Ethanol accumulation in drought-stressed conifer seedlings.

Authors: Manter, Daniel; KELSEY, R - USDA FS, CORVALLIS, OR

Submitted to: International Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2007
Publication Date: 3/1/2008
Citation: Manter, D.K., Kelsey, R.G. 2008. Ethanol accumulation in drought-stressed conifer seedlings. International Journal of Plant Science. 169:361-369.

Interpretive Summary: In this study, we investigated the effect of drought-stress on ethanol production and accumulation in tissues of three conifer species (Douglas-fir, ponderosa pine, and lodgepole pine). Significant ethanol accumulation was observed for all three species at severe levels of drought stress (pre-dawn xylem pressure potential below ca. -30 bars or water contents ca. 0.4 g g-1 dw), but the amounts accumulated differed significantly among species and tissue type, with Douglas-fir typically accumulating the highest levels. Averaged across all three species, the constitutive ethanol increased by ca. 5-, 4-, 2-, and 0.7-fold for sapwood, needle, phloem, and root tissues, respectively. Interestingly, ethanol production rates in anaerobic phloem declined with increasing water stress, and at the onset of ethanol accumulation, phloem production rates were reduced by ca. 98 %. Thus, in conifer seedlings, ethanol accumulation in response to water stress is not associated with an increase in production, but rather a reduction in the dissipation and/or metabolism of constitutive ethanol.

Technical Abstract: In this study, we investigated the effect of drought-stress on ethanol production and accumulation in tissues of three conifer species (Douglas-fir, ponderosa pine, and lodgepole pine). Significant ethanol accumulation was observed for all three species at severe levels of drought stress (pre-dawn xylem pressure potential below ca. -30 bars or water contents ca. 0.4 g g-1 dw), but the amounts accumulated differed significantly among species and tissue type, with Douglas-fir typically accumulating the highest levels. Averaged across all three species, the constitutive ethanol increased by ca. 5-, 4-, 2-, and 0.7-fold for sapwood, needle, phloem, and root tissues, respectively. Interestingly, ethanol production rates in anaerobic phloem declined with increasing water stress, and at the onset of ethanol accumulation, phloem production rates were reduced by ca. 98 %. Thus, in conifer seedlings, ethanol accumulation in response to water stress is not associated with an increase in production, but rather a reduction in the dissipation and/or metabolism of constitutive ethanol.