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KINETICS OF LEAF TEMPERATURE FLUCTUATION AFFECT ISOPRENE EMISSION FROM RED OAK (QUERCUS RUBRA) LEAVES
Citation:
Singsaas, E. L., M. M. Laporte, J. Z. Shi, R. K. Monson, D. R. Bowling, K. Johnson, M. Lerdau, A. Jasentuliytana, AND T. D. Sharkey. KINETICS OF LEAF TEMPERATURE FLUCTUATION AFFECT ISOPRENE EMISSION FROM RED OAK (QUERCUS RUBRA) LEAVES. TREE PHYSIOLOGY. Heron Publishing, Victoria, B.C, Canada, 19(14):917-924, (1999).
Description:
Because the rate of isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperature-dependent, we investigated the natural fluctuations on leaf temperature and the effects of rapid temperature change on isoprene emission of red oak (Quercus rubra L.) leaves at the top of the canopy at Harvard Forest. Leaves reached temperatures as much as 15 degrees C above air temperature often throughout the day. The highest temperatures were reached for only a few seconds at a time. To determine the effects of rapid leaf temperature fluctuations on isoprene emission rate, we compared isoprene emission rates measured by changing leaf temperature quickly with those measured by changing leaf temperature slowly. In all cases, isoprene emission rate increased with leaf temperature below 32 degrees C and began to decrease with higher temperatures. The temperature at which isoprene began to decrease depended upon how quickly measurements were made. When measurements were made once per hour, isoprene emission rate peaked at 32.5 degrees C, but when measurements were made every four minutes isoprene emission rate peaked at 39 degrees C. This behavior occurred because isoprene emission rate increased rapidly after an increase in leaf temperature, but decreased again when leaf temperature was held steady for longer than 20 minutes. We concluded that the temperature response of isoprene emission rate is a function of measurement protocol. Dropping this parameter from isoprene emission models will not affect simulated isoprene emission rates at mild temperatures, but can increase isoprene emission rates at high temperatures.