A Comparison of the Uptake and Translocation of Some Organic Herbicides and a Systemic Fungicide by Barley

Abstract

The relationship between uptake by barley roots and translocation to shoots has been examined under different conditions for six herbicides and a systemic fungicide (four triazines, diuron, 2,4-dichlorophenoxyacetic acid and ethirimol). For all these compounds a large proportion of the material taken up by roots does not appear to move readily to the shoots. Elution with water of the roots of intact plants which had previously been placed in labelled solutions of these compounds enabled the material released to be separated into three fractions differing in their rates of diffusion out of the roots. There was reasonably good correlation between the concentration of the most readily diffusible fraction in the roots and the concentration in the transpiration stream. The results obtained were consistent with the postulate that lipophilic compounds can diffuse into the vacuoles of the cortical cells where they are available for transport to the shoots, whereas for lipophobic compounds material reaching the shoots originates largely from the free space in the roots.