N pentane

The collection of volatiles was done as described by Anastasaki et al. [31 (link)]. A single potted tomato plant was placed in a glass container (10 L), with the pot and soil covered with aluminum foil to prevent interaction with VOCs from the soil and roots, and was left for 30 min for acclimatization prior to volatile collection. Purified air, through an activated charcoal filter (10-cm length x 1.5-cm id), was passed through the glass container. Plant volatiles were drawn by a vacuum pump (Dymax 5, Charles Austen Pumps Ltd., West Byfleet, UK) at a rate of 360 mL/min onto a Teflon-made trap (5-cm length x 4-mm id) containing 75 mg Porapak Q (80/100 mesh, Supelco, Bellefonte, PA, USA) tapped with a 2-mm glass wool and 3-mm Teflon tubes in each end. Prior to the analysis, traps were sequentially washed with 1 mL of methanol, diethyl ether, and n-pentane (Fisher Chemicals, Bishop, UK) and blown dry with N₂. The collection of headspace volatiles was done for 6 h. Immediately after volatile collection, traps were extracted with 500 μL of n-pentane. Sample volumes were reduced to 100 μL and stored in a freezer (at −20 °C) in a sealed vial with a conical inserter until use.

Dimethylchloride (DCM; HPLC grade > 99%), diethyl ether (DEE; anhydrous, HPLC grade > 99%), n-pentane (anhydrous, >99%), hexanes (>98.5%), and diallyl disulfide (DADS, >80%) were purchased from Fisher Scientific (Hampton, NH, U.S.A.). Polytetrafluoroethylene (PFTE; 0.45 μm) filters were also purchased from Fischer Scientific.

The adsorbent material 80/100 mesh Porapak Q was supplied from Supelco (Supelco Inc. Bellefonte, USA). MS-grade methanol, diethyl ether and n-pentane were purchased from Fisher (Fisher Chemicals, Bishop, UK). The standard mixture of n-alkanes C₈–C₂₀ 40 mg L^-1 for the calculation of the retention indices was purchased from Sigma-Aldrich (Stenheim, Germany).