Zamioculcas zamiifolia has the potential to reduce the concentration of benzene, toluene, ethylbenzene, and xylene (BTEX) from contaminated indoor air. It can remove all four pollutant gases. Benzene, toluene, ethylbenzene, and xylene uptake per unit area of Z. zamiifolia leaf were about 0.96+/-0.01, 0.93+/-0.02, 0.92+/-0.02, and 0.86+/-0.07 mmol m(-2) at 72 h of exposure, respectively. The physicochemical properties of each BTEX may affect its removal. Benzene, a smaller molecule, is taken up by plants faster than toluene, ethylbenzene, and xylene. The toxicity of BTEX on plant leaves and roots was not found. The chlorophyll fluorescence measurement (F-v/F-m) showed no significantly difference between controlled and treated plants, indicating that a concentration of 20 ppm of each gas is not high enough to affect the photosynthesis of the plants. The ratio of stomata and cuticles showed that 80 % of benzene, 76 % of toluene, 75 % of ethylbenzene, and 73 % of xylene were removed by stomata pathways, while 20, 23, 25, and 26 % of them were removed by cuticles. The BTEX removal efficiency by well-watered Z. zamiifolia was involved with day stomata opening and night closing, while the BTEX removal efficiency by water-stressed Z. zamiifolia can occur both day and night at a slightly lower rate than well-watered plants.
