Measurement of ethylene emission from Japanese red pine (Pinus densiflora)under field conditions in NOx-polluted areas

Emission of ethylene from the needles of Japanese red pine, Pinus densiflor a, was measured in air-polluted areas in Hiroshima, Japan. We applied a sui table protocol to determine the rate of ethylene emission from the excised needles. The influence of excision of needles on ethylene emission was not detected during the first 4 h of incubation at 20 degreesC. Ethylene emissi ons were low in the unpolluted (clean) areas regardless of the altitude or season. The emission of stress ethylene increased with the atmospheric NO2 concentration, suggesting that atmospheric NOx or related substances induce d the higher ethylene emission in the polluted areas (near urban and indust rial areas). In all cases, 1-year-old needles emitted significantly larger amounts of ethylene than the current needles. Ethylene emission did not inc rease evenly in the polluted areas, but the frequency of trees emitting hig h ethylene increased. Therefore, threshold rates for the baseline ethylene emission were proposed. (C) 2000 Elsevier Science Ltd. All rights reserved.