Plant roots are able to accumulate polycyclic aromatic hydrocarbons（PAHs） from soil and water. However，the mechanism for PAHs uptake is little understood. The possibility that plant roots may take up PAHs via active process was investigated using intact wheat（Triticum acstivnm L.） seedlings in a series of hydroponic experiments. The time course for phenanthrene（PHE） uptake into wheat roots grown in Hoagland solution containing 5.62μM PHE for 36 h could be separated into two periods: a fast uptake process during the initial 2 h and a slow uptake component thereafter.