Uptake pathways of chlorobenzenes in plants and their correlation with N-octanol/water partition coefficients

The bioconcentration factors of 14C-labeled chlorinated benzenes in plants from soil were quantified in short-term laboratory experiments and correlated to Kow. The correlation was negative for barley and positive for cress. In order to interpret these opposite results, the log/log correlation between partition coefficients and Kow of the chemicals was established also for each step of the uptake, via both roots and leaves. For the first step of root uptake--the partition of the chemicals from soil solids into soil water--the correlation with Kow was negative, whereas it was positive for the second step, the partition roots/soil water, of both plant species. Similarly, the correlation between the first step of foliar uptake--the partition of the chemical from soil into air--and Kow was negative, and that between the second step--the partition between aerial plant parts and air--and Kow was positive for both plant species. The slopes of the regression lines differed between plant species. It may be concluded that Kow can be used as a parameter to predict the uptake of chemicals from soil by plants only if the same class of chemicals and the same plant species is considered.