No abstract

We performed uptake experiments with 12 different organic chemicals using 16 plant species and determined differences in the ability of plant species to take up and translocate these chemicals. There were differences among the plant species in the shoot and root concentrations of each organic chemical. The root concentration factor values increased with an increasing log of the noctanol-water partition coefficient (log K OW) of organic chemicals. Thus, the concentrations in roots may be predicted to a certain extent because the root concentration factor values were related to the log K OW. The root-to-shoot translocation was related to the log K OW because the shoot-to-root concentration ratio decreased with an increasing log K OW ; however, there was no clear relationship between the shoot concentration factor value and the log K OW , and this differed among plant species.

To compare the uptake and translocation of hydrophobic organic chemicals (HOCs) by plant species, we performed uptake experiments with β-1,2,3,4,5,6-hexachlorocyclohexane (β-HCH) and 1,2,3,4,10,4,4a,5,6,7,8,8-dimethanonaphthalene (dieldrin) using 5 species: Hordeum vulgare, Glycine max, Solanum lycopersicum, Brassica oleracea, and Cucurbita pepo. We evaluated uptake ability by root concentration factor (RCF) and translocation ability by transpiration stream concentration factor (TSCF). RCFs of β-HCH and dieldrin did not differ remarkably among species, except that that of β-HCH in B. oleracea was high. TSCFs of β-HCH and dieldrin were high in C. pepo, which was not superior in uptake as estimated by RCF. TSCF of dieldrin in C. pepo was decreased in darkness, and was markedly decreased by heating of roots. These results support the hypothesis that transport proteins produced in the root contribute to dieldrin translocation. On the other hand, TSCF of β-HCH was not decreased by these treatments. Therefore, translocation of β-HCH might not need the contribution of transport proteins. It is possible that C. pepo has a certain function to transport HOCs smoothly in root tissues.

We cultivated Brassica rapa var. perviridis in soil mixed with four pesticides (fenobucarb, procymidone, flutolanil, and tolclofosmethyl) at different temperatures, day lengths, and soil water contents. We compared plants' uptake and translocation abilities of the pesticides as affected by growth conditions. The root concentration factor (RCF) of pesticides tended to increase with rising temperature; however, but the influence of temperature on the transpiration stream concentration factor (TSCF) differed for each pesticide. The RCFs and TSCFs of pesticides were high for short days. The soil water content had little or no effect on the uptake and translocation of pesticides. These results showed that it is necessary to consider growth conditions, especially the temperature and day length in plant uptake models for these pesticides.

The relationships between plant growth stage and pesticide-uptake ability were investigated via cultivation of Brassica rapa L. var. perviridis in soil to which was added four pesticides of relatively high log K OW : fenobucarb, procymidone, flutolanil, and tolclofos-methyl. The root concentrations of pesticides were low in very young seedlings with undeveloped root systems, highest in seedlings with developed root systems, and tended to decrease until the usual harvesting stage. Additionally, the shoot concentrations of tested pesticides showed the same trends as the roots. The pesticide-uptake abilities of roots were lowest in very young seedlings and then constant for seedlings until the harvesting stage. In contrast, the pesticide-translocation abilities from root to shoot were constant regardless of growth stage. The results indicated that changes in shoot concentrations with growth stage were affected by the development of the root system and pesticide-uptake ability of roots.