Seasonal variation in ethylene concentration in the wood of Pinus sylvestris L.

Ethylene concentrations were determined in gas samples extracted from sealed holes made in the sapwood and heartwood of stems of 70-100-year-old Scots pine (Pinus sylvestris L). Gas could be collected from the heartwood holes by lowering the pressure by means of a large syringe. However, attempts to extract gas from air spaces in the sapwood with the same technique failed, presumably because of lack of an interconnected system of gas-filled canals. High ethylene concentrations, usually in excess of 1 ppm, accumulated in the sapwood holes within one day after sealing. Ethylene concentrations in the sapwood rose to 3-7 ppm during the growing season, and decreased to 0.1-0.3 ppm during the winter. In response to extreme drought, sapwood ethylene concentration increased to 30 ppm, followed by a rapid decrease after the onset of rain. Ethylene concentrations in gas samples from the heartwood were consistently lower than 1 ppm. The lowest values, about 0.1 ppm, were found during the autumn and early winter, whereas values around 0.5 ppm were typical from February to August.