Chemical sensing of plant stress at the ecosystem scale T. Karl, A. Guenther, A. Turnipseed, E. G. Patton, and K. Jardine National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, 80301, CO, USA
Abstract. Significant ecosystem-scale emissions of methylsalicylate
(MeSA), a semivolatile plant hormone thought to act as the mobile signal for
systemic acquired resistance (SAR), were observed in an agroforest. Our
measurements show that plant internal defence mechanisms can be activated in
response to temperature stress and are modulated by water availability on
large scales. Highest MeSA fluxes (up to 0.25 mg/m2/h) were observed
after plants experienced ambient night-time temperatures of ~7.5°C
followed by a large daytime temperature increase (e.g. up to 22°C).
Under these conditions estimated night-time leaf temperatures were as low as
~4.6°C, likely inducing a response to prevent chilling injury.
Our observations imply that plant hormones can be a significant component of
ecosystem scale volatile organic compound (VOC) fluxes (e.g. as high as the
total monoterpene (MT) flux) and therefore contribute to the missing VOC
budget. If generalized to other ecosystems and different types of stresses
these findings suggest that semivolatile plant hormones have been overlooked
by investigations of the impact of biogenic VOCs on aerosol formation events
in forested regions. Our observations show that the presence of MeSA in
canopy air serves as an early chemical warning signal indicating
ecosystem-scale stresses before visible damage becomes apparent. As a
chemical metric, ecosystem emission measurements of MeSA in ambient air
could therefore support field studies investigating factors that adversely
affect plant growth.
Citation: Karl, T., Guenther, A., Turnipseed, A., Patton, E. G., and Jardine, K.: Chemical sensing of plant stress at the ecosystem scale, Biogeosciences, 5, 1287-1294, doi:10.5194/bg-5-1287-2008, 2008.