Plant carbon metabolism and climate change: elevated CO2 and temperature impacts on photosynthesis, photorespiration and respiration

Ozone risk assessment of common cypress (Cupressus sempervirens L.) clones and effects of Seiridium cardinale infection

Cupressus sempervirens is a relevant species in the Mediterranean for its cultural, economic and landscape value. This species is threatened by Seiridium cardinale, the causal agent of the cypress canker disease (CCD). The effects of biotic stressors on O3 risk assessment are unknown and a comprehensive O3 risk assessment in C. sempervirens is missing. To fill these gaps, two clones of C. sempervirens, one resistant (Clone R) and one susceptible to CCD (Clone S), were subjected to three levels of O3 (Ambient Air - AA; 1.5 × AA; 2.0 × AA) for two consecutive years in an O3-free-air controlled exposure facility and artificially inoculated with S. cardinale. Both the exposure- (AOT40) and flux-based (PODy) indices were tested. We found that PODy performed better than AOT40 to assess O3 effects on biomass and the critical level for a 4% biomass loss was 2.51 mmol/m2 POD2. However, significant O3 dose-response relationships were not found for the inoculated cypresses because the combination of middle level O3 (1.5 × AA) and inoculation stimulated a biomass growth in Clone S as hormetic response. Moreover, we found a different inter-clonal response to both stressors with a statistically significant reduction of total and belowground biomass following O3, and lower root biomass in Clone S than in Clone R following pathogen infection. In summary, Clone R was more resistant to O3, and inoculation altered O3 risk via an hormetic effect on biomass. These results warrant further studies on how biotic stressors affect O3 responses and risk assessment.

Some Like It Hot: Differential Photosynthetic Performance and Recovery of English Walnut Accessions Under Emerging California Heat Waves

Heat waves (HWs) pose a significant threat to California agriculture, with potential adverse effects on crop photosynthetic capacity, quality and yield, all of which contribute to significant economic loss. Lack of heat-resilient cultivars puts perennial crop production under severe threat due to increasing HW frequency, duration and intensity. Currently, available walnut cultivars are highly sensitive to abiotic stress, and germplasm collections provide potential solutions via genotypes native to varied climates. We screened nine English walnut accessions (Juglans regia) for physiological heat stress resilience and recovery in the USDA-ARS National Clonal Germplasm over 2-years, and identified accessions with superior resilience to heat stress. Heat stress impacted photosynthetic capacity in most accessions, as evidenced by reductions in net (An) and maximum (Amax) assimilation rates, quantum efficiency of PSII, and changes in stomatal conductance (gs). However, two accessions exhibited either higher or complete recovery post-irrigation. This aligns with the established practice of using irrigation to mitigate heat stress, as it improved recovery for several accessions, with A3 and A5 demonstrating the most resilience. One of these two superior accessions is native to one of the hottest and driest habitats of all studied accessions. These same accessions exhibited the highest An under non-stressed conditions and at higher temperatures of 35° to 45°C. Higher performance for A3 and A5 under HWs was associated with greater carboxylation rates, electron transport rates, and Amax. All accessions suffered significant declines in photosynthetic performance at 45°C, which were the ambient leaf temperatures approached during record-setting heat waves in California during September 2022.

Leaf trait networks of subtropical woody plants weaken along an elevation gradient

The leaf economic spectrum (LES) captures key leaf functional trait relationships, defining a conservative-acquisitive axis of plant resource utilization strategies. Examining the leaf trait network (LTN) is useful for understanding resource utilization strategies but also more broadly, the ecological strategies of plants. However, the relationship between the LES conservation-acquisition axis and LTN correlations across environmental gradients is unclear. To address this knowledge gap, we measured physiological, chemical, and structural traits in 52 broad-leaved tree species spanning an elevation gradient (1400 m, 1600 m, 1800 m) in Wuyi Mountain, China. A total of 12 leaf traits were selected, including: photosynthetic rate (A25), respiration rate (R25), optimum photosynthetic temperature (Topt), rate of photosynthesis at optimum temperature (Aopt), mean temperature at which 90 % of Aopt is reached (T90), temperature sensitivity of respiration (Q10), N and P content, N/P, leaf mass per area (LMA), photosynthetic nitrogen use efficiency (PNUE) and photosynthetic phosphorus use efficiency (PPUE). We found that leaf physiological traits exhibited signs of thermal acclimation along the elevation gradient. We also observed significant changes in leaf N and P content, N/P, photosynthetic phosphorus utilization efficiency (PPUE) and LMA with elevation. The resource utilization strategies of plants changed from conservative to acquisitive as elevation increased. The LTN analysis showed that as elevation increased, the links among traits weakened and modularity (modularity is used to describe the degree of separation between networks) increased. Collectively, our results indicate that elevation changes can trigger moderate shifts in the resource utilization and ecological strategies of plants via leaf functional traits.

3,4-dimethylpyrazole phosphate (DMPP) may negate the expected stimulation of elevated atmospheric CO2 and warming on fertilizer-N loss

People have accepted the clear fact that elevated CO2 (eCO2) and climate warming are happening, but sustainable agricultural systems are still struggling to adapt. 3,4-dimethyl-1H-pyrazol phosphate (DMPP) is currently recognized as a highly effective strategy for reducing nitrogen (N) loss and related environmental impacts. There is still uncertainty, however, whether DMPP could contribute to building climate-resilient ecosystems in a future climate scenario with co-elevated CO2 and temperature. Thus, this study evaluated the responses of plant N derived from soil or fertilizer and strawberry growth to the tested climate conditions. Plants were supplied with or without DMPP, grown in controlled climate chambers under ambient CO2 and temperature (aCT; 400 ppm + 25℃), and co-elevated CO2 and temperature (eCT; 800 ppm + 27℃). The results showed that DMPP increased plant N accumulation by 9 % and 19 % under aCT and eCT conditions, respectively, compared to N treatment without DMPP. We also found a similar trend in total C content in the plants. Compared with aCT, DMPP demonstrated higher efficiency in improving N use efficiency (NUE, 51 % vs. 36 %) and reducing N loss (21 % vs. 29 %) under eCT, which could ensure higher N demand of plant, making fertilizer-N, rather than soil-N, a primary contributor to the N accumulation increment. Moreover, in terms of combating climate challenge, the combination with DMPP further strengthened the beneficial influence of eCT on the N accumulation and biomass in strawberry but reduced fertilizer-N loss. In summary, DMPP exhibits better performance under eCT, which may alleviate the potential adverse effects of co-elevated CO2 and temperature on ecosystem by reducing fertilizer-N loss and soil-N mineralization more efficiently, providing a promising approach to optimizing sustainable agricultural management under future climate change.

Plant-microbiome interactions and their impacts on plant adaptation to climate change

Plants have co-evolved with a wide range of microbial communities over hundreds of millions of years, this has drastically influenced their adaptation to biotic and abiotic stress. The rapid development of multi-omics approaches has greatly improved our understanding of the diversity, composition, and functions of plant microbiomes, but how global climate change affects the assembly of plant microbiomes and their roles in regulating host plant adaptation to changing environmental conditions is not fully known. In this review, we summarize recent advancements in the community assembly of plant microbiomes, and their responses to climate change factors such as elevated CO2 levels, warming, and drought. We further delineate the research trends and hotspots in plant-microbiome interactions in the context of climate change, and summarize the key mechanisms by which plant microbiomes influence plant adaptation to the changing climate. We propose that future research is urgently needed to unravel the impact of key plant genes and signal molecules modulated by climate change on microbial communities, to elucidate the evolutionary response of plant-microbe interactions at the community level, and to engineer synthetic microbial communities to mitigate the effects of climate change on plant fitness.

Vertical canopy gradients of respiration drive plant carbon budgets and leaf area index

Despite its importance for determining global carbon fluxes, leaf respiration remains poorly constrained in land surface models (LSMs). We tested the sensitivity of the Energy Exascale Earth System Model Land Model - Functionally Assembled Terrestrial Ecosystem Simulator (ELM-FATES) to variation in the canopy gradients of leaf maintenance respiration (Rdark). We ran global and point simulations varying the canopy gradient of Rdark to explore the impacts on forest structure, composition, and carbon cycling. In global simulations, steeper canopy gradients of Rdark lead to increased understory survival and leaf biomass. Leaf area index (LAI) increased up to 77% in tropical regions compared with the default parameterization, improving alignment with remotely sensed benchmarks. Global vegetation carbon varied from 308 Pg C to 449 Pg C across the ensemble. In tropical forest simulations, steeper gradients of Rdark had a large impact on successional dynamics. Results show the importance of canopy gradients in leaf traits and fluxes for determining plant carbon budgets and emergent ecosystem properties such as competitive dynamics, LAI, and vegetation carbon. The high-model sensitivity to canopy gradients in Rdark highlights the need for more observations of how leaf traits and fluxes vary along light micro-environments to inform critical dynamics in LSMs.

Understanding the photosynthesis in relation to climate change in grapevines

Due to predicted global climate change, there have been significant alterations in agricultural production patterns, which had a negative impact on ecosystems as well as the commercial and export prospects for the production of grapevines. The natural biochemistry of grapevines, including their chlorophyll content, net photosynthetic rate, Fv/Fm ratio, photorespiration, reduced yield, and quality is also anticipated to be negatively impacted by the various effects of light, temperature, and carbon dioxide at elevated scales. Grapevine phenology, physiology, and quality are impacted by the inactivation of photosystems (I and II), the Rubisco enzyme system, pigments, chloroplast integrity, and light intensity by temperature and increasing CO2 levels. Grape phenological events are considerably altered by climatic conditions; in particular, berries mature earlier, increasing the sugar-to-acid ratio. In enology, the sugar-to-acid ratio is crucial since it determines the wine's final alcohol concentration and flavour. As light intensity and CO2 levels rise, the biosynthesis of anthocyanins and tannins declines. As the temperature rises, the production of antioxidants diminishes, affecting the quality of raisins. Table grapes are more sensitive to temperature because of physiological problems like pink berries and a higher sugar-to-acidity ratio. Therefore, the systemic impact of light intensity, temperature, and increasing CO2 levels on grapevine physiology, phenology, photosystems, photosynthesis enzyme system, and adaptive strategies for grape producers and researchers are highlighted in this article.

Untargeted metabolomics of Aloe volatiles: Implications in pathway enrichments for improved bioactivities

Enhancing the production of economically and medically important plant metabolites by genetic and metabolic manipulation is a lucrative approach for enhancing crop quality. Nevertheless, the task of identifying suitable biosynthetic pathways related to certain bioactivities has proven to be challenging due to the intricate interconnections of the major metabolic and biochemical processes in commercially important plants. The commercial significance of plants belonging to the genus Aloe stems from their extensive utilization across several industries, such as cosmetics, pharmaceuticals, and wellness items, due to their medicinal properties. In the present study, we have utilized a reverse association approach to identify potential target metabolic pathways for enhancing the production of commercially important metabolites of Aloe spp., based on their metabolic pathway enrichment profile. The leaves of five highly utilized Aloe sp. were subjected to untargeted gas chromatography-mass spectrometry analysis followed by testing of free-radical scavenging effects against components of the Fenton and Haber-Weiss reaction. Through the application of appropriate bioinformatics tools, we identified distinct phytochemical classes and determined the enrichment of their corresponding biosynthetic pathways, associated the pathways with bioactivities, and also identified the inter-relation between the commonly enriched pathways. The strong association between metabolic pathways and antioxidant potentials suggested the necessity to enhance distinct but closely related metabolic pathways in order to enhance the quality of Aloe spp. and maximize their antioxidant effects for commercial exploitation in cosmetic industries.

Towards carbon neutrality: Enhancing CO2 sequestration by plants to reduce carbon footprint

To achieve carbon neutrality and address climate change effectively, strategies emphasizing plant-based CO2 sequestration are essential. This research integrates process optimization, sustainable practices, and technological innovations to augment plants' natural CO2 absorption, thereby enhancing ecosystem carbon storage and aiding in greenhouse gas (GHG) mitigation. The study highlights the critical role of merging process integration with sustainable farming, precision agriculture, and bioengineering to enhance CO2 sequestration. The research emphasizes employing Life Cycle Assessment (LCA) and Carbon Footprint Analysis (CFA) as vital tools for quantifying CO2 sequestration strategies' environmental benefits and effectiveness, ensuring a comprehensive approach to cleaner production and waste management. By examining case studies and models, this research assesses the contribution of these approaches to reducing carbon footprints and advancing towards carbon neutrality. The findings advocate for a cohesive strategy that blends technological advancements with sustainable agricultural practices, aimed at reducing global carbon emissions and achieving carbon neutrality.

Influence of day and night temperature and carbon dioxide concentration on growth, yield, and quality of green butterhead and red oakleaf lettuce

Production of lettuce (Lactuca sativa) within vertical farms is an expanding segment of controlled environment agriculture-precise manipulation of environmental parameters including mean daily temperature (MDT) and carbon dioxide (CO2) concentration enables year-round production, alongside color, yield, and crop size regulation. Our objectives included 1) quantify how MDT and CO2 interact to influence lettuce growth, development, and quality; 2) model lettuce growth under several MDTs and CO2 concentrations. Green butterhead 'Rex' and red oakleaf 'Rouxaï RZ' seedlings were transplanted into hydroponic tanks under a photosynthetic photon flux density of 300 μmol·m‒2·s‒1 for 17-h·d‒1. CO2 concentrations of 500, 800, or 1200 μmol·mol-1 and day/night and MDT setpoints of 22/15°C (MDT 20°C), 25/18°C (23°C), or 28/21°C (26°C) were maintained within growth chambers. 'Rex' fresh mass increased linearly with MDT, increasing by 18% from 20 to 26°C. 'Rouxaï RZ' fresh mass increased quadratically with MDT, with a 32% increase from 20 to 23°C, then a 7% increase from 23 to 26°C. Elevating CO2 concentrations from 500 to 800 μmol·mol-1 increased 'Rouxaï RZ' and 'Rex' fresh mass by 33 and 16%, respectively, while fresh mass did not increase from 800 to 1200 μmol·mol-1. Both cultivars had the greatest dry mass at 800 μmol·mol-1 CO2 across temperatures. At a high MDT, 'Rouxaï RZ' foliage color became more light, vibrant, and green, while a low MDT induced darker, grayer, and redder foliage. Tipburn occurred on 'Rex' across treatments, while 25% of 'Rouxaï RZ' were afflicted at 500 μmol·mol-1 CO2 and 67% at 1200 μmol·mol-1. At the light intensity studied, we recommend growing 'Rex' and 'Rouxaï RZ' at an 800 μmol·mol-1 CO2 concentration and MDT of 23°C for greatest biomass and leaf number, and slightly redder foliage in 'Rouxaï RZ' than at a 26°C MDT.

New insights into the responses of phosphite, as a plant biostimulator, on PSII photochemistry, gas exchange, redox state and antioxidant system in maize plants under boron toxicity

This study focused on boron (B), an essential micronutrient for plant development that becomes toxic at high concentrations, adversely affecting plant growth and yield. Phosphite (PHI) is recognized for its easy absorption by plant leaves and roots and its well-documented positive effects on plant growth. The effects of phosphite (PHI-1, 2 g L⁻1; PHI-2, 4 g L⁻1) under boron stress (B, 2 mM) were evaluated in Zea mays. Under B stress, a 58% reduction in growth was observed in maize leaves. However, PHI applied at both concentrations positively influenced growth parameters and regulated water relations in the leaves of stressed plants. Under B stress, gas exchange was restricted, the photochemical quantum efficiency of PSII (Fv/Fm) was suppressed, and non-photochemical quenching (NPQ) values increased. Treatments with B + PHI-1 and B + PHI-2 enhanced carbon assimilation rates (A) by 37% and 23%, respectively. In OJIP transition parameters, it was observed that PHI-1 and PHI-2 treatments supported photochemical reactions by reducing the dissipated energy flux (DIo/RC). Additionally, high levels of H₂O₂ accumulation and lipid peroxidation occurred under B stress However, PHI treatments increased the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX), mitigating oxidative damage caused by B stress. Furthermore, PHI effectively preserved ascorbate regeneration and enhanced the ascorbate-glutathione cycle, contributing to the reduction of reactive oxygen species (ROS) accumulation. Consequently, PHI treatment demonstrated its effectiveness in mitigating boron toxicity by improving the antioxidant defense system, reducing ROS accumulation, and enhancing photosynthetic efficiency, thereby increasing stress tolerance in maize plants.

Mechanism of Bacillus cooperating with silicon to re-balance chlorophyll metabolism and restore carbon metabolism of Glycyrrhiza uralensis Fisch. Seedlings exposed to salt-drought stress

Salt-drought is a major environmental event affecting crop productivity and quality by causing chlorophyll (Chl) and carbon balance disorder. There has been growing interest in the application of endophyte and silicon (Si), as inoculants for saline and drought land restoration. This study investigates the impact of Bacillus (Bs), Si, and Bs + Si on the disorder of Chl metabolism and carbon balance of G. uralensis seedlings under salt-drought stress (SD). Results showed that both Bs and Si treatments enhanced Chl and carbon metabolism, with the combined Bs and Si treatment showing a synergistic effect. Specifically, Bs + Si enhanced the mutual conversion of Chl a and Chl b, restored the equilibrium in Chl a and Chl b content, and increased RuBisco activity by 31.07%, thereby promoting carbon fixation. Subsequently, Bs + Si re-balanced the carbohydrate content, by increasing the sucrose synthase (SS), and β-amylase (BMY) activities by 49.57%, and 83.59% respectively, and decreasing sucrose phosphate synthase (SPS), and granule-bound starch synthase (GBSS) activities by 38.93%, 40.93% respectively etc involved in the metabolism of sucrose and starch. Furthermore, Bs + Si facilitated the restoration of the typical progression of the tricarboxylic acid (TCA) cycle and glycolysis pathway (EMP). These findings highlight the synergistic role of Bs and Si in enhancing the salt and drought resilience of G. uralensis seedlings, offering promising strategies for sustainable agriculture, improving crop resilience to climate change, and achieving the "dual carbon" goals of carbon peaking and carbon neutrality.

Assessing environmental gradients in relation to dark CO2 fixation in estuarine wetland microbiomes

The rising atmospheric concentration of CO2 is a major concern to society due to its global warming potential. In soils, CO2-fixing microorganisms are preventing some of the CO2 from entering the atmosphere. Yet, the controls of dark CO2 fixation are rarely studied in situ. Here, we examined the gene and transcript abundance of key genes involved in microbial CO2 fixation along major environmental gradients within estuarine wetlands. A combined multi-omics approach incorporating metabarcoding, deep metagenomic, and metatranscriptomic analyses confirmed that wetland microbiota harbor four out of seven known CO2 fixation pathways, namely, the Calvin cycle, reverse tricarboxylic acid cycle, Wood-Ljungdahl pathway, and reverse glycine pathway. These pathways are transcribed at high frequencies along several environmental gradients, albeit at different levels depending on the environmental niche. Notably, the transcription of the key genes for the reverse tricarboxylic acid cycle was associated with high nitrate concentration, while the transcription of key genes for the Wood-Ljungdahl pathway was favored by reducing, O2-poor conditions. The transcript abundance of the Calvin cycle was favored by niches high in organic matter. Taxonomic assignment of transcripts implied that dark CO2 fixation was mainly linked to a few bacterial phyla, namely, Desulfobacterota, Methylomirabilota, Nitrospirota, Chloroflexota, and Pseudomonadota.

IMPORTANCE

The increasing concentration of atmospheric CO2 has been identified as the primary driver of climate change and poses a major threat to human society. This work explores the mostly overlooked potential of light-independent CO2 fixation by soil microbes (a.k.a. dark CO2 fixation) in climate change mitigation efforts. Applying a combination of molecular microbial tools, our research provides new insights into the ecological niches where CO2-fixing pathways are most active. By identifying how environmental factors, like oxygen, salinity and organic matter availability, influence these pathways in an estuarine wetland environment, potential strategies for enhancing natural carbon sinks can be developed. The importance of our research is in advancing the understanding of microbial CO2 fixation and its potential role in the global climate system.

Comparative transcriptome analysis reveals the key role of photosynthetic traits in the formation of differences in photothermal sensitivity in tobacco

BACKGROUND

The photothermal sensitivity of tobacco refers to how tobacco plants respond to variations in the photothermal conditions of their growth environment. The degree of this sensitivity is crucial for determining the optimal planting regions for specific varieties, as well as for improving the quality and yield of tobacco leaves. However, the precise mechanisms underlying the development of photothermal sensitivity in tobacco remain unclear.

RESULTS

In this study, two tobacco varieties with significant differences in sensitivity, previously selected using a photothermal sensitivity model, were chosen as materials. Two experimental sites with considerable differences in photothermal conditions were selected for planting. The aim was to comparatively analyze the changes in agronomic traits, biomass, and physiological indices of the varieties under different experimental conditions, as well as to conduct transcriptome analyses. The transcriptome results revealed significant enrichment of differentially expressed genes (DEGs) related to photosynthesis, plant hormone signal transduction, and flavonoid biosynthesis pathways. In the photosynthesis and plant hormone signaling pathways, genes such as Lhcb, aldo, AUX/IAA, and SAUR were significantly upregulated. This upregulation promoted photosynthetic efficiency by enhancing the process of photosynthesis. However, this promotion also led to the increased production of harmful substances such as hydrogen peroxide and superoxide radicals, which can damage cellular structure and function. In the flavonoid biosynthesis pathway, genes such as FLS, CHI, and PAL were significantly upregulated, which enhanced the plant's antioxidant capacity. This effectively mitigated the harmful effects of oxidative stress, helping to maintain normal photosynthetic function.

CONCLUSION

The findings of this study suggest that the photosynthetic capacity of tobacco plants is enhanced through the coordinated regulation of the photosynthesis, plant hormone signaling, and flavonoid biosynthesis pathways. This enhancement plays a pivotal role in modulating the plants' photothermal adaptability, ultimately contributing to variations in their photothermal sensitivity.

Foliage development and resource allocation determine the growth responses of silver birch (Betula pendula) to elevated environmental humidity

Scenarios for future climate predict an increase in precipitation amounts and frequency of rain events, resulting in higher air humidity and soil moisture at high latitudes, including in northern Europe. We analysed the effects of artificially elevated environmental humidity (air relative humidity and soil moisture) on leaf gas exchange, water relations, growth and phenology of silver birch (Betula pendula) trees growing at the free air humidity manipulation experimental site situated in the hemiboreal vegetation zone, in eastern Estonia, with no occurring water deficit to the trees. The environmental humidity manipulation did not significantly affect the water relations traits but did affect some leaf gas exchange parameters, growth and phenology of the trees. Elevated air humidity (H) did not influence photosynthetic capacity and stomatal conductance, while the trees exhibited higher stomatal sensitivity to leaf-to-air vapour pressure difference compared with the trees at ambient conditions (C) or at elevated soil moisture (I). H trees demonstrated reduced height growth and foliage biomass, increased allocation to stem radial growth and prolonged leaf retention in autumn compared with the C trees. Increased air humidity supports longer leaf retention and growth period, but this does not translate into increased growth parameters at the tree level. The changes in tree growth in response to increasing atmospheric humidity could plausibly be explained by (i) retardation of foliage development and (ii) changes in resource allocation, causing a shift in the ratio of photosynthetic to non-photosynthetic tissues in favour of the latter. Under high atmospheric evaporative demand, higher stomatal sensitivity in H trees induces faster stomatal closure, which may result in carbon starvation. A future rise in atmospheric humidity at high latitudes may lead to reduced tree growth and forest productivity, in contrast to the predicted future of forests.

Elevated CO2 alters soybean physiology and defense responses, and has disparate effects on susceptibility to diverse microbial pathogens

Increasing atmospheric CO2 levels have a variety of effects that can influence plant responses to microbial pathogens. However, these responses are varied, and it is challenging to predict how elevated CO2 (eCO2) will affect a particular plant-pathogen interaction. We investigated how eCO2 may influence disease development and responses to diverse pathogens in the major oilseed crop, soybean. Soybean plants grown in ambient CO2 (aCO2, 419 parts per million (ppm)) or in eCO2 (550 ppm) were challenged with bacterial, viral, fungal, and oomycete pathogens. Disease severity, pathogen growth, gene expression, and molecular plant defense responses were quantified. In eCO2, plants were less susceptible to Pseudomonas syringae pv. glycinea (Psg) but more susceptible to bean pod mottle virus, soybean mosaic virus, and Fusarium virguliforme. Susceptibility to Pythium sylvaticum was unchanged, although a greater loss in biomass occurred in eCO2. Reduced susceptibility to Psg was associated with enhanced defense responses. Increased susceptibility to the viruses was associated with reduced expression of antiviral defenses. This work provides a foundation for understanding how future eCO2 levels may impact molecular responses to pathogen challenges in soybean and demonstrates that microbes infecting both shoots and roots are of potential concern in future climatic conditions.

Leaf Photosynthetic and Respiratory Thermal Acclimation in Terrestrial Plants in Response to Warming: A Global Synthesis

Leaf photosynthesis and respiration are two of the largest carbon fluxes between the atmosphere and biosphere. Although experiments examining the warming effects on photosynthetic and respiratory thermal acclimation have been widely conducted, the sensitivity of various ecosystem and vegetation types to warming remains uncertain. Here we conducted a meta-analysis on experimental observations of thermal acclimation worldwide. We found that the optimum temperature for photosynthetic rate (Topt) and the maximum rate of carboxylation of Rubisco (ToptV) in tropical forest plants increased by 0.51°C and 2.12°C per 1°C of warming, respectively. Similarly, Topt and the optimum temperature for maximum electron transport rate for RuBP regeneration (ToptJ) in temperate forest plants increased by 0.91°C and 0.15°C per 1°C of warming, respectively. However, reduced photosynthetic rates at optimum temperature (Aopt) were observed in tropical forest (17.2%) and grassland (16.5%) plants, indicating that they exhibited limited photosynthetic thermal acclimation to warming. Warming reduced respiration rate (R25) in boreal forest plants by 6.2%, suggesting that respiration can acclimate to warming. Photosynthesis and respiration of broadleaved deciduous trees may adapt to warming, as indicated by higher Aopt (7.5%) and Topt (1.08°C per 1°C of warming), but lower R25 (7.7%). We found limited photosynthetic thermal acclimation in needleleaved evergreen trees (-14.1%) and herbs (-16.3%), both associated with reduced Aopt. Respiration of needleleaved deciduous trees acclimated to warming (reduced R25 and temperature sensitivity of respiration (Q10)); however, broadleaved evergreen trees did not acclimate (increased R25). Plants in grasslands and herbaceous species displayed the weakest photosynthetic acclimation to warming, primarily due to the significant reductions in Aopt. Our global synthesis provides a comprehensive analysis of the divergent effects of warming on thermal acclimation across ecosystem and vegetation types, and provides a framework for modeling responses of vegetation carbon cycling to warming.

Stomatal opening under high temperatures is controlled by the OST1-regulated TOT3-AHA1 module

Plants continuously respond to changing environmental conditions to prevent damage and maintain optimal performance. To regulate gas exchange with the environment and to control abiotic stress relief, plants have pores in their leaf epidermis, called stomata. Multiple environmental signals affect the opening and closing of these stomata. High temperatures promote stomatal opening (to cool down), and drought induces stomatal closing (to prevent water loss). Coinciding stress conditions may evoke conflicting stomatal responses, but the cellular mechanisms to resolve these conflicts are unknown. Here we demonstrate that the high-temperature-associated kinase TARGET OF TEMPERATURE 3 directly controls the activity of plasma membrane H+-ATPases to induce stomatal opening. OPEN STOMATA 1, which regulates stomatal closure to prevent water loss during drought stress, directly inactivates TARGET OF TEMPERATURE 3 through phosphorylation. Taken together, this signalling axis harmonizes stomatal opening and closing under high temperatures and/or drought. In the context of global climate change, understanding how different stress signals converge on stomatal regulation allows the development of climate-change-ready crops.

Tree Lifespans in a Warming World: Unravelling the Universal Trade-Off Between Growth and Lifespan in Temperate Forests

Tree growth and lifespan are key determinants of forest dynamics, and ultimately control carbon stocks. Warming and increasing CO2 have been observed to increase growth but such increases may not result in large net biomass gains due to trade-offs between growth and lifespan. A deeper understanding of the nature of the trade-off and its potential spatial variation is crucial to improve predictions of the future carbon sink. This study aims to identify key drivers of growth and lifespan, assess the universality of tree growth-lifespan trade-offs, explore the possible latitudinal patterns of trade-off strengths and their determinants, and project growth and lifespan under future climate scenarios. We analyzed 21,193 trees of 69 species (48 included in further analysis) at 445 sites (417 included in further analysis) in temperate forests in northeastern China to estimate early growth rate and tree lifespan. We find that temperature and human pressure enhance tree growth and reduce lifespan, while altitude increases lifespan. We further find evidence for growth-lifespan trade-offs at all studied levels, that is, among trees, among species and communities, and within species and communities. Trade-offs are stronger at colder, higher latitudes compared to warmer sites, because of larger variation in tree growth and climate, larger range sizes for individual species, and lower species' diversity for communities at high latitudes. We predict future increases in growth and reductions in tree lifespan in response to climate change for the 2050s. Taking growth lifespan trade-offs into account resulted in even larger predictions of decreases in tree lifespan of up to 8%. In conclusion, growth-lifespan trade-offs are universal, but the strengths may vary by environment and between different forests. Its effects are important to include in predictions of forest responses to global change and need to be considered more widely.

Bicarbonate use reduces the photorespiration in Ottelia alismoides adapting to the CO2-fluctuated aquatic systems

Underwater CO2 concentration fluctuates extremely in natural water bodies. Under low CO2, the unique CO2 concentrating mechanism in aquatic plants, bicarbonate use, can suppress photorespiration. However, it remains unknown (1) to what extent bicarbonate use reduces photorespiration, (2) how exactly photorespiration varies between bicarbonate-users and CO2-obligate users under CO2-fluctuated environments, and (3) what are differences in Rubisco characteristics between these two types of aquatic plants. In the present study, the bicarbonate user Ottelia alismoides and its phylogenetically close CO2-obligate user Blyxa japonica were chosen to answer these questions. The results showed that bicarbonate use saved ~13% carbon loss under low CO2 via decreasing photorespiration in O. alismoides. Through bicarbonate use, the photorespiration of O. alismoides was kept stable both under high and low underwater CO2 concentrations, while the photorespiration significantly increased in the CO2-obligate user B. japonica under low CO2. However, B. japonica showed a significantly higher photosynthesis rate than O. alsimoides when CO2 was sufficient. These differences could be related to the kinetic characteristics of Rubisco showing a higher carboxylation turnover rate (Kcat) in B. japonica, and the similar affinity to CO2 (Kc) and specificity factor (Sc/o) in these two species that might be determined by the variation of six amino acid residuals in Rubisco large subunit sequences, especially the site 281 (A vs. S) and 282 (H vs. F). All these differences in photorespiration and kinetic characteristics of Rubisco could explain the distribution patterns of bicarbonate users and CO2-obligate users in the field.

Unravelling the photosynthetic dynamics and fluorescence parameters under ameliorative effects of 24-epibrassinolide in wheat (Triticum aestivum L.) grown under heat stress regime

An experiment was performed at the Banaras Hindu University, India to study the effect of terminal heat stress on photosynthetic dynamics and fluorescence parameters of wheat genotypes and ameliorative effects of epibrassinolide by taking two genotypes with four concentrations as foliar spray at two growth stages of wheat. The highest values were observed in plots foliar sprayed with 1.0 µM 24-epibrassinolide (T1) under normal conditions (D1) where the genotype Sonalika (V1) performed significantly well w.r.t. the parameters viz. steady-state fluorescence (Fs) 116.22, quantum efficiency of PSII 0.59, maximum fluorescence (Fm) 776.5, normalized stress detection ratio (Fv/Fo) 4.47, maximum potential quantum efficiency of PSII (Fv/Fm) 0.82.Whereas under heat stress condition (late sown D2), there was significant reduction in these parameters in both the genotypes which was improved by the application of epibrassinolide suggesting its potential role in improving the photoinhibition process by raising the efficiency of PSII. Overall, the calibrated application of 24-epibrassinolide was found to be a potent growth regulator involved in the positive modulation of heat stress tolerance in wheat, coupled with improved photosynthetic efficiency in treated plots as compared to control.

Changes in morphological and physiological traits of urban trees in response to elevated temperatures within an Urban Heat Island

Urban heat islands (UHIs) are a common phenomenon in metropolitan areas worldwide where the air temperature is significantly higher in urban areas than in surrounding suburban, rural or natural areas. Mitigation strategies to counteract UHI effects include increasing tree cover and green spaces to reduce heat. The successful application of these approaches necessitates a deep understanding of the thermal tolerances in urban trees and their susceptibility to elevated urban temperatures. We evaluated how the photosynthetic thermal optimum (Topt), photosynthetic heat tolerance (T50) and key leaf thermoregulatory morphological traits (leaf area [LA], specific leaf area, leaf width, thickness and leaf dry matter content) differ between conspecific trees growing in 'hot' (UHI) vs 'cool' parts of Montreal, Canada (with a difference of 3.4 °C in air temperature), to assess the ability of seven common tree species to acclimation to higher temperatures. We hypothesized that individuals with hotter growing temperatures would exhibit higher Topt and T50, as well as leaf thermoregulatory morphological traits aligned with conservative strategies (e.g., reduced LA and increased leaf mass) compared with their counterparts in the cooler parts of the city. Contrary to our a priori hypotheses, LA increased with growing temperatures and only four of the seven species had higher T50 and only three had higher Topt values in the hotter area. These results suggest that many tree species cannot acclimate to elevated temperatures and that the important services they provide, such as carbon capture, can be negatively affected by high temperatures caused by climate change and/or the UHI effect. The ability vs inability of tree species to acclimate to high temperatures should be considered when implementing long term tree planting programs in urban areas.

Heat Wave Adaptations: Unraveling the Competitive Dynamics Between Invasive Wedelia trilobata and Native Wedelia chinensis

Heat waves (HW) are projected to become more frequent and intense with climate change, potentially enhancing the invasiveness of certain plant species. This study aims to compare the physiological and photosynthetic responses of the invasive Wedelia trilobata and its native congener Wedelia chinensis under simulated heat wave conditions (40.1 °C, derived from local historical data). Results show that W. trilobata maintained higher photosynthetic efficiency, water-use efficiency (WUE), and total biomass under HW, suggesting that its ability to optimize above-ground growth contributes to its success in heat-prone environments. In contrast, W. chinensis focused more on root development and antioxidant protection, exhibiting a decrease in total biomass under heat wave conditions. These results indicate that W. trilobata employs a more effective strategy to cope with heat stress, likely enhancing its competitive advantage in regions affected by heat waves. This study highlights the importance of understanding species-specific responses to extreme climate events and underscores the potential for heat waves to drive ecological shifts, favoring invasive species with higher phenotypic plasticity.

Does the response of Rubisco and photosynthesis to elevated [CO2] change with unfavourable environmental conditions?

Climate change due to anthropogenic CO2 emissions affects plant performance globally. To improve crop resilience, we need to understand the effects of elevated CO2 concentration (e[CO2]) on CO2 assimilation and Rubisco biochemistry. However, the interactive effects of e[CO2] and abiotic stress are especially unclear. This study examined the CO2 effect on photosynthetic capacity under different water availability and temperature conditions in 42 different crop species, varying in functional group, photosynthetic pathway, and phenological stage. We analysed close to 3000 data points extracted from 120 published papers. For C3 species, e[CO2] increased net photosynthesis and intercellular [CO2], while reducing stomatal conductance and transpiration. Maximum carboxylation rate and Rubisco in vitro extractable maximal activity and content also decreased with e[CO2] in C3 species, while C4 crops are less responsive to e[CO2]. The interaction with drought and/or heat stress did not significantly alter these photosynthetic responses, indicating that the photosynthetic capacity of stressed plants responded to e[CO2]. Moreover, e[CO2] had a strong effect on the photosynthetic capacity of grasses mainly in the final stages of development. This study provides insight into the intricate interactions within the plant photosynthetic apparatus under the influence of climate change, enhancing the understanding of mechanisms governing plant responses to environmental parameters.

Transcriptome and Metabolome Analyses Reveal the Regulatory Mechanism of TC1a in the Sucrose and Starch Synthesis Pathways in Arabidopsis thaliana

Tumor necrosis factor receptor-associated factor (TRAF) proteins, originally identified in mammals, have since been found in most plants. TRAF proteins in plants have been shown to be involved in cellular autophagy, immunity, drought resistance, and ABA induction. However, the role in regulating sucrose and starch metabolism has not been reported. In this study, we confirmed that TC1a can regulate sucrose and starch metabolism through gene editing, phenotypic observation, transcriptomics and metabolomics analyses. Initially, 200 and 81 TRAF proteins were identified in rapeseed (Brassica napus L.) and Arabidopsis thaliana, respectively, and divided into five classes. We found that overexpression of TC1a inhibited root length, plant height, flowering, and leaf development in A. thaliana. Additionally, 12 differentially expressed genes (DEGs) related to sucrose and starch metabolism pathways were identified in overexpressing and knockout plants, respectively. Six differentially accumulated metabolites (DAMs)-fructose, sucrose, glucose, trehalose, maltose, and 6-phosphate fructose-were identified using widely targeted metabolomics analysis. The results show that TC1a affects the growth and development of Arabidopsis, and induces the expression of sucrose and starch synthase and hydrolases, providing a foundation for further research into its molecular mechanisms.

Cross-kingdom nutrient exchange in the plant-arbuscular mycorrhizal fungus-bacterium continuum

The association between plants and arbuscular mycorrhizal fungi (AMF) affects plant performance and ecosystem functioning. Recent studies have identified AMF-associated bacteria as cooperative partners that participate in AMF-plant symbiosis: specific endobacteria live inside AMF, and hyphospheric bacteria colonize the soil that surrounds the extraradical hyphae. In this Review, we describe the concept of a plant-AMF-bacterium continuum, summarize current advances and provide perspectives on soil microbiology. First, we review the top-down carbon flow and the bottom-up mineral flow (especially phosphorus and nitrogen) in this continuum, as well as how AMF-bacteria interactions influence the biogeochemical cycling of nutrients (for example, carbon, phosphorus and nitrogen). Second, we discuss how AMF interact with hyphospheric bacteria or endobacteria to regulate nutrient exchange between plants and AMF, and the possible molecular mechanisms that underpin this continuum. Finally, we explore future prospects for studies on the hyphosphere to facilitate the utilization of AMF and hyphospheric bacteria in sustainable agriculture.

The regulatory roles of a plant neurotransmitter, acetylcholine, on growth, PSII photochemistry and antioxidant systems in wheat exposed to cadmium and/or mercury stress

Heavy metals increase in nature due to anthropogenic activities and negatively impact the growth, progress, and efficiency of plants. Among the toxic metal pollutants that can cause dangerous effects when accumulated by plants, mercury (Hg) and cadmium (Cd) were investigated in this study. These metals typically inhibit important enzymes and halt their functioning, thereby adversely affecting the capability of plants to achieve photosynthesis, respiration, and produce quality crops. Acetylcholine (ACh) serves as a potent neurotransmitter present in both primitive and advanced plant species. Its significant involvement in diverse metabolic processes, particularly in regulating growth and adaptation to stress, needs to be further elucidated. For this aim, effects of acetylcholine (ACh1, 10 μM; ACh2, 100 μM) were survey in Triticum aestivum under Hg and/or Cd stress (Hg, 50 μM; Cd, 100 μM). Wheat seedlings exhibited a growth retardation of about 24% under Hg or Cd stress. Combined stress conditions (Cd + Hg) resulted in a decrease in RWC by approximately 16%. Two different doses of ACh treatment to stressed plants positively affected growth parameters and regulated the water relations. Gas exchange was limited in stress groups, and the photochemical quantum competency of PSII (Fv/Fm) was suppressed. Cd + ACh1 and Cd + ACh2 treatments resulted in approximately 2-fold and 1.5-fold improvement in stomatal conductance and carbon assimilation rate, respectively. Similarly, improvement was observed with ACh treatments in wheat seedlings under Hg stress. Under Cd and/or Hg stress, high levels of H2O2 accumulated and lipid peroxidation occurred. According to our results, ACh treatment upon Cd and Hg stresses improved the activities of SOD, POX, and APX, thereby reducing oxidative damage. In conclusion, ACh treatment was found to ensure stress tolerance and limit the adverse effects caused by heavy metals.

Photosynthetic capacity in middle-aged larch and spruce acclimates independently to experimental warming and elevated CO2

Photosynthetic acclimation to both warming and elevated CO2 of boreal trees remains a key uncertainty in modelling the response of photosynthesis to future climates. We investigated the impact of increased growth temperature and elevated CO2 on photosynthetic capacity (Vcmax and Jmax) in mature trees of two North American boreal conifers, tamarack and black spruce. We show that Vcmax and Jmax at a standard temperature of 25°C did not change with warming, while Vcmax and Jmax at their thermal optima (Topt) and growth temperature (Tg) increased. Moreover, Vcmax and Jmax at either 25°C, Topt or Tg decreased with elevated CO2. The Jmax/Vcmax ratio decreased with warming when assessed at both Topt and Tg but did not significantly vary at 25°C. The Jmax/Vcmax increased with elevated CO2 at either reference temperature. We found no significant interaction between warming and elevated CO2 on all traits. If this lack of interaction between warming and elevated CO2 on the Vcmax, Jmax and Jmax/Vcmax ratio is a general trend, it would have significant implications for improving photosynthesis representation in vegetation models. However, future research is required to investigate the widespread nature of this response in a larger number of species and biomes.

Understanding the impact of elevated CO2 and O3 on growth and yield in Indian wheat cultivars: Implications for food security in a changing climate

The pressing issue of increasing tropospheric ozone (O3) levels necessitates the development of effective stress management strategies for plant protection. While considerable research has elucidated the adverse impacts of O3, understanding the combined effects of O3 and CO2 requires further investigation. This study focuses on assessing the response of stomatal O3 flux under various O3 and CO2 treatments, individually and in combination, and their repercussions on physiological, growth, and yield attributes in two Indian wheat cultivars, HUW-55 and PBW-550, which exhibit varying levels of sensitivities against elevated O3. Results indicated significant alterations in stomatal O3 flux in both O3-sensitive and tolerant wheat cultivars across different treatments, influencing the overall yield outcomes. Particularly, the ECO2+EO3 treatment demonstrated more positive yield protection in the O3-sensitive cultivar PBW-550, compared to HUW-55 indicating enhanced allocation of photosynthates towards reproductive development in PBW-550, compared to the tolerant cultivar HUW-55, as evidenced by higher harvest index (HI). Furthermore, the study revealed a stronger correlation between yield response and stomatal O3 flux in PBW-550 (R2 = 0.88) compared to HUW-55 (R2 = 0.79), as indicated by a steeper regression slope for PBW-550. The research also confirmed the role of elevated CO2 in reducing stomatal O3- flux in the tested cultivars, with discernible effects on their respective yield responses. Further experimentation is necessary to confirm these results across different cultivars exhibiting varying sensitivities to O3. These findings can potentially revolutionize agricultural productivity in regions affected by O3 stress. The criteria for recommending cultivars for agricultural practices should not be based only on their sensitivity/tolerance to O3. Still, they should also consider the effect of CO2 fertilization in the growing area. This experiment offers hope to sustain global food security, as the O3-sensitive wheat cultivar also showed promising results at elevated CO2. In essence, this research could pave the way for more resilient agricultural systems in the era of changing climate under elevated O3 and CO2 conditions.

A new dimension of leaf economic spectrum: temporal instability of relationships among genotypes

Leaf economic spectrum (LES) relationships have been studied across many different plant lineages and at different organizational scales. However, the temporal stability of the LES relationships is largely unknown. We used the wild blueberry system with high genotypic diversity to test whether trait-trait relationships across genotypes demonstrate the same LES relationships found in the global database (GLOPNET) and whether they are stable across years. We studied leaf structure, photosynthesis, and leaf nutrients for 16 genotypes of two wild blueberry species semi-naturally grown in a common farm in Maine, USA, across 4 yr. We found substantial variation in leaf structure, physiology, and nutrient traits within and among genotypes, as well as across years in wild blueberries. The LES trait-trait relationships (covariance structure) across genotypes were not always found in all years. The trait syndrome of wild blueberries was shifted by changing environmental conditions over the years. Additionally, traits in 1 yr cannot be used to predict those of another year. Our findings show that LES generally holds among genotypes but is temporally unstable, stressing the significant influence of trait plasticity in response to fluctuating environmental conditions across years, and the importance of temporal dimensions in shaping functional traits and species coexistence.

Exploring genetics and genomics trends to understand the link between secondary metabolic genes and agronomic traits in cereals under stress

The plant metabolome is considered an important interface between the genome and its phenome, where it plays a significant role in regulating plant growth in response to various environmental cues. A wide array of specialized metabolites is produced by plants, which are essential for mediating environmental interactions and their adaptation. Notably, enhanced accumulation of these specialized metabolites, particularly plant secondary metabolites (PSMs), is a part of the chemical defense response that is directly linked to improved stress tolerance. Therefore, exploring the genetic diversity underlying the immense variation of the secondary metabolite pool could unravel the adaptation mechanisms in plants against different environmental stresses. The post-genomic profiling platforms have enabled the exploration of the link between metabolic diversity and important agronomic traits. The current review focuses on the major achievements and future challenges associated with plant secondary metabolite (PSM) research in graminaceous crops using advanced omics approaches. Given this, we briefly summarize different strategies adopted to explore the genetic diversity and evolution of PSMs in cereal crops. Further, we have discussed the recent technological advancements to integrate multi-omics approaches linking the metabolome diversity with the genome, transcriptome, and proteome of these crops under stress. Combining these data with phenomics (the omics of phenotypes) provides a holistic view of how plants respond to stress. Next, we outlined the genetic manipulation studies performed so far in cereals to engineer secondary metabolic pathways for enhanced stress tolerance. In summary, our review provides new insight into developing genetic and genomic trends in exploring the secondary metabolite diversity in graminaceous crops and discusses how this information can be utilized in designing strategies to generate future stress-resilient crops.

SAGA1 and MITH1 produce matrix-traversing membranes in the CO2-fixing pyrenoid

Approximately one-third of global CO2 assimilation is performed by the pyrenoid, a liquid-like organelle found in most algae and some plants. Specialized pyrenoid-traversing membranes are hypothesized to drive CO2 assimilation in the pyrenoid by delivering concentrated CO2, but how these membranes are made to traverse the pyrenoid matrix remains unknown. Here we show that proteins SAGA1 and MITH1 cause membranes to traverse the pyrenoid matrix in the model alga Chlamydomonas reinhardtii. Mutants deficient in SAGA1 or MITH1 lack matrix-traversing membranes and exhibit growth defects under CO2-limiting conditions. Expression of SAGA1 and MITH1 together in a heterologous system, the model plant Arabidopsis thaliana, produces matrix-traversing membranes. Both proteins localize to matrix-traversing membranes. SAGA1 binds to the major matrix component, Rubisco, and is necessary to initiate matrix-traversing membranes. MITH1 binds to SAGA1 and is necessary for extension of membranes through the matrix. Our data suggest that SAGA1 and MITH1 cause membranes to traverse the matrix by creating an adhesive interaction between the membrane and matrix. Our study identifies and characterizes key factors in the biogenesis of pyrenoid matrix-traversing membranes, demonstrates the importance of these membranes to pyrenoid function and marks a key milestone toward pyrenoid engineering into crops for improving yields.

Identification of key chlorophyll fluorescence parameters as biomarkers for dryland wheat under future climate conditions

Nowadays, climate change is the primary factor shaping the future of food and nutritional security. To investigate the interactive effects of various climate variables on photosynthetic efficiency, an experiment was conducted using 10 dryland wheat genotypes. These genotypes were exposed to different conditions: temperatures of 25 ± 3 °C and 34 ± 3 °C, carbon dioxide concentrations of 380 ± 50 ppm and 800 ± 50 ppm, and irrigation regimes of 50% field capacity and well-watered. Our results indicated that the wheat genotypes responded differently to both individual and combined climate stress factors. The traditional winter wheat genotype *Sardari*, along with the newly developed dryland wheat genotype *Ivan*, exhibited resilience to anticipated climate conditions. This resilience was reflected in enhancements in photochemical quantum efficiency parameters (Y(II), qP, and qL) under combined stress conditions. Resilient genotypes demonstrated superior regulation of the stomatal conductance (GS) and electron transport rate (ETR) under elevated temperature and CO2 levels. Principal component analysis (PCA) revealed significant correlations between chlorophyll fluorescence parameters and climate factors, such as NPQ with temperature, Y(NO) with CO2, qL in response to drought stress, and both qP and Y(II) with the interactions among temperature, CO2, and drought stress. Elevated CO2 reduced the ETR and GS across all genotypes. Our findings underscore the importance of assessing not only fundamental chlorophyll fluorescence parameters like Fm and Fo but also the efficiency of NPQ and Y(II) to understand climate change impacts on dryland wheat genotypes. We suggest that these parameters could serve as valuable biomarkers for breeding programs aimed at improving plant adaptation to future dryland climate conditions.

Assessing impact of elevated CO2 on heavy metal accumulation in crops: meta-analysis and implications for food security

Human activities led to elevation in carbon dioxide (CO2) concentrations in atmosphere. While such increase per se may be beneficial for the growth of some crops, it comes with a caveat of affecting crop nutritional status. Here, we present a comprehensive analysis of changes in concentration of essential (Cu, Fe, Mn, Zn, Mo, Ni) and non-essential (Ba, Cd, Cr, Hg, Pb, and Sr) heavy metals in response to elevated CO2, drawing on a meta-analysis of 1216 paired observations. The major findings are as follows: (1) Elevated CO2 leads to reduced concentrations of Cu, Fe, Mn, and Zn in crops; (2) the extent of above reduction varies among plants species and is most pronounced in cereals and then in legumes and vegetables; (3) reduction in accumulation of non-essential (toxic) metals is less pronounced, potentially leading to an unfavorable essential/non-essential metal ratio in plants; (4) the above effects will come with significant implication to human health, exacerbating effects of the "hidden hunger" caused by the lack of Fe and Zn in the human diets. The paper also analyses the mechanistic basis of nutrient acquisition (both at physiological and molecular levels) and calls for the changes in the governmental policies to increase efforts of plant breeders to create genotypes with improved nutrient use efficiency for essential micronutrients while uncoupling their transport from non-essential (toxic) heavy metals.

Amplified photosynthetic responses to drought events offset the positive effects of warming on arid desert plants

Ongoing warming will influence plant photosynthesis via thermal effects and by enhancing water deficit. As the primary limiting factor for the growth and development of plants in arid deserts, water may alter the potential warming effects on plant photosynthesis and lead to increased uncertainty in plant dynamics. Here, we used open-top chambers (OTCs) to evaluate the impacts of in situ warming (+0.5 and +1.5 °C) on the photosynthesis and growth of two representative desert plants, Artemisia ordosica and Grubovia dasyphylla, from wet to dry spells. The plant traits associated with photosynthetic diffusive and biochemical processes were also measured to explore the underlying mechanisms involved. We found that warming significantly increased the net photosynthetic rate (Anet) during wet spells under 1.5 °C warming in both plants, while only increased that of A. ordosica under 0.5 °C warming. During dry spells, Anet decreased both in A. ordosica and G. dasyphylla, with the rates of declining being 48 % and 41 %, respectively, higher than control under warming. Consequently, warming significantly amplified photosynthetic responses to drought events, which offset the positive warming effects during wet spells and led to unchanged plant biomass in both species. Besides, alterations in plant traits tended to be associated with positive warming effects during wet spells, and the negative effects of drought were mainly due to stomatal limitation. Our results emphasised that the potential benefits of warming during wet spells may be reversed during drought events. Thus, the adverse effects of ongoing warming on desert productivity may increase during dry spells in growing seasons and during dry years.

Enhanced CO2 Coordinates the Spatial Recruitment of Diazotrophs in Rice Via Root Development

Understanding the reciprocal interaction between root development and coadapted beneficial microbes in response to elevated CO2 (eCO2) will facilitate the identification of nutrient-efficient cultivars for sustainable agriculture. Here, systematic morphological, anatomical, chemical and gene expression assays performed under low-nitrogen conditions revealed that eCO2 drove the development of the endodermal barrier with respect to L-/S-shaped lateral roots (LRs) in rice. Next, we applied metabolome and endodermal-cell-specific RNA sequencing and showed that rice adapts to eCO2 by spatially recruiting diazotrophs via flavonoid secretion in L-shaped LRs. Using the rice Casparian strip mutant Oscasp1-1, we confirmed that reduced lignin deposition selectively recruits the diazotrophic family of Oxalobacteraceae to confer tolerance to low nitrogen availability.

Divergent responses of woody plant leaf and root non-structural carbohydrates to nitrogen addition in China: Seasonal variations and ecological implications

Plant non-structural carbohydrates (NSCs), which largely comprise starch and soluble sugars, are essential energy reserves to support plant growth and physiological functions. While it is known that increasing global deposition of nitrogen (N) affects plant concentration of NSCs, quantification of seasonal responses and drivers of woody species leaf and root NSCs to N addition at larger spatial scales remains lacking. Here, we systematically analyzed data from 53 field experiments distributed across China, comprising 1202 observations, to test for effects of N addition on woody plant leaf and root NSCs across and within growing and non-growing seasons. We found (1) no overall effects of N addition on the concentrations of leaf and root NSCs, soluble sugars or starch during the growing season or the non-growing season for leaves. However, N addition decreased root NSC and starch concentrations by 13.8 % and 39.0 %, respectively, and increased soluble sugars concentration by 15.0 % during the non-growing season. (2) Shifts in leaf NSC concentration under N addition were driven by responses by soluble sugars in both seasons, while shifts in root NSC were driven by soluble sugars in the non-growing season and starch and soluble sugars in the growing season. (3) Relationships between N, carbon, and phosphorus stoichiometry with leaf and root NSCs indicated effects of N addition on woody plant NSCs allocation through impacts on plant photosynthesis, respiration, and growth. (4) Effects of N addition on leaf and root NSCs varied with plant functional types, where effects were more pronounced in roots than in leaves during the non-growing season. Overall, our results reveal divergent responses of woody plant leaf and root NSCs to N addition within non-growing season and highlight the role of ecological stoichiometry and plant functional types in woody plant allocation patterns of NSCs in response to ongoing N deposition under global change.

Impacts of future climate change on rice yield based on crop model simulation-A meta-analysis

Rice is one of the world's major food crops. Changes in major climatic factors such as temperature, rainfall, solar radiation and carbon dioxide (CO2) concentration have an important impact on rice growth and yield. However, many of the current studies that predict the impact of future climate change on rice yield are affected by uncertainties such as climate models, climate scenarios, model parameters and structure, and showing great differences. This study was based on the assessment results of the impact of climate change on rice in the future of 111 published literature, and comprehensively analyzed the impact and uncertainty of climate change on rice yield. This study utilized local polynomial (Loess) regression analysis to investigate the impact of changes in mean temperature, minimum temperature, maximum temperature, solar radiation, and precipitation on relative rice yield variations within a complete dataset. A linear mixed-effects model was used to quantitatively analyze the relationships between the restricted datasets. The qualitative analysis based on the entire dataset revealed that rice yields decreased with increasing average temperature. The precipitation changed between 0 and 25 %, it was conducive to the stable production of rice, and when the precipitation changed >25 %, it would cause rice yield reduction. The change of solar radiation was less than -1.15 %, the rice yield increases with the increase of solar radiation, and when the change of solar radiation exceeds -1.15 %, the rice yield decreases. Elevated CO2 concentrations and management practices could mitigate the negative effects of climate change. The results of a quantitative analysis utilizing the mixed effects model revealed that average temperature, precipitation, CO2 concentration, and adaptation methods all had a substantial impact on rice production, and elevated CO2 concentrations and management practices could exert positive influences on rice production. For every 1 °C and 1 % increase in average temperature and precipitation, rice yield decreased by 3.85 % and 0.56 %, respectively. For every 100 ppm increase in CO2 concentration, rice yield increased by 7.1 %. The variation of rice yield under different climate models, study sites and climate scenarios had significant variability. Elevated CO2 concentrations and management practices could compensate for the negative effects of climate change, benefiting rice production. This study comprehensively collected and analyzed a wide range of literature and research, which provides an in-depth understanding of the impacts of climate change on rice production and informs future research and policy development.

An insight into heat stress response and adaptive mechanism in cotton

The growing worldwide population is driving up demand for cotton fibers, but production is hampered by unpredictable temperature rises caused by shifting climatic conditions. Numerous research based on breeding and genomics have been conducted to increase the production of cotton in environments with high and low-temperature stress. High temperature (HT) is a major environmental stressor with global consequences, influencing several aspects of cotton plant growth and metabolism. Heat stress-induced physiological and biochemical changes are research topics, and molecular techniques are used to improve cotton plants' heat tolerance. To preserve internal balance, heat stress activates various stress-responsive processes, including repairing damaged proteins and membranes, through various molecular networks. Recent research has investigated the diverse reactions of cotton cultivars to temperature stress, indicating that cotton plant adaptation mechanisms include the accumulation of sugars, proline, phenolics, flavonoids, and heat shock proteins. To overcome the obstacles caused by heat stress, it is crucial to develop and choose heat-tolerant cotton cultivars. Food security and sustainable agriculture depend on the application of genetic, agronomic, and, biotechnological methods to lessen the impacts of heat stress on cotton crops. Cotton producers and the textile industry both benefit from increased heat tolerance. Future studies should examine the developmental responses of cotton at different growth stages, emphasize the significance of breeding heat-tolerant cultivars, and assess the biochemical, physiological, and molecular pathways involved in seed germination under high temperatures. In a nutshell, a concentrated effort is required to raise cotton's heat tolerance due to the rising global temperatures and the rise in the frequency of extreme weather occurrences. Furthermore, emerging advances in sequencing technologies have made major progress toward successfully se sequencing the complex cotton genome.

Acclimation of Photosynthesis to CO2 Increases Ecosystem Carbon Storage due to Leaf Nitrogen Savings

Photosynthesis is the largest flux of carbon between the atmosphere and Earth's surface and is driven by enzymes that require nitrogen, namely, ribulose-1,5-bisphosphate (RuBisCO). Thus, photosynthesis is a key link between the terrestrial carbon and nitrogen cycle, and the representation of this link is critical for coupled carbon-nitrogen land surface models. Models and observations suggest that soil nitrogen availability can limit plant productivity increases under elevated CO2. Plants acclimate to elevated CO2 by downregulating RuBisCO and thus nitrogen in leaves, but this acclimation response is not currently included in land surface models. Acclimation of photosynthesis to CO2 can be simulated by the photosynthetic optimality theory in a way that matches observations. Here, we incorporated this theory into the land surface component of the Energy Exascale Earth System Model (ELM). We simulated land surface carbon and nitrogen processes under future elevated CO2 conditions to 2100 using the RCP8.5 high emission scenario. Our simulations showed that when photosynthetic acclimation is considered, photosynthesis increases under future conditions, but maximum RuBisCO carboxylation and thus photosynthetic nitrogen demand decline. We analyzed two simulations that differed as to whether the saved nitrogen could be used in other parts of the plant. The allocation of saved leaf nitrogen to other parts of the plant led to (1) a direct alleviation of plant nitrogen limitation through reduced leaf nitrogen requirements and (2) an indirect reduction in plant nitrogen limitation through an enhancement of root growth that led to increased plant nitrogen uptake. As a result, reallocation of saved leaf nitrogen increased ecosystem carbon stocks by 50.3% in 2100 as compared to a simulation without reallocation of saved leaf nitrogen. These results suggest that land surface models may overestimate future ecosystem nitrogen limitation if they do not incorporate leaf nitrogen savings resulting from photosynthetic acclimation to elevated CO2.

Long-term soil warming changes the profile of primary metabolites in fine roots of Norway spruce in a temperate montane forest

Climate warming poses major threats to temperate forests, but the response of tree root metabolism has largely remained unclear. We examined the impact of long-term soil warming (>14 years, +4°C) on the fine root metabolome across three seasons for 2 years in an old spruce forest, using a liquid chromatography-mass spectrometry platform for primary metabolite analysis. A total of 44 primary metabolites were identified in roots (19 amino acids, 12 organic acids and 13 sugars). Warming increased the concentration of total amino acids and of total sugars by 15% and 21%, respectively, but not organic acids. We found that soil warming and sampling date, along with their interaction, directly influenced the primary metabolite profiles. Specifically, in warming plots, concentrations of arginine, glycine, lysine, threonine, tryptophan, mannose, ribose, fructose, glucose and oxaloacetic acid increased by 51.4%, 19.9%, 21.5%, 19.3%, 22.1%, 23.0%, 38.0%, 40.7%, 19.8% and 16.7%, respectively. Rather than being driven by single compounds, changes in metabolite profiles reflected a general up- or downregulation of most metabolic pathway network. This emphasises the importance of metabolomics approaches in investigating root metabolic pathways and understanding the effects of climate change on tree root metabolism.

Clomazone exposure-driven photosynthetic responses plasticity of Pontederia crassipes

Clomazone is known to contaminate aquatic environments and have a negative impact on macrophytes. However, recent reports suggests that Pontederia crassipes Mart. can withstand clomazone exposure while maintaining growth rates. We hypothesized that this maintenance of growth is supported by photosynthetic plasticity of old leaves (developed before herbicide application), while new leaves (developed after application) exhibit phytotoxic symptoms. To investigate, two experiments were conducted with doses ranging from 0.1 mg L-1 to 0.5 mg L-1 plus untreated controls. Various parameters were measured in old and new leaves over 7, 12, and 15 d post-application, including visual symptoms, chlorophyll index, photosynthetic pigments, chlorophyll fluorescence, gas exchange, glycolate oxidase activity, carbohydrate content, leaf epidermis anatomy, and growth parameters. Clomazone exposure induced chlorosis, particularly in new leaves across all doses. These visual symptoms were accompanied by stomatal closure, restricting gas exchange and CO2 fixation, leading to reduced photosynthetic rates and carbohydrate synthesis. However, clomazone did not affect old leaves, which maintained photosynthetic activity, sustaining essential metabolic processes of the plant, including reproductive functions. By ensuring high reproductive rates and metabolic continuity, old leaves supported the species' persistence despite clomazone presence.

Responses of particulate and mineral-associated organic carbon to temperature changes and their mineral protection mechanisms: A soil translocation experiment

Mineral protection mechanisms are important in determining the response of particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) to temperature changes. However, the underlying mechanisms for how POC and MAOC respond to temperature changes are remain unclear. By translocating soils across 1304 m, 1425 m and 2202 m elevation gradient in a temperate forest, simulate nine months of warming (with soil temperature change of +1.41 °C and +3.91 °C) and cooling (with soil temperature change of -1.86 °C and -4.20 °C), we found that warming translocation significantly decreased POC by an average of 10.84 %, but increased MAOC by an average of 4.25 %. Conversely, cooling translocation led to an average increase of 8.64 % in POC and 13.48 % in MAOC. Exchangeable calcium (Caexe) had a significant positive correlation with POC and MAOC during temperature changes, and Fe/Al-(hydr)oxides had no significant correlation or a significant negative correlation with POC and MAOC. Our results showed that POC was more sensitive than MAOC to temperature changes. Caexe mediated the stability of POC and MAOC under temperature changes, and Fe/Al-(hydr)oxides had no obvious protective effect on POC and MAOC. Our results support the role of mineral protection in the stabilization mechanism of POC and MAOC in response to climate change and are critical for understanding the consequences of global change on soil organic carbon (SOC) dynamics.

Identification and Evaluation of Diploid and Tetraploid Passiflora edulis Sims

Passiflora edulis Sims (2n = 18) is a perennial plant with high utilization values, but its spontaneous polyploidy in nature has yet to be seen. Thus, this study aims to enhance our understanding of polyploidy P. edulis and provide rudimentary knowledge for breeding new cultivars. In this study, colchicine-induced tetraploid P. edulis (2n = 36) was used as experimental material (T1, T2, and T3) to explore the variances between it and its diploid counterpart in morphology, physiology, and biochemical characteristics, and a comparison of their performance under cold stress was conducted. We measured and collected data on phenotype parameters, chlorophyll contents, chlorophyll fluorescence, photosynthesis, osmotic substances, and antioxidant enzymes. The results showed that tetraploid P. edulis exhibited a shorter phenotype, more giant leaves, darker leaf color, and longer and fewer roots. Moreover, the physiological and biochemical analysis indicated that the tetraploid P. edulis had better photosynthesis systems and higher chlorophyll fluorescence parameters than the diploid P. edulis. Additionally, the tetraploid P. edulis had higher activity of antioxidant enzymes (SOD, POD, CAT) and lower MDA content to maintain better resistance in low temperatures. Overall, we conclude that there were apparent differences in the morphological, physiological, and biochemical traits of the tetraploid and diploid P. edulis. The tetraploid plants showed better photosynthesis systems, higher osmotic substance content, and antioxidant enzyme activity than the diploid, even under cold stress. Our results suggest that tetraploids with more abundant phenotype variation and better physiological and biochemical traits may be used as a new genetic germplasm resource for producing new P. edulis cultivars.

Quality vs. Quantity: The Consequences of Elevated CO2 on Wood Biomaterial Properties

Since the late 1800s, anthropogenic activities such as fossil fuel consumption and deforestation have driven up the concentration of atmospheric CO2 around the globe by >45%. Such heightened concentrations of carbon dioxide in the atmosphere are a leading contributor to global climate change, with estimates of a 2-5° increase in global air temperature by the end of the century. While such climatic changes are mostly considered detrimental, a great deal of experimental work has shown that increased atmospheric CO2 will actually increase growth in various plants, which may lead to increased biomass for potential harvesting or CO2 sequestration. However, it is not clear whether this increase in growth or biomass will be beneficial to the plants, as such increases may lead to weaker plant materials. In this review, I examine our current understanding of how elevated atmospheric CO2 caused by anthropogenic effects may influence plant material properties, focusing on potential effects on wood. For the first part of the review, I explore how aspects of wood anatomy and structure influence resistance to bending and breakage. This information is then used to review how changes in CO2 levels may later these aspects of wood anatomy and structure in ways that have mechanical consequences. The major pattern that emerges is that the consequences of elevated CO2 on wood properties are highly dependent on species and environment, with different tree species showing contradictory responses to atmospheric changes. In the end, I describe a couple avenues for future research into better understanding the influence of atmospheric CO2 levels on plant biomaterial mechanics.

Potassium indole-3-butyric acid affects rice's adaptability to salt stress by regulating carbon metabolism, transcription factor genes expression, and biosynthesis of secondary metabolites

Soil salinity pollution is increasing worldwide, seriously affecting plant growth and crop production. Existing reports on how potassium indole-3-butyric acid (IBAK) regulates rice salt stress adaptation by affecting rice carbon metabolism, transcription factor (TF) genes expression, and biosynthesis of secondary metabolites still have limitations. In this study, an IBAK solution at 40 mg L-1 was sprayed on rice leaves at the seedling stage. The results showed that the IBAK application could promote shoot and root growth, decrease sucrose and fructose content, increase starch content, and enhance acid invertase (AI) and neutral invertase (NI) activity under salt stress, indicating altered carbon allocation. Furthermore, the expression of TF genes belonging to the ethylene responsive factor (ERF), WRKY, and basic helix-loop-helix (bHLH) families was influenced by IBAK. Many key genes (OsSSIIc, OsSHM1, and OsPPDKB) and metabolites (2-oxoglutaric acid, fumaric acid, and succinic acid) were upregulated in the carbon metabolism pathway. In addition, this study highlighted the role of IBAK in regulating the biosynthesis of secondary metabolites pathway, potentially contributing to rice stress adaptability. The results of this study can provide new sustainable development solutions for agricultural production.

Different model assumptions about plant hydraulics and photosynthetic temperature acclimation yield diverging implications for tropical forest gross primary production under warming

Tropical forest photosynthesis can decline at high temperatures due to (1) biochemical responses to increasing temperature and (2) stomatal responses to increasing vapor pressure deficit (VPD), which is associated with increasing temperature. It is challenging to disentangle the influence of these two mechanisms on photosynthesis in observations, because temperature and VPD are tightly correlated in tropical forests. Nonetheless, quantifying the relative strength of these two mechanisms is essential for understanding how tropical gross primary production (GPP) will respond to climate change, because increasing atmospheric CO2 concentration may partially offset VPD-driven stomatal responses, but is not expected to mitigate the effects of temperature-driven biochemical responses. We used two terrestrial biosphere models to quantify how physiological process assumptions (photosynthetic temperature acclimation and plant hydraulic stress) and functional traits (e.g., maximum xylem conductivity) influence the relative strength of modeled temperature versus VPD effects on light-saturated GPP at an Amazonian forest site, a seasonally dry tropical forest site, and an experimental tropical forest mesocosm. By simulating idealized climate change scenarios, we quantified the divergence in GPP predictions under model configurations with stronger VPD effects compared with stronger direct temperature effects. Assumptions consistent with stronger direct temperature effects resulted in larger GPP declines under warming, while assumptions consistent with stronger VPD effects resulted in more resilient GPP under warming. Our findings underscore the importance of quantifying the role of direct temperature and indirect VPD effects for projecting the resilience of tropical forests in the future, and demonstrate that the relative strength of temperature versus VPD effects in models is highly sensitive to plant functional parameters and structural assumptions about photosynthetic temperature acclimation and plant hydraulics.

Impact of Agricultural Activities on Climate Change: A Review of Greenhouse Gas Emission Patterns in Field Crop Systems

This review paper synthesizes the current understanding of greenhouse gas (GHG) emissions from field cropping systems. It examines the key factors influencing GHG emissions, including crop type, management practices, and soil conditions. The review highlights the variability in GHG emissions across different cropping systems. Conventional tillage systems generally emit higher levels of carbon dioxide (CO2) and nitrous oxide (N2O) than no-till or reduced tillage systems. Crop rotation, cover cropping, and residue management can significantly reduce GHG emissions by improving soil carbon sequestration and reducing nitrogen fertilizer requirements. The paper also discusses the challenges and opportunities for mitigating GHG emissions in field cropping systems. Precision agriculture techniques, such as variable rate application of fertilizers and water, can optimize crop production while minimizing environmental impacts. Agroforestry systems, which integrate trees and crops, offer the potential for carbon sequestration and reducing N2O emissions. This review provides insights into the latest research on GHG emissions from field cropping systems and identifies areas for further study. It emphasizes the importance of adopting sustainable management practices to reduce GHG emissions and enhance the environmental sustainability of agricultural systems.

Biogenesis, engineering and function of membranes in the CO 2 -fixing pyrenoid

Approximately one-third of global CO 2 assimilation is performed by the pyrenoid 1 , a liquid-like organelle found in most algae and some plants 2 . Specialized membranes are hypothesized to drive CO 2 assimilation in the pyrenoid by delivering concentrated CO 2 3,4 , but their biogenesis and function have not been experimentally characterized. Here, we show that homologous proteins SAGA1 and MITH1 mediate the biogenesis of the pyrenoid membrane tubules in the model alga Chlamydomonas reinhardtii and are sufficient to reconstitute pyrenoid-traversing membranes in a heterologous system, the plant Arabidopsis thaliana . SAGA1 localizes to the regions where thylakoid membranes transition into tubules and is necessary to initiate tubule formation. MITH1 localizes to the tubules and is necessary for their extension through the pyrenoid. Tubule-deficient mutants exhibit growth defects under CO 2 -limiting conditions, providing evidence for the function of membrane tubules in CO 2 delivery to the pyrenoid. Furthermore, these mutants form multiple aberrant condensates of pyrenoid matrix, indicating that a normal tubule network promotes the coalescence of a single pyrenoid. The reconstitution of pyrenoid-traversing membranes in a plant represents a key milestone toward engineering a functional pyrenoid into crops for improving crop yields. More broadly, our study demonstrates the functional importance of pyrenoid membranes, identifies key biogenesis factors, and paves the way for the molecular characterization of pyrenoid membranes across the tree of life.

The role of GmHSP23.9 in regulating soybean nodulation under elevated CO2 condition

Legume-rhizobia symbiosis offers a unique approach to increase leguminous crop yields. Previous studies have indicated that the number of soybean nodules are increased under elevated CO2 concentration. However, the underlying mechanism behind this phenomenon remains elusive. In this study, transcriptome analysis was applied to identify candidate genes involved in regulating soybean nodulation mediated by elevated CO2 concentration. Among the different expression genes (DEGs), we identified a gene encoding small heat shock protein (sHSP) called GmHSP23.9, which mainly expressed in soybean roots and nodules, and its expression was significantly induced by rhizobium USDA110 infection at 14 days after inoculation (DAI) under elevated CO2 conditions. We further investigated the role of GmHSP23.9 by generating transgenic composite plants carrying GmHSP23.9 overexpression (GmHSP23.9-OE), RNA interference (GmHSP23.9-RNAi), and CRISPR-Cas9 (GmHSP23.9-KO), and these modifications resulted in notable changes in nodule number and the root hairs deformation and suggesting that GmHSP23.9 function as an important positive regulator in soybean. Moreover, we found that altering the expression of GmHSP23.9 influenced the expression of genes involved in the Nod factor signaling pathway and AON signaling pathway to modulate soybean nodulation. Interestingly, we found that knocking down of GmHSP23.9 prevented the increase in the nodule number of soybean in response to elevated CO2 concentration. This research has successfully identified a crucial regulator that influences soybean nodulation under elevated CO2 level and shedding new light on the role of sHSPs in legume nodulation.