Future environments are predicted to be hotter and drier than today. Therefore, crop growth and yield will likely diminish in many areas of the globe that are experiencing rapid population growth. Current research efforts are focused on understanding the mitigating effects of CO2 enrichment on responses of crop plants to abioitic stress. A systems approach employing metabolite analysis along with changes of transcript abundance was used to determine the effects of drought on maize genotypes differing in water stress tolerance. Heat shock studies with maize identified key C4 pathway enzymes that were down regulated by 1h of exposure to 45 ?C leaf temperatures. Metabolite analysis also was used to show that the conversion of sugars to organic acids was inhibited by elevated growth temperatures in soybean leaflets. This inhibition was largely reversed by elevated CO2 treatments. Transcript analysis revealed that carbon dioxide levels in the air modulated the induction of various cold regulated genes in Arabidopsis. This research showed that atmospheric CO2 affected freezing tolerance and also identified a link between stomatal aperture and cold signaling at the molecular level.