Climate change is multi-faceted, and includes changing concentrations of greenhouse gases in the atmosphere, rising temperatures, changes in precipitation patterns, and increasing frequency of extreme weather events. Here, we focus on the effects of rising atmospheric CO concentrations, rising temperature, and drought stress and their interaction on plant developmental processes in leaves, roots, and in reproductive structures. While in some cases these responses are conserved across species, such as decreased root elongation, perturbation of root growth angle and reduced seed yield in response to drought, or an increase in root biomass in shallow soil in response to elevated CO, most responses are variable within and between species and are dependent on developmental stage. These variable responses include species-specific thresholds that arrest development of reproductive structures, reduce root growth rate and the rate of leaf initiation and expansion in response to elevated temperature. Leaf developmental responses to elevated CO vary by cell type and by species. Variability also exists between C and C species in response to elevated CO, especially in terms of growth and seed yield stimulation. At the molecular level, significantly less is understood regarding conservation and variability in molecular mechanisms underlying these traits. Abscisic acid-mediated changes in cell wall expansion likely underlie reductions in growth rate in response to drought, and changes in known regulators of flowering time likely underlie altered reproductive transitions in response to elevated temperature and CO. Genes that underlie most other organ or tissue-level responses have largely only been identified in a single species in response to a single stress and their level of conservation is unknown. We conclude that there is a need for further research regarding the molecular mechanisms of plant developmental responses to climate change factors in general, and that this lack of data is particularly prevalent in the case of interactive effects of multiple climate change factors. As future growing conditions will likely expose plants to multiple climate change factors simultaneously, with a sum negative influence on global agriculture, further research in this area is critical.

Stimulation of C3 crop yield by rising concentrations of atmospheric carbon dioxide ([CO2]) is widely expected to counteract crop losses that are due to greater drought this century. But these expectations come from sparse field trials that have been biased towards mesic growth conditions. This eight-year study used precipitation manipulation and year-to-year variation in weather conditions at a unique open-air field facility to show that the stimulation of soybean yield by elevated [CO2] diminished to zero as drought intensified. Contrary to the prevalent expectation in the literature, rising [CO2] did not counteract the effect of strong drought on photosynthesis and yield because elevated [CO2] interacted with drought to modify stomatal function and canopy energy balance. This new insight from field experimentation under hot and dry conditions, which will become increasingly prevalent in the coming decades, highlights the likelihood of negative impacts from interacting global change factors on a key global commodity crop in its primary region of production.

Extensive evidence shows that increasing carbon dioxide concentration ([CO 2 ]) stimulates, and increasing temperature decreases, both net photosynthetic carbon assimilation (A) and biomass production for C 3 plants. However the [CO 2 ]-induced stimulation in A is projected to increase further with warmer temperature. While the influence of increasing temperature and [CO 2 ], independent of each other, on A and biomass production have been widely investigated, the interaction between these two major global changes has not been tested on field-grown crops. Here, the interactive effect of both elevated [CO 2 ] (approximately 585 mmol mol 21) and temperature (+3.5°C) on soybean (Glycine max) A, biomass, and yield were tested over two growing seasons in the Temperature by Free-Air CO 2 Enrichment experiment at the Soybean Free Air CO 2 Enrichment facility. Measurements of A, stomatal conductance, and intercellular [CO 2 ] were collected along with meteorological, water potential, and growth data. Elevated temperatures caused lower A, which was largely attributed to declines in stomatal conductance and intercellular [CO 2 ] and led in turn to lower yields. Increasing both [CO 2 ] and temperature stimulated A relative to elevated [CO 2 ] alone on only two sampling days during 2009 and on no days in 2011. In 2011, the warmer of the two years, there were no observed increases in yield in the elevated temperature plots regardless of whether [CO 2 ] was elevated. All treatments lowered the harvest index for soybean, although the effect of elevated [CO 2 ] in 2011 was not statistically significant. These results provide a better understanding of the physiological responses of soybean to future climate change conditions and suggest that the potential is limited for elevated [CO 2 ] to mitigate the influence of rising temperatures on photosynthesis, growth, and yields of C 3 crops.

Additional supporting information may be found in the online version of this article.

Innovation, conservation, and repurposing of gene function in root cell type development Graphical abstract Highlights d Tomato cell type-resolution translatome atlas reveals cell type function d Conservation and repurposing in gene regulation between Arabidopsis and tomato d The tomato exodermis is lignified, suberized, and enriched for nitrogen regulation d The root meristem is molecularly homologous across plant species

Climate change hai the potential to alter both the composition and function of a soil's microbial communit), and interactions among climate change factors may alter soil communities in ways that are not possible to predict from experiments based on a single factor. This study evaluated the direct and interactive effects ot three climate change factors-elevated CO,, altered amounts of precipitation, and elevated air temperature-on soil microbial communities from an old-field climate change experiment being conducted at Oak Ridge, TN. Soil microbial community composition and biomass were determined by phospholipid fatty acid (PLFA) and neutral lipid fatty acid compsition.We found that the interactive effects of precipitation and temperature treatments, as well as the interactive effects ot precipitation and COj treatments, had significant impacts on microbial community compsition. We found that total soil PLFA concentration, a measure of microbial biomass, was greater in the low-precipitadon treatments, especially when low precipitation was combined with ambient COj concentrations or ambient temperature. Ordination analysis indicated that temperature was the most significant predictor of shifts in the soil microbial communit)' composition, explaining approximately 12% of the variance in relative abundance of PLFA biomarkers. The elevated-tempetature treatment increa.sed the abundance of Firmkutes (low-guanine-cytosine Gram positive) and decreased the abundance of Gram-negative bacteria. Elevated temperature also reduced the abundance of the arbusctilar mycorrhizal limgi PLFA biomarker 16:15)5c and saprophytic fungal PLFA biomarker 18:2Sé,9. Overall, our data indicate diat the interactions among climate change faaors alter the composition ofsoil microbial communities in old-field ecosystems, suggesting potential for changes in microbial community function under predicted future climate conditions.

The rate of N2 fixation by a leguminous plant is a product of the activity of individual nodules and the number of nodules. Initiation of new nodules and N2 fixation per nodule are highly sensitive to environmental conditions. However, the effects of global environmental change on nodulation in the field are largely unknown. It is also unclear whether legumes regulate nodulation in response to environment solely by varying root production or also by varying nodule density per unit of root length. This study utilised minirhizotron imaging as a novel in situ method for assessing the number, size and distribution of nodules in field-grown soybean (Glycine max (L.) Merr.) exposed to elevated atmospheric CO2 ([CO2]) and reduced precipitation. We found that nodule numbers were 134–229% greater in soybeans grown at elevated [CO2] in combination with reduced precipitation, and this response was driven by greater nodule density per unit of root length. The benefits of additional nodules were probably offset by an unfavourable distribution of nodules in shallow, dry soil in reduced precipitation treatment under elevated [CO2] but not ambient [CO2]. In fact, significant decreases in seed and leaf nitrogen concentration also occurred only in elevated [CO2] with reduced precipitation. This study demonstrates the potential of minirhizotron imaging to reveal previously uncharacterised changes in nodule production and distribution in response to global environmental change.

Rosenthala, David M.; Ruiz-Vera, Ursula M.; Siebers, Matthew H.; Gray, Sharon B.; Bernacchi, Carl J.; and Ort, Donald R., "Biochemical acclimation, stomatal limitation and precipitationpatterns underlie decreases in photosynthetic stimulation of soybean(Glycine max) at elevated [CO 2 Contents lists available at ScienceDirect Plant Science j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p l a n t s c i (1) the acclimation of two biochemical parameters that frequently limit photosynthesis (A), the maximum carboxylation capacity of Rubisco (V c,max ) and the maximum potential linear electron flux through photosystem II (J max ), (2) the associated responses of leaf structural and chemical properties related to A, as well as (3) the stomatal limitation (l) imposed on A, for soybean over two growing seasons in a conventionally managed agricultural field in Illinois, USA. Acclimation to elevated [CO 2 ] was consistent over two growing seasons with respect to V c,max and J max . However, elevated temperature significantly decreased J max contributing to lower photosynthetic stimulation by elevated CO 2 . Large seasonal differences in precipitation altered soil moisture availability modulating the complex effects of elevated temperature and CO 2 on biochemical and structural properties related to A. Elevated temperature also reduced the benefit of elevated [CO 2 ] by eliminating decreases in stomatal limitation at elevated [CO 2 ]. These results highlight the critical importance of considering multiple environmental factors (i.e. temperature, moisture, [CO 2 ]) when trying to predict plant productivity in the context of climate change.