(E.J.W., H.C.P.M.V.) coincides with the climacteric rise in respiration (Biale and Young, 1981). As has been remarked by Saltveit (19931, classification of fruit as climacteric is based on experiments with harvested fruit, and a rise in respiration and ethylene production are considered climacteric only if both coincide with ripening. However, there are characteristic differences between attached and detached tomato fruits. Although detached and attached tomatoes both demonstrate the Same ripening ScOre and strong increase of ethylene production , the emission of co, for harvested fruit shows a The function of the coronet region of the cherry tomato (LYCO-persicon esculentum Cherry) as the main emission channel for ethylene was investigated. Ethylene was measured employing two laser-based detection systems, the photothermal deflection instrument and the photoacoustic detection setup. It is possible to detect minimum ethylene concentrations of 1 nL L-' locally and rapidly with the first instrument and concentrations of 6 pL L-' in a continuous flow system with the second setup. The continuous flow system makes it possible to change the air composition and to monitor its influence on the ethvlene oroduction of the tomato. The I. response times of the two instruments are 30 s and 4 min, respectively. The local character of the measurements makes it possible to determine the emission sites of the gaseous plant hormone ethylene and their relative importance. Transient anoxic conditions stop production of ethylene; return to aerobic conditions shows the evolution of the accumulated ethylene precursor 1-aminocyclopro-pane-1-carboxylic acid and its renewed production on the measured ethylene emission, with a time resolution of severa1 minutes. Temporarily sealing the main emission channel yields results comparable to anoxia.