Accumulation of polar compounds in leaves and fruits - questioning the suitability of widely used TSCF - log Kow regressons: Abstract P771

Although the specific mechanisms are not completely understood, plant uptake of most xenobiotic organic compounds is believed to be a passive process related at least in part to the lipophilicity of the compound. The transpiration stream concentration factor (TSCF), a ratio of xylem to root-zone solution concentrations, is one of the most widely used descriptors in plant uptake modeling.

Unfortunately, experimentally determined TSCF values are extremely limited and TSCF used in modeling efforts are often estimated from empirically derived bell-shaped curves that relate TSCF to the log octanol/water partition coefficient (Kow). The shape of the curve implies that there is an optimal lipophilicity for uptake and translocation and compounds that are highly polar are not expected to be significantly translocated.However, recent experimental uptake data generated for highly water-soluble and water miscible compounds (e.g.. sulfolane, 1,4- dioxane, MTBE) suggest that this relationship may not be appropriate.

An alternative TSCF-log Kow relationship in combination with a refined model for predicting uptake and accumulation in edible fruits.