Effects Of Elevated CO2 Research Articles

Consistent responses of vegetation gas exchange to elevated atmospheric CO2emerge from heuristic and optimization models

Abstract. Elevated atmospheric CO2 concentration is expected to increase leaf CO2 assimilation rates, thus promoting plant growth and increasing leaf area. It also decreases stomatal conductance, allowing water savings, which have been hypothesized to drive large-scale greening, in particular in arid and semiarid climates. However, the increase in leaf area could reduce the benefits of elevated CO2 concentration through soil water depletion. The net effect of elevated CO2 on leaf- and canopy-level gas exchange remains uncertain. To address this question, we compare the outcomes of a heuristic model based on the Partitioning of Equilibrium Transpiration and Assimilation (PETA) hypothesis and three model variants based on stomatal optimization theory. Predicted relative changes in leaf- and canopy-level gas exchange rates are used as a metric of plant responses to changes in atmospheric CO2 concentration. Both model approaches predict reductions in leaf-level transpiration rate due to decreased stomatal conductance under elevated CO2, but negligible (PETA) or no (optimization) changes in canopy-level transpiration due to the compensatory effect of increased leaf area. Leaf- and canopy-level CO2 assimilation is predicted to increase, with an amplification of the CO2 fertilization effect at the canopy level due to the enhanced leaf area. The expected increase in vapour pressure deficit (VPD) under warmer conditions is generally predicted to decrease the sensitivity of gas exchange to atmospheric CO2 concentration in both models. The consistent predictions by different models that canopy-level transpiration varies little under elevated CO2 due to combined stomatal conductance reduction and leaf area increase highlight the coordination of physiological and morphological characteristics in vegetation to maximize resource use (here water) under altered climatic conditions.

Physiological and Antioxidant Response to Different Water Deficit Regimes of Flag Leaves and Ears of Wheat Grown under Combined Elevated CO2 and High Temperature.

Triticum aestivum L. cv. Gazul is a spring wheat widely cultivated in Castilla y León (Spain). Potted plants were grown in a scenario emulating the climate change environmental conditions expected by the end of this century, i.e., with elevated CO2 and high temperature under two water deficit regimes: long (LWD) and terminal (TWD). Changes in biomass and morphology, the content of proline (Pro), ascorbate (AsA) and glutathione (GSH), and enzymatic antioxidant activities were analyzed in flag leaves and ears. Additionally, leaf gas exchange was measured. LWD caused a decrease in biomass and AsA content but an increase in Pro content and catalase and GSH reductase activities in flag leaves, whereas TWD produced no significant changes. Photosynthesis was enhanced under both water deficit regimes. Increase in superoxide dismutase activity and Pro content was only observed in ears under TWD. The lack of a more acute effect of LWD and TWD on both organs was attributed to the ROS relieving effect of elevated CO2. Gazul acted as a drought tolerant variety with anisohydric behavior. A multifactorial analysis showed better adaptation of ears to water deficit than flag leaves, underlining the importance of this finding for breeding programs to improve grain yield under future climate change.

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.

Limited mitigating effects of elevated CO2 in young aspen trees to face drought stress

Elevated atmospheric CO 2 concentration (eCO 2 ) is expected to mitigate the adverse effects of moderate drought on leaf and whole-tree functioning. However, tree responses to eCO 2 under severe drought and throughout the growing season remain largely unknown. One-year-old Populus tremula L. trees were grown in two controlled treatment chambers under ambient and elevated CO 2 conditions, while progressive drought was imposed early (spring/summer 2019) and late (summer/autumn 2018) during the growing season. Leaf level responses to eCO 2 (i.e., stomatal conductance, leaf carbon assimilation and leaf respiration) were monitored in concert with whole-tree level responses (i.e., canopy conductance, radial stem growth, stem CO 2 efflux, xylem water potential and non-structural carbohydrates (NSC)). At the leaf level, eCO 2 lowered the drought susceptibility of stomatal closure and delayed drought-induced reduction in leaf carbon assimilation during late season drought, but these responses were not observed during the early season drought. Drought effects on whole-tree functioning and NSC depletion remained unaltered by eCO 2 . Under moderate drought, stem volumetric growth ceased earlier than photosynthesis, while leaf and stem respiratory metabolism were maintained at 30 % of well-watered levels even under severe drought, independent of the CO 2 treatment and timing of drought. Therefore, the ability of eCO 2 to mitigate drought was mainly limited to leaf processes during the late season and under moderate drought (> − 2 MPa), while drought offset any beneficial effect of eCO 2 at the whole-tree level. These results urge us to revisit predictions of forests' potential to sequester carbon under climate change scenarios. • Mitigating effects of elevated CO 2 under drought are limited in young Populus trees. • Elevated CO 2 mitigates drought at the leaf level, while whole-tree processes remain unaffected. • Mitigating effects of elevated CO 2 were limited to a late-season drought event.

Elevated CO2 Could Reduce Spikelet Fertility and Grain Appearance Quality of Rice(Oryza sativa L.) Grown under High-temperature Conditions

Two Japanese rice cultivars with different heat-tolerance, Hinohikari (sensitive) and Nikomaru (tolerant), were grown in pots inside open-top chambers and exposed to ambient CO2 (400 µmol mol−1) or elevated CO2 (550 µmol mol−1) from the beginning of the tillering stage to maturity. The study was conducted in Nagasaki, in the Kyushu region of Japan, where heat stress on rice has become increasingly evident. Although elevated CO2 significantly improved the net photosynthesis and whole-plant growth of the cultivars, there were no significant effects on grain yield, which in turn reduced harvest index. In both cultivars, adverse effects occurred with elevated CO2, such as reductions in spikelet fertility and grain appearance quality, which are typical manifestations of heat stress in rice. During the flowering period, the air temperature was high that spikelet fertility was reduced even under ambient CO2 conditions for both cultivars. These results suggest that, under high-temperature conditions, elevated CO2 could induce or exacerbate the manifestations of heat stress in rice. Because transpiration rate in the flag leaf was significantly reduced by the exposure to elevated CO2, it is possible that elevated CO2 increased plant temperature via a reduction in transpiration during flowering period, although we did not detect significance of the increase in leaf and panicle temperature. To ensure a more confident conclusion, further studies focusing on the effects of elevated CO2 on the determinants of spikelet fertility and grain appearance quality with other cultivars in different year are required.

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.

Effects of drought stress and elevated CO2 on starch fine structures and functional properties in indica rice

The changes in rice starch fine structures and functional properties induced by drought, elevated CO2 (eCO2) and combined treatments remain to be elucidated comprehensively. In this study, starch molecular structures were characterized by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis, and the data from amylopectin chain-length distributions was fitted with a mathematical model to obtain parameters for statistical analysis. Starch crystalline structures, thermal and pasting properties of rice flour were also analyzed. All the treatments decreased the seed setting rate and increased chalky grains, reflecting the abnormal starch accumulation. However, eCO2 partially increased the seed setting rate and chalky grains under drought stress. The stress-treated starch samples had shorter amylopectin short and intermediate chains, the lower degree of ordered structures, but similar amylose content and relative crystallinity. This led to lower onset gelatinization temperature and paste viscosities, which may be responsible for the worse sensory quality of rice grains.

A global meta-analysis of woody plant responses to elevated CO2: implications on biomass, growth, leaf N content, photosynthesis and water relations

BackgroundAtmospheric CO2 may double by the year 2100, thereby altering plant growth, photosynthesis, leaf nutrient contents and water relations. Specifically, atmospheric CO2 is currently 50% higher than pre-industrial levels and is projected to rise as high as 936 μmol mol−1 under worst-case scenario in 2100. The objective of the study was to investigate the effects of elevated CO2 on woody plant growth, production, photosynthetic characteristics, leaf N and water relations.MethodsA meta-analysis of 611 observations from 100 peer-reviewed articles published from 1985 to 2021 was conducted. We selected articles in which elevated CO2 and ambient CO2 range from 600–1000 and 300–400 μmol mol−1, respectively. Elevated CO2 was categorized into < 700, 700 and > 700 μmol mol−1 concentrations.ResultsTotal biomass increased similarly across the three elevated CO2 concentrations, with leguminous trees (LTs) investing more biomass to shoot, whereas non-leguminous trees (NLTs) invested to root production. Leaf area index, shoot height, and light-saturated photosynthesis (Amax) were unresponsive at < 700 μmol mol−1, but increased significantly at 700 and > 700 μmol mol−1. However, shoot biomass and Amax acclimatized as the duration of woody plants exposure to elevated CO2 increased. Maximum rate of photosynthetic Rubisco carboxylation (Vcmax) and apparent maximum rate of photosynthetic electron transport (Jmax) were downregulated. Elevated CO2 reduced stomatal conductance (gs) by 32% on average and increased water use efficiency by 34, 43 and 63% for < 700, 700 and > 700 μmol mol−1, respectively. Leaf N content decreased two times more in NLTs than LTs growing at elevated CO2 than ambient CO2.ConclusionsOur results suggest that woody plants will benefit from elevated CO2 through increased photosynthetic rate, productivity and improved water status, but the responses will vary by woody plant traits and length of exposure to elevated CO2.

Effects of Elevated CO2 Levels on the Growth and Yield of Summer-Grown Cucumbers Cultivated under Different Day and Night Temperatures

The effects of elevated CO2 (eCO2) levels on field-grown cucumbers have been extensively studied. However, the variations in photosynthate accumulation in summer-grown cucumbers simultaneously exposed to eCO2 and varying day-night temperatures (DNF) still remain unexplored. This study aimed to investigate the effects of DNF different CO2 conditions [ambient CO2 (aCO2; 400–600 μmol mol−1) and eCO2 (800–1000 μmol mol−1)] on dry matter production and dry matter distribution in summer-grown cucumbers under two DNF treatments (35/10 °C and 25/20 °C, day/night). We observed that long-term eCO2 exposure increased C assimilation and photosynthate accumulation in leaves, resulting in feedback inhibition of the leaf area. Under both DNF treatments, the total dry matter distribution to fruits under eCO2 conditions was approximately 15% higher than that under aCO2 conditions. Furthermore, soluble sugar content and C:N ratio increased with long-term eCO2 exposure, indicating increased C allocation, photosynthate accumulation, and distribution. However, low night temperatures (LT) inhibited respiration and increased dry matter accumulation by 30% under eCO2 conditions. Additionally, eCO2 increased fruit fresh weight by 8% and 12% under both DNF treatments compared to aCO2. This suggests that long-term eCO2 exposure and varying DNF exhibited different effects through different metabolic mechanisms on cucumber growth at high temperatures. eCO2 conditions probably increased dry matter distribution to improve fruit quality, and LT treatment altered the respiration rate to restore photosynthesis, thereby increasing photosynthate distribution to fruits. Therefore, a combination of CO2 enrichment and DNF can be used to improve fruit quality and yield at high temperatures.

Trading water for carbon in the future: Effects of elevated CO2 and warming on leaf hydraulic traits in a semiarid grassland.

The effects of climate change on plants and ecosystems are mediated by plant hydraulic traits, including interspecific and intraspecific variability of trait phenotypes. Yet, integrative and realistic studies of hydraulic traits and climate change are rare. In a semiarid grassland, we assessed the response of several plant hydraulic traits to elevated CO2 (+200 ppm) and warming (+1.5 to 3°C; day to night). For leaves of five dominant species (three graminoids and two forbs), and in replicated plots exposed to 7 years of elevated CO2, warming, or ambient climate, we measured: stomatal density and size, xylem vessel size, turgor loss point, and water potential (pre‐dawn). Interspecific differences in hydraulic traits were larger than intraspecific shifts induced by elevated CO2 and/or warming. Effects of elevated CO2 were greater than effects of warming, and interactions between treatments were weak or not detected. The forbs showed little phenotypic plasticity. The graminoids had leaf water potentials and turgor loss points that were 10% to 50% less negative under elevated CO2; thus, climate change might cause these species to adjust their drought resistance strategy away from tolerance and toward avoidance. The C4 grass also reduced allocation of leaf area to stomata under elevated CO2, which helps explain observations of higher soil moisture. The shifts in hydraulic traits under elevated CO2 were not, however, simply due to higher soil moisture. Integration of our results with others' indicates that common species in this grassland are more likely to adjust stomatal aperture in response to near‐term climate change, rather than anatomical traits; this contrasts with apparent effects of changing CO2 on plant anatomy over evolutionary time. Future studies should assess how plant responses to drought may be constrained by the apparent shift from tolerance (via low turgor loss point) to avoidance (via stomatal regulation and/or access to deeper soil moisture).

Heat wave event facilitates defensive responses in invasive C3 plant Ambrosia artemisiifolia L. under elevated CO2 concentration to the detriment of Ophraella communa.

To predict and mitigate the effects of climate change on communities and ecosystems, the joint effects of extreme climatic events on species interactions need to be understood. Using the common ragweed (Ambrosia artemisiifolia L.)—leaf beetle (Ophraella communa) system, we investigated the effects of heat wave and elevated CO2 on common ragweed growth, secondary metabolism, and the consequent impacts on the beetle. The results showed that elevated CO2 and heat wave facilitated A. artemisiifolia growth; further, A. artemisiifolia accumulated large amounts of defensive secondary metabolites. Being fed on A. artemisiifolia grown under elevated CO2 and heat wave conditions resulted in the poor performance of O. communa (high mortality, long development period, and low reproduction). Overall, under elevated CO2, heat wave improved the defensive ability of A. artemisiifolia against herbivores. On the other hand, enhanced adaptability to climatic changes may aggravate invasive plant distribution, posing a challenge to the control of invasive plants in the future.

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 Reciprocal Effect of Elevated CO2 and Drought on Wheat-Aphid Interaction System

Due to the rising concentration of atmospheric CO2, climate change is predicted to intensify episodes of drought. However, our understanding of how combined environmental conditions, such as elevated CO2 and drought together, will influence crop-insect interactions is limited. In the present study, the direct effects of combined elevated CO2 and drought stress on wheat (Triticum aestivum) nutritional quality and insect resistance, and the indirect effects on the grain aphid (Sitobion miscanthi) performance were investigated. The results showed that, in wheat, elevated CO2 alleviated low water content caused by drought stress. Both elevated CO2 and drought promoted soluble sugar accumulation. However, opposite effects were found on amino acid content—it was decreased by elevated CO2 and increased by drought. Further, elevated CO2 down-regulated the jasmonic acid (JA) -dependent defense, but up-regulated the salicylic acid (SA)-dependent defense. Meanwhile, drought enhanced abscisic acid accumulation that promoted the JA-dependent defense. For aphids, their feeding always induced phytohormone resistance in wheat under either elevated CO2 or drought conditions. Similar aphid performance between the control and the combined two factors were observed. We concluded that the aphid damage suffered by wheat in the future under combined elevated CO2 and drier conditions tends to maintain the status quo. We further revealed the mechanism by which it happened from the aspects of wheat water content, nutrition, and resistance to aphids.

The effect of ocean acidification on the escape behaviour of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar

Ocean acidification (OA) driven by sea water uptake of anthropogenic atmospheric CO2 has broad deleterious effects on marine species including modified behavioural interactions such as between predators and prey. Predatory sea stars are key species in many marine ecosystems and often elicit defensive responses in their prey. This study investigated the effect of elevated CO2 on the escape response of the sea star Parvulastra exigua to its sea star predator Meridiastra calcar. In response to touch by M. calcar, P. exigua exhibits a distinct fleeing response. The escape response of P. exigua with respect to velocity and escape trajectory was investigated after both species were acclimated in OA conditions. At pHT 7.6 and 7.8 velocity and escape trajectory of the fleeing response of P. exigua did not differ from that seen in the ambient treatment. However, there was a delay in the time that P. exigua started to flee with the initiation time being 2.8 times slower (10 vs 28 s) at pHT 7.6. This delay may increase the vulnerability of P. exigua to predation by M. calcar and have ecological effects with respect to the role of this species as an algal grazer on rocky shores of southeast Australia where these sea star species co-occur.

Effects of anthropogenic nitrogen additions and elevated CO2 on microbial community, carbon and nitrogen content in a replicated wetland.

Anthropogenic deposition of nitrogen (N) and elevated CO2 (eaCO2) are expected to increase continuously and rapidly in the near future and influence global carbon cycling. These parameters affect the ecosystem by regulating the microbial community and contribute to soil organic matter decomposition. The study was performed to understand the effects of N additions (4 and 6mgl-1) and eaCO2 (700ppm) on carbon (C)/nitrogen (N) content in the soil, microbial community, and plant biomass (Alternanthera philoxeroides species). The results showed that when the atmospheric CO2 concentration was raised, the total organic carbon (TOC) in the soil statistically increased (P < 0.05) by 4% and 3% under low and high N additions respectively, while the inorganic carbon content also increased by 1% and 3% (P > 0.05) under the same conditions. The increase in the soil TOC content was a result of the movement of carbon from water to the soil due to the presence of vascular tissues of plants in the water. The redundancy analysis (RDA) results revealed that the presence of plant species was responsible for the carbon content increment in the soil. The plant biomass content increased by 30.96% (P = 0.081) and 31.36%, (P = 0.002) under low and high N addition respectively due to the increment in atmospheric CO2. The nitrogen content in the plant species decreased (p > 0.05) by 8.62% and 6.25% at low and high N addition respectively when atmospheric CO2 was raised. This suggests that soil microbes competed with the plants for inorganic nitrogen in the soil and the microbes used up the inorganic nitrogen before it got to the plants. The gram-positive bacteria and fungi population decreased under high N addition and eaCO2 while gram-negative bacteria increased, suggesting that N additions and eaCO2 affected the microbial function and correlated with the nitrogen reduction in the soil. The results from this study serve as a guide to researchers and stakeholders in making policies with regard to the constant increasing CO2 concentration in the atmosphere.

Preference of carbon absorption determines the competitive ability of algae along atmospheric CO2 concentration.

Although many studies have focused on the effects of elevated atmospheric CO2 on algal growth, few of them have demonstrated how CO2 interacts with carbon absorption capacity to determine the algal competition at the population level. We conducted a pairwise competition experiment of Phormidium sp., Scenedesmus quadricauda, Chlorella vulgaris and Synedra ulna. The results showed that when the CO2 concentration increased from 400 to 760 ppm, the competitiveness of S. quadricauda increased, the competitiveness of Phormidium sp. and C. vulgaris decreased, and the competitiveness of S. ulna was always the lowest. We constructed a model to explore whether interspecific differences in affinity and flux rate for CO2 and HCO3 − could explain changes in competitiveness between algae species along the gradient of atmospheric CO2 concentration. Affinity and flux rates are the capture capacity and transport capacity of substrate respectively, and are inversely proportional to each other. The simulation results showed that, when the atmospheric CO2 concentration was low, species with high affinity for both CO2 and HCO3 − (HCHH) had the highest competitiveness, followed by the species with high affinity for CO2 and low affinity for HCO3 − (HCLH), the species with low affinity for CO2 and high affinity for HCO3 − (LCHH) and the species with low affinity for both CO2 and HCO3 − (LCLH); when the CO2 concentration was high, the species were ranked according to the competitive ability: LCHH > LCLH > HCHH > HCLH. Thus, low resource concentration is beneficial to the growth and reproduction of algae with high affinity. With the increase in atmospheric CO2 concentration, the competitive advantage changed from HCHH species to LCHH species. These results indicate the important species types contributing to water bloom under the background of increasing global atmospheric CO2, highlighting the importance of carbon absorption characteristics in understanding, predicting and regulating population dynamics and community composition of algae.

CO2 -induced biochemical changes in leaf volatiles decreased fire-intensity in the run-up to the Triassic-Jurassic boundary.

Summary The Triassic–Jurassic boundary marks the third largest mass extinction event in the Phanerozoic, characterized by a rise in CO2‐concentrations from c. 600 ppm to c. 2100–2400 ppm, coupled with a c. 3.0–4.0°C temperature rise. This is hypothesized to have induced major floral turnover, altering vegetation structure, composition and leaf morphology, which in turn are hypothesized to have driven changes in wildfire. However, the effects of elevated CO2 on fuel properties, such as chemical composition of leaves, are also important in influencing fire behaviour, but yet have not been considered.We test this by selecting three Triassic analogue species grown experimentally in different atmospheric compositions, and analyse variations in leaf chemistry, and leaf level flammability. These data were used to inform a fire behaviour model.We find that all three species tested showed a reduction in their volatile component, leading to lower flammability. Accounting for these variations in a model, our results suggest that leaf intrinsic flammability has a measurable impact on modelled fire behaviour.If scaled up to ecosystem level, periods of elevated CO2 may therefore be capable of inducing both biochemical and morphological changes in fuel properties, and thus may be capable of influencing fire behaviour.

Transgenerational effects of elevated CO2 on rice photosynthesis and grain yield.

Transgenerational effects of elevated CO2 on rice photosynthesis and grain yield.

Impact of Future Elevated Carbon Dioxide on C3 Plant Resistance to Biotic Stresses.

Before the end of the century, atmospheric carbon dioxide levels are predicted to increase to approximately 900 ppm. This will dramatically affect plant physiology and influence environmental interactions and, in particular, plant resistance to biotic stresses. This review is a broad survey of the current research on the effects of elevated CO2 (eCO2) on phytohormone-mediated resistance of C3 agricultural crops and related model species to pathogens and insect herbivores. In general, while plants grown in eCO2 often have increased constitutive and induced salicylic acid levels and suppressed induced jasmonate levels, there are exceptions that implicate other environmental factors, such as light and nitrogen fertilization in modulating these responses. Therefore, this review sets the stage for future studies to delve into understanding the mechanistic basis behind how eCO2 will affect plant defensive phytohormone signaling pathways under future predicted environmental conditions that could threaten global food security to inform the best agricultural management practices.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Elevated CO2 Altered Rice VOCs Aggravate Population Occurrence of Brown Planthoppers by Improving Host Selection Ability.

Simple SummaryIn recent years, the atmospheric CO2 concentration was increasing continuously, which has led to the change in the photosynthesis and chemical composition of rice plants. The growth and development of brown planthopper (BPH) Nilaparvata lugens are further affected. Plants release volatile organic compounds (VOCs) to mediate intra- and inter-specific interactions with other organisms in the surrounding environment. Therefore, here we aim to explore the effect of rice VOCs on the host selection ability of BPH under elevated CO2. Among the identified thirty-six rice VOCs, the contents of heptadecane, linalool and limonene from rice plants were significantly decreased under elevated CO2. Moreover, we found that the VOCs of rice damaged by BPH were also changed. Undecane, hexadecane, nonanal and 2,6-diphenylphenol from BPH-damaged rice plants under elevated CO2 were all significantly higher than those from healthy rice plants, which might lead to enhancement of the host selection ability of BPH, eventually aggravating the damage caused by BPH. However, the role of these VOCs in host selection ability of BPH is not clear, and more experiments are needed to verify their function.It is predicted that plant volatile organic compounds (VOCs) are affected by the atmospheric CO2 levels rising globally, which further affects the interaction between plants and herbivorous insects, especially the host selection behavior of herbivorous insects. In this study, the effects of elevated CO2 on the host-selection behavior of the brown planthopper (BPH) Nilaparvata lugens, and the emission of VOCs from the healthy and BPH-damaged rice plants were studied simultaneously to make clear the population occurrence of BPH under global climate change. Compared with ambient CO2, elevated CO2 significantly increased the host selection percent of BPH for the healthy (CK) and BPH-damaged rice plants, and the host selection percent of BPH for the BPH-damaged rice plants was significantly higher than that for the healthy rice plants under elevated CO2, which might be regulated by the transcription levels of OBP1, OBP2 and CSP8 in BPH due to the upregulated transcriptional levels of these three genes of BPH under elevated CO2. In addition, we analyzed and quantified the emission of VOCs in rice plants grown under ambient CO2 and elevated CO2 by GS-MS. A total of 36 VOCs from rice plants were identified into eight categories, including alkanes, alkenes, alcohols, aldehydes, ketones, esters, phenols and aromatic hydrocarbons. Elevated CO2 significantly decreased the contents of heptadecane, linalool and limonene from rice plants compared with ambient CO2. Besides, the contents of linalool, phytol, decanal, 1-methyldecalin and 2,6-diphenylphenol from BPH-damaged rice plants under ambient CO2, and undecane, hexadecane, nonanal and 2,6-diphenylphenol from BPH-damaged rice plants under elevated CO2 were all significantly higher than those from healthy rice plants. The percentage composition of phenols was positively correlated with the host selection rate of BPH. Our study indicates that elevated CO2 is beneficial to promote the host selection ability of BPH for rice plants damaged by BPHs due to the changed plant VOCs.