the EDS1 silencing level. Both transgenic lines produced more lateral shoots in comparison to the wild-type (WT) plants, which resulted in the modification of tree morphology. Photosynthetic parameters, such as quantum yield of photosystem II (ϕPSII), photochemical and non-photochemical quenching (qP and NPQ, respectively), as well as chlorophyll content were found to be increased in both transgenic lines, which resulted in changes in photosynthetic efficiency. Our data also revealed lower foliar concentrations of SA and ROS, the latter resulting most probably from more efficient antioxidant system in both transgenic lines. In addition, our data indicated significantly decreased rate of leaf senescence during several autumn seasons. Transcriptomic analysis revealed deregulation of 2215 and 376 genes in eds1-12 and eds1-7 , respectively, and also revealed 207 genes that were commonly deregulated in both transgenic lines. The deregulation was primarily observed in the genes involved in photosynthesis, signaling, hormonal metabolism, and development, which was found to agree with the results of biochemical and physiological tests. In general, our data proved that poplar EDS1 affects tree morphology, photosynthetic efficiency, ROS and SA metabolism, as well as leaf senescence. [ABSTRACT FROM AUTHOR]

Many studies have discussed the influence of elevated carbon dioxide (eCO 2 ) on modeling and crop plants. However, much less effort has been dedicated to herbal plants. In this study, a robust monitoring for the levels of 94 primary and secondary metabolites and minerals in two medicinal herbs, basil ( Ocimum basilicum L.) and peppermint ( Mentha piperita L.), grwon under both ambient (aCO 2 , 360 ppm) and eCO 2 (620 ppm) was performed. We also assessed how the changes in herbal tissue chemistry affected their biological activity. Elevated CO 2 significantly increased herbal biomass, improved the rates of photosynthesis and dark respiration, and altered the tissue chemistry. Principal Component Analysis of the full data set revealed that eCO 2 induced a global change in the metabolomes of the two plants. Moreover, Hierarchical Clustering Analyses showed quantitative differences in the metabolic profiles of the two plants and in their responsiveness to eCO 2 . Out of 94 metabolites, 38 and 31 significantly increased in basil and peppermint, respectively, as affected by eCO 2 . Regardless of the plant species, the levels of non-structural carbohydrates, fumarate, glutamine, glutathione, ascorbate, phylloquinone (vitamin K1), anthocyanins and a majority of flavonoids and minerals were significantly improved by eCO 2 . However, some metabolites tended to show species specificity. Interestingly, eCO 2 caused enhancement in antioxidant, antiprotozoal, anti-bacterial and anticancer (against urinary bladder carcinoma; T24P) activities in both plants, which was consequent with improvement in the levels of antioxidant metabolites such as glutathione, ascorbate and flavonoids. Therefore, this study suggests that the metabolic changes triggered by eCO 2 in the target herbal plants improved their biological activities. [ABSTRACT FROM AUTHOR]

Phosphatidylglycerol is an essential phospholipid for photosynthesis and other cellular processes. We investigated the role of phosphatidylglycerol in cell division and metabolism in a phophatidylglycerol-auxotrophic strain of Synechococcus PCC7942. Here we show that phosphatidylglycerol is essential for the photosynthetic electron transfer and for the oligomerisation of the photosynthetic complexes, notably, we revealed that this lipid is important for non-linear electron transport. Furthermore, we demonstrate that phosphatidylglycerol starvation elevated the expressions of proteins of nitrogen and carbon metabolism. Moreover, we show that phosphatidylglycerol-deficient cells changed the morphology, became elongated, the FtsZ ring did not assemble correctly, and subsequently the division was hindered. However, supplementation with phosphatidylglycerol restored the ring-like structure at the mid-cell region and the normal cell size, demonstrating the phosphatidylglycerol is needed for normal septum formation. Taken together, central roles of phosphatidylglycerol were revealed; it is implicated in the photosynthetic activity, the metabolism and the fission of bacteria. [ABSTRACT FROM AUTHOR]

Under field conditions, plants are exposed to cycles of dehydration and rehydration during their lifespan. In this study, we hypothesized that sugarcane plants previously exposed to cycles of water deficits will perform better than plants that have never faced water deficits when both are subjected to low water availability. Sugarcane plants were grown in a nutrient solution and exposed to one (1WD), two (2WD) or three (3WD) water deficit cycles. As the reference, plants were grown in a nutrient solution without adding polyethylene glycol. Under water deficits, leaf gas exchange was significantly reduced in 1WD and 2WD plants. However, 3WD plants showed similar CO 2 assimilation and lower stomatal conductance compared to the reference plants, with increases in intrinsic water-use efficiency. Abscisic acid concentrations were lower in 3WD plants than in 1WD plants. Our data revealed root H 2 O 2 concentration as an important chemical signal, with the highest root H 2 O 2 concentrations found in 3WD plants. These plants presented higher root dry matter and root:shoot ratios compared to the reference plants, as well as higher biomass production when water was available. Our data suggest that sugarcane plants were able to store information from previous stressful events, with plant performance improving under water deficits. In addition, our findings provide a new perspective for increasing drought tolerance in sugarcane plants under nursery conditions. [ABSTRACT FROM AUTHOR]

Ultraviolet-B (UV-B) radiation plays an important role in plant photomorphogenesis. Whilst the morpho-functional disorders induced by excessive UV irradiation are well-known, it remains unclear how this irradiation modulates the metabolome, and which metabolic shifts improve plants’ tolerance to UV-B. In this study, we use an important Mediterranean crop, Olea europaea , to decipher the impacts of enhanced UV-B radiation on the physiological performance and lipophilic metabolite profile. Young olive plants (cv . ‘ Galega Vulgar’) were exposed for five days to UV-B biologically effective doses of 6.5 kJ m −2  d −1 and 12.4 kJ m −2 d −1 . Cell cycle/ploidy, photosynthesis and oxidative stress, as well as GC–MS metabolites were assessed. Both UV-B treatments impaired net CO 2 assimilation rate, transpiration rate, photosynthetic pigments, and RuBisCO activity, but 12.4 kJ m −2  d −1 also decreased the photochemical quenching (qP) and the effective efficiency of PSII (Φ PSII ). UV-B treatments promoted mono/triperpene pathways, while only 12.4 kJ m −2  d −1 increased fatty acids and alkanes, and decreased geranylgeranyl-diphosphate. The interplay between physiology and metabolomics suggests some innate ability of these plants to tolerate moderate UV-B doses (6.5 kJ m −2  d −1 ). Also their tolerance to higher doses (12.4 kJ m −2  d −1 ) relies on plants’ metabolic adjustments, where the accumulation of specific compounds such as long-chain alkanes, palmitic acid, oleic acid and particularly oleamide (which is described for the first time in olive leaves) play an important protective role. This is the first study demonstrating photosynthetic changes and lipophilic metabolite adjustments in olive leaves under moderate and high UV-B doses. [ABSTRACT FROM AUTHOR]

Drought stress is a considerable environmental factor that restrains photosynthesis. Lutein, the most prolific carotenoid in plant photosynthetic tissues, plays vital roles in the light-harvesting complexes. However, its biological functions under abiotic stresses remain unclear. In our research, transgenic tobacco plants were utilized to investigate the function of the tomato chloroplast-targeted carotenoid epsilon-ring hydroxylase (SlLUT1) in drought stress tolerance. The analysis of SlLUT1- pro- LUC and qRT-PCR showed that drought stress induced SlLUT1 expression. Transgenic tobacco plants exhibit higher lutein content than wild-type (WT) tobacco. Under drought stress, transgenic plants overexpressing SlLUT1 showed better growth performance, higher chlorophyll and relative water contents and more intact chloroplast and PSII supercomplex structures than WT tobacco. The Fv/Fm, Pn, NPQ, and content of D1 protein in transgenic plants were higher than those in WT plants under drought stress. The accumulation of H 2 O 2 and O 2 − decreased in transgenic tobacco plants. Moreover, transgenic plants exhibited lower MDA accumulation and REL. These results indicate that overexpression of SlLUT1 enhances tolerance to drought stress by maintaining photosynthesis and scavenging ROS in transgenic tobacco. [ABSTRACT FROM AUTHOR]

Bienertia sinuspersici performs single cell C 4 photosynthesis without Kranz anatomy. Peripheral and central cytoplasmic compartments in a single chlorenchyma cell act as mesophyll cells and bundle sheath cells. Development of this specialized mechanism is gradual during plant development. Young leaves perform C 3 photosynthesis, while mature leaves have complete C 4 cycle. The aim of this work was to investigate changes in redox regulation and antioxidant defence during transition from C 3 to single cell C 4 photosynthesis in B. sinuspersici leaves. First, we confirmed gradual development of C 4 with protein blot and qRT-PCR analysis of C 4 enzymes. After this activities and isoenzymes of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and H 2 O 2 and TBARS and glutathione pool and redox status (GSH/GSSG) were determined in young, developing and mature leaves during transition from C 3 to single cell C 4 photosynthesis. Activities of SOD, APX and POX decrease, while GR and DHAR were increased. However, most striking results were the changes in isoenzyme patterns of SOD, CAT and GR which were gradual through transition to C 4 photosynthesis. [ABSTRACT FROM AUTHOR]

Total phenolics and the profile of phenolic acids and flavonoids were investigated in the roots and leaves of Ulmus laevis cultured on the medium with inorganic and organic arsenic – As(III), As(V) and DMA(V) at 0.06 mM and their equimolar combinations. Further, the accumulation of salicylic acid (free and glucoside-bound) and lipid oxidation were assayed following a three-month long experiment. As treatment caused elevated production of phenolics, which was higher in photosynthetic tissue than in roots for all As forms and their combinations, and their overall content was correlated with the accumulation of organic As in roots and As(III) in leaves. The accumulation of organic As strongly induced shikimate-derived protocatechiuc acid in roots. Contrary to this, shikimate-derived phenolics (protocatechuic, gallic acids and 4-HBA) were suppressed in leaves, while the accumulation of C6C3 acids (caffeic, p -coumaric and chlorogenic) was stimulated by As(V) application. Surprisingly, these acids were not detected in the leaves of As(III)-treated plants, and mutually applied As(III) and DMA(V) reduced their content. DMA(V) negatively influenced the level of salicylic acid and its storage mechanism and this effect correlated with elevated MDA content in leaves. Quercetin accumulation was observed in both organs (mainly leaves) of DMA(V)-treated plants thereby proving its function in defensive response of Ulmus laevis to organic forms of As. [ABSTRACT FROM AUTHOR]

Polyamines (PAs) and hydrogen peroxide (H 2 O 2 ), the product of PA oxidation by polyamine oxidase (PAO), are potential players affecting plant growth, development and responses to abiotic/biotic stresses. Genetically modified Nicotiana tabacum plants with altered PA/H 2 O 2 homeostasis due to over/underexpression of the ZmPAO gene (S- ZmPAO /AS- ZmPAO , respectively) were assessed under heat stress (HS). Underexpression of ZmPAO correlates with increased thermotolerance of the photosynthetic machinery and improved biomass accumulation, accompanied by enhanced levels of the enzymatic and non-enzymatic antioxidants, whereas ZmPAO overexpressors exhibit significant impairment of thermotolerance. These data provide important clues on PA catabolism/H 2 O 2 /thermotolerance, which merit further exploitation. [ABSTRACT FROM AUTHOR]

The plant phenolic compound ( E )-chalcone has been previously found to induce noticeable seedling size reduction and progressive de-greening (bleaching) in shoots of Arabidopsis thaliana seedlings. In this work, we demonstrate that this progressive de-greening occurring on Arabidopsis shoots after ( E )-chalcone treatment, is directly linked to early plasma membrane depolarization and dramatic effects on chloroplasts structure and function. Later effects in chalcone-treated seedlings included ROS accumulation, pigment degradation, reduced photosynthetic activity, bleaching, and eventually cell death. De-greening and pigment degradation induced by ( E )-chalcone were partially reversed when NaCl was added together with chalcone, which could be related to restoration of altered pH gradients. All these results suggest that rapid alteration of plasma membrane potential after chalcone treatment is a major component of the mode of action of ( E )-chalcone on Arabidopsis metabolism. [ABSTRACT FROM AUTHOR]

Manganese (Mn)-intolerant ‘Sour pummelo’ ( Citrus grandis ) and Mn-tolerant ‘Xuegan’ ( Citrus sinensis ) seedlings were irrigated for 17 weeks with 2 (control) or 600 μM (Mn-toxicity or −excess) MnSO 4 . C. sinensis had higher Mn-tolerance than C. grandis , as indicated by the higher photosynthesis rates in Mn-excess C. sinensis leaves. Under Mn-toxicity, Mn levels were similar between C. sinensis and C. grandis roots, but lower in C. sinensis leaves than in C. grandis leaves. This might be responsible for C. sinensis Mn-tolerance. Using two-dimensional electrophoresis, we identified more differentially abundant proteins (DAPs) in Mn-excess C. grandis than in Mn-excess C . sinensis leaves, which agrees with the higher Mn levels in Mn-excess C. grandis leaves. DAPs were mainly related to carbohydrate and energy metabolism, stress response, and protein and amino acid metabolism. DAPs involved in the cytoskeleton and signal transduction were found only in Mn-excess C. grandis leaves. We isolated more photosynthesis-related proteins with decreased abundances in Mn-excess C. grandis leaves than in Mn-excess C. sinensis leaves, which might account for the larger decrease in photosynthesis rates in C. grandis leaves. The abundances of proteins involved in reactive oxygen species (ROS) scavenging and photorespiration were increased in Mn-excess C. grandis leaves, while only proteins involved in ROS detoxification were increased in Mn-excess C. sinensis leaves. This agrees with the increased requirement for dissipating the excess absorbed light energy, which was higher in Mn-excess C. grandis leaves than Mn-excess C. sinensis leaves because Mn-toxicity inhibited photosynthesis to a greater degree in C. grandis leaves. [ABSTRACT FROM AUTHOR]

Bigelowiella natans is a mixotrophic flagellate and member of the chlorarachniophytes (Rhizaria), whose plastid is derived from a green algal endosymbiont. With the completion of the B. natans nuclear genome we are able to begin the analysis of the structure, function and evolution of the photosynthetic apparatus. B. natans has undergone substantial changes in photosystem structure during the evolution of the plastid from a green alga. While Photosystem II (PSII) composition is well conserved, Photosystem I (PSI) composition has undergone a dramatic reduction in accessory protein subunits. Coinciding with these changes, there was a loss of green algal LHCI orthologs while the PSII-like antenna system has the expected green algal-like proteins (encoded by genes Lhcbm1-8 , Lhcb4 ). There are also a collection of LHCX-like proteins, which are commonly associated with stramenopiles and other eukaryotes with red-algal derived plastids, along with two other unique classes of LHCs— LHCY and LHCZ— whose function remains cryptic. To understand the regulation of the LHC gene family as an initial probe of function, we conducted an RNA-seq experiment under a short-term, high-light (HL) and low-light stress. The most abundant LHCII transcript ( Lhcbm6 ) plus two other LHCBM types ( Lhcbm1, 2 ) were down regulated under HL and up-regulated following a shift to very-low light (VL), as is common in antenna specializing in light harvesting. Many of the other LHCII and LHCY genes had a small, but significant increase in HL and most were only moderately affected under VL. The LHCX and LHCZ genes, however, had a strong up-regulation under HL-stress and most declined under VL, suggesting that they primarily have a role in photoprotection. This contrasts to the LHCY family that is only moderately responsive to light and a much higher basal level of expression, despite being within the LHCSR/LHCX clade. The expression of LHCX/Z proteins under HL-stress may be related to the induction of long-term, non-photochemical quenching mechanisms. [ABSTRACT FROM AUTHOR]

Light is important for algae, as it warrants metabolic independence via photosynthesis. In addition to the absorption of light by the photosystems, algae possess a variety of specific photoreceptors that allow the quantification of the light fluxes as well as the assessment of light qualities. About a decade ago, aureochromes have been described in the xanthophyte alga Vaucheria frigida . These proteins represent a new type of blue light photoreceptor as they possess both a light-oxygen-voltage (LOV) domain for light reception as well as a basic region leucine zipper (bZIP) domain for DNA binding, indicating that they represent light-driven transcription factors. Aureochromes so far have been detected only in a single group of algae, photosynthetic stramenopiles, but not in any other prokaryotic or eukaryotic organisms. Recent biophysical work on aureochromes in the absence and the presence of DNA revealed the mechanism of allosteric communication between the sensor and effector domains despite their unusual inversed arrangement. Different molecular models have been proposed to describe the effect of light on DNA binding. Functional characterization of mutants of the diatom Phaeodactylum tricornutum , in which the aureochrome genes have been silenced or deleted, indicate that different aureochromes may have different functions, being involved in central processes like light acclimation and regulation of the cell cycle. [ABSTRACT FROM AUTHOR]

A better understanding of the photosynthesis and soil water storage regulation of soybean production will be helpful to develop a water conservation strategy under a rain-fed farming system. Reducing the leakage of CO 2 bundle sheath cells and improving the photosynthesis capacity and gas exchange characteristics of soybean leaves will contribute to increase yield under the dryland agricultural system and provide a scientific basis. Therefore, during 2019 and 2020, soybean exposed to different cultivation modes to analyze the response curves of photosynthesis and CO 2 under different deficit irrigation strategies. In this study, we used two cultivation models: RB: ridge covered with biodegradable film and furrow area not covered; CF: conventional flat land planting under four deficit irrigation modes (R: rainwater irrigation; IB: branch stage irrigation (220 mm); IP: Irrigation during podding (220 mm); IBP: branch stage irrigation (110 mm), podding stage irrigation (110 mm). Compared with CF-IBP treatment, RB-IBP had significant effects on rainwater collection, SWS, and soybean yield. Photo-response curve analysis showed that RB-IBP treatment a significant increase in P n , G s , C i , T r , leaf WUE, and chlorophyll ab content. Under different irrigation strategies, maximum net photosynthetic rate (P nmax), light saturation point (LSP), and apparent quantum efficiency under RB-IBP treatment (α), P n under respiration rate and CO 2 response curve were significantly higher than that under CF cultivation mode. Compared with RB culture mode under different irrigation strategies, CF cultivation mode significantly increases Δ13C and CO 2 sheath cell leakage (Փ); it also led to a significant decline in the ratio of Ci/Ca concentration. This study shows that RB-IBP treatment is the best water-saving strategy because it means reducing the leakage of CO 2 from the bundle sheath, thus significantly increasing soil water storage, photosynthetic capacity, and soybean yield. [ABSTRACT FROM AUTHOR]