The PTR-MS was calibrated using standard certified gas mixture (lot 3821, Ionimed Analytik, Innsbruck, Austria), consisting of 17 key plant-emitted compounds at 1?ppm (��5%) range. In all experiments, we used ambient air low in volatile organics (isoprene <1?ppb), ozone (<20?ppb) and NOX close to detection limit (?0.01?ppb). The ambient air was further purified by passing through <a href="http://en.wikipedia.org/wiki/FKBP
">FKBP an ozone trap and charcoal filter, resulting in very low ozone (1�C2?ppb, and close to or below the detection limit of VOC and NOX concentrations). For the gas-exchange measurements, the above-ground part of the plant was enclosed in the chamber, photosynthetic quantum flux density was set to 650??mol?m?2?s?1, air temperature to 30?��C (leaf temperature 29�C31?��C) and relative humidity 60%, and the CO2 concentration inside the chamber was selleck chemicals
ambient 380�C400??mol?mol?1. All gas exchange rates were recorded after the steady-state values were reached, typically 30?min after the plant enclosure in the chamber. Foliage CO2, water vapour and trace gas exchange measurements were conducted continuously for the first three days of the experiment, and thereafter, once per day between 11:00 and 14:00?h in both flooded and control plants. The net assimilation rate (A), transpiration rate (E), stomatal conductance (gs) to water vapour and CO2 concentration in sub-stomatal cavities (Ci) were calculated from the measurements of CO2 and H2O concentrations at chamber in- and outlets according to von Caemmerer & Farquhar (1981). Analogously, NO, isoprene and LOX product flux rates were calculated (Beauchamp et?al. 2005). All gas exchange rates were expressed per unit projected leaf area of all leaves enclosed in the chamber. The trace gas i, emission flux rate out of the leaf, ��i, is expressed as: (1) where gs,i is the stomatal conductance to compound i (mol?m?2?s?1) and ci,i is the internal concentration and ca,i is the ambient concentration of this compound (mol?mol?1). From this, the internal concentration is given as: (2) gs,i for a given compound can be calculated from stomatal conductance to water vapour, gs, as (Ball 1987; Niinemets & Reichstein 2003): (3) where Di is the binary diffusion coefficient for the given CSF-1R inhibitor
compound and DH2O is that for the water (m2?s?1). Diffusion coefficients at given temperature for most trace gases were from Niinemets & Reichstein (2003). For the compounds not reported in their study, the binary diffusion coefficient at a given temperature was calculated according to Chapman and Enskog (Tucker & Nelken 1982; Niinemets & Reichstein 2003). For instance, for NO a diffusion coefficient of 2.25?��?10?5?m2?s?1 was obtained. This value agrees well with previous estimates used in simulating NO diffusion in biological systems (Velikova et?al. 2008; Hemmingsson & Linnarsson 2009).