Effects Of Elevated CO2 Concentration Research Articles

Evaluation of potential increase in photosynthetic efficiency of cassava (Manihot esculenta Crantz) plants exposed to elevated carbon dioxide.

Cassava (Manihot esculenta Crantz), an important tropical crop, is affected by extreme climatic events, including rising CO2 levels. We evaluated the short-term effect of elevated CO2 concentration (ECO2 ) (600, 800 and 1000ppm) on the photosynthetic efficiency of 14 cassava genotypes. ECO2 significantly altered gaseous exchange parameters (net photosynthetic rate (P n ), stomatal conductance (g s ), intercellular CO2 (C i ) and transpiration (E )) in cassava leaves. There were significant but varying interactive effects between ECO2 and varieties on these physiological characteristics. ECO2 at 600 and 800ppm increased the P n rate in the range of 13-24% in comparison to 400ppm (ambient CO2 ), followed by acclimation at the highest concentration of 1000ppm. A similar trend was observed in g s and E . Conversely, C i increased significantly and linearly across increasing CO2 concentration. Along with C i , a steady increase in water use efficiency [WUEintrinsic (P n /g s ) and WUEinstantaneous (P n /E )] across various CO2 concentrations corresponded with the central role of restricted stomatal activity, a common response under ECO2 . Furthermore, P n had a significant quadratic relationship with the ECO2 (R 2 =0.489) and a significant and linear relationship with C i (R 2 =0.227). Relative humidity and vapour pressure deficit during the time of measurements remained at 70-85% and ~0.9-1.31kPa, respectively, at 26±2°C leaf temperature. Notably, not a single variety exhibited constant performance for any of the parameters across CO2 concentrations. Our results indicate that the potential photosynthesis can be increased up to 800ppm cassava varieties with high sink capacity can be cultivated under protected cultivation to attain higher productivity.

Differential physiological and production responses of C3 and C4 crops to climate factor interactions.

This study examined the effect of the interactions of key factors associated with predicted climate change (increased temperature, and drought) and elevated CO2 concentration on C3 and C4 crop representatives, barley and sorghum. The effect of two levels of atmospheric CO2 concentration (400 and 800 ppm), three levels of temperature regime (21/7, 26/12 and 33/19°C) and two regimes of water availability (simulation of drought by gradual reduction of irrigation and well-watered control) in all combinations was investigated in a pot experiment within growth chambers for barley variety Bojos and sorghum variety Ruby. Due to differences in photosynthetic metabolism in C3 barley and C4 sorghum, leading to different responses to elevated CO2 concentration, we hypothesized mitigation of the negative drought impact in barley under elevated CO2 concentration and, conversely, improved performance of sorghum at high temperatures. The results demonstrate the decoupling of photosynthetic CO2 assimilation and production parameters in sorghum. High temperatures and elevated CO2 concentration resulted in a significant increase in sorghum above- and below-ground biomass under sufficient water availability despite the enhanced sensitivity of photosynthesis to high temperatures. However, the negative effect of drought is amplified by the effect of high temperature, similarly for biomass and photosynthetic rates. Sorghum also showed a mitigating effect of elevated CO2 concentration on the negative drought impact, particularly in reducing the decrease of relative water content in leaves. In barley, no significant factor interactions were observed, indicating the absence of mitigating the negative drought effects by elevated CO2 concentration. These complex interactions imply that, unlike barley, sorghum can be predicted to have a much higher variability in response to climate change. However, under conditions combining elevated CO2 concentration, high temperature, and sufficient water availability, the outperforming of C4 crops can be expected. On the contrary, the C3 crops can be expected to perform even better under drought conditions when accompanied by lower temperatures.

Defensive traits of Fagus crenata leaves after long-term CO2 exposure in free-air CO2 enrichment (FACE) system

ABSTRACT We aim to elucidate the long-term effects of elevated CO2 concentrations on the defensive traits of forest tree leaves using Fagus crenata saplings grown for 7–9 years in the free-air CO2 enrichment (FACE) system from 2003 to 2011. During 2009–2011, we checked the leaf phenology from budburst to leaf expansion and seasonal changes in defensive traits of leaves such as leaf mass per area (LMA) and concentration of condensed tannin because phenological synchrony between the leaf maturing process and herbivorous insects’ emergence and feeding timing is essential. As a result, there was little difference in leaf phenology and the emergence of herbivorous insects between FACE and control sites. LMA increased significantly in 2010 and 2011, and carbon/nitrogen ratio increased significantly in 2009 and 2011 in FACE sites than in control sites. There were significantly higher total phenolics and condensed tannin concentrations at FACE sites than at control sites in only 2009. On the other hand, microscopic observation revealed no differences in the distribution of phenolic substances between FACE and control sites. Our results after 9 years of CO2 exposure showed that the effect of CO2 on each defensive trait varied from year to year. This could be because the experimental CO2 concentration was not high enough to have an effect or because it was a field experiment and other environmental factors were more critical.

Feeding of leaf beetle to two species of alder grown under two different soils in a free-air CO2 enrichment

ABSTRACT The effects of elevated CO2 concentration on the defensive ability of two Alnus species (A. maximowiczii, A. hirsuta) against herbivory attacks (alder leaf beetle; Agelastica coerulea) were investigated using a free-air CO2 enrichment. Elevated CO2 significantly affected consumed leaf area index (CLI) of A. maximowiczii but soil fertility did not, while more significant effects on CLI of A. hirsuta were found in both CO2 and soil fertility. As found in natural conditions, A. hirsuta was grazed five times more than A. maximowiczii in both CO2 levels, which was explained with the low condensed tannin (CT) concentration of the leaves. The value of leaf mass per area in fertile soil was 10 g m−2 lower than that in infertile soil under ambient CO2 in July. Leaf C/N ratio was not affected by elevated CO2 for both species but that of A. hirsuta was little higher in infertile soil when compared to fertile soil in July. CT of A. maximowiczii tended to increase in September under elevated CO2. CT of A. hirsuta was higher in infertile soil than in fertile soil in July and showed an overall decrease in September compared to July. Nitrogen-fixing activity by a nodule of Frankia sp. on A. maximowiczii was higher in elevated CO2 treatments than in ambient CO2 independent of soil fertility. As a result of changes in these parameters, except for fertile soil, the peak of the herbivorous damage was later in elevated CO2 for the Alnus species than in the control.

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.

Effects of Elevated CO2 Concentration and Temperature on the Growth and Photosynthetic Characteristics of Populus simonii × P. nigra ‘1307’ Leaves

This study aimed to establish the effects of elevated CO2 concentration and temperature on the photosystem II (PSII) performance and photosynthetic characteristics of Populus simonii × P. nigra ‘1307’ leaves. Different CO2 concentrations (400 and 800 µmol·mol−1) and temperatures (room temperature and room temperature +2 °C) were set in artificial climate change simulation and control chambers, and the rapid chlorophyll fluorescence induction kinetics curve (OJIP curve) of Populus simonii × P. nigra ‘1307’ was determined. The generated OJIP curve was used to analyze the change characteristics in photosynthetic performance. The results revealed that under elevated temperature conditions, the concentrations of chlorophyll a, b in Populus simonii × P. nigra ‘1307’ leaves were significantly increased. At the same time, there were no significant changes in the chlorophyll concentration under the superimposed effect of elevated CO2 concentration and temperature. The PSII comprehensive performance index (PIABS) of Populus simonii × P. nigra ‘1307’ was significantly inhibited under elevated temperatures due to the increased closure degree (Vj) of the PSII reaction center and the damage of the receptor side. This reduced the electron transfer capacity per unit reaction center (ETo/RC) and unit cross-sectional area, which decreased the quantum yield of the electron transfer. Under the elevated CO2 concentration, ETo/RC was also inhibited. Still, PIABS was enhanced owing to the increased number of active PSII per unit area and the low reduction rate of the primary quinone receptor (QA). Under the superimposed effect of the two factors, the electron transfer performance of the donor and receptor sides of PSII was improved compared to the treatments only subjected to elevated temperature; thus, PIABS was not significantly reduced compared to the control. Therefore, the continuous increase in temperature by 2 °C significantly inhibits the electron transfer capacity of the photosynthetic system of Populus simonii × P. nigra ‘1307’ leaves. On the other hand, an increase in CO2 concentration expands the PSII reaction center, while enhancing the electron transfer capacity of the donor and receptor sides, which alleviates the photosynthetic inhibition caused by the elevated temperature.

How will increased atmospheric CO2 and climate change-induced wind trends alter the probability of tree failures from wind gusts

Trees provide numerous benefits to communities, but pose a risk when they are damaged. The likelihood that trees will be damaged in a windstorm is increasing due to climate change, as wind trends are changing as the climate warms, and rising atmospheric CO2 concentrations could alter the resistance of trees to wind damage.To address these concerns, we created a tree damage model that integrates results from a meta-analysis about the effects of elevated CO2 concentrations on tree growth and an analysis of the return period of damaging winds in Toronto, Canada from 1990 to 2080. This joint analysis is applied for a simulated silver birch (Betula pendula) tree. Our model predicts that by 2080, due both to a high CO2-induced decrease in tree resilience and an increased likelihood of more frequent and intense windstorms, damaging windstorms will occur about twice as frequently as they do today.

Methanogenic and methanotrophic communities determine lower CH4 fluxes in a subtropical paddy field under long-term elevated CO2

Clarifying the effects of elevated CO2 concentration (e[CO2]) on CH4 emissions from paddy fields and its mechanisms is a crucial part of the research on agricultural systems in response to global climate change. However, the response of CH4 fluxes from rice fields to long-term e[CO2] (e[CO2] duration >10 years) and its microbial mechanism is still lacking. In this study, we used a long-term free-air CO2 enrichment experiment to examine the relationship between CH4 fluxes and the methanogenic and methanotrophic consortia under long- and short-term e[CO2]. We demonstrated that contrary to the effect of short-term e[CO2], long-term e[CO2] decreased CH4 fluxes. This may be associated with the reduction of methanogenic abundance and the increase of methanotrophic abundance under long-term e[CO2]. In addition, long-term e[CO2] also changed the community structure and composition of methanogens and methanotrophs compared with short-term e[CO2]. Partial least squares path modeling analysis showed that long-term e[CO2] also could affect the abundance and composition of methanogens and methanotrophs indirectly by influencing soil physical and chemical properties, thereby ultimately altering CH4 fluxes in paddy soils. These findings suggest that current estimates of short-term e[CO2]-induced CH4 fluxes from paddy fields may be overestimated. Therefore, a comprehensive assessment of climate‑carbon cycle feedbacks may need to consider the microbial regulation of CH4 production and oxidation processes in paddy ecosystems under long-term e[CO2].

Elevated CO2 Influences the Growth, Root Morphology, and Leaf Photosynthesis of Cacao (Theobroma cacao L.) Seedlings

Growing quality seedlings is a challenge for sustainable cacao production as the survival rate of young seedlings is strongly influenced by environmental factors that affect the productivity of cacao farmers. In this study, cacao (Theobroma cacao L.) seedlings were cultivated in a nursery, and the effects of elevated CO2 concentrations (approximately 800 ppm) applied to cacao seedlings during daytime (6:00–17:59) on the root growth, morphology, and leaf photosynthetic capacity were examined. Treatment with elevated CO2 significantly improved root growth, dry matter weight, and root/shoot ratio. Three-dimensional imaging of roots showed that lateral roots grew longer horizontally, lateral roots and fine roots were distributed over a larger area, and root surface and root volume increased significantly under elevated CO2 treatment. Accurate quantification of root morphology using X-ray CT indicated that the treatment with elevated CO2 concentrations may significantly affect root quality during the seedling stage by expanding the distribution range of lateral and fine roots, which increases the ability of lateral roots to elongate and absorb water and nutrients from the superficial layers. The photosynthetic characteristics of the aboveground leaves of cacao seedlings exposed to elevated CO2 concentrations showed a tendency to adapt to elevated CO2 concentrations by increasing light-use efficiency and CO2-use efficiency. Therefore, the treatment of cacao seedlings with elevated CO2 concentrations improved the growth quality of seedlings due to the characteristics of the roots as large sinks.

Effects of elevated CO2 concentration and experimental warming on morphological, physiological, and biochemical responses of winter wheat under soil water deficiency.

Global climate change and freshwater scarcity have become two major environmental issues that constrain the sustainable development of the world economy. Climate warming caused by increasing atmospheric CO2 concentration can change global/regional rainfall patterns, leading to uneven global seasonal precipitation distribution and frequent regional extreme drought events, resulting in a drastic reduction of available water resources during the critical crop reproduction period, thus causing many important food-producing regions to face severe water deficiency problems. Understanding the potential processes and mechanisms of crops in response to elevated CO2 concentration and temperature under soil water deficiency may further shed lights on the potential risks of climate change on the primary productivity and grain yield of agriculture. We examined the effects of elevated CO2 concentration (e[CO2]) and temperature (experimental warming) on plant biomass and leaf area, stomatal morphology and distribution, leaf gas exchange and mesophyll anatomy, rubisco activity and gene expression level of winter wheat grown at soil water deficiency with environmental growth chambers. We found that e[CO2] × water × warming sharply reduced plant biomass by 57% and leaf photosynthesis (P n) 50%, although elevated [CO2] could alleviated the stress from water × warming at the amount of gene expression in RbcL3 (128%) and RbcS2 (215%). At ambient [CO2], the combined stress of warming and water deficiency resulted in a significant decrease in biomass (52%), leaf area (50%), P n (71%), and G s (90%) of winter wheat. Furthermore, the total nonstructural carbohydrates were accumulated 10% and 27% and increased R d by 127% and 99% when subjected to water × warming and e[CO2] × water × warming. These results suggest that water × warming may cause irreversible damage in winter wheat and thus the effect of "CO2 fertilization effect" may be overestimated by the current process-based ecological model.

Mitigation of Elevated CO2 Concentration on Warming-Induced Changes in Wheat Is Limited under Extreme Temperature during the Grain Filling Period

Elevated CO2 concentration (eCO2) generally increases plant growth by improving photosynthesis, but it is unclear whether eCO2 can alleviate the negative effects of elevated temperatures, especially in high-temperature years. Manipulative experiments with elevated [CO2] and temperature were conducted in North China to understand the effect of elevated CO2 concentration and temperature on wheat. The photosynthesis, An–PAR and A–Ci curve parameters, growth period, biomass, yield component, and yield of wheat were investigated under different [CO2] (around 400 and 600 ppm) and temperatures (ambient temperature and ambient temperature +2 °C) for 3 years by using controlled chambers. Results showed that elevated temperature significantly shortened the growth period and decreased the yield and biomass of wheat. Elevated [CO2] significantly increased the maximum net photosynthetic rate (Anmax) but reduced the maximum carboxylation rate (Vcmax) and the maximum electron transport rate (Jmax). The extremely high temperature during the grain filling period in 2019 exerted a serious negative impact on wheat production. Elevated [CO2] stimulated photosynthesis, increased kernel number per spike, and extended the duration of the grain filling period, which consequently increased biomass and grain yield under elevated temperatures in normal years (2018 and 2020). Although the combination of CO2 and temperature reduced photosynthesis and biomass, it also alleviated the negative impact of elevated temperatures on grain yield to some extent under extremely high temperature during the grain filling period in 2019. The mitigative effect of eCO2 under extreme high temperature is limited, and planting early-maturing cultivars or increasing the genotypes of kernel number per spike help to escape the extreme high temperature of the critical growth period.

Effects of elevated CO2 concentration on cell structure and stress resistance physiology of Setaria italica under drought stress.

The frequency of drought will increase under further warming. The increase in atmospheric CO2 concentration, along with more frequent drought, will affect crop growth. We examined the changes of cell structure, photosynthetic physiology, antioxidant enzymes, osmotic regulatory substances, and yield of foxtail millet (Setaria ita-lica) leaves under different CO2 concentrations (ambient air CO2 concentration and ambient atmospheric CO2 concentration + 200 μmol·mol-1) and water treatment (soil moisture content maintained at 45%-55%, and 70%-80% of field capacity, representing mild drought and normal water condition, respectively). The results showed that elevated CO2 concentration increased the number of starch grains, the area of single starch grains, and the total area of starch grains in the chloroplast of millet mesophyll cells. Under mild drought condition, elevated CO2 concentration increased net photosynthetic rate of millet leaves at the booting stage by 37.9%, but did not affect water use efficiency at this stage. Elevated CO2 concentration increased net photosynthetic rate and water use efficiency of millet leaves under mild drought condition at the filling stage by 15.0% and 44.2%, respectively. Under mild drought condition, elevated CO2 concentration increased the content of peroxidase (POD) and soluble sugar in millet leaves at the booting stage by 39.3% and 8.0%, respectively, but decreased proline content by 31.5%. It increased the content of POD in millet leaves at the filling stage by 26.5% but decreased the content of MDA and proline by 37.2% and 39.3%, respectively. Under mild drought condition, elevated CO2 concentration significantly increased the number of grain spikes by 44.7% and yield by 52.3% in both years compared with normal water condition. The effect of elevated CO2 concentration on grain yield under mild drought conditions was higher than that under normal water condition. Under mild drought conditions, elevated CO2 concentration increased leaf thickness, vascular bundle sheath cross-sectional area, net photosynthetic rate, and water use efficiency of millet, improved the antioxidant oxidase activity, and changed the concentration of osmotic regulatory substances, alleviated the nega-tive effect of drought on foxtail millet, and finally increased the number of grains per ear and yield of foxtail millet. This study would provide a theoretical basis for millet production and sustainable agricultural development in arid areas under future climate change.

The Beneficial Roles of Elevated [CO2] on Exogenous ABA-Enhanced Drought Tolerance of Cucumber Seedlings

Drought stress severely limits crop growth and yield. With the atmospheric CO2 constantly increasing, plants will be affected by multiple effects of drought and increased CO2 in the future. Abscisic acid (ABA) plays vital roles in plant stress tolerance, especially drought stress. However, little is known about the effects of elevated CO2 concentration (e[CO2]) and exogenous ABA in cucumber (Cucumis sativus L.) response to drought stress. In the present study, we investigated the effects of e[CO2] and exogenous ABA on the drought tolerance of cucumber seedlings under the simulated drought stress induced by 5% polyethylene glycol 6000. The experiment was a split-plot design, in which the main factor was CO2 concentrations; atmospheric and elevated CO2 concentrations (~400 and 800 ± 40 μmol mol−1, respectively). The subplot factor was the combinations of exogenous ABA and its synthesis inhibitor sodium tungstate (Na2WO4); deionized water (control), 20 μM ABA, 2 mM Na2WO4, and 2 mM Na2WO4 + 20 μM ABA, which were applied to plant leaves. The results showed that compared with exogenous ABA application only, e[CO2] combined with exogenous ABA significantly increased the biomass, chlorophyll content, and net photosynthetic rate (Pn) of cucumber seedlings under drought stress. Meanwhile, e[CO2] and exogenous ABA were more efficient in reducing the contents of reactive oxygen species and malondialdehyde, promoting the accumulation of proline, soluble sugar, soluble protein, free amino acid, ascorbic acid, and glutathione. The ratios of ascorbic acid/dehydroascorbic acid (ASA/DHA), glutathione/oxidized glutathione (GSH/GSSG), as well as the activities of antioxidant enzymes were increased. In conclusion, e[CO2] and exogenous ABA synergistically alleviated oxidative damage of drought stress on cucumber seedlings by increasing antioxidant enzyme activities and accelerating the ASA–GSH cycle in cucumber seedlings, which in turn improved the drought tolerance of cucumber seedlings, and provided theoretical and practical support for further studies on the alleviation of drought stress in protected horticulture.

The effect of elevated CO2 on photosynthesis is modulated by nitrogen supply and reduced water availability in Picea abies.

It is assumed that the stimulatory effects of elevated CO2 concentration ([CO2]) on photosynthesis and growth may be substantially reduced by co-occurring environmental factors and the length of CO2 treatment. Here, we present the study exploring the interactive effects of three manipulated factors ([CO2], nitrogen supply and water availability) on physiological (gas-exchange and chlorophyll fluorescence), morphological and stoichiometric traits of Norway spruce (Picea abies) saplings after 2 and 3 years of the treatment under natural field conditions. Such multifactorial studies, going beyond two-way interactions, have received only limited attention until now. Our findings imply a significant reduction of [CO2]-enhanced rate of CO2 assimilation under reduced water availability which deepens with the severity of water depletion. Similarly, insufficient nitrogen availability leads to a down-regulation of photosynthesis under elevated [CO2] being particularly associated with reduced carboxylation efficiency of the Rubisco enzyme. Such adjustments in the photosynthesis machinery result in the stimulation of water-use efficiency under elevated [CO2] only when it is combined with a high nitrogen supply and reduced water availability. These findings indicate limited effects of elevated [CO2] on carbon uptake in temperate coniferous forests when combined with naturally low nitrogen availability and intensifying droughts during the summer periods. Such interactions have to be incorporated into the mechanistic models predicting changes in terrestrial carbon sequestration and forest growth in the future.

Different characteristics of soil CH4 emissions and methanogenic communities in paddy fields under gradually and abruptly elevated CO2 concentrations

Studying methanogenesis in paddy fields under future climate change scenarios is important for carbon sequestration and reduction in agroecosystems. Most studies have investigated the effects of elevated CO2 concentrations (e[CO2]) on CH4 emissions in paddy fields under a constant CO2 concentration ([CO2]). However, the increase in the [CO2] in the atmosphere is a gradual process rather than an abrupt increase, and the [CO2] in the atmosphere has remained high and relatively constant. In this research, we explored the differences in methanogenesis in paddy fields under gradually and abruptly e[CO2] using open-top chambers (OTCs). CH4 flux, soil physicochemical properties, enzyme activities, methane production potential (MPP), and methanogenic (mcrA gene) characteristics were analyzed under CK (ambient [CO2]), C1 (gradually e[CO2] by 200 μmol mol−1), and C2 (abruptly e[CO2] by 200 μmol mol−1) treatments. The results showed that the C1 and C2 treatments significantly promoted the cumulative amount of CH4 emissions (CAC) by 63.3% and 86.5%, respectively, and significantly increased the CAC/yield by 30.8% and 47.3%, respectively, compared with the CK treatment. In addition, the C1 and C2 treatments increased the DOC concentration, enzyme activities (urease, invertase, and catalase), MPP, and mcrA gene abundance in paddy soils. Notably, CAC/yield, shoot biomass, and soil seasonal average urease activity under the C2 treatment were increased by 12.6%, 12.2%, and 3.0%, respectively, compared with those in C1. The methanogenic activity of the C2 treatment was significantly increased by 24.1% and 24.4% during the tillering and grain-filling stages, respectively, and the methanogenic abundance of the C2 treatment was significantly increased by 53.9% and 72.2% during the tillering and elongation stages, respectively, compared with that of C1. Therefore, it is inappropriate to ignore the fact that [CO2] increases gradually and to only examine the effects of high e[CO2] on agroecosystems.

Physiological and transcriptome analysis of response of soybean (Glycine max) to cadmium stress under elevated CO2 concentration

The continuous accumulation of Cd has long-lasting detrimental effects on plant growth and food safety. Although elevated CO2 concentration (EC) has been reported to reduce Cd accumulation and toxicity in plants, evidence on the functions of elevated CO2 concentration and its mechanisms in the possible alleviation of Cd toxicity in soybean are limited. Here, we used physiological and biochemical methods together with transcriptomic comparison to explore the effects of EC on Cd-stressed soybean. Under Cd stress, EC significantly increased the weight of roots and leaves, promoted the accumulations of proline, soluble sugars, and flavonoid. In addition, the enhancement of GSH activity and GST gene expressions promoted Cd detoxification. These defensive mechanisms reduced the contents of Cd2+, MDA, and H2O2 in soybean leaves. The up-regulation of genes encoding phytochelatin synthase, MTPs, NRAMP, and vacuoles protein storage might play vital roles in the transportation and compartmentalization process of Cd. The MAPK and some transcription factors such as bHLH, AP2/ERF, and WRKY showed changed expressions and might be engaged in mediation of stress response. These findings provide a boarder view on the regulatory mechanism of EC on Cd stress and provide numerous potential target genes for future engineering of Cd-tolerant cultivars in soybean breeding programs under climate changes scenarios.

Elevated CO2 increases soil redox potential by promoting root radial oxygen loss in paddy field

Soil redox potential (Eh) plays an important role in the biogeochemical cycling of soil nutrients. Whereas its effect soil process and nutrients’ availability under elevated atmospheric CO2 concentration and warming has seldom been investigated. Thus, in this study, a field experiment was used to elucidate the effect of elevated CO2 concentration and warming on soil Eh, redox-sensitive elements and root radial oxygen loss (ROL). We hypothesized elevated CO2 and warming could alter soil Eh by promoting or inhibiting ROL. We found that soil Eh in the rhizosphere was significantly higher than that of non-rhizosphere. Elevated CO2 enhanced soil Eh by 11.5%, which corresponded to a significant decrease in soil Fe2+ and Mn2+concentration. Under elevated CO2, the concentration of Fe2+ and Mn2+ decreased by 14.7% and 13.7%, respectively. We also found that elevated CO2 altered rice root aerenchyma structure and promoted rice root ROL. Under elevated CO2, rice root ROL increased by 79.5% and 112.2% for Yangdao 6 and Changyou 5, respectively. Warming had no effect on soil Eh and rice root ROL. While warming increased the concentration of Mn2+ and SO42− by 4.9% and 19.3%, respectively. There was a significant interaction between elevated CO2 and warming on Fe2+ and Mn2+. Under elevated CO2, warming had no effect on the concentration of Fe2+ but decreased Mn2+ concentration significantly. Our study demonstrated that elevated atmospheric CO2 in the future could increase soil Eh by promoting rice root ROL, which will alter some soil nutrients’ availability, such as Fe2+ and Mn2+.

O CO2 elevado induz a regulação negativa da fotossíntese e alivia o efeito do déficit hídrico em Ceiba pentandra (Malvaceae)

ABSTRACT The simultaneous effect of elevated CO2 concentration and drought on trees is still under investigation in the Amazon. We evaluated the effect of CO2 levels (400 and 800 ppm) and water regimes (50% and 100% soil field capacity) on photosynthetic traits, chlorophyll fluorescence, and total biomass accumulation in Ceiba pentandra. In well-watered plants, light-saturated photosynthesis (PN-sat) increased in plants exposed to elevated CO2, but both PN-sat and stomatal conductance decreased in response to water deficit. The maximum carboxylation rate of Rubisco declined under elevated CO2, which indicates down-regulation of photosynthesis at elevated CO2. The Fv/Fm ratio was not affected by treatments. Notwithstanding, total plant biomass and leaf area were reduced by 34-37% under water deficit, but they were not affected by CO2 levels. The PN-sat values measured in well-irrigated plants at ambient CO2 were similar to those observed in plants subjected to elevated CO2 and water deficit (p = 0.26). We concluded that the effect of water deficit on PN-sat was mitigated by elevated CO2. These results suggest that the increase of atmospheric CO2 concentrations associated to climate changes can at least partly offset the negative effect of drought in this multiuse and widely distributed species.

Evaluation of the effects of elevated CO2 concentrations on the growth of cassava storage roots by destructive harvests and ground penetrating radar scanning approaches.

Cassava (Manihot esculenta Crantz) production will need to be improved to meet future food demands in Sub-Saharan Africa. The selection of high-yielding cassava cultivars requires a better understanding of storage root development. Additionally, since future production will happen under increasing atmospheric CO2 concentrations ([CO2 ]), cultivar selection should include responsiveness to elevated [CO2 ]. Five farmer-preferred African cassava cultivars were grown for three and a half months in a Free Air CO2 Enrichment experiment in central Illinois. Compared to ambient [CO2 ] (~400 ppm), cassava storage roots grown under elevated [CO2 ] (~600 ppm) had a higher biomass with some cultivars having lower storage root water content. The elevated [CO2 ] stimulation in storage root biomass ranged from 33% to 86% across the five cultivars tested documenting the importance of this trait in developing new cultivars. In addition to the destructive harvests to obtain storage root parameters, we explored ground penetrating radar as a nondestructive method to determine storage root growth across the growing season.

Effects of Elevated CO2 Concentration on Host Adaptability and Chlorantraniliprole Susceptibility in Spodoptera frugiperda.

Elevated atmospheric carbon dioxide concentrations (eCO2) can affect both herbivorous insects and their host plants. The fall armyworm (FAW), Spodoptera frugiperda, is a highly polyphagous agricultural pest that may attack more than 350 host plant species and has developed resistance to both conventional and novel-action insecticides. However, the effects of eCO2 on host adaptability and insecticide resistance of FAW are unclear. We hypothesized that eCO2 might affect insecticide resistance of FAW by affecting its host plants. To test this hypothesis, we investigated the effect of eCO2 on (1) FAW's susceptibility to chlorantraniliprole after feeding on wheat, (2) FAW's population performance traits (including the growth and reproduction), and (3) changes in gene expression in the FAW by transcriptome sequencing. The toxicity of chlorantraniliprole against the FAW under eCO2 (800 µL/L) stress showed that the LC50 values were 2.40, 2.06, and 1.46 times the values at the ambient CO2 concentration (400 µL/L, aCO2) for the three generations, respectively. Under eCO2, the life span of pupae and adults and the total number of generations were significantly shorter than the FAW under aCO2. Compared to the aCO2 treatment, the weights of the 3rd and 4th instar larvae and pupae of FAW under eCO2 were significantly heavier. Transcriptome sequencing results showed that more than 79 detoxification enzyme genes in FAW were upregulated under eCO2 treatment, including 40 P450, 5 CarE, 17 ABC, and 7 UGT genes. Our results showed that eCO2 increased the population performance of FAW on wheat and reduced its susceptibility to chlorantraniliprole by inducing the expression of detoxification enzyme genes. This study has important implications for assessing the damage of FAW in the future under the environment of increasing atmospheric CO2 concentration.