T he most recent assessment report from the Intergovernmental Panel of Climate Change (IPCC) clearly illustrates the links between atmospheric CO2 and climate (1) and the impacts of climate change on life (2). The geologic record contains a treasure trove of ‘‘alternative Earths’’ that allow scientists to study how the various components of the Earth system respond to a range of climatic forcin...

Leaf-level measurements have shown that mesophyll conductance (gm) can vary rapidly in response to CO2 and other environmental factors, but similar studies at the canopyscale are missing. Here, we report the effect of short-term variation of CO2 concentration on canopy-scale gm and other CO2 exchange parameters of sunflower (Helianthus annuus L.) stands in the presence and absence of abscisic a...

The expression and activity of glutamine synthetase (GS, EC 6.3.1.2) were examined in relation to the rate of CO2 assimilation in sun ̄ower (Helianthus annuus L.) leaves. Intact plants were kept in the dark for 72 h and subsequently exposed to light under different atmospheric CO2 concentrations (100, 400 and 1200 ml l) for 6 h. The in vivo rates of net CO2 assimilation correlated with atmospher...

The expression and activity of glutamine synthetase (GS, EC 6.3.1.2) were examined in relation to the rate of CO2 assimilation in sunflower (Helianthus annuus L.) leaves. Intact plants were kept in the dark for 72 h and subsequently exposed to light under different atmospheric CO2 concentrations (100, 400 and 1200 microl l-1) for 6 h. The in vivo rates of net CO2 assimilation correlated with at...

We investigated how leaf hydraulic conductance (Kleaf) of loblolly pine trees is influenced by soil nitrogen amendment (N) in stands subjected to ambient or elevated CO2 concentrations (CO2 and CO2, respectively). We also examined how Kleaf varies with changes in reference leaf water potential (Yleaf-ref) and stomatal conductance (gs-ref) calculated at vapour pressure deficit, D of 1 kPa. We de...

During the Miocene period, from 25 to 12 million years ago, climate change drove plants and animals to evolve toward their modern forms and distribution. The fossil and geological records show considerable fluctuation in global temperature during this time, but not all proxies for atmospheric CO2 data show a link between CO2 and Miocene climate. Wolfram Kürschner et al. tap a new source of CO2 ...

Two cultivars of sugarcane (Saccharum officinarum cv. CP73-1547 and CP88-1508) were grown for 3 months in paired-companion, temperature-gradient, sunlit greenhouses under daytime [CO2] of 360 (ambient) and 720 (double ambient) micromol mol(-1) and at temperatures of 1.5 degrees C (near ambient) and 6.0 degrees C higher than outside ambient temperature. Leaf area and biomass, stem biomass and ju...

Abaxial epidermal strips, containing guard cells as the only viable cells, were prepared from leaves of Vicia faba following a period in darkness, and floated, under CO(2)-free air, on 2 mm RbCl + 0.1 mm CaCl(2) labeled with (86)Rb(+). Under white light (high pressure mercury vapor lamp), stomatal opening in these strips approached its maximum at less than 0.02 calorie per square centimeter per...

Increasing concentrations of atmospheric carbon dioxide (CO2) and tropospheric ozone (O3) have the potential to affect tree physiology and structure, and hence forest feedbacks on climate. Here, we investigated how elevated concentrations of CO2 (+45%) and O3 (+35%), alone and in combination, affected conductance for mass transfer at the leaf and canopy levels in pure aspen (Populus tremuloides...