Interactive Effects Of Elevated CO2 Research Articles

Interactive effects of elevated CO2 with combined heat and drought stresses on the physiology and yield of C3 and C4 plants

Interactive effects of elevated CO2 with combined heat and drought stresses on the physiology and yield of C3 and C4 plants

Effects of elevated CO2 and warming on the root-associated microbiota in an agricultural ecosystem.

Plant root-associated microbial communities profoundly affect plant nutrition and productivity. Although elevated atmospheric CO2 and warming affect above- and belowground plant processes, it remains unclear how root-associated microbial communities respond to elevated CO2 and warming. In this study, an open-air field experiment was conducted to assay the interactive effects of elevated CO2 (500 ppm) and warming (+2°C) on the root-associated microbiota and soil enzyme activities in a rice-wheat rotation ecosystem. The results revealed that elevated CO2 significantly increased rhizosphere soil organic carbon (SOC) and total nitrogen contents. In addition, glucosidase, β-xylosidase, and phosphatase activities significantly increased. The richness and Shannon diversity indices were significantly higher in rhizosphere soil than in root endosphere. Elevated CO2 and warming significantly impacted the rhizosphere soil microbiota and altered their composition by changing the relative abundance of some specific groups. Soil pH, SOC, and available potassium content significantly altered the dominant bacterial phyla in the rhizosphere. SOC affected root endophytic bacterial phyla. Bacterial and fungal genera were significantly correlated with soil variables in the rhizosphere than in the root endosphere. These results indicate that microbial communities in the rhizosphere are more sensitive to elevated CO2 and warming than those in the root endosphere.

Elevated CO2 and biochar differentially affect plant C:N:P stoichiometry and soil microbiota in the rhizosphere of white lupin (Lupinus albus L.)

Biochar application is a potent climate change mitigation strategy in agroecosystems. However, little is known about the interactive effects of elevated CO2 (eCO2) and biochar on plant nutrient uptake and soil microbial processes. A pot experiment was conducted to investigate the effects of eCO2 and biochar addition on plant C:N:P stoichiometry and rhizobacterial community for better management of nutrient balance and use efficiency in a future climate scenario. White lupin (Lupinus albus L.) was grown for 30 days in topsoil and subsoil with or without 2% corn-stubble biochar under ambient CO2 (aCO2: 390 ppm) or eCO2 (550 ppm). Elevated CO2 increased, but biochar decreased, plant biomass and shoot N and P uptake, with no interactions in either soil layer. Elevated CO2 decreased shoot N concentration by 16% and biochar decreased shoot P concentration by 11%. As a result, eCO2 increased shoot C:N ratio by 20% and decreased the N:P ratio by 11%. Biochar decreased shoot C:N ratio by 8% in the subsoil under eCO2. However, biochar increased shoot C:P ratio by an average of 13% and N:P ratio by 23% in the subsoil. Moreover, plants grown in the subsoil showed lower shoot N (35%) and P (70%) uptake compared to the topsoil. The results indicate that N and P are the more limiting factors that regulate plant growth under eCO2 and biochar application, respectively. Elevated CO2 and biochar oppositely affected dominant rhizobacterial community composition, with the eCO2 effect being greater. The microbiota in the subsoil held a greater diversity of contrasting species than the topsoil, which were associated with nutrient cycling, hydrocarbon degradation and plant productivity. These results enrich our understanding of potential soil nutrient cycling and plant nutrient balance in future agroecosystems.

Differential effects of elevated atmosphere CO2 concentration on root growth in association with regulation of auxin and cytokinins under different nitrate supply

An extensive root system is one of the highly desirable traits for plant growth and adaptation to environmental stresses which is affected by the availability of atmosphere CO 2 and nitrogen (N) nutrition. The objectives of this study were to examine the interactive effects of elevated CO 2 and nitrogen on root growth and underlying regulatory mechanisms related to hormones metabolism in tall fescue ( Festuca arundinacea ). Plants (cv. ‘Barlexas’) were hydroponically grown in nutrient solution with low N (0.25 mM) and moderate N (4 mM) conditions and exposed to ambient CO 2 concentration (400 µmol·mol −1 ) or elevated CO 2 concentration (800 µmol·mol −1 ) for 35 days. Elevated CO 2 differentially promoted root growth under different nitrate levels. The longest root length, root biomass and all types of roots including the length, number, volume and surface area of both crown and lateral roots were enhanced by elevated CO 2 under moderate nitrate but without significant effects on crown root number under low nitrate condition. The extent of elevated CO 2 -promotion on lateral root was greater under moderate nitrate than that under low nitrate condition. The improvement of elevated CO 2 on root growth under moderate nitrate condition was related with increased content of indoleacetic acid (IAA) and isopentenyl adenosine (iPA) through up-regulating genes in auxin synthesis, cytokinin synthesis and down-regulating cytokinin degradation gene. Our results indicated that elevated CO 2 had differential promotive effects on crown and lateral root growth in tall fescue under low and moderate nitrate conditions in association with the regulation of endogenous auxin and cytokinin metabolism. • Elevated CO 2 had differentially positive effects on fibrous root characteristics under different nitrate supply. • Elevated CO 2 -regulated root growth under moderate nitrate was related with the endogenous auxin and cytokinin metabolism. • Elevated CO 2 -induced the higher IAA content was mainly attributed to the up-regulation of IAA synthesis gene. • Elevate CO 2 caused iPA accumulation by the up-regulation of synthesis gene and the down-regulation of degradation gene.

Moderate heat stress prevented the observed biomass and yield stimulation caused by elevated CO2 in two well-watered wheat cultivars

Key messageHeat stress (HS) under well-watered conditions was not detrimental to leaf photosynthesis or yield but modified the elevated CO2 response of photosynthesis and yield in two contrasting wheat cultivars.Climate change is increasing the frequency of extreme events such as heat waves, adversely affecting crop productivity. While positive impacts of elevated carbon dioxide (eCO2) on crop productivity are evident, the interactive effects of eCO2 and environmental stresses are still unclear. To investigate the interactive effects of elevated CO2 and heat stress (HS), we grew two contrasting wheat cultivars, early-maturing Scout and high-tillering Yitpi, under non-limiting water and nutrients at ambient (aCO2, 450 ppm) or elevated (eCO2, 650 ppm) CO2 and 22 °C in the glasshouse. Plants were exposed to two 3-day HS cycles at the vegetative (38.1 °C) and/or flowering (33.5 °C) stage. At aCO2, both wheat cultivars showed similar responses of photosynthesis and mesophyll conductance to temperature and produced similar grain yield. Relative to aCO2, eCO2 enhanced photosynthesis rate and reduced stomatal conductance and maximal carboxylation rate (Vcmax). During HS, high temperature stimulated photosynthesis at eCO2 in both cultivars, while eCO2 stimulated photosynthesis in Scout. Electron transport rate (Jmax) was unaffected by any treatment. eCO2 equally enhanced biomass and grain yield of both cultivars in control, but not HS, plants. HS reduced biomass and yield of Scout at eCO2. Yitpi, the cultivar with higher grain nitrogen, underwent a trade-off between grain yield and nitrogen. In conclusion, eCO2 improved photosynthesis of control and HS wheat, and improved biomass and grain yield of control plants only. Under well-watered conditions, HS was not detrimental to photosynthesis or growth but precluded a yield response to eCO2.

Elevated CO2 and Nitrogen dose affect grain ionome, grain morphology and associated gene expression in wheat (Triticum aestivum L.)

The rise in atmospheric CO2 levels impacts humankind by threatening food and nutritional security. The strong correlation between crop yield and grain weight in cereals is an essential component of yield stability. Further, improving grain protein and mineral nutrient content is a crucial breeding target for cereal crops. The study was performed to understand the interactive effects of elevated CO2 (EC) and nitrogen (N) fertilization on grain ionome, grain yield parameters, grain morphology, and the expression of genes related to grain morphology. The changes in ionome and grain parameters were examined in response to two N levels optimal N (ON: 500 mg/pot) and high N (HN: 625 mg/pot) along with atmospheric CO2 enrichment [ambient (CO2) of 400 ±10 ppm and elevated (CO2) of 700 ±10 ppm]. Grain ionome (N, K, Ca and Fe) showed a general decrease in EC-grown wheat plants. The expression of genes related to grain length (TaGL3 and TaGL7) were upregulated, and those genes related to grain width (TaGW2 and TaGW6) were downregulated under EC in maturing spikelet of wheat. In the case of TaSnRK2, the expression was promoted by EC in HN treatment. The complex regulation of source and sink-associated gene transcript abundance indicates an EC mediated alteration in N and sugar signalling in wheat.

Growth and photosynthetic responses to ozone of Siebold's beech seedlings grown under elevated CO2 and soil nitrogen supply

Ozone (O3) is a phytotoxic air pollutant, the adverse effects of which on growth and photosynthesis are modified by other environmental factors. In this study, we examined the combined effects of O3, elevated CO2, and soil nitrogen supply on Siebold's beech seedlings. Seedlings were grown under combinations of two levels of O3 (low and two times ambient O3 concentration), two levels of CO2 (ambient and 700 ppm), and three levels of soil nitrogen supply (0, 50, and 100 kg N ha−1 year−1) during two growing seasons (2019 and 2020), with leaf photosynthetic traits being determined during the second season. We found that elevated CO2 ameliorated O3-induced reductions in photosynthetic activity, whereas the negative effects of O3 on photosynthetic traits were enhanced by soil nitrogen supply. We observed three-factor interactions in photosynthetic traits, with the ameliorative effects of elevated CO2 on O3-induced reductions in the maximum rate of carboxylation being more pronounced under high than under low soil nitrogen conditions in July. In contrast, elevated CO2-induced amelioration of the effects of O3 on stomatal function-related traits was more pronounced under low soil nitrogen conditions. Although we observed several two- or three-factor interactions of gas and soil treatments with respect to leaf photosynthetic traits, the shoot to root dry mass (S/R) ratio was the only parameter for which a significant interaction was detected among seedling growth parameters. O3 caused a significant increase in S/R under ambient CO2 conditions, whereas no similar effects were observed under elevated CO2 conditions. Collectively, our findings reveal the complex interactive effects of elevated CO2 and soil nitrogen supply on the detrimental effects of O3 on leaf photosynthetic traits, and highlight the importance of taking into consideration differences between the responses of CO2 uptake and growth to these three environmental factors.

Physiological Plasticity of Green Gram Stomata to Photosynthesis Traits under Interactive Effects of Elevated CO2, Drought and Heat Stress

Heat waves and droughts are projected to become more widespread as a result of climate change. At the same time, CO2 levels are predicted to have doubled by 2100. The stomatal regulation and gas exchange characteristics were assessed in 25 days old plants of green gram (var Co 8) by exposing them to six different treatments namely, T1: a [CO2] + a T+ irrigation (100%), T2: a [CO2] + a T+ irrigation (50%), T3: a [CO2] + e T (40ºC) + irrigation (100%), T4: e [CO2] – 800 ppm + a T+ irrigation (100%), T5: a [CO2] + combined stress [e T (40ºC) + irrigation (50%) T6: e [CO2] – 800 ppm + combined stress [e T (40ºC) + irrigation (50%)]. The experiment was carried out using Completely Randomized Design (CRD) with three replications. All gas exchange parameters viz., ((photosynthesis rate, stomatal conductance, and transpiration rate) were determined before imposing stress and two weeks after imposing stress. Stomatal characters was examined two weeks after imposing stress. Elevated CO2 stress caused a reduction in stomatal frequency accompanied by larger stomatal size. The study revealed the positive effect of higher CO2 concentration on gas exchange traits of the C3 crops viz., green gram.

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 thepresence 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.

The direct and interactive effects of elevated CO2 and additional nitrate on relative costs and benefits of legume-rhizobia symbiosis

Rising concentrations of carbon dioxide (CO2) is likely to have important effects on growth and development of plants and on their relationship with symbiotic microbes. A rise in CO2 could increase demand by plant hosts for nutrient resources, which may increase host investments in beneficial symbionts. In the legume-rhizobia mutualism, while elevated CO2 is often associated with increased nodule growth and investment in N2-fixing rhizobia, it is yet unclear if this response depends on the mutualistic quality of the rhizobia. To test if host carbon allocation towards more-beneficial nodules are similar to less-beneficial (but still effective) nodules when plant N demand changes, we manipulated plant C and N status with elevated CO2 and additional nitrate. We used two isogenic Rhizobium etli strains that differ in their ability to synthesize an energy reserve compound, poly-beta-hydroxybutyrate (PHB), as well as their efficiencies for nitrogen fixation and nodulation rates, resulting in two Phaseolus vulgaris host groups with either large number of small nodules or small number of large nodules. The addition of nitrate negatively affected carbon allocation towards nodules, and elevated CO2 reversed this effect, as expected. However, this alleviation of nodule inhibition was greater on plants that started with greater numbers of smaller nodules. If smaller nodules indicate less-efficient or low-fixing rhizobia, this study suggests that increased demand for nitrogen in the face of elevated CO2 has the potential to disproportionately favor less-beneficial strains and increase variation of nitrogen fixation quality among rhizobia.

Divergent terrestrial responses of soil N2O emissions to different levels of elevated CO2 and temperature

Understanding the responses of soil nitrous oxide (N2O) emissions from terrestrial ecosystems to future CO2 enrichment and warming is critical for the development of mitigation and adaptation policies. The effects of continuous increase in elevated CO2 (EC) and elevated temperature (ET) on N2O emissions are not fully known. We synthesized 209 measurements from 70 published studies and carried out a meta‐analysis to examine individual and interactive effects of EC and ET on N2O emissions from grasslands, croplands and forests. On average, a significant increase of 23% in N2O emissions was observed under EC across all case studies. EC did not affect N2O emissions from grasslands or forests, but significantly increased N2O emissions in croplands by 38%. The extent of ET effects on N2O emissions was nonsignificant and there was no significant difference in N2O emission responses among these three terrestrial systems. ET only promoted N2O emissions in forest by about 32% when ET was less than 2°C. The interactive effect of EC and ET on N2O emissions was significantly synergistic, showing a greater increase than the sum of the effects caused by EC and ET alone. Our findings indicated that the combination of EC and ET substantially promoted soil N2O and highlighted the urgent need to explore its mechanisms to better understand N2O responses under future climate change.

Interactive effects of elevated CO2 and nitrogen fertilization levels on photosynthesized carbon allocation in a temperate spring wheat and soil system

Increasing atmospheric CO 2 concentration impacts the terrestrial carbon (C) cycle by affecting plant photosynthesis, the flow of photosynthetically fixed C belowground, and soil C pool turnover. For managed agroecosystems, how and to what extent the interactions between elevated CO 2 and N fertilization levels influence the accumulation of photosynthesized C in crops and the incorporation of photosynthesized C into arable soil are in urgent need of exploration. We conducted an experiment simulating elevated CO 2 with spring wheat ( Triticum aestivum L.) planted in growth chambers. 13 C-enriched CO 2 with an identical 13 C abundance was continuously supplied at ambient and elevated CO 2 concentrations (350 and 600 μmol mol –1 , respectively) until wheat harvest. Three levels of N fertilizer application (equivalent to 80, 120, and 180 kg N ha -1 soil) were supplied for wheat growth at both CO 2 concentrations. During the continuous 62-d 13 CO 2 labeling period, elevated CO 2 and increased N fertilizer application increased photosynthesized C accumulation in wheat by 14%–24% and 11%–20%, respectively, as indicated by increased biomass production, whereas the C/N ratio in the roots increased under elevated CO 2 but declined with increasing N fertilizer application levels. Wheat root deposition induced 1%–2.5% renewal of soil C after 62 d of 13 CO 2 labeling. Compared to ambient CO 2 , elevated CO 2 increased the amount of photosynthesized C incorporated into soil by 20%–44%. However, higher application rates of N fertilizer reduced the net input of root-derived C in soil by approximately 8% under elevated CO 2 . For the wheat-soil system, elevated CO 2 and increased N fertilizer application levels synergistically increased the amount of photosynthesized C. The pivotal role of plants in photosynthesized C accumulation under elevated CO 2 was thereby enhanced in the short term by the increased N application. Therefore, robust N management could mediate C cycling and sequestration by influencing the interactions between plants and soil in agroecosystems under elevated CO 2 .

Composition and activity of nitrifier communities in soil are unresponsive to elevated temperature and CO2, but strongly affected by drought

Nitrification is a fundamental process in terrestrial nitrogen cycling. However, detailed information on how climate change affects the structure of nitrifier communities is lacking, specifically from experiments in which multiple climate change factors are manipulated simultaneously. Consequently, our ability to predict how soil nitrogen (N) cycling will change in a future climate is limited. We conducted a field experiment in a managed grassland and simultaneously tested the effects of elevated atmospheric CO2, temperature, and drought on the abundance of active ammonia-oxidizing bacteria (AOB) and archaea (AOA), comammox (CMX) Nitrospira, and nitrite-oxidizing bacteria (NOB), and on gross mineralization and nitrification rates. We found that N transformation processes, as well as gene and transcript abundances, and nitrifier community composition were remarkably resistant to individual and interactive effects of elevated CO2 and temperature. During drought however, process rates were increased or at least maintained. At the same time, the abundance of active AOB increased probably due to higher NH4+ availability. Both, AOA and comammox Nitrospira decreased in response to drought and the active community composition of AOA and NOB was also significantly affected. In summary, our findings suggest that warming and elevated CO2 have only minor effects on nitrifier communities and soil biogeochemical variables in managed grasslands, whereas drought favors AOB and increases nitrification rates. This highlights the overriding importance of drought as a global change driver impacting on soil microbial community structure and its consequences for N cycling.

Carbon dioxide elevation combined with sufficient irrigation and nitrogen fertilization improves fruit quality of tomato grown in glasshouse

ABSTRACT To investigate the interactive effects of elevated CO2 (e[CO2]), nitrogen (N) supply and irrigation regimes on tomato (Solanum lycopersicum L., cv. Elin) yield, water use efficiency (WUE) and fruit quality, potted plants were grown in glasshouse compartments with CO2 concentration of 400 and 800 ppm, separately, with 0 or 0.5 g N kg−1 soil. Since anthesis, the plants were subjected to three irrigation levels (I1, I2 and I3 – irrigated to 35% soil water content (SWC, v/v), 30% SWC and 25% SWC, respectively). e[CO2] had a slight effect on fruit yield and sugar, acid, soluble solids content (SSC) and total antioxidant capacity (TAC) in fruit juice, while it enhanced Mn, B and Fe contents in fruit biomass. WUE was improved by e[CO2] and I3 irrigation, but reduced by N supply. Though N supply lowered SSC, TAC, K+, Ca2+ and Mg2+ in fruit juice, it increased micro-nutrient (Mn, Mo, Cu, Zn, Fe) contents in fruit biomass. Most notably, principal component analysis revealed the best comprehensive quality of tomato fruits was found for plants grown under e[CO2] with sufficient irrigation and N supply, suggesting optimal irrigation and N fertilization are essential for good tomato quality in glasshouse production under CO2-enriched environment.

Interactive effects of elevated CO2 and neighbourhood competition on the radial growth of European beech (Fagus sylvatica L.) seedlings

This paper explores the effects of three types of admixture treatments: (1) monospecific (M: European beech surrounded by six European beech seedlings), (2) single-admixture (S: European beech surrounded by six Norway spruce seedlings), and (3) group-admixture (G: European beech surrounded by three Norway spruce and three European beech seedlings), and two different CO2 concentrations ([CO2]): ambient [AMBCO2, 385 μmol (CO2) mol−1] and elevated [ELECO2, 770 μmol (CO2) mol−1] on the stem diameter increment (DI), based on a 7-year monitoring of the diameter growth of European beech (Fagus sylvatica L.) seedlings. Furthermore, to improve our understanding of the influence of climatic variables, we assessed the effects of precipitation and temperature on radial growth. After 7 years’ experience (irrespective of admixture treatment), our data were not able to confirm the effect of elevated CO2 on the diameter growth (p value = 0.35), but the result was changed when the effect of elevated CO2 was considered under the different types of admixture. Elevated CO2 along with single-admixture increased the diameter increment significantly (p value = 0.001). In contrast, we characterized a significant effect of AMBCO2 × G interaction on DI (p value = 0.002). But DI was unaffected by elevated CO2 in M (p value = 0.77). In both [CO2], inter-specific competition with spruce resulted in the highest radial growth. The inter-specific interaction was most pronounced in the lower proportion with spruce (S) in ELECO2, while in ambient CO2, the higher proportion with spruce (G) had the greatest effect on the radial growth. With respect to the climatic factors, our observations showed that temperature had a stronger influence than precipitation in ELECO2, but in AMBCO2, precipitation had the strongest effect on the radial growth as indicated by the statistically significant correlation between climatic variables and radial growth. Overall, our result suggested that seedlings growth was more under the control of climate and edaphic factors than dependent on tree species diversity and CO2 concentrations.

Hypoxia aggravates the effects of ocean acidification on the physiological energetics of the blue mussel Mytilus edulis.

Apart from ocean acidification, hypoxia is another stressor to marine organisms, especially those in coastal waters. Their interactive effects of elevated CO2 and hypoxia on the physiological energetics in mussel Mytilus edulis were evaluated. Mussels were exposed to three pH levels (8.1, 7.7, 7.3) at two dissolved oxygen levels (6 and 2 mg L-1) and clearance rate, absorption efficiency, respiration rate, excretion rate, scope for growth and O: N ratio were measured during a14-day exposure. After exposure, all parameters (except excretion rate) were significantly reduced under low pH and hypoxic conditions, whereas excretion rate was significantly increased. Additive effects of low pH and hypoxia were evident for all parameters and low pH appeared to elicit a stronger effect than hypoxia (2.0 mg L-1). Overall, hypoxia can aggravate the effects of acidification on the physiological energetics of mussels, and their populations may be diminished by these stressors.

Proteomic Profiling for Metabolic Pathways Involved in Interactive Effects of Elevated Carbon Dioxide and Nitrogen on Leaf Growth in a Perennial Grass Species

Elevated atmospheric CO2 and nitrogen are major environmental factors affecting shoot growth. The objectives of this study are to determine the interactive effects of elevated CO2 and nitrogen on leaf growth in tall fescue ( Festuca arundinacea) and to identify major proteins and associated metabolic pathways underlying CO2-regulation of leaf growth under insufficient and sufficient nitrate conditions using proteomic analysis. Plants of tall fescue treated with low nitrate level (0.25 mM, LN), moderate nitrate level (4 mM, MN) and high nitrate level (32 mM, HN) were exposed to ambient (400 μmol mol-1) and elevated (800 μmol mol-1) CO2 concentrations in environment-controlled growth chambers. Increased atmospheric CO2 concentration increased leaf length and shoot biomass, which corresponded to increased content of indo-acetic acid, gibberellic acid, cytokinins and reduced content of abscisic acid under sufficient nitrate conditions (MN and HN conditions). Low nitrate supply limited shoot growth and hormonal responses to elevated CO2. Proteomic analysis of plants exposed to elevated CO2 under LN and MN conditions demonstrated the increases in the abundance of many proteins due to elevated CO2 under MN condition involved with cell cycle and proliferation, transcription and translation, photosynthesis (ribosomal and chlorophyll a/b-binding proteins), amino acids synthesis, sucrose and starch metabolism, as well as ABA signaling pathways (ABA-induced proteins). Our results revealed major proteins and associated metabolic pathways associated with the interactive effects of elevated CO2 and nitrate regulating leaf growth in a perennial grass species.

Elevated atmospheric CO2 might increase the health risk of long-term ingestion of leafy vegetables cultivated in residual DDT polluted soil

Residual dichlorodiphenyltrichloroethane (DDT) in the environment and a continuously increasing atmospheric carbon dioxide (CO2) concentration are two issues that have received a lot of attention. This study was conducted using a pot experiment to investigate the interactive effects of elevated CO2 and DDT on the uptake of DDT, the physiological responses and the resulting health risks in three vegetables. These vegetables included Brassica juncea var. foliosa Bailey (B. Bailey), Brassica campestris L. var. communis Tsen et Lee Suzhou Qing (B. Lee) and Brassica campestris L. ssp. pekinensis (Lour.) Olsson Chun Dawang (B. Olsson). Two levels of CO2 and four DDT treatment levels were set up. Results showed 5 mg kg−1 DDT significantly reduced the shoot biomass of B. Bailey when compared to 0 mg kg−1 DDT treatment under ambient CO2 condition. Elevated CO2 concentration stimulated the growth of B. Bailey and B. Lee, increased the DDT uptake in the shoots of both vegetables and the values of some photosynthesis indices, and triggered the activity of peroxidase and catalase in the shoots when compared to the related ambient CO2 treatment. Elevated CO2 concentration increased the values of hazard indexes for non-carcinogenic and cancer risks of all vegetables when compared to the individual ambient CO2 treatment (each of vegetable has an ambient CO2 treatment), especially for B. Bailey (increase amplitude of 123.81%–127.78% at 5 mg kg−1 DDT). Long-term ingestion with these DDT-polluted vegetables might result in an elevated carcinogenic risk and elevated atmospheric CO2 may enhance the non-carcinogenic and carcinogenic risks.

Stomatal movements are involved in elevated CO2 -mitigated high temperature stress in tomato.

Climate changes such as heat waves often affect plant growth and pose a growing threat to natural and agricultural ecosystems. Elevated atmospheric CO2 can mitigate the negative effects of heat stress, but the underlying mechanisms remain largely unclear. We examined the interactive effects of elevated CO2 (eCO2 ) and temperature on the generation of the hydrogen peroxide (H2 O2 ) and stomatal movement characteristics associated with heat tolerance in tomato seedlings grown under two CO2 concentrations (400 and 800 µmol mol-1 ) and two temperatures (25 and 42°C). eCO2 ameliorated the negative effects of heat stress, which was accompanied by greater amounts of RESPIRATORY BURST OXIDASE 1 (RBOH1) transcripts, apoplastic H2 O2 accumulation and decreased stomatal aperture. Silencing RBOH1 and SLOW-TYPE ANION CHANNEL, impeded eCO2 -induced stomatal closure and compromised the eCO2 -enhanced water use efficiency as well as the heat tolerance. Our findings suggest that RBOH1-dependent H2 O2 accumulation was involved in the eCO2 -induced stomatal closure, which participate in maintaining balance between water retention and heat loss under eCO2 concentrations. This phenomenon may be a contributor to eCO2 -induced heat tolerance in tomato, which will be critical for understanding how plants respond to both future climate extremes and changes in CO2 .

Effects of elevated CO2 and endophytic bacterium on photosynthetic characteristics and cadmium accumulation in Sedum alfredii

Elevated CO2 and use of endophytic microorganisms have been considered as efficient and novel ways to improve phytoextraction efficiency. However, the interactive effects of elevated CO2 and endophytes on hyperaccumulator is poorly understood. In this study, a hydroponics experiment was conducted to investigate the combined effect of elevated CO2 (eCO2) and inoculation with endophyte SaMR12 (ES) on the photosynthetic characteristics and cadmium (Cd) accumulation in hyperaccumulator Sedum alfredii. The results showed that eCO2 × ES interaction promoted the growth of S. alfredii, shoot and root biomass net increment were increased by 264.7 and 392.3%, respectively, as compared with plants grown in ambient CO2 (aCO2). The interaction of eCO2 and ES significantly (P < 0.05) increased chlorophyll content (53.2%), Pn (111.6%), Pnmax (59.8%), AQY (65.1%), and Lsp (28.8%), but reduced Gs, Tr, Rd, and Lcp. Increased photosynthetic efficiency was associated with higher activities of rubisco, Ca2+-ATPase, and Mg2+-ATPase, and linked with over-expression of two photosystem related genes (SaPsbS and SaLhcb2). PS II activities were significantly (P < 0.05) enhanced with Fv/Fm and Φ(II) increased by 12.3 and 13.0%, respectively, compared with plants grown in aCO2. In addition, the net uptake of Cd in the shoot and root tissue of S. alfredii grown in eCO2 × ES treatment was increased by 260.7 and 434.9%, respectively, due to increased expression of SaHMA2 and SaCAX2 Cd transporter genes. Our results suggest that eCO2 × ES can promote the growth of S. alfredii due to increased photosynthetic efficiency, and improve Cd accumulation and showed considerable potential of improving the phytoextraction ability of Cd by S. alfredii.