All about FACE – plants in a high-[CO 2] world (original) (raw)

Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE

Journal of Experimental Botany, 2009

Plant responses to the projected future levels of CO 2 were first characterized in short-term experiments lasting days to weeks. However, longer term acclimation responses to elevated CO 2 were subsequently discovered to be very important in determining plant and ecosystem function. Free-Air CO 2 Enrichment (FACE) experiments are the culmination of efforts to assess the impact of elevated CO 2 on plants over multiple seasons and, in the case of crops, over their entire lifetime. FACE has been used to expose vegetation to elevated concentrations of atmospheric CO 2 under completely open-air conditions for nearly two decades. This review describes some of the lessons learned from the long-term investment in these experiments. First, elevated CO 2 stimulates photosynthetic carbon gain and net primary production over the long term despite down-regulation of Rubisco activity. Second, elevated CO 2 improves nitrogen use efficiency and, third, decreases water use at both the leaf and canopy scale. Fourth, elevated CO 2 stimulates dark respiration via a transcriptional reprogramming of metabolism. Fifth, elevated CO 2 does not directly stimulate C 4 photosynthesis, but can indirectly stimulate carbon gain in times and places of drought. Finally, the stimulation of yield by elevated CO 2 in crop species is much smaller than expected. While many of these lessons have been most clearly demonstrated in crop systems, all of the lessons have important implications for natural systems.

Functional responses of plants to elevated atmospheric CO2- do photosynthetic and productivity data from FACE experiments support early predictions?

New Phytologist, 2004

Results from 16 free-air CO 2 enrichment (FACE) sites representing four different global vegetation types indicate that only some early predictions of the effects of increasing CO 2 concentration (elevated [CO 2 ]) on plant and ecosystem processes are well supported. Predictions for leaf CO 2 assimilation (A net ) generally fit our understanding of limitations to photosynthesis, and the FACE experiments indicate concurrent enhancement of photosynthesis and of partial downregulation. In addition, most herbaceous species had reduced leaf nitrogen (N)-content under elevated [CO 2 ] and thus only a modest enhancement of A net , whereas most woody species had little change in leaf N with elevated [CO 2 ] but a larger enhancement of A net . Early predictions for primary production are more mixed. Predictions that enhancement of productivity would be greater in drier ecosystems or in drier years has only limited support. Furthermore, differences in productivity enhancements among six plant functional types were not significant. By contrast, increases in productivity enhancements with increased N availability are well supported by the FACE results. Thus, neither a resource-based conceptual model nor a plant functional type conceptual model is exclusively supported by FACE results, but rather both species identity and resource

The impact of global elevated CO2 concentration on photosynthesis and plant productivity

2010

The alarming and unprecedented rise in the atmospheric concentration of greenhouse gases under global climate change warrants an urgent need to understand the synergistic and holistic mechanisms associated with plant growth and productivity. Photosynthesis is a major process of sequestration and turnover of the total carbon on the planet. The extensive literature on the impacts of climate change demonstrates both positive and negative effects of rising CO 2 on photosynthesis in different groups of higher plants. Significant variation exists in the physiological, biochemical and molecular responsiveness to elevated CO 2 atmosphere, among terrestrial plant species including those with C 3 , C 4 and crassulacean acid metabolic (CAM) pathways. However, the regulatory events associated with the inter-and intraspecific metabolic plasticity governed by genetic organization in different plants are little understood. The adaptive acclimation responses of plants to changing climate remain contradictory. This review focuses primarily on the impacts of global climate change on plant growth and productivity with special reference to adaptive photosynthetic acclimative responses to elevated CO 2 concentration. The effects of elevated CO 2 concentration on plant growth and development, source-sink balance as well as its interactive mechanisms with other environmental factors including water availability, temperature and mineral nutrition are discussed.

Plant Responses to Elevated CO 2

eLS, 2012

Carbon dioxide (CO 2) has two unique properties: physically it absorbs in the infra-red (heat) portion of the spectrum, and plays a role in maintaining global surface temperatures; secondly, it is the source of carbon for plant photosynthesis and growth. Recent, rapid anthropogenic increases in CO 2 have been well-characterised with respect to climatic change; less recognised is that increase in CO 2 will also impact how plants supply food, energy and carbon to all living things. At present, numerous experiments have documented the response of single leaves or whole plants to elevated CO 2 ; however, it is difficult to scale up or integrate these observations to plant biology in toto. To that end, a greater emphasis on multiple factor experiments for managed and unmanaged systems, in combination with simulative vegetative modelling, could increase our predictive capabilities regarding the impact of elevated CO 2 on plant communities (e.g. agriculture, forestry) of human interest. Advanced article Article Contents This is a US Government work and is in the public domain in the United States of America. eLS. www.els.net. John Wiley & Sons, Ltd

Integration of photosynthetic acclimation to CO2 at the whole-plant level

Global Change Biology - GLOB CHANGE BIOL, 1998

Primary events in photosynthetic (PS) acclimation to elevated CO2 concentration ([CO2]) occur at the molecular level in leaf mesophyll cells, but final growth response to [CO2] involves acclimation responses associated with photosynthate partitioning among plant organs in relation to resources limiting growth. Source–sink interactions, particularly with regard to carbon (C) and nitrogen (N), are key determinants of PS acclimation to elevated [CO2] at the whole-plant level. In the long term, PS and growth response to [CO2] are dependent on genotypic and environmental factors affecting the plant's ability to develop new sinks for C, and acquire adequate N and other resources to support an enhanced growth potential. Growth at elevated [CO2] usually increases N use efficiency because PS rates can be maintained at levels comparable to those observed at ambient [CO2] with less N investment in PS enzymes. A frequent acclimation response, particularly under N-limited conditions, is for the accumulation of leaf carbohydrates at elevated [CO2] to lead to repression of genes associated with the production of PS enzymes. The hypothesis that this is an adaptive response, leading to a diversion of N to plant organs where it is of greatest benefit in terms of competitive ability and reproductive fitness, needs to be more rigorously tested.The biological control mechanisms which plants have evolved to acclimate to shifts in source–sink balance caused by elevated [CO2] are complex, and will only be fully elucidated by probing at all scales along the hierarchy from molecular to ecosystem. Use of environmental manipulations and genotypic comparisons will facilitate the testing of specific hypotheses. Improving our ability to predict PS acclimation to [CO2] will require the integration of results from laboratory studies using simple model systems with results from whole-plant studies that include measurements of processes operating at several scales.Abbreviations: CAM, crassulacean acid metabolism; FACE, Free-Air CO2 Enrichment; Pi, inorganic phosphate; LAR, leaf area ratio (m2 g-1); LWR, leaf weight ratio (g g-1); NAR, net assimilation rate (g m-2 d- 1); PS, photosynthetic; RGR, relative growth rate (g g-1 d-1); R:S, root/shoot ratio; rubisco, ribulose bisphosphate carboxylase/oxygenase; RuBP, ribulose bisphosphate; SLA, specific leaf area (m2 g-1); SPS, sucrose phosphate synthase; WUE, water use efficiency (g biomass g H2O-1).

Nutrients and sink activity drive plant CO2 responses - caution with literature-based analysis

New Phytologist, 2003

Climate change and plant pathosystems-future disease prevention starts here The concentration of carbon dioxide (CO 2) in the atmosphere is increasing (Keeling et al ., 1989) and may double during this century (Bolin, 1986). The opportunities available for those interested in the study of plant diseases within the emerging field of global change science were noted over a decade ago (Bruck & Shafer, 1991). However, the manner in which increasing levels of atmospheric CO 2 will affect crop diseases remains virtually unstudied. One group which has taken up this challenge and has begun to address the effects of climate change and elevated atmospheric CO 2 on plant diseases is Sukumar Chakraborty and colleagues in Queensland, Australia. In this issue of New Phytologist (pp. 733-742), Chakraborty & Datta present results from an indepth investigation of the effects of elevated atmospheric CO 2 on a crop, Stylosanthes scabra , to one of its major diseases (anthracnose, caused by the fungus Colletotrichum gloeosporioides).

Plant Respiration and Elevated Atmospheric CO 2 Concentration: Cellular Responses and Global Significance

Background Elevated levels of atmospheric [CO 2 ] are likely to enhance photosynthesis and plant growth, which, in turn, should result in increased specific and whole-plant respiration rates. However, a large body of literature has shown that specific respiration rates of plant tissues are often reduced when plants are exposed to, or grown at, high [CO 2 ] due to direct effects on enzymes and indirect effects derived from changes in the plant's chemical composition.

Why are Nitrogen Concentrations in Plant Tissues Lower under Elevated CO2? A Critical Examination of the Hypotheses

Journal of Integrative Plant Biology, 2008

Plants grown under elevated atmospheric [CO 2 ] typically have decreased tissue concentrations of N compared with plants grown under current ambient [CO 2 ]. The physiological mechanisms responsible for this phenomenon have not been definitely established, although a considerable number of hypotheses have been advanced to account for it. In this review we discuss and critically evaluate these hypotheses. One contributing factor to the decreases in tissue N concentrations clearly is dilution of N by increased photosynthetic assimilation of C. In addition, studies on intact plants show strong evidence for a general decrease in the specific uptake rates (uptake per unit mass or length of root) of N by roots under elevated CO 2. This decreased root uptake appears likely to be the result both of decreased N demand by shoots and of decreased ability of the soil-root system to supply N. The best-supported mechanism for decreased N supply is a decrease in transpiration-driven mass flow of N in soils due to decreased stomatal conductance at elevated CO 2 , although some evidence suggests that altered root system architecture may also play a role. There is also limited evidence suggesting that under elevated CO 2 , plants may exhibit increased rates of N loss through volatilization and/or root exudation, further contributing to lowering tissue N concentrations.