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Tropical grasslands are very important to global carbon and water cycles. C4 plants have increased heat tolerance and a CO2 concentrating mechanism that often reduces responses to elevated concentrations of CO2 ([CO2]). Despite the importance of tropical grasslands, there is a scarcity of studies that elucidate how managed tropical grasslands will be affected by elevated [CO2] and warming. In our study, we used a combination of a temperature-free air-controlled enhancement (T-FACE) and a free-air carbon dioxide enrichment (FACE) systems to increase canopy temperature and [CO2] under field conditions, respectively. We warmed a field-grown pasture dominated by the C4 tropical forage grass Megathyrsus maximus by 2°C above ambient under two levels of [CO2] (ambient (aC) and elevated (eC - 600 ppm) to investigate how these two factors isolated or combined regulate water relations through stomatal regulation, and how this combination affects PSII functioning, biochemistry, forage nutritive value, and digestibility. We demonstrated that the effects of warming negated the effects of eC in plant transpiration, water potential, proline content, and soil moisture conservation, resulting in warming canceling the eCO2-induced improvement in these parameters. Furthermore, there were additive effects between eC and warming for chlorophyll fluorescence parameters and aboveground nutritive value. Warming sharply intensified the eCO2-induced decrease in crude protein content and increases in forage fibrous fraction and lignin, resulting in a smaller forage digestibility under a warmer CO2-enriched atmosphere. Our results highlight the importance of multifactorial studies when investigating global change impacts on managed ecosystems and the potential consequences for the global carbon cycle like amplification in methane emissions by ruminants and feeding a positive climate feedback system. [ABSTRACT FROM AUTHOR]

Aims: To identify factors driving soil respiration (Rsoil) in a tropical C4-dominated perennial managed grassland ecosystem exposed to elevated carbon (C) dioxide concentration ([CO2]) and temperature. Methods: The perennial grass Panicum maximum was grown at 600 μmol CO2 mol−1 and + 2 °C above ambient temperatures for one full growing cycle (from grazing to regrowth for about ~30–45 days) using a free-air CO2 and infrared warming system. Plant growth and CO2 fluxes were measured during the growing cycle. Results: Both high [CO2] and warming increased canopy photosynthesis but warming alone increased biomass by 53% and Rsoil by 26%. There was a strong diel effect on Rsoil, which was 16% greater at noon than at 18:00 h. Rsoil had low sensitivity to soil temperature (Q10 ~ 1) regardless of the CO2 treatment. Conclusions: In this tropical managed pasture, diel variation in photosynthesis strongly affected Rsoil, suggesting that Rsoil may be more limited by substrate availability than abiotic factors such as temperature. Predicted changes in climate for the region will likely affect the C dynamics of C4-dominated tropical pastures. Although, the short-term experiment may limit the extrapolations of our findings, the highly controlled settings of the experiment highlighted the role of canopy photosynthesis on Rsoil respiration in tropical C4-pastures. [ABSTRACT FROM AUTHOR]

The opening and closing of stomata are controlled by the integration of environmental and endogenous signals. Here, we show the effects of combining elevated atmospheric carbon dioxide concentration (eCO 2; 600 μmol mol-1) and warming (+2°C) on stomatal properties and their consequence to plant function in a Stylosanthes capitata Vogel (C3) tropical pasture. The eCO 2 treatment alone reduced stomatal density, stomatal index, and stomatal conductance (gs), resulting in reduced transpiration, increased leaf temperature, and leading to maintenance of soil moisture during the growing season. Increased CO2 concentration inside leaves stimulated photosynthesis, starch content levels, water use efficiency, and PSII photochemistry. Under warming, plants developed leaves with smaller stomata on both leaf surfaces; however, we did not see effects of warming on stomatal conductance, transpiration, or leaf water status. Warming alone enhanced PSII photochemistry and photosynthesis, and likely starch exports from chloroplasts. Under the combination of warming and eCO 2, leaf temperature was higher than that of leaves from the warming or eCO 2 treatments. Thus, warming counterbalanced the effects of CO2 on transpiration and soil water content but not on stomatal functioning, which was independent of temperature treatment. Under warming, and in combination with eCO 2, leaves also produced more carotenoids and a more efficient heat and fluorescence dissipation. Our combined results suggest that control on stomatal opening under eCO 2 was not changed by a warmer environment; however, their combination significantly improved whole-plant functioning. [ABSTRACT FROM AUTHOR]

The response of wheat to the variables of climate change includes elevated CO2, high temperature, and drought which vary according to the levels of each variable and genotype. Independently, elevated CO2, high temperature, and terminal drought affect wheat biomass and grain yield, but the interactive effects of these three variables are not well known. The aim of this study was to determine the effects of elevated CO2 when combined with high temperature and terminal drought on the high-yielding traits of restricted-tillering and vigorous growth. It was hypothesized that elevated CO2 alone, rather than combined with high temperature, ameliorates the effects of terminal drought on wheat biomass and grain yield. It was also hypothesized that wheat genotypes with more sink capacity (e.g. high-tillering capacity and leaf area) have more grain yield under combined elevated CO2, high temperature, and terminal drought. Two pairs of sister lines with contrasting tillering and vigorous growth were grown in poly-tunnels in a four-factor completely randomized split-plot design with elevated CO2 (700 µL L−1), high day time temperature (3 °C above ambient), and drought (induced from anthesis) in all combinations to test whether elevated CO2 ameliorates the effects of high temperature and terminal drought on biomass accumulation and grain yield. For biomass and grain yield, only main effects for climate change variables were significant. Elevated CO2 significantly increased grain yield by 24-35% in all four lines and terminal drought significantly reduced grain yield by 16-17% in all four lines, while high temperature (3 °C above the ambient) had no significant effect. A trade-off between yield components limited grain yield in lines with greater sink capacity (free-tillering lines). This response suggests that any positive response to predicted changes in climate will not overcome the limitations imposed by the trade-off in yield components. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) production may be affected by the future climate, but the impact of the combined increases in atmospheric CO [sub 2] concentration, temperature and incidence of drought that are predicted has not been evaluated. The combined effect of elevated CO [sub 2], high temperature and terminal drought on biomass accumulation and grain yield was evaluated in vigorous (38-19) and nonvigorous (Janz) wheat genotypes grown under elevated CO [sub 2] (700 μL L-1) combined with temperatures 2°C, 4°C and 6°C above the current ambient temperature. Terminal drought was induced in all combinations at anthesis in a split-plot design to test whether the effect of elevated CO [sub 2] combined with high temperature ameliorates the negative effects of terminal drought on biomass accumulation and grain yield. Biomass and grain yield were enhanced under elevated CO [sub 2] with 2°C above the ambient temperature, regardless of the watering regimen. The combinations of elevated CO [sub 2] plus 4°C or 6°C above the ambient temperature did not enhance biomass and grain yield, but tended to decrease them. The reductions in biomass and grain yield (45-50%) caused by terminal drought were less severe (21-28%) under elevated CO [sub 2] with 2°C above the ambient temperature. The amelioration resulted from a 63% increase in the rate of leaf net photosynthesis in 38-19 and a 39% increase in tillering and leaf area in Janz. The contrasting responses and phenological development of these two genotypes to the combination of elevated CO [sub 2], temperature and terminal drought, and the possible influences on their source-sink relationships are discussed. Wheat may have different responses to future climates in Australia. Grain yield and biomass under elevated CO [sub 2] increased when the temperature was 2°C higher than the ambient, regardless of irrigation or terminal drought, but not when temperatures were >2°C higher than the ambient. The interaction of elevated CO [sub 2] × temperature × drought should be considered in the new generation of studies on crop adaptation to future climates in Australia. [ABSTRACT FROM AUTHOR]

Tropical grasslands are very important to global carbon and water cycles. C 4 plants have increased heat tolerance and a CO 2 concentrating mechanism that often reduces responses to elevated concentrations of CO 2 ([CO 2 ]). Despite the importance of tropical grasslands, there is a scarcity of studies that elucidate how managed tropical grasslands will be affected by elevated [CO 2 ] and warming. In our study, we used a combination of a temperature-free air-controlled enhancement (T-FACE) and a free-air carbon dioxide enrichment (FACE) systems to increase canopy temperature and [CO 2 ] under field conditions, respectively. We warmed a field-grown pasture dominated by the C 4 tropical forage grass Megathyrsus maximus by 2°C above ambient under two levels of [CO 2 ] (ambient ( aC ) and elevated ( eC - 600 ppm) to investigate how these two factors isolated or combined regulate water relations through stomatal regulation, and how this combination affects PSII functioning, biochemistry, forage nutritive value, and digestibility. We demonstrated that the effects of warming negated the effects of eC in plant transpiration, water potential, proline content, and soil moisture conservation, resulting in warming canceling the eCO 2 -induced improvement in these parameters. Furthermore, there were additive effects between eC and warming for chlorophyll fluorescence parameters and aboveground nutritive value. Warming sharply intensified the eCO 2 -induced decrease in crude protein content and increases in forage fibrous fraction and lignin, resulting in a smaller forage digestibility under a warmer CO 2 -enriched atmosphere. Our results highlight the importance of multifactorial studies when investigating global change impacts on managed ecosystems and the potential consequences for the global carbon cycle like amplification in methane emissions by ruminants and feeding a positive climate feedback system., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer AG declared a shared affiliation with the authors EH, ED, DC, CM to the handling editor at the time of the review., (Copyright © 2022 Habermann, Dias de Oliveira, Contin, Costa, Costa and Martinez.)

The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is historically a pest of both corn (Zea mays L. (Poales: Poaceae)) and dry beans (Phaseolus sp. L. (Fabales: Fabaceae)) in the western Great Plains. However, it has recently undergone an eastward range expansion establishing itself across the Corn Belt in 25 states and 4 Canadian provinces. To mitigate the effects of infestation in Michigan, foliar insecticides are used in dry beans, whereas management of the pest in corn relies more heavily on the use of Bt-expressing hybrids. In this study stable carbon isotope analysis was used to determine what crop adult moths developed on as larvae with analysis showing that very few of the adult moths developed on dry beans. These results suggest that beans and corn are not suitable as co-refuges and that mainly adults which developed on corn are contributing to the next generation of western bean cutworm in Michigan., (© The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The opening and closing of stomata are controlled by the integration of environmental and endogenous signals. Here, we show the effects of combining elevated atmospheric carbon dioxide concentration ( eCO 2 ; 600 μmol mol -1 ) and warming (+2°C) on stomatal properties and their consequence to plant function in a Stylosanthes capitata Vogel (C 3 ) tropical pasture. The eCO 2 treatment alone reduced stomatal density, stomatal index, and stomatal conductance ( g s ), resulting in reduced transpiration, increased leaf temperature, and leading to maintenance of soil moisture during the growing season. Increased CO 2 concentration inside leaves stimulated photosynthesis, starch content levels, water use efficiency, and PSII photochemistry. Under warming, plants developed leaves with smaller stomata on both leaf surfaces; however, we did not see effects of warming on stomatal conductance, transpiration, or leaf water status. Warming alone enhanced PSII photochemistry and photosynthesis, and likely starch exports from chloroplasts. Under the combination of warming and eCO 2 , leaf temperature was higher than that of leaves from the warming or eCO 2 treatments. Thus, warming counterbalanced the effects of CO 2 on transpiration and soil water content but not on stomatal functioning, which was independent of temperature treatment. Under warming, and in combination with eCO 2 , leaves also produced more carotenoids and a more efficient heat and fluorescence dissipation. Our combined results suggest that control on stomatal opening under eCO 2 was not changed by a warmer environment; however, their combination significantly improved whole-plant functioning.

Elevated CO2 often increases grain yield in wheat by enhancing grain number per ear, which can result from an increase in the potential number of florets or a reduction in the death of developed florets. The hypotheses that elevated CO2 reduces floret death rather than increases floret development, and that grain size in a genotype with more grains per unit area is limited by the rate of grain filling, were tested in a pair of sister lines contrasting in tillering capacity (restricted- vs. free-tillering). The hypotheses were tested under elevated CO2, combined with +3°C above ambient temperature and terminal drought, using specialized field tunnel houses. Elevated CO2 increased net leaf photosynthetic rates and likely the availability of carbon assimilates, which significantly reduced the rates of floret death and increased the potential number of grains at anthesis in both sister lines by an average of 42%. The restricted-tillering line had faster grain-filling rates than the free-tillering line because the free-tillering line had more grains to fill. Furthermore, grain-filling rates were faster under elevated CO2 and +3°C above ambient. Terminal drought reduced grain yield in both lines by 19%. Elevated CO2 alone increased the potential number of grains, but a trade-off in yield components limited grain yield in the free-tillering line. This emphasizes the need for breeding cultivars with a greater potential number of florets, since this was not affected by the predicted future climate variables.