The fate of methyl salicylate in the environment and its role as signal in multitrophic interactions

Abstract

Phytohormones emitted into the atmosphere perform many functions relating to the defence, pollination and competitiveness of plants. To be effective, their atmospheric lifetimes must be sufficient that these signals can be delivered to their numerous recipients. We investigate the atmospheric loss processes for methyl salicylate (MeSA), a widely emitted plant volatile. Simulation chambers were used to determine gas-phase reaction rates with OH, NO 3 , Cl and O 3 ; photolysis rates; and deposition rates of gas-phase MeSA onto organic aerosols. Room temperature rate coefficients are determined (in units of cm 3 molecule-1 s-1) to be (3.20±0.46)×10-12 , (4.19±0.92)×10-15 , (1.65±0.44)×10-12 and (3.33±2.01)×10-19 for the reactions with OH, NO 3 , Cl and O 3 respectively. Photolysis is negligible in the actinic range, despite having a large reported near-UV chromophore. Conversely, aerosol uptake can be competitive with oxidation under humid conditions, suggesting that this compound has a high affinity for hydrated surfaces. A total lifetime of gas-phase MeSA of 1-4 days was estimated based on all these loss processes. The competing sinks of MeSA demonstrate the need to assess lifetimes of semiochemicals holistically, and we gain understanding of how atmospheric sinks influence natural communication channels within complex multitrophic interactions. This approach can be extended to other compounds that play vital roles in ecosystems, such as insect pheromones, which may be similarly affected during atmospheric transport.

Green Leaf Volatiles in the Atmosphere—Properties, Transformation, and Significance

“…a upper limits, 0-10 km above the Earth's surface; b at 254 nm; c at 365 nm and > 300 nm. Photolysis was an insignificant degradation path in the troposphere for 1-penten-3-ol and (Z)-3-hexen -1-ol [57], (Z)-3-hexen-1-al [161], MBO [165], and MeSa [227]. Photodegradation of (Z)-3-hexenal was faster than its reaction with O 3 (1 × 10 12 molecule cm −3 ) and slower than its reaction with OH (2 × 10 6 molecule cm −3 ).…”

Gas-phase rate coefficient of OH + cyclohexene oxide measured from 251 to 373 K

“…This system consists of a large PTFE Teflon chamber equipped with in situ multipass FTIR and high-resolution time-of-flight proton-transfer reaction mass spectrometry (PTR-ToF-MS) measurements. This apparatus has been employed recently to measure the reaction rates of compounds of low volatility [17], and is therefore considered to be a good additional test of kinetic determinations for potentially surface-active chemicals such as an epoxide, that may be affected by the higher surface area:volume ratiosas well as higher reactant and OH precursor concentrationsencountered in the LIF reactor and its accompanying FTIR cell.…”

How Adsorption of Pheromones on Aerosols Controls Their Transport

“…A description of the aggregation dynamics of pheromones on the aerosol surface, unable to penetrate in the aerosol bulk, was achieved using the general framework introduced by Gibbs and refined by Tanford for the two-dimensional pseudophases created by amphiphilic molecules. ,,,, Occupancy of the surface by aerosols can be estimated with high precision as long as the gain of energy of moving the pheromone from the gas phase to the interface can be determined. Appropriated experimental and theoretical methods can lead to such results. ,− We developed here the generic theory in the case of independent pheromone molecules adsorbed on the surface of aerosols composed of pure water.…”

“…Our general theory might offer the first clues to understand the mechanisms underlying these observations. Progress in this direction depends on experimental advances in order to characterize the molecules transported in one aerosol of control type and history. , Proper characterization of aerosol surface composition and properties is still a challenging task and is limited to rare studies. , Further investigation would need to discriminate which values of parameters are mostly fitting a specific chemical communication context.…”