Transport via xylem of atrazine, 2,4-dinitrotoluene, and 1,2,3-trichlorobenzene in tomato and wheat seedlings

Transport of atrazine (ATR), 2,4-dinitrotoluene (DNT), and 1,2,3-trichlorobenzene (TCB) from roots to shoots via xylem of wheat and tomato seedlings was measured following a 24-h exposure of plant roots to hydroponic solutions of these organic compounds. Transport of the compounds from roots to shoots reached equilibrium within 24 h, consistent with an earlier finding. Low concentrations of TCB were detected in the final external solution and the xylem efflux of control wheat seedlings. This suggested that there was a fast foliar uptake of TCB and its downward movement via phloem of the wheat seedlings. Concentrations of DNT, ATR, and TCB in xylem effluxes of wheat and tomato increased significantly with increases of their external concentrations. The translocation stream concentration factors (TSCF), i.e., the ratios of the concentrations in xylem sap to those in external solution, of the compounds with tomato seedlings followed the order of ATR > DNT >> TCB, which was inversely correlated with the log Kow (the octanol–water partition coefficient) of the compounds. The observed xylem transports of DNT and TCB from roots to shoots with wheat seedlings were lower than those with tomato seedlings. ATR exhibited a high xylem transport with the two plant species, which resulted presumably from an atrazine–metal complex formation.

Concentration-dependent xylem translocation of TCB in wheat seedlings.Figure optionsDownload as PowerPoint slideHighlights
► Transport of atrazine (ATR), 2,4-dinitrotoluene (DNT), and 1,2,3-trichlorobenzene (TCB) from roots to shoots via plant xylem was investigated in hydroponic experiment.
► There was a fast foliar uptake of TCB and its downward movement via phloem of the wheat seedlings.
► The observed xylem transports of DNT and TCB from roots to shoots with wheat seedlings were lower than those with tomato seedlings.
► ATR exhibited a high xylem transport with the two plant species, which resulted presumably from an atrazine-metal complex formation.