Effects of environmental conditions on isoprene emission from live oak

Abstract

Live-oak plants (Quercus virginiana Mill.) were subjected to various levels of CO2, water stress or photosynthetic photon flux density to test the hypothesis that isoprene biosynthesis occurred only under conditions of restricted CO2 availability. Isoprene emission increases as the ambient CO2 concentration decreased, independent of the amount of time that plants had photosynthesized at ambient CO2 levels. When plants were water-stressed over a 4-d period photosynthesis and leaf conductance decreased 98 and 94%, respectively, while isoprene emissions remained constant. Significant isoprene emissions occurred when plants were saturated with CO2, i.e., below the light compensation level for net photosynthesis (100 μmol m(-2) s(-1)). Isoprene emission rates increased with photosynthetic photon flux density and at 25 and 50 μmol m(-2) s(-1) were 7 and 18 times greater than emissions in the dark. These data indicate that isoprene is a normal plant metabolite and not - as has been suggested - formed exclusively in response to restricted CO2 or various stresses.

Effect of drought on isoprene emission rates from leaves of Quercus virginiana Mill.

“…Our results indicate that although F iso decreased when the water-stress was severe, it was considerably less sensitive to drought than A and g s (Tingey et al, 1981;Sharkey and Loreto, 1993;Fang et al, 1996;Lerdau et al, 1997;Guenther et al, 1999;Bruggemann and Schnitzler, 2002). It was also apparent that F iso could recover from water-stress much more quickly than A and g s .…”

“…Some studies have focused on the effect of water-stress on isoprene emission rates (F iso ) (e.g. Tingey et al, 1981;Sharkey and Loreto, 1993;Lerdau et al, 1997;Guenther et al, 1999;Bruggemann and Schnitzler, 2002). Although in general F iso were much less sensitive to drought than photosynthetic rates pattern has been observed.…”

Light dependency of VOC emissions from selected Mediterranean plant species

“…Tingey et al, 1981) and monoterpenes (Loreto et al, 1996), further studies have shown that G s had no effect on isoprene emissions (e.g. Tingey et al, 1981;Monson and Fall, 1989;Sharkey and Loreto, 1993), nor on monoterpene emissions (e.g. Tingey et al, 1980;Loreto et al, 1996), The apparent non-dependence of VOC emissions on G s has been explained by the low concentrations of these compounds in the leaf tissue, which increase when G s decreases and which compensate for stomatal closure.…”

“…But although a number of studies demonstrated stomatal emissions of isoprene (e.g. Tingey et al, 1981) and monoterpenes (Loreto et al, 1996), further studies have shown that G s had no effect on isoprene emissions (e.g. Tingey et al, 1981;Monson and Fall, 1989;Sharkey and Loreto, 1993), nor on monoterpene emissions (e.g.…”

An ecological implication of glandular trichome-sequestered artemisinin: as a sink of biotic/abiotic stress-triggered singlet oxygen

“…Although artemisinin exists in A. annua with or without ecological implications is unknown, plant volatile isoprenoids have been suggested to play protective roles against damage from abiotic stress-triggered ROS (Vickers et al 2009). Indeed, the emission of volatile isoprenoids frequently increments under abiotic stress conditions at least including intense light, extreme heat, and drought stress (Brilli et al 2007;Loreto and Sharkey 1990;Loreto et al 1998;Loreto et al 2006;Sharkey and Loreto 1993;Sharkey and Yeh 2001;Tingy et al 1981). Strikingly, even the stored carbon resource for growth and development can be urgently mobilized to produce the volatile isoprenoids for fighting abiotic stress (Brilli et al 2007;Loreto and Sharkey 1990;Monson and Fall 1989).…”