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.