[Characterization comparison of polycyclic aromatic hydrocarbon uptake by roots of different crops]

It is important to investigate the differences in polycyclic aromatic hydrocarbon (PAH) uptake by roots of different crops for selecting and breeding less or excess uptake species of PAHs by genetic engineering, and further yielding safe production and phytoremediating the soil or water contaminated with PAHs. Hydroponic experiments were performed to study characterization comparison of phenanthrene (a representative of PAHs) uptake by soybean, wheat and carrot roots. Soybean, carrot and wheat roots can take up phenanthrene from Hoagland nutrient solution and the phenanthrene absorbed by roots increases with incubation time. The uptake process consists of two sequential phases: a fast accumulation process followed by a slow one. The capability to take up phenanthrene for the three crops can be arranged as soybean > carrot > wheat. The relationship between the phenanthrene absorbed and time fits Elovich equation well. Uptake rate constants for soybean, carrot and wheat roots are 4.31, 4.10 and 2.84 mg x (kg x h)(-1), respectively. Concentration-dependent uptake of phenanthrene by roots of soybean, carrot and wheat can be described with Michaelis-Menten equation and the Km values for soybean, carrot and wheat are 0.117, 0.124 and 0.540 mg x L(-1). Hydroponic solution pH increases due to phenanthrene uptake and the trend in pH increase significantly correlates with those in uptake rate constant and Km value. In addition, the orders of uptake rate constant, Km value and pH increase for soybean, carrot and wheat are the same as that of uptake capability. Therefore, it is concluded that uptake rate constant, Km value and pH increase can be employed as indicators for the capability to take up PAHs by crop roots, and uptake rate constant and Km value are better indicators than pH increase because of less affecting factors.