Induced plant signaling and its implications for environmental sensing.

The sophisticated chemical responses of plants to environmental stimuli have profound implications for the development of remote sensing systems. Recent advances in the investigation of these responses have demonstrated that plants can be developed as reliable reporters of numerous environmental stimuli including soil and water conditions, light levels, temperature, mechanical damage, insect feeding, exposure to pathogens--including those that affect animals and humans--and exposure to airborne chemicals. Researchers are just beginning to understand the full range of plant phenotypic responses to these and other stimuli. These responses often have measurable physiological and molecular components that are readily observed. Other responses (e.g., internal biochemical changes) are less readily assayed, although sensing devices are being developed. Plant volatile emission "signatures" are particularly promising modes of plant reporting that can provide highly specific information regarding a diverse range of environmental variables on short time scales, but new approaches are needed for sensing these responses remotely. Modern molecular techniques promise to allow us to refine plant sensing and reporting, greatly enhancing the potential utility of plants as "sentinels." Continued basic research aimed at characterizing the physiological, biochemical, and molecular responses of plants to environmental stimuli (including airborne chemicals, insects and pathogenic microbes) are essential to achieving that promise.