Abstract:The gas exchange characteristics of aerial roots of Ficus microcarpa L. f. were measured by using LI-6400XT portable photosynthesis system. The results showed that the aerial roots had obvious respiration and transpiration function. The effect factors on respiration were in order of root age > air temperature >light intensity > relative humidity by orthogonal experiment, and root age > relative humidity > air temperature > light intensity for transpiration. The young aerial root had higher respiration and transpiration rates than the old roots, which highly lignified old aerial roots had low respiratory rate, their transpiration turned to absorption of moisture from air. On the basis of single-factor-analysis, the CO2 exchange rate and H2O exchange rate of young aerial root had linear relationship with temperature and relative humidity, respectively. The higher of temperature, the higher of the CO2 exchange rate, the the stronger of the respiration, the higher of relative humidity, the smaller of the H2O exchange rate, the lower of transpiration. The H2O exchange rate of old mature aerial root had linear relationship with air relative humidity, the higher of relative humidity, the smaller of the H2O exchange rate, the lower of transpiration.