SEASONAL-VARIATIONS OF O-2, CO2, AND ETHYLENE IN OAK AND MAPLE STEMS

Oxygen, carbon dioxide, and ethylene in the outer sapwood of English o ak (Quercus robur L.) and Norway maple (Acer platanoides L.) were moni tored from May through September. Oxygen and carbon dioxide were measu red by gas chromatography - mass spectrometry, and ethylene by gas chr omatography. In both species, the level of ethylene increased when cam bial growth resumed in early May, peaked in June, and thereafter decre ased, reaching the springtime level in August. In contrast, the concen tration of oxygen in both species was high when growth started, but su bsequently decreased to a minimum of about 5% in July. Thereafter the oxygen concentration increased and in September attained the early spr ing level. In maple, the concentration of carbon dioxide was steady th roughout the experimental period, except for a decrease in June. In oa k, the carbon dioxide level increased after growth resumed and peaked in August. The seasonal patterns of change in ethylene, oxygen, and ca rbon dioxide resembled those observed in conifers. However, the amplit ude of the seasonal variations in oxygen and carbon dioxide was less t han that found in conifers, suggesting that the system for delivering oxygen and removing carbon dioxide is more effective in deciduous spec ies than in conifers.