叶片气孔扩散阻抗大小是植物净化空气能力的指标之一。应用气孔仪在自然条件下调查了50科115种植物的气孔阻抗和蒸腾速率，包括落叶树84种，常绿树25种，藤本和草本6种，其中列入中国植物红皮书的稀有濒危植物33种。叶面气孔扩散阻抗平均值为2．28s／cm，最小值为桑（Morusalba）0．49s／cm，最大值为紫楠（Phoebe sheareri）和夏蜡梅（Calycanthus chinensis）7．6s／cm。调查结果表明：叶片气孔扩散阻抗小，净化空气能力强又不易受环境变化影响的阔叶树种有桑、棕榈、臭椿、构树、白腊树、栾树等，藤本植物爬山虎也有很好的净化效率。

The stomatal diffusive resistance (SDR) of leaves is one of the indexes of the air-filtering ability of plants. The SDR and the transpiration rate in 115 species of broadleaved trees belonging to 50 families, which included 84 species of deciduous trees, 25species of evergreen trees, 6 species of liana and herbs, among them 33 species are rare and endangered trees, were investigated by stomatal instrument (in feild) . The average value of the SDR was 2.28 s/cm, while the minimum value was 0.49 s/cm in Morus alba , and the maximum was 7.6 s/cm in Phoebe sbeareri and Calvcanthus chinensis.The results showed that the broad-leaved trees, which had the low SDR, high air-filtering ability and were not easily to be effected by the environment changes, were Morus alba , Trachycarpus fortunei , Ailanthus altissima , Broussonetia papyri fera , Fraxinus chinensis, Koelreuteria integri folia , etc. Parthenocissus tricuspidata , a liana, also had high air-filtering efficiency.