Vegetation emits a vast array and substantial quantities of biogenic volatile organic compounds (BVOC), which play a major role in air quality, secondary aerosol formation (SAF), carbon sequestration and biosphere-atmosphere interactions. Early BVOC studies focused on isoprene (Greenberg and Zimmerman, 1984; Lamb et al., 1985, Monson et al., 1991a,b; Andronache et al., 1994; Guenther et al., 1996), while more recent research has also included numerous non-isoprene BVOC (Llusia and Penuelas, 1998; Schade and Goldstein, 2001; Greenberg et al., 2001), and indicates that BVOC fluxes recycle a considerable amount of sequestered carbon to the atmosphere. Aside from their atmospheric implications, many classes of BVOC (especially terpenoids) have been discovered to be mediators of plant-insect and plant-plant interactions. There are still many questions surrounding the quantity of BVOC emitted by vegetation and the role these compounds play in atmospheric and biospheric interactions. Many species of BVOC are implicated in attracting pollinators (Fall, 1999; Pichersky and Gershenzon, 2002), and are likely involved in indirect defenses against insect herbivory (Turlings et al., 1995; Fall, 1999). Aside from these functions, some BVOC species may also be involved in allelopathic activity, protection against thermal damage, and other roles (Fall, 1999). An area of research that has received less attention, however, is the uptake of BVOC by plants. Very little knowledge exists about which compounds are taken up by vegetation, what the uptake rates are and on the physiological role of BVOCs in plant-plant interactions. The research proposed for the present study will address these questions. From preliminary previous observations we hypothesize that 1. foliage does take up a significant amount of emitted BVOC, 2. this process diminishes the emission rate that is captured using cuvette or bag enclosure techniques and 3. that the BVOC uptake rate will depend on the experimental design, in particular on the amount of foliage and surface area in the enclosure and the enclosure purge rate. If these assumptions are correct, then the process of BVOC uptake needs to be considered for scaling enclosure data to landscape level emission rates. Secondly, this study will address the question of how plants communicate with each other, both within species and possibly among different genera. Emission and uptake rates of numerous species of BVOC will be studied and plant responses will be investigated in controlled exposure experiments, including studying plant VOC response to different types of plant stressors. This research will involve the use of enclosure-based experiments coupled with analytical detection by an online gas chromatograph-mass spectrometer. BVOC uptake of a variety of compounds will be studied for plant species representative of those at University of Michigan Biological Station (UMBS) site. The amounts and types of BVOC taken up by plants will be investigated, and whether uptake is selective for specific compounds and/or plant species. The present study will also seek to identify whether plants take up mainly what they emit and, if so, what fraction of their emissions is taken back up. This research will yield more accurate estimates of the current BVOC contribution to atmospheric chemical processes, and a better understanding of the role that BVOC emission and uptake plays in biospheric interactions.