New insights into the cellular mechanisms of plant growth at elevated atmospheric carbon dioxide concentrations

Response of photosynthetic characteristics and yield of grape to different CO2 concentrations in a greenhouse

Due to the enclosed environment of greenhouse grape production, the supply of CO2 required for photosynthesis is often insufficient, leading to photosynthetic downregulation and reduced yield. Currently, the optimal CO2 concentration for grape production in greenhouses is unknown, and the precise control of actual CO2 levels remains a challenge. This study aims to investigate the effects of different CO2 concentrations on the photosynthetic characteristics and yield of grapes, to validate the feasibility of a CO2 gas irrigation system, and to identify the optimal CO2 concentration for greenhouse grape production. In this study, a CO2 gas irrigation system combining CO2 enrichment and gas irrigation techniques was used with a 5-year-old Eurasian grape variety (Vitis vinifera L.) 'Flame Seedless.' Four CO2 concentration treatments were applied: 500 ppm (500 ± 30 µmol·mol-1), 700 ppm (700 ± 30 µmol·mol-1), 850 ppm (850 ± 30 µmol·mol-1), and 1,000 ppm (1,000 ± 30 µmol·mol-1). As CO2 concentration increased, chlorophyll a, chlorophyll b, and carotenoids in grape leaves all reached maximum values at 700 ppm and 850 ppm during the same irrigation cycle, while the chlorophyll a/b ratio was lower than at other concentrations. The net photosynthetic rate (Pn) and water use efficiency (WUE) of grape leaves were the highest at 700 ppm. The transpiration rate and stomatal conductance at 700 ppm and 850 ppm were significantly lower than those at other concentrations. The light saturation point and apparent quantum efficiency reached their maximum at 850 ppm, followed by 700 ppm. Additionally, the maximum net photosynthetic rate, carboxylation efficiency, electron transport rate, and activities of SOD, CAT, POD, PPO, and RuBisCO at 700 ppm were significantly higher than at other concentrations, with the highest yield recorded at 14.54 t·hm-2. However, when the CO2 concentration reached 1,000 ppm, both photosynthesis and yield declined to varying degrees. Under the experimental conditions, the optimal CO2 concentration for greenhouse grape production was 700 ppm, with excessive CO2 levels gradually inhibiting photosynthesis and yield. The results provide a theoretical basis for the future application of CO2 fertilization and gas irrigation techniques in controlled greenhouse grape production.

Comparative transcriptome analysis reveals major genes, transcription factors and biosynthetic pathways associated with leaf senescence in rice under different nitrogen application

BACKGROUND

Rice (Oryza sativa L.) is one of the most important food crops in the world and the application of nitrogen fertilizer is an effective means of ensuring stable and high rice yields. However, excessive application of nitrogen fertilizer not only causes a decline in the quality of rice, but also leads to a series of environmental costs. Nitrogen reutilization is closely related to leaf senescence, and nitrogen deficiency will lead to early functional leaf senescence, whereas moderate nitrogen application will help to delay leaf senescence and promote the production of photosynthetic assimilation products in leaves to achieve yield increase. Therefore, it is important to explore the mechanism by which nitrogen affects rice senescence, to search for genes that are tolerant to low nitrogen, and to delay the premature senescence of rice functional leaves.

RESULTS

The present study was investigated the transcriptional changes in flag leaves between full heading and mature grain stages of rice (O. sativa) sp. japonica 'NanGeng 5718' under varying nitrogen (N) application: 0 kg/ha (no nitrogen; 0N), 240 kg/ha (moderate nitrogen; MN), and 300 kg/ha (high nitrogen; HN). Compared to MN condition, a total of 10427 and 8177 differentially expressed genes (DEGs) were detected in 0N and HN, respectively. We selected DEGs with opposite expression trends under 0N and HN conditions for GO and KEGG analyses to reveal the molecular mechanisms of nitrogen response involving DEGs. We confirmed that different N applications caused reprogramming of plant hormone signal transduction, glycolysis/gluconeogenesis, ascorbate and aldarate metabolism and photosynthesis pathways in regulating leaf senescence. Most DEGs of the jasmonic acid, ethylene, abscisic acid and salicylic acid metabolic pathways were up-regulated under 0N condition, whereas DEGs related to cytokinin and ascorbate metabolic pathways were induced in HN. Major transcription factors include ERF, WRKY, NAC and bZIP TF families have similar expression patterns which were induced under N starvation condition.

CONCLUSION

Our results revealed that different nitrogen levels regulate rice leaf senescence mainly by affecting hormone levels and ascorbic acid biosynthesis. Jasmonic acid, ethylene, abscisic acid and salicylic acid promote early leaf senescence under low nitrogen condition, ethylene and ascorbate delay senescence under high nitrogen condition. In addition, ERF, WRKY, NAC and bZIP TF families promote early leaf senescence. The relevant genes can be used as candidate genes for the regulation of senescence. The results will provide gene reference for further genomic studies and new insights into the gene functions, pathways and transcription factors of N level regulates leaf senescence in rice, thereby improving NUE and reducing the adverse effects of over-application of N.

Temperature extremes nip invasive macrophyte Cabomba caroliniana A. Gray in the bud: potential geographic distributions and risk assessment based on future climate change and anthropogenic influences

Cabomba caroliniana A. Gray, an ornamental submerged plant indigenous to tropical America, has been introduced to numerous countries in Europe, Asia, and Oceania, impacting native aquatic ecosystems. Given this species is a popular aquarium plant and widely traded, there is a high risk of introduction and invasion into other environments. In the current study the potential global geographic distribution of C. caroliniana was predicted under the effects of climate change and human influence in an optimised MaxEnt model. The model used rigorously screened occurrence records of C. caroliniana from hydro informatic datasets and 20 associated influencing factors. The findings indicate that temperature and human-mediated activities significantly influenced the distribution of C. caroliniana. At present, C. caroliniana covers an area of approximately 1531×104 km2 of appropriate habitat, especially in the south-eastern parts of South, central and North America, Southeast Asia, eastern Australia, and most of Europe. The suitable regions are anticipated to expand under future climate scenarios; however, the dynamics of the changes vary between different extents of climate change. For example, C. caroliniana is expected to expand to higher latitudes, following global temperature increases under SSP1-2.6 and SSP2-4.5 scenarios, however, intolerance to temperature extremes may mediate invasion at higher latitudes under future extreme climate scenarios, e.g., SSP5-8.5. Owing to the severe impacts its invasion causes, early warning and stringent border quarantine processes are required to guard against the introduction of C. caroliniana especially in the invasion hotspots such as, Peru, Italy, and South Korea.

Climate gradient and leaf carbon investment influence the effects of climate change on water use efficiency of forests: A meta-analysis

Forest ecosystems cover a large area of the global land surface and are important carbon sinks. The water-carbon cycles of forests are prone to climate change, but uncertainties remain regarding the magnitude of water use efficiency (WUE) response to climate change and the underpinning mechanism driving WUE variation. We conducted a meta-analysis of the effects of elevated CO2 concentration (eCO2 ), drought and elevated temperature (eT) on the leaf- to plant-level WUE, covering 80 field studies and 95 tree species. The results showed that eCO2 increased leaf intrinsic and instantaneous WUE (WUEi, WUEt), whereas drought enhanced both leaf- and plant-level WUEs. eT increased WUEi but decreased carbon isotope-based WUE, possibly due to the influence of mesophyll conductance. Stimulated leaf-level WUE by drought showed a progressing trend with increasing latitude, while eCO2 -induced WUE enhancement showed decreasing trends after >40° N. These latitudinal gradients might influence the spatial pattern of climate and further drove WUE variation. Moreover, high leaf-level WUE under eCO2 and drought was accompanied by low leaf carbon contents. Such a trade-off between growth efficiency and defence suggests a potentially compromised tolerance to diseases and pests. These findings add important ecophysiological parameters into climate models to predict carbon-water cycles of forests.

Revisiting Changes in Growth, Physiology and Stress Responses of Plants under the Effect of Enhanced CO2 and Temperature

Climate change has universally affected the whole ecosystem in a unified manner and is known to have improbable effects on agricultural productivity and food security. Carbon dioxide (CO2) and temperature are the major environmental factors that have been shown to increase sharply during the last century and are directly responsible for affecting plant growth and development. A number of previous investigations have deliberated the positive effects of elevated CO2 on plant growth and development of various C3 crops, while detrimental effects of enhanced temperature on different crop plants like rice, wheat, maize and legumes are generally observed. A combined effect of elevated CO2 and temperature has yet to be studied in great detail; therefore, this review attempts to delineate the interactive effects of enhanced CO2 and temperature on plant growth, development, physiological and molecular responses. Elevated CO2 maintains leaf photosynthesis rate, respiration, transpiration and stomatal conductance in the presence of elevated temperature and sustains plant growth and productivity in the presence of both these environmental factors. Concomitantly, their interaction also affects the nutritional quality of seeds and leads to alterations in the composition of secondary metabolites. Elevated CO2 and temperature modulate phytohormone concentration in plants, and due to this fact, both environmental factors have substantial effects on abiotic and biotic stresses. Elevated CO2 and temperature have been shown to have mitigating effects on plants in the presence of other abiotic stress agents like drought and salinity, while no such pattern has been observed in the presence of biotic stress agents. This review focuses on the interactive effects of enhanced CO2 and temperature on different plants and is the first of its kind to deliver their combined responses in such detail.

Characteristics of photosynthetic rates in different vegetation types at high-altitude in mountainous regions

Mountains play an important role in the carbon cycle of the terrestrial ecosystem and are one of the most sensitive ecosystems to climate change. However, our current knowledge regarding the physiological responses of alpine plants to environmental changes remains limited due to the severe climatic conditions prevailing in these high-altitude regions. Therefore, this study quantified the variations in photosynthetic rates (An) and identified their driving factors of herbaceous plants, shrubs, and trees along an elevation gradient (2200 m asl to 3200 m asl) on Mount Gongga. Elevation emerged as a significant determinant of An, with a general increase observed, albeit followed by a decline above 3000 m asl. In high-altitude regions, trees displayed more significant fluctuations in An compared to herbaceous plants and shrubs. The lower levels of atmospheric carbon dioxide concentration (eCO2) and temperature in high-altitude regions resulted in a 16 % increase in An for herbaceous plants, 60 % increase for shrubs, and 43 % increase for trees compared to the low-altitude areas. Structural equation modeling (SEM) analyses underscored the considerable impact of environmental factors on An. Notably, photosynthetically active radiation, eCO2, and stomatal conductance were identified as positive influencers, while other factors exerted negative effects. Our results further highlighted that trees were subject to greater constraints from multiple factors compared to herbs and shrubs, aligning with the outcomes of our variance analysis. In summary, our study presents a comprehensive assessment of vegetation responses to environmental factors along elevational gradients. The significance of An in plants at high altitude to external factors suggests the potential adaptability of alpine plants, and also indicates that changes in photosynthetic physiological functions at high altitude should be paid more attention to in the study of climate change.

Elevated atmospheric CO2 concentration mitigates salt damages to safflower: Evidence from physiological and biochemical examinations

The physiological and biochemical responses of salt-stressed safflower to elevated CO2 remain inadequately known. This study investigated the interactive effects of high CO2 concentration (700 ± 50 vs. 400 ± 50 μmol mol-1) and salinity stress levels (0.4, 6, and 12 dS m-1, NaCl) on growth and physiological properties of four safflower (Carthamus tinctorius L.) genotypes, under open chamber conditions. Results showed that the effects of CO2 on biomass of shoot and grains depend on salt stress and plant genotype. Elevated CO2 conditions increased shoot dry weight under moderate salinity stress and decreased it under severe stress. The increased CO2 concentration also increased the safflower genotypes' relative water content and their K+/Na + concentrations. Also enriched CO2 increased total carotenoid levels in safflower genotypes and improved membrane stability index by reducing H2O2 levels. In addition, increased CO2 level led to an increase in seed oil content, under both saline and non-saline conditions. This effect was particularly pronounced under severe saline conditions. Under conditions of high CO2 and salinity, the Koseh genotype exhibited higher grain weight and seed oil content than other genotypes. This advantage is due to the higher relative water content, maximum quantum efficiency of photosystem II (Fv/Fm), and K+/Na+, as well as the lower Na+ and H2O2 concentrations. Results indicate that the high CO2 level mitigated the destructive effect of salinity on safflower growth by reducing Na + uptake and increasing the Fv/Fm, total soluble carbohydrates, and membrane stability index. This finding can be used in safflower breeding programs to develop cultivars that can thrive in arid regions with changing climatic conditions.

Crosstalk between ABA and ethylene in regulating stomatal behavior in tomato under high CO2 and progressive soil drying

Increasing atmospheric CO2 concentrations accompanied by intensifying drought markedly impact plant growth and physiology. This study aimed to explore the role of abscisic acid (ABA) in mediating the response of stomata to elevated CO2 (e[CO2]) and drought. Tomato plants with different endogenous ABA concentrations [Ailsa Craig (AC), the ABA-deficient mutant flacca, and ABA-overproducing transgenic tomato SP5] were grown in ambient (a[CO2], 400 μmol mol-1) and elevated (e[CO2],800 μmol mol-1) CO2 environments and subjected to progressive soil drying. Compared with a[CO2] plants, e[CO2] plants had significantly lower stomatal conductance in AC and SP5 but not in flacca. Under drought, e[CO2] plants had better water status and higher water use efficiency. e[CO2] promoted the accumulation of ABA in leaves of plants subjected to drought, which coincided with the up-regulation of ABA biosynthetic genes and down-regulation of ABA metabolic genes. Although the increase of ABA induced by drought in flacca was much less than in AC and SP5, flacca accumulated large amounts of ethylene, suggesting that in plants with ABA deficiency, ethylene might play a compensatory role in inducing stomatal closure during soil drying. Collectively, these findings improve our understanding of plant performance in a future drier and higher-CO2 environment.

Evaluation of Climate Change Impacts on the Potential Distribution of Wild Radish in East Asia

Climate change can exert a considerable influence on the geographic distribution of many taxa, including coastal plants and populations of some plant species closely related to those used as agricultural crops. East Asian wild radish, Raphanus raphanistrum subsp. sativus, is an annual coastal plant that is a wild relative of the cultivated radish (R. sativus). It has served as source of genetic material that has been helpful to develop and improve the quality and yield of radish crops. To assess the impact of climate change on wild radish in East Asia, we analyzed its distribution at different periods using the maximum entropy model (MaxEnt). The results indicated that the precipitation of the driest month (bio14) and precipitation seasonality (bio15) were the two most dominant environmental factors that affected the geographical distribution of wild radish in East Asia. The total potential area suitable for wild radish is 102.5574 × 104 km2, mainly located along the seacoasts of southern China, Korea, and the Japanese archipelago. Compared with its current distribution regions, the potentially suitable areas for wild radish in the 2070s will further increase and expand northwards in Japan, especially on the sand beach habitats of Hokkaido. This research reveals the spatiotemporal changes for the coastal plant wild radish under global warming and simultaneously provides a vital scientific basis for effective utilization and germplasm innovation for radish cultivars to achieve sustainable agriculture development.

A high efficiency CO2 concentration interval optimization method for lettuce growth

The decline in carbon fertilization effects has shifted scientific focus toward the efficient and suitable regulation of CO2 concentration ([CO2]) for plant growth. In this study, the rapid A/CO2 response curve (RAC) data of lettuce were analyzed statistically under nine photosynthetic photon flux densities (PPFDs) and four temperatures. An efficient CO2 supplementation interval acquisition method based on the frequency distribution characteristics of RACs was proposed. The characteristic subsections of jumping were obtained depending on the frequency distribution of RACs. The cumulative contribution rate (CCR) of the characteristic subsections were >97 %, which showed the efficiency of the method. Additionally, U-chord curvature theory was used to simultaneously obtain the optimal regulated [CO2] for the same RAC curves, and the results showed that the [CO2] obtained by U-chord length were all within the interval obtained by the method, which proved the rationality of the method. The [CO2] interval supplement improved the daily CO2 exchange rate by 20.27 % and 21.64 % at 150 and 200 μmol·m-2·s-1, and increased the lettuce fresh biomass by 26.78 % at 150 μmol·m-2·s-1. Based on the interval of [CO2] efficient utilization regulation at various temperatures and PPFDs, a genetic algorithm-support vector regression model was built with R2 of the model was >0.84 and the root mean square error was <35.2256 μmol·mol-1. In conclusion, the [CO2] interval obtained by this method has a positive effect on lettuce growth. This work provides a new method for obtaining high-efficiency supplementary concentration of CO2 during the growth of lettuce.

FLOWERING LOCUS C drives delayed flowering in Arabidopsis grown and selected at elevated CO 2

Altered flowering time at elevated [CO ₂ ] is well documented, although mechanisms are not well understood. An Arabidopsis genotype previously selected for high fitness at elevated [CO ₂ ] (SG) showed delayed flowering and larger size at flowering when grown at elevated (700 ppm) versus current (380 ppm) [CO ₂ ]. This response was correlated with prolonged expression of FLOWERING LOCUS C ( FLC ), a vernalization-responsive floral repressor gene. To determine if FLC directly delays flowering at elevated [CO ₂ ] in SG, we used vernalization (extended cold) to downregulate FLC expression. We hypothesized that vernalization would eliminate delayed flowering at elevated [CO ₂ ] through the direct reduction of FLC expression, eliminating differences in flowering time between current and elevated [CO ₂ ]. We found that with downregulation of FLC expression via vernalization, SG plants grown at elevated [CO ₂ ] no longer delayed flowering compared to current [CO ₂ ]. Thus, vernalization returned the earlier flowering phenotype, counteracting effects of elevated [CO ₂ ] on flowering. This study indicates that elevated [CO ₂ ] can delay flowering directly through FLC , and downregulation of FLC under elevated [CO ₂ ] reverses this effect. Moreover, this study demonstrates that increasing [CO ₂ ] may potentially drive major changes in development through FLC .

Differential Effect of Free-Air CO2 Enrichment (FACE) in Different Organs and Growth Stages of Two Cultivars of Durum Wheat

Wheat is a target crop within the food security context. The responses of wheat plants under elevated concentrations of CO₂ (e[CO₂]) have been previously studied; however, few of these studies have evaluated several organs at different phenological stages simultaneously under free-air CO₂ enrichment (FACE) conditions. The main objective of this study was to evaluate the effect of e[CO₂] in two cultivars of wheat (Triumph and Norin), analyzed at three phenological stages (elongation, anthesis, and maturation) and in different organs at each stage, under FACE conditions. Agronomic, biomass, physiological, and carbon (C) and nitrogen (N) dynamics were examined in both ambient CO₂ (a[CO₂]) fixed at 415 µmol mol^-1 CO₂ and e[CO₂] at 550 µmol mol^-1 CO₂. We found minimal effect of e[CO₂] compared to a[CO₂] on agronomic and biomass parameters. Also, while exposure to 550 µmol mol^-1 CO₂ increased the photosynthetic rate of CO₂ assimilation (An), the current study showed a diminishment in the maximum carboxylation (V_c,max) and maximum electron transport (J_max) under e[CO₂] conditions compared to a[CO₂] at physiological level in both cultivars. However, even if no significant differences were detected between cultivars on photosynthetic machinery, differential responses between cultivars were detected in C and N dynamics at e[CO₂]. Triumph showed starch accumulation in most organs during anthesis and maturation, but a decline in N content was observed. Contrastingly, in Norin, a decrease in starch content during the three stages and an increase in N content was observed. The amino acid content decreased in grain and shells at maturation in both cultivars, which might indicate a minimal translocation from source to sink organs. These results suggest a greater acclimation to e[CO₂] enrichment in Triumph than Norin, because both the elongation stage and e[CO₂] modified the source-sink relationship. According to the differences between cultivars, future studies should be performed to test genetic variation under FACE technology and explore the potential of cultivars to cope with projected climate scenarios.

Anatomical adjustments of the tree hydraulic pathway decrease canopy conductance under long-term elevated CO2

The cause of reduced leaf-level transpiration under elevated CO2 remains largely elusive. Here, we assessed stomatal, hydraulic, and morphological adjustments in a long-term experiment on Aleppo pine (Pinus halepensis) seedlings germinated and grown for 22-40 months under elevated (eCO2; c. 860 ppm) or ambient (aCO2; c. 410 ppm) CO2. We assessed if eCO2-triggered reductions in canopy conductance (gc) alter the response to soil or atmospheric drought and are reversible or lasting due to anatomical adjustments by exposing eCO2 seedlings to decreasing [CO2]. To quantify underlying mechanisms, we analyzed leaf abscisic acid (ABA) level, stomatal and leaf morphology, xylem structure, hydraulic efficiency, and hydraulic safety. Effects of eCO2 manifested in a strong reduction in leaf-level gc (-55%) not caused by ABA and not reversible under low CO2 (c. 200 ppm). Stomatal development and size were unchanged, while stomatal density increased (+18%). An increased vein-to-epidermis distance (+65%) suggested a larger leaf resistance to water flow. This was supported by anatomical adjustments of branch xylem having smaller conduits (-8%) and lower conduit lumen fraction (-11%), which resulted in a lower specific conductivity (-19%) and leaf-specific conductivity (-34%). These adaptations to CO2 did not change stomatal sensitivity to soil or atmospheric drought, consistent with similar xylem safety thresholds. In summary, we found reductions of gc under elevated CO2 to be reflected in anatomical adjustments and decreases in hydraulic conductivity. As these water savings were largely annulled by increases in leaf biomass, we do not expect alleviation of drought stress in a high CO2 atmosphere.

Plant secondary metabolic responses to global climate change: A meta-analysis in medicinal and aromatic plants

Plant secondary metabolites (SMs) play crucial roles in plant-environment interactions and contribute greatly to human health. Global climate changes are expected to dramatically affect plant secondary metabolism, yet a systematic understanding of such influences is still lacking. Here, we employed medicinal and aromatic plants (MAAPs) as model plant taxa and performed a meta-analysis from 360 publications using 1828 paired observations to assess the responses of different SMs levels and the accompanying plant traits to elevated carbon dioxide (eCO₂ ), elevated temperature (eT), elevated nitrogen deposition (eN) and decreased precipitation (dP). The overall results showed that phenolic and terpenoid levels generally respond positively to eCO₂ but negatively to eN, while the total alkaloid concentration was increased remarkably by eN. By contrast, dP promotes the levels of all SMs, while eT exclusively exerts a positive influence on the levels of phenolic compounds. Further analysis highlighted the dependence of SM responses on different moderators such as plant functional types, climate change levels or exposure durations, mean annual temperature and mean annual precipitation. Moreover, plant phenolic and terpenoid responses to climate changes could be attributed to the variations of C/N ratio and total soluble sugar levels, while the trade-off supposition contributed to SM responses to climate changes other than eCO₂ . Taken together, our results predicted the distinctive SM responses to diverse climate changes in MAAPs and allowed us to define potential moderators responsible for these variations. Further, linking SM responses to C-N metabolism and growth-defence balance provided biological understandings in terms of plant secondary metabolic regulation.

Individual and mutual effects of elevated carbon dioxide and temperature on salt and cadmium uptake and translocation by rice seedlings

Plant kingdoms are facing increasingly harsh environmental challenges marked by the coexposure of salinity and pollution in the pedosphere and elevated CO₂ and temperature in the atmosphere due to the rapid acceleration of industrialization and global climate change. In this study, we deployed a hydroponics-based experiment to explore the individual and mutual effects of different temperatures (low temperature, T1: 23°C; high temperature, T2: 27°C) and CO₂ concentrations (ambient CO₂: 360 ppm; medium CO₂: 450 ppm; high CO₂: 700 ppm) on the uptake and translocation of sodium chloride (NaCl, 0.0, 0.2, 0.6, and 1.1 g Na/L) and cadmium nitrate (Cd(NO₃)₂·4H₂O, 0.0, 0.2, 1.8, and 5.4 mg Cd/L) by rice seedlings. The results indicated that Cd and Na exposure significantly (P< 0.05) inhibited plant growth, but T2 and medium/high CO₂ alleviated the effects of Cd and Na on plant growth. Neither significant synergistic nor antagonistic effects of Cd and Na were observed, particularly not at T1 or high CO₂. At increasing temperatures, relative growth rates increased despite higher concentrations of Cd and Na in both rice roots and shoots. Similarly, higher CO₂ stimulated the growth rate but resulted in significantly lower concentrations of Na, while the Cd concentration was highest at medium CO₂. Coexposure experiments suggested that the concentration of Cd in roots slightly declined with additional Na and more at T2. Overall, our preliminary study suggested that global climate change may alter the distribution of mineral and toxic elements in rice plants as well as the tolerance of the plants.

Grain protein concentration at elevated [CO2] is determined by genotype dependent variations in nitrogen remobilisation and nitrogen utilisation efficiency in wheat

Predictions for wheat grown under future climate conditions indicate a decline in grain protein concentration accompanied with an increase in yield due to increasing carbon dioxide concentrations. Currently, there is a lack of understanding as to the complete mechanism that governs the response of grain protein concentration (GPC) to elevated carbon dioxide (e[CO2]). We investigated the GPC of 18 wheat genotypes from a doubled haploid wheat population and the two parental genotypes, Kukri and RAC0875. In addition, other nitrogen and biomass related traits were analysed to further elucidate which traits are connected with the decline in GPC. Wheat was grown under ambient and elevated [CO2] in an environmentally controlled glasshouse. Plant nitrogen and biomass accumulation were measured at anthesis and maturity. We found that GPC declined under e[CO2] and that the response of GPC to e[CO2] was negatively correlated with nitrogen utilisation efficiency and harvest index. The extent that total biomass (anthesis), harvest index, photosynthesis, nitrogen utilisation and remobilisation efficiency, total nitrogen remobilisation and post-anthesis nitrogen uptake impacted GPC in response to e[CO2] varied across genotype, suggesting that multiple mechanisms are responsible for GPC decline at e[CO2] and that these mechanisms are effected differentially across genotypes.

Physiological and Molecular Responses of Woody Plants Exposed to Future Atmospheric CO2 Levels under Abiotic Stresses

Climate change is mainly driven by the accumulation of carbon dioxide (CO2) in the atmosphere in the last century. Plant growth is constantly challenged by environmental fluctuations including heat waves, severe drought and salinity, along with ozone accumulation in the atmosphere. Food security is at risk in an increasing world population, and it is necessary to face the current and the expected effects of global warming. The effects of the predicted environment scenario of elevated CO2 concentration (e[CO2]) and more severe abiotic stresses have been scarcely investigated in woody plants, and an integrated view involving physiological, biochemical and molecular data is missing. This review highlights the effects of elevated CO2 in the metabolism of woody plants and the main findings of its interaction with abiotic stresses, including a molecular point of view, aiming to improve the understanding of how woody plants will face the predicted environmental conditions. Overall, e[CO2] stimulates photosynthesis and growth and attenuates mild to moderate abiotic stress in woody plants if root growth and nutrients are not limited. Moreover, e[CO2] does not induce acclimation in most tree species. Some high-throughput analyses involving omics techniques were conducted to better understand how these processes are regulated. Finally, knowledge gaps in the understanding of how the predicted climate condition will affect woody plant metabolism were identified, with the aim of improving the growth and production of this plant species.

The Future Potential Distribution and Sustainable Management of Ancient Pu’er Tea Trees (Camellia sinensis var. assamica (J. W. Mast.) Kitam.)

Ancient Pu’er tea trees (Camellia sinensis var. assamica (J. W. Mast.) Kitam.) are an important ecological resource with high economic value. Knowledge of the environmental variables shaping the original distribution and the effects of climate change on the future potential distribution of these trees, as well as the identification of sustainable management approaches, is essential for ensuring their future health and production. Here, we used 28 current environmental variables and the future climate data to model the suitable areas for ancient Pu’er tea trees. We also compared the health of these ancient trees in areas under different local management strategies. The results suggested the general distribution is likely to remain stable, but there are environmentally suitable areas outside its current habitats. To achieve more sustainable management, the main areas in which the management of poorly-managed trees can be improved include learning from managers of well-managed trees and following the common technical management regulations stipulated by the local government. The suitable value ranges for environmental factors, potentially suitable areas under climate change, and assessment of management approaches will aid the future cultivation and transplantation of ancient Pu’er tea trees. The methodology includes management-level analysis and provides practical insights that could be applied to regions outside the most suitable areas identified.

Enhancement of Bioactive Constituents in Fresh Cauliflower By-Products in Challenging Climate Conditions

In order to mitigate the detrimental impact that climate change is having on plants, the study of new practices that allow for the reduction of such effects has become imperative. In addition, the revaluation of the promotion of healthy plant by-products has also markedly increased in importance in recent years. In this work, the modifications in biomass and some antioxidant compounds of cauliflower by-products treated with putrescine under extreme temperatures in two different CO₂ scenarios (the control (400 ppm) and a high concentration of CO₂ (1000 ppm)) were studied. Additionally, the compositions of inner and outer leaves were also compared. According to results found in this work, cauliflower grown under elevated CO₂ and treated with putrescine (2.5 mM) prior to heat stress showed the highest biomass accumulation (20%) compared to the control. Moreover, in the outer leaves from cauliflower grown under elevated CO₂ and treated with putrescine prior to high temperature exposure, the highest biosynthesis of sugars (20%) was recorded. Although cauliflower by-products turned out to be rich in polyamines (208.6 nmoles g⁻¹ fresh weight (FW) and 124.3 nmoles g⁻¹ FW for outer and inner leaves, respectively) and phenolic compounds (1070.2 mg gallic acid equivalents ( (GAE) 100 g⁻¹ FW in outer leaves and 772.0 mg GAE 100 g⁻¹ FW in inner leaves), it was the outer leaves that after applying the new strategy showed the greatest increase in polyamines (68%) and phenolic compounds (39%), obtaining here the highest increase in antioxidant activity (3%). Thus, they should no longer be regarded as mere by-products and should be used for pharmaceutical or nutraceutical purposes. The novel strategy presented in this work may allow us to take advantage of both the continued increase in CO₂ and heat waves that are becoming more frequent.

Molecular and Metabolic Changes under Environmental Stresses: The Biosynthesis of Quality Components in Preharvest Tea Shoots

Severe environments impose various abiotic stresses on tea plants. Although much is known about the physiological and biochemical responses of tea (Camellia sinensis L.) shoots under environmental stresses, little is known about how these stresses impact the biosynthesis of quality components. This review summarizes and analyzes the changes in molecular and quality components in tea shoots subjected to major environmental stresses during the past 20 years, including light (shade, blue light, green light, and UV-B), drought, high/low temperature, CO2, and salinity. These studies reveal that carbon and nitrogen metabolism is critical to the downstream biosynthesis of quality components. Based on the molecular responses of tea plants to stresses, a series of artificial methods have been suggested to treat the pre-harvest tea plants that are exposed to inhospitable environments to improve the quality components in shoots. Furthermore, many pleiotropic genes that are up- or down-regulated under both single and concurrent stresses were analyzed as the most effective genes for regulating multi-resistance and quality components. These findings deepen our understanding of how environmental stresses affect the quality components of tea, providing novel insights into strategies for balancing plant resistance, growth, and quality components in field-based cultivation and for breeding plants using pleiotropic genes.

A meta-analysis of responses of C3 plants to atmospheric CO2 : dose-response curves for 85 traits ranging from the molecular to the whole-plant level

Generalised dose-response curves are essential to understand how plants acclimate to atmospheric CO₂ . We carried out a meta-analysis of 630 experiments in which C₃ plants were experimentally grown at different [CO₂ ] under relatively benign conditions, and derived dose-response curves for 85 phenotypic traits. These curves were characterised by form, plasticity, consistency and reliability. Considered over a range of 200-1200 µmol mol^-1 CO₂ , some traits more than doubled (e.g. area-based photosynthesis; intrinsic water-use efficiency), whereas others more than halved (area-based transpiration). At current atmospheric [CO₂ ], 64% of the total stimulation in biomass over the 200-1200 µmol mol^-1 range has already been realised. We also mapped the trait responses of plants to [CO₂ ] against those we have quantified before for light intensity. For most traits, CO₂ and light responses were of similar direction. However, some traits (such as reproductive effort) only responded to light, others (such as plant height) only to [CO₂ ], and some traits (such as area-based transpiration) responded in opposite directions. This synthesis provides a comprehensive picture of plant responses to [CO₂ ] at different integration levels and offers the quantitative dose-response curves that can be used to improve global change simulation models.

Climate change regulated abiotic stress mechanisms in plants: a comprehensive review

Global climate change is identified as a major threat to survival of natural ecosystems. Climate change is a dynamic, multifaceted system of alterations in environmental conditions that affect abiotic and biotic components of the world. It results in alteration in environmental conditions such as heat waves, intensity of rainfall, CO₂ concentration and temperature that lead to rise in new pests, weeds and pathogens. Climate change is one of the major constraints limiting plant growth and development worldwide. It impairs growth, disturbs photosynthesis, and reduces physiological responses in plants. The variations in global climate have gained the attention of researchers worldwide, as these changes negatively affect the agriculture by reducing crop productivity and food security. With this background, this review focuses on the effects of elevated atmospheric CO₂ concentration, temperature, drought and salinity on the morphology, physiology and biochemistry of plants. Furthermore, this paper outlines an overview on the reactive oxygen species (ROS) production and their impact on the biochemical and molecular status of plants with increased climatic variations. Also additionally, different tolerance strategies adopted by plants to combat environmental adversities have been discussed.

Identifying Traits Associated With Terminal Drought Tolerance in Sesame (Sesamum indicum L.) Genotypes

Sesame is predominantly cultivated in rainfed and low fertile lands and is frequently exposed to terminal drought. Sesamum species inhabiting dryland ecosystems adaptively diverge from those inhabiting rainfed habitats, and drought-specific traits have a genetic basis. In sesame, traits associated with drought conditions have not been explored to date, yet studies of these traits are needed given that drought is predicted to become more frequent and severe in many parts of the world because of climate change. Here, 76 accessions from the available Indian core set were used to quantify variation in several traits under irrigated (WW) and terminal drought stress (WS) conditions as well as their association with seed yield over two consecutive years. The range of trait variation among the studied genotypes under WW and WS was significant. Furthermore, the traits associated with seed yield under WW and WS differed. The per se performance of the accessions indicated that the expression of most traits was reduced under WS. The correlation analysis revealed that the number of branches, leaf area (LA), leaves dry weight (LDW), number of capsules plant^-1, and harvest index (HI) were positively correlated with seed yield under WW and WS, and total dry matter (TDM), plant stem weight, and canopy temperature (CT) were negatively correlated with seed yield under WW and WS, indicating that smaller and cooler canopy genotypes had higher yields. The genotypes IC-131936, IC-204045, IC-204861, IC-205363, IC-205311, and IC-73576 with the highest seed yields were characterized by low canopy temperature, high relative water content, and high harvest index under WS. Phenotypic and molecular diversity analysis was conducted on genotypes along with checks. Phenotypic diversity was assessed using multivariate analysis, whereas molecular diversity was estimated using simple sequence repeat (SSR) loci to facilitate the use of sesame in breeding and genetic mapping. SSRs showed low allelic variation, as indicated by a low average number of alleles (2.31) per locus, gene diversity (0.25), and polymorphism information content (0.22). Cluster analysis (CA) [neighbor-joining (NJ) tree] revealed three major genotypic groups and structure analysis showed 4 populations. The diverse genotypes identified with promising morpho-physiological traits can be used in breeding programs to develop new varieties.

Deep dive into CO2-dependent molecular mechanisms driving stomatal responses in plants

Recent advances are revealing mechanisms mediating CO₂-regulated stomatal movements in Arabidopsis, stomatal architecture and stomatal movements in grasses, and the long-term impact of CO₂ on growth.

Climate Change Impacts on Sunflower (Helianthus annus L.) Plants

The biochemical, biological, and morphogenetic processes of plants are affected by ongoing climate change, causing alterations in crop development, growth, and productivity. Climate change is currently producing ecosystem modifications, making it essential to study plants with an improved adaptive capacity in the face of environmental modifications. This work examines the physiological and metabolic changes taking place during the development of sunflower plants due to environmental modifications resulting from climate change: elevated concentrations of atmospheric carbon dioxide (CO2) and increased temperatures. Variations in growth, and carbon and nitrogen metabolism, as well as their effect on the plant's oxidative state in sunflower (Helianthus annus L.) plants, are studied. An understanding of the effect of these interacting factors (elevated CO2 and elevated temperatures) on plant development and stress response is imperative to understand the impact of climate change on plant productivity.

Mechanisms of elevated CO2-induced thermotolerance in plants: the role of phytohormones

Rising atmospheric CO₂ is a key driver of climate change, intensifying drastic changes in meteorological parameters. Plants can sense and respond to changes in environmental parameters including atmospheric CO₂ and temperatures. High temperatures beyond the physiological threshold can significantly affect plant growth and development and thus attenuate crop productivity. However, elevated atmospheric CO₂ can mitigate the deleterious effects of heat stress on plants. Despite a large body of literature supporting the positive impact of elevated CO₂ on thermotolerance, the underlying biological mechanisms and precise molecular pathways that lead to enhanced tolerance to heat stress remain largely unclear. Under heat stress, elevated CO₂-induced expression of respiratory burst oxidase homologs (RBOHs) and reactive oxygen species (ROS) signaling play a critical role in stomatal movement, which optimizes gas exchange to enhance photosynthesis and water use efficiency. Notably, elevated CO₂ also fortifies antioxidant defense and redox homeostasis to alleviate heat-induced oxidative damage. Both hormone-dependent and independent pathways have been shown to mediate high CO₂-induced thermotolerance. The activation of heat-shock factors and subsequent expression of heat-shock proteins are thought to be the essential mechanism downstream of hormone and ROS signaling. Here we review the role of phytohormones in plant response to high atmospheric CO₂ and temperatures. We also discuss the potential mechanisms of elevated CO₂-induced thermotolerance by focusing on several key phytohormones such as ethylene. Finally, we address some limitations of our current understanding and the need for further research to unveil the yet-unknown crosstalk between plant hormones in mediating high CO₂-induced thermotolerance in plants.

Amelioration of plant responses to drought under elevated CO2 by rejuvenating photosynthesis and nitrogen use efficiency: implications for future climate-resilient crops

The contemporary global agriculture is beset with serious threats from diverse eco-environmental conditions causing decreases in crop yields by ~ 15%. These yield losses might increase further due to climate change scenarios leading to increased food prices triggering social unrest and famines. Urbanization and industrialization are often associated with rapid increases in greenhouse gases (GHGs) especially atmospheric CO₂ concentration [(CO₂)]. Increase in atmospheric [CO₂] significantly improved crop photosynthesis and productivity initially which vary with plant species, genotype, [CO₂] exposure time and biotic as well as abiotic stress factors. Numerous attempts have been made using different plant species to unravel the physiological, cellular and molecular effects of elevated [CO₂] as well as drought. This review focuses on plant responses to elevated [CO₂] and drought individually as well as in combination with special reference to physiology of photosynthesis including its acclimation. Furthermore, the functional role of nitrogen use efficiency (NUE) and its relation to photosynthetic acclimation and crop productivity under elevated [CO₂] and drought are reviewed. In addition, we also discussed different strategies to ameliorate the limitations of ribulose-1,5-bisphosphate (RuBP) carboxylation and RuBP regeneration. Further, improved stomatal and mesophyll conductance and NUE for enhanced crop productivity under fast changing global climate conditions through biotechnological approaches are also discussed here. We conclude that multiple gene editing approaches for key events in photosynthetic processes would serve as the best strategy to generate resilient crop plants with improved productivity under fast changing climate.

Leaf and tree responses of young European aspen trees to elevated atmospheric CO2 concentration vary over the season

Elevated atmospheric CO2 concentration (eCO2) commonly stimulates net leaf assimilation, decreases stomatal conductance and has no clear effect on leaf respiration. However, effects of eCO2 on whole-tree functioning and its seasonal dynamics remain far more uncertain. To evaluate temporal and spatial variability in eCO2 effects, 1-year-old European aspen trees were grown in two treatment chambers under ambient (aCO2, 400 p.p.m.) and elevated (eCO2, 700 p.p.m.) CO2 concentrations during an early (spring 2019) and late (autumn 2018) seasonal experiment. Leaf (net carbon assimilation, stomatal conductance and leaf respiration) and whole-tree (stem growth, sap flow and stem CO2 efflux) responses to eCO2 were measured. Under eCO2, carbon assimilation was stimulated during the early (1.63-fold) and late (1.26-fold) seasonal experiments. Stimulation of carbon assimilation changed over time with largest increases observed in spring when stem volumetric growth was highest, followed by late season down-regulation, when stem volumetric growth ceased. The neutral eCO2 effect on stomatal conductance and leaf respiration measured at leaf level paralleled the unresponsive canopy conductance (derived from sap flow measurements) and stem CO2 efflux measured at tree level. Our results highlight that seasonality in carbon demand for tree growth substantially affects the magnitude of the response to eCO2 at both leaf and whole-tree level.

Leaf nitrogen have a better relationship with photosynthesis performance across wheat species under elevated CO2 and drought

Elevated CO₂ concentrations and persistent drought are predicted to inhibit the photosynthetic performance and yield of crops. Such effects vary considerably between species groups. Modern cultivated (Triticum aestivum L., AABBDD) and wild (Triticum dicoccoides Korn L., AABB and Triticum monococcum L., AA) species of wheat were subjected to elevated CO₂ concentration (ambient concentration +200 μmol mol^-1) and drought (well watered: 75-85% of the field water capacity; drought: 50-60% of the field water capacity) at open-top chamber experimental facilities. Elevated CO₂ concentration decreased the limitation of stomatal morphology traits on stomatal conductance regulation. This could compensate the disadvantage of plants who has low stomatal density and large single stomatal area as well as low leaf water use efficiency such as modern wheat Z9023 in drought acclimation in the future CO₂ rising world. Moreover, elevated CO₂ concentration largely increased the dependence of light harvesting and electron transportation performance per photosynthesis system II reaction center, maximum rubisco carboxylation rate, and maximum Ribulose-1,5-bisphosphate regeneration rate on leaf nitrogen concentration across the selected wheat species and water regimes. Modern cultivated cultivars Z9023 and CH58 have higher photosynthetic performance per unit of leaf nitrogen than wild species under elevated CO₂ concentrations. The increasing CO₂ may present opportunities to breeders and possibly allow them to select for cultivars with better photosynthetic nitrogen use efficiency response to future CO₂ rising climate.

Delineating the mechanisms of elevated CO2 mediated growth, stress tolerance and phytohormonal regulation in plants

Global climate change has drastically affected natural ecosystems and crop productivity. Among several factors of global climate change, CO₂ is considered to be the dynamic parameter that will regulate the responses of all biological system on earth in the coming decade. A number of experimental studies in the past have demonstrated the positive effects of elevated CO₂ on photosynthesis, growth and biomass, biochemical and physiological processes such as increased C:N ratio, secondary metabolite production, as well as phytohormone concentrations. On the other hand, elevated CO₂ imparts an adverse effect on the nutritional quality of crop plants and seed quality. Investigations have also revealed effects of elevated CO₂ both at cellular and molecular level altering expression of various genes involved in various metabolic processes and stress signaling pathways. Elevated CO₂ is known to have mitigating effect on plants in presence of abiotic stresses such as drought, salinity, temperature etc., while contrasting effects in the presence of different biotic agents i.e. phytopathogens, insects and herbivores. However, a well-defined crosstalk is incited by elevated CO₂ both under abiotic and biotic stresses in terms of phytohormones concentration and secondary metabolites production. With this background, the present review attempts to shed light on the major effects of elevated CO₂ on plant growth, physiological and molecular responses and will highlight the interactive effects of elevated CO₂ with other abiotic and biotic factors. The article will also provide deep insights into the phytohormones modulation under elevated CO₂.

Elevated [CO2] Mitigates Drought Effects and Increases Leaf 5-O-Caffeoylquinic Acid and Caffeine Concentrations During the Early Growth of Coffea Arabica Plants

Increasing atmospheric [CO2] is thought to contribute to changes in precipitation patterns, increasing heatwaves and severe drought scenarios. However, how the combination of elevated [CO2] and progressive drought affect plant metabolism is poorly understood. Aiming to investigate the effects of this environmental condition on photosynthesis and specialized metabolites in leaves of Coffea arabica during the early growth, plants fertilized with ambient (a[CO2]-400 ppm) and elevated (e[CO2]-800 ppm) [CO2] were exposed to well-watered (WW) or water-deficit (WD) regimes for 40 days. Over the 40-day-water-withdrawal, soil moisture, and leaf water potential decreased compared to WW-condition. Elevated [CO2] stimulates CO2 assimilation (A) and intrinsic water use efficiency (iWUE) even under WD. Drought condition slightly changed stomatal conductance, transpiration rate and maximum quantum efficiency of photosystem II (PSII) regardless of [CO2] compared to WW-plants. Total soluble amino acid concentration did not change significantly, while total phenolic compounds concentration decreased under e[CO2] regardless of water regimes. The combination of e[CO2]+WD increased the 5-O-caffeoylquinic acid (5-CQA) and caffeine amounts by 40-day when compared to a[CO2]+WD plants. Altogether, these results suggest that e[CO2] buffers mild-drought stress in young C. arabica by increasing A, iWUE and stimulating changes in the leaf contents of 5-CQA and caffeine.

G protein γ subunit qPE9-1 is involved in rice adaptation under elevated CO2 concentration by regulating leaf photosynthesis

G protein γ subunit qPE9-1 plays multiple roles in rice growth and development. However, the role of qPE9-1 in rice exposed to elevated carbon dioxide concentration (eCO₂) is unknown. Here, we investigated its role in the regulation of rice growth under eCO₂ conditions using qPE9-1 overexpression (OE) lines, RNAi lines and corresponding WT rice. Compared to atmospheric carbon dioxide concentration (aCO₂), relative expression of qPE9-1 in rice leaf was approximately tenfold higher under eCO₂. Under eCO₂, the growth of WT and qPE9-1-overexpressing rice was significantly higher than under aCO₂. Moreover, there was no significant effect of eCO₂ on the growth of qPE9-1 RNAi lines. Furthermore, WT and qPE9-1-overexpressing rice showed higher net photosynthetic rate and carbohydrate content under eCO₂ than under aCO₂. Moreover, the relative expression of some photosynthesis related genes in WT, but not in RNAi3 line, showed significant difference under eCO₂ in RNA-seq analysis. Compared to WT and RNAi lines, the rbcL gene expression and Rubisco content of rice leaves in qPE9-1-overexpressors were higher under eCO₂. Overall, these results suggest that qPE9-1 is involved in rice adaptation under elevated CO₂ concentration by regulating leaf photosynthesis via moderating rice photosynthetic light reaction and Rubisco content.

Genotypic Variability on Grain Yield and Grain Nutritional Quality Characteristics of Wheat Grown under Elevated CO2 and High Temperature

The progressive rise in atmospheric CO2 concentrations and temperature associated with climate change is predicted to have a major impact on the productivity and quality of food crops. Therefore, food security is highly dependent on climate change. Following a survey with 60 bread wheat genotypes, here we investigated the genetic variation in grain yield and nutritional quality among 10 of these genotypes grown under elevated CO2 and temperature. With this purpose, the biomass production, grain yield-related traits, the grain concentration of starch, total protein, phenolic compounds, and mineral nutrients, together with the total antioxidant capacity, were determined. Variation among genotypes was found for almost all the studied traits. Higher grain and ear numbers were associated with increased grain yield but decreased grain total protein concentration and minerals such as Cu, Fe, Mg, Na, P, and Zn. Mineral nutrients were mainly associated with wheat biomass, whereas protein concentration was affected by plant biomass and yield-related traits. Associations among different nutrients and promising nutrient concentrations in some wheat genotypes were also found. This study demonstrates that the exploration of genetic diversity is a powerful approach, not only for selecting genotypes with improved quality, but also for dissecting the effect of the environment on grain yield and nutritional composition.

Temporal variability in tree responses to elevated atmospheric CO2

At leaf level, elevated atmospheric CO₂ concentration (eCO₂ ) results in stimulation of carbon net assimilation and reduction of stomatal conductance. However, a comprehensive understanding of the impact of eCO₂ at larger temporal (seasonal and annual) and spatial (from leaf to whole-tree) scales is still lacking. Here, we review overall trends, magnitude and drivers of dynamic tree responses to eCO₂ , including carbon and water relations at the leaf and the whole-tree level. Spring and early season leaf responses are most susceptible to eCO₂ and are followed by a down-regulation towards the onset of autumn. At the whole-tree level, CO₂ fertilization causes consistent biomass increments in young seedlings only, whereas mature trees show a variable response. Elevated CO₂ -induced reductions in leaf stomatal conductance do not systematically translate into limitation of whole-tree transpiration due to the unpredictable response of canopy area. Reduction in the end-of-season carbon sink demand and water-limiting strategies are considered the main drivers of seasonal tree responses to eCO₂ . These large temporal and spatial variabilities in tree responses to eCO₂ highlight the risk of predicting tree behavior to eCO₂ based on single leaf-level point measurements as they only reveal snapshots of the dynamic responses to eCO₂ .

Climate-proofing a malaria eradication strategy

Two recent initiatives, the World Health Organization (WHO) Strategic Advisory Group on Malaria Eradication and the Lancet Commission on Malaria Eradication, have assessed the feasibility of achieving global malaria eradication and proposed strategies to achieve it. Both reports rely on a climate-driven model of malaria transmission to conclude that long-term trends in climate will assist eradication efforts overall and, consequently, neither prioritize strategies to manage the effects of climate variability and change on malaria programming. This review discusses the pathways via which climate affects malaria and reviews the suitability of climate-driven models of malaria transmission to inform long-term strategies such as an eradication programme. Climate can influence malaria directly, through transmission dynamics, or indirectly, through myriad pathways including the many socioeconomic factors that underpin malaria risk. These indirect effects are largely unpredictable and so are not included in climate-driven disease models. Such models have been effective at predicting transmission from weeks to months ahead. However, due to several well-documented limitations, climate projections cannot accurately predict the medium- or long-term effects of climate change on malaria, especially on local scales. Long-term climate trends are shifting disease patterns, but climate shocks (extreme weather and climate events) and variability from sub-seasonal to decadal timeframes have a much greater influence than trends and are also more easily integrated into control programmes. In light of these conclusions, a pragmatic approach is proposed to assessing and managing the effects of climate variability and change on long-term malaria risk and on programmes to control, eliminate and ultimately eradicate the disease. A range of practical measures are proposed to climate-proof a malaria eradication strategy, which can be implemented today and will ensure that climate variability and change do not derail progress towards eradication.

The da1 mutation in wheat increases grain size under ambient and elevated CO2 but not grain yield due to trade-off between grain size and grain number

Grain size is potentially yield determining in wheat, controlled by the ubiquitin pathway and negatively regulated by ubiquitin receptor DA1. We analyzed whether increased thousand grain weight in wheat da1 mutant is translated into higher grain yield and whether additional carbon provided by elevated (e)CO₂ can be better used by the da1, displaying higher grain sink strength and size. Yield-related, biomass, grain quality traits, and grain dimensions were analyzed by two-factorial mixed-model analysis, regarding genotype and eCO₂. da1 increased grain size but reduced spikes and grains per plant, grains per spike, and spikelets per spike, independent of eCO₂ treatment, leaving total grain yield unchanged. eCO₂ increased yield and grain number additively and independently of da1 but did not overcome the trade-off between grain size and number observed for da1. eCO₂ but not da1 impaired grain quality, strongly decreasing concentrations of several macroelement and microelement. In conclusion, intrinsic stimulation of grain sink strength and grain size, achieved by da1, is not benefitting total yield unless trade-offs between grain size and numbers can be overcome. The results reveal interactions of yield components in da1-wheat under ambient and eCO₂, thereby uncovering limitations enhancing wheat yield potential.

Dying by drying: Timing of physiological stress thresholds related to tree death is not significantly altered by highly elevated CO2

Drought-induced tree mortality is expected to occur more frequently under predicted climate change. However, the extent of a possibly mitigating effect of simultaneously rising atmospheric [CO₂ ] on stress thresholds leading to tree death is not fully understood, yet. Here, we studied the drought response, the time until critical stress thresholds were reached and mortality occurrence of Pinus halepensis (Miller). In order to observe a large potential benefit from eCO₂ , the seedlings were grown with ample of water and nutrient supply under either highly elevated [CO₂ ] (eCO₂ , c. 936 ppm) or ambient (aCO₂ , c. 407 ppm) during 2 years. The subsequent exposure to a fast or a slow lethal drought was monitored using whole-tree gas exchange chambers, measured leaf water potential and non-structural carbohydrates. Using logistic regressions to derive probabilities for physiological parameters to reach critical drought stress thresholds, indicated a longer period for halving needle starch storage under eCO₂ than aCO₂ . Stomatal closure, turgor loss, the duration until the daily tree C balance turned negative, leaf water potential at thresholds and time-of-death were unaffected by eCO₂ . Overall, our study provides for the first-time insights into the chronological interplay of physiological drought thresholds under long-term acclimation to elevated [CO₂ ].

Narrowing uncertainties in the effects of elevated CO2 on crops

Plant responses to rising atmospheric carbon dioxide (CO₂) concentrations, together with projected variations in temperature and precipitation will determine future agricultural production. Estimates of the impacts of climate change on agriculture provide essential information to design effective adaptation strategies, and develop sustainable food systems. Here, we review the current experimental evidence and crop models on the effects of elevated CO₂ concentrations. Recent concerted efforts have narrowed the uncertainties in CO₂-induced crop responses so that climate change impact simulations omitting CO₂ can now be eliminated. To address remaining knowledge gaps and uncertainties in estimating the effects of elevated CO₂ and climate change on crops, future research should expand experiments on more crop species under a wider range of growing conditions, improve the representation of responses to climate extremes in crop models, and simulate additional crop physiological processes related to nutritional quality.

The methylome is altered for plants in a high CO2 world: Insights into the response of a wild plant population to multigenerational exposure to elevated atmospheric [CO2 ]

Unravelling plant responses to rising atmospheric CO₂ concentration ([CO₂ ]) has largely focussed on plastic functional attributes to single generation [CO₂ ] exposure. Quantifying the consequences of long-term, decadal multigenerational exposure to elevated [CO₂ ] and the genetic changes that may underpin evolutionary mechanisms with [CO₂ ] as a driver remain largely unexplored. Here, we investigated both plastic and evolutionary plant responses to elevated [CO₂ ] by applying multi-omic technologies using populations of Plantago lanceolata L., grown in naturally high [CO₂ ] for many generations in a CO₂ spring. Seed from populations at the CO₂ spring and an adjacent control site (ambient [CO₂ ]) were grown in a common environment for one generation, and then offspring were grown in ambient or elevated [CO₂ ] growth chambers. Low overall genetic differentiation between the CO₂ spring and control site populations was found, with evidence of weak selection in exons. We identified evolutionary divergence in the DNA methylation profiles of populations derived from the spring relative to the control population, providing the first evidence that plant methylomes may respond to elevated [CO₂ ] over multiple generations. In contrast, growth at elevated [CO₂ ] for a single generation induced limited methylome remodelling (an order of magnitude fewer differential methylation events than observed between populations), although some of this appeared to be stably transgenerationally inherited. In all, 59 regions of the genome were identified where transcripts exhibiting differential expression (associated with single generation or long-term natural exposure to elevated [CO₂ ]) co-located with sites of differential methylation or with single nucleotide polymorphisms exhibiting significant inter-population divergence. This included genes in pathways known to respond to elevated [CO₂ ], such as nitrogen use efficiency and stomatal patterning. This study provides the first indication that DNA methylation may contribute to plant adaptation to future atmospheric [CO₂ ] and identifies several areas of the genome that are targets for future study.

Woody tissue photosynthesis increases radial stem growth of young poplar trees under ambient atmospheric CO2 but its contribution ceases under elevated CO2

Woody tissue photosynthesis (Pwt) contributes to the tree carbon (C) budget and generally stimulates radial stem growth under ambient atmospheric CO2 concentration (aCO2). Moreover, Pwt has potential to enhance tree survival under changing climates by delaying negative effects of drought stress on tree hydraulic functioning. However, the relevance of Pwt on tree performance under elevated atmospheric CO2 concentration (eCO2) remains unexplored. To fill this knowledge gap, 1-year-old Populus tremula L. seedlings were grown in two treatment chambers at aCO2 and eCO2 (400 and 660 ppm, respectively), and woody tissues of half of the seedlings in each treatment chamber were light-excluded to prevent Pwt. Radial stem growth, sap flow, leaf photosynthesis and stomatal and canopy conductance were measured throughout the growing season, and the concentration of non-structural carbohydrates (NSC) in stem tissues was determined at the end of the experiment. Fuelled by eCO2, an increase in stem growth of 18 and 50% was observed in control and light-excluded trees, respectively. Woody tissue photosynthesis increased radial stem growth by 39% under aCO2, while, surprisingly, no impact of Pwt on stem growth was observed under eCO2. By the end of the growing season, eCO2 and Pwt had little effect on stem growth, leaf photosynthesis acclimated to eCO2, but stomatal conductance did not, and homeostatic stem NSC pools were observed among combined treatments. Our results highlight that eCO2 potentially fulfils plant C requirements, limiting the contribution of Pwt to stem growth as atmospheric [CO2] rises, and that radial stem growth in young developing trees was C (source) limited during early phenological stages but transitioned towards sink-driven control at the end of the growing season.

Potential effects of a high CO2 future on leguminous species

Legumes provide an important source of food and feed due to their high protein levels and many health benefits, and also impart environmental and agronomic advantages as a consequence of their ability to fix nitrogen through their symbiotic relationship with rhizobia. As a result of our growing population, the demand for products derived from legumes will likely expand considerably in coming years. Since there is little scope for increasing production area, improving the productivity of such crops in the face of climate change will be essential. While a growing number of studies have assessed the effects of climate change on legume yield, there is a paucity of information regarding the direct impact of elevated CO₂ concentration (e[CO₂]) itself, which is a main driver of climate change and has a substantial physiological effect on plants. In this review, we discuss current knowledge regarding the influence of e[CO₂] on the photosynthetic process, as well as biomass production, seed yield, quality, and stress tolerance in legumes, and examine how these responses differ from those observed in non-nodulating plants. Although these relationships are proving to be extremely complex, mounting evidence suggests that under limiting conditions, overall declines in many of these parameters could ensue. While further research will be required to unravel precise mechanisms underlying e[CO₂] responses of legumes, it is clear that integrating such knowledge into legume breeding programs will be indispensable for achieving yield gains by harnessing the potential positive effects, and minimizing the detrimental impacts, of CO₂ in the future.

Atmospheric CO2 and VPD alter the diel oscillation of leaf elongation in perennial ryegrass: compensation of hydraulic limitation by stored-growth

We explored the effects of atmospheric CO₂ concentration (C_a ) and vapor pressure deficit (VPD) on putative mechanisms controlling leaf elongation in perennial ryegrass. Plants were grown in stands at a C_a of 200, 400 or 800 μmol mol^-1 combined with high (1.17 kPa) or low (0.59 kPa) VPD during the 16 h-day in well-watered conditions with reduced nitrogen supply. We measured day : night-variation of leaf elongation rate (LER_day  : LER_night ), final leaf length and width, epidermal cell number and length, stomatal conductance, transpiration, leaf water potential and water-soluble carbohydrates and osmotic potential in the leaf growth-and-differentiation zone (LGDZ). Daily mean LER or morphometric parameters did not differ between treatments, but LER_night strongly exceeded LER_day , particularly at low C_a and high VPD. Across treatments LER_day was negatively related to transpiration (R²  = 0.75) and leaf water potential (R²  = 0.81), while LER_night was independent of leaf water potential or turgor. Enhancement of LER_night over LER_day was proportional to the turgor-change between day and night (R²  = 0.93). LGDZ sugar concentration was high throughout diel cycles, providing no evidence of source limitation in any treatment. Our data indicate a mechanism of diel cycling between daytime hydraulic and night-time stored-growth controls of LER, buffering C_a and daytime VPD effects on leaf elongation.

An Oxygen Delivery Polymer Enhances Seed Germination in a Martian-like Environment

Critical to the success of establishing a sustainable human presence on Mars is the ability to economically grow crop plants. Several environmental factors make it difficult to fully rely on local resources for agriculture. These include nutrient sparse regolith, low and fluctuating temperatures, a high amount of ultraviolet radiation, and water trapped locally in the form of ice or metal oxides. While the 96% CO2 martian atmosphere is ideal to support photosynthesis, high CO2 concentrations inhibit germination. An added difficulty is the fact that a vast majority of crop plants require oxygen for germination. Here, we report the production of a polymer-based oxygen delivery system that supports the germination and growth of cress seeds (Lepidium sativum) in a martian regolith simulant under a martian atmosphere at 101 kPa. The oxygen-donating system is based on a low-density lightly cross-linked polyacrylate that is foamed and converted into a dry powder. It is lightweight, added in low amounts to regolith simulant, and efficiently donates enough oxygen throughout the volume of hydrated regolith simulant to fully support seed germination and plant growth. Germination rates, plant development, and plant mass are nearly identical for L. sativum grown in 100% CO2 in the presence of the oxygen-donating lightly cross-linked polyacrylate compared with plants grown in air. The polymer system also serves to protect root structures and better anchors plants in the regolith simulant.

Plasticity of adult coralline algae to prolonged increased temperature and pCO2 exposure but reduced survival in their first generation

Crustose coralline algae (CCA) are vital to coral reefs worldwide, providing structural integrity and inducing the settlement of important invertebrate larvae. CCA are known to be impacted by changes in their environment, both during early development and adulthood. However, long-term studies on either life history stage are lacking in the literature, therefore not allowing time to explore the acclimatory or potential adaptive responses of CCA to future global change scenarios. Here, we exposed a widely distributed, slow growing, species of CCA, Sporolithon cf. durum, to elevated temperature and pCO2 for five months and their first set of offspring (F1) for eleven weeks. Survival, reproductive output, and metabolic rate were measured in adult S. cf. durum, and survival and growth were measured in the F1 generation. Adult S. cf. durum experienced 0% mortality across treatments and reduced their O2 production after five months exposure to global stressors, indicating a possible expression of plasticity. In contrast, the combined stressors of elevated temperature and pCO2 resulted in 50% higher mortality and 61% lower growth on germlings. On the other hand, under the independent elevated pCO2 treatment, germling growth was higher than all other treatments. These results show the robustness and plasticity of S. cf. durum adults, indicating the potential for them to acclimate to increased temperature and pCO2. However, the germlings of this species are highly sensitive to global stressors and this could negatively impact this species in future oceans, and ultimately the structure and stability of coral reefs.

Early growth phase and caffeine content response to recent and projected increases in atmospheric carbon dioxide in coffee (Coffea arabica and C. canephora)

While [CO2] effects on growth and secondary chemistry are well characterized for annual plant species, little is known about perennials. Among perennials, production of Coffea arabica and C. canephora (robusta) have enormous economic importance worldwide. Three Arabica cultivars (Bourbon, Catimor, Typica) and robusta coffee were grown from germination to ca. 12 months at four CO2 concentrations: 300, 400, 500 or 600 ppm. There were significant increases in all leaf area and biomass markers in response to [CO2] with significant [CO2] by taxa differences beginning at 122-124 days after sowing (DAS). At 366-368 DAS, CO2 by cultivar variation in growth and biomass response among Arabica cultivars was not significant; however, significant trends in leaf area, branch number and total above-ground biomass were observed between Arabica and robusta. For caffeine concentration, there were significant differences in [CO2] response between Arabica and robusta. A reduction in caffeine in coffee leaves and seeds might result in decreased ability against deterrence, and consequently, an increase in pest pressure. We suggest that the interspecific differences observed (robusta vs. Arabica) may be due to differences in ploidy level (2n = 22 vs. 2n = 4x = 44). Differential quantitative and qualitative responses during early growth and development of Arabica and robusta may have already occurred with recent [CO2] increases, and such differences may be exacerbated, with production and quality consequences, as [CO2] continues to increase.

Plant Cell Walls Tackling Climate Change: Insights into Plant Cell Wall Remodeling, Its Regulation, and Biotechnological Strategies to Improve Crop Adaptations and Photosynthesis in Response to Global Warming

Plant cell wall (CW) is a complex and intricate structure that performs several functions throughout the plant life cycle. The CW of plants is critical to the maintenance of cells' structural integrity by resisting internal hydrostatic pressures, providing flexibility to support cell division and expansion during tissue differentiation, and acting as an environmental barrier that protects the cells in response to abiotic stress. Plant CW, comprised primarily of polysaccharides, represents the largest sink for photosynthetically fixed carbon, both in plants and in the biosphere. The CW structure is highly varied, not only between plant species but also among different organs, tissues, and cell types in the same organism. During the developmental processes, the main CW components, i.e., cellulose, pectins, hemicelluloses, and different types of CW-glycoproteins, interact constantly with each other and with the environment to maintain cell homeostasis. Differentiation processes are altered by positional effect and are also tightly linked to environmental changes, affecting CW both at the molecular and biochemical levels. The negative effect of climate change on the environment is multifaceted, from high temperatures, altered concentrations of greenhouse gases such as increasing CO2 in the atmosphere, soil salinity, and drought, to increasing frequency of extreme weather events taking place concomitantly, therefore, climate change affects crop productivity in multiple ways. Rising CO2 concentration in the atmosphere is expected to increase photosynthetic rates, especially at high temperatures and under water-limited conditions. This review aims to synthesize current knowledge regarding the effects of climate change on CW biogenesis and modification. We discuss specific cases in crops of interest carrying cell wall modifications that enhance tolerance to climate change-related stresses; from cereals such as rice, wheat, barley, or maize to dicots of interest such as brassica oilseed, cotton, soybean, tomato, or potato. This information could be used for the rational design of genetic engineering traits that aim to increase the stress tolerance in key crops. Future growing conditions expose plants to variable and extreme climate change factors, which negatively impact global agriculture, and therefore further research in this area is critical.

Endophytes alleviate the elevated CO2-dependent decrease in photosynthesis in rice, particularly under nitrogen limitation

The positive effects of high atmospheric CO2 concentrations [CO2] decrease over time in most C3 plants because of down-regulation of photosynthesis. A notable exception to this trend is plants hosting N-fixing bacteria. The decrease in photosynthetic capacity associated with an extended exposure to high [CO2] was therefore studied in non-nodulating rice that can establish endophytic interactions. Rice plants were inoculated with diazotrophic endophytes isolated from the Salicaceae and CO2 response curves of photosynthesis were determined in the absence or presence of endophytes at the panicle initiation stage. Non-inoculated plants grown under elevated [CO2] showed a down-regulation of photosynthesis compared to those grown under ambient [CO2]. In contrast, the endophyte-inoculated plants did not show a decrease in photosynthesis associated with high [CO2], and they exhibited higher photosynthetic electron transport and mesophyll conductance rates than non-inoculated plants under high [CO2]. The endophyte-dependent alleviation of decreases in photosynthesis under high [CO2] led to an increase in water-use efficiency. These effects were most pronounced when the N supply was limited. The results suggest that inoculation with N-fixing endophytes could be an effective means of improving plant growth under high [CO2] by alleviating N limitations.