The adaptation of qualitative and quantitative techniques for determination of radioactive dalapon in plant tissues

Abstract

In studying the absorption, distribution, and metabolism of dalapon (2,2-dichloropropionic acid) in relation to phytotoxicity, a number of simplified techniques were developed, and other established procedures were usefully modified. The techniques of autoradiography, extraction and fractionation, counting, and paper partition cochromatography were effectively combined, thus permitting qualitative and quantitative determination of distribution patterns and, to some extent, of the metabolic fate of translocated herbicides. Although this report is concerned specifically with dalapon, the approach employed -w ith that compound should be applicable, with minor changes, to the study of others.Physiological findings resulting from application of these techniques will be published separately.3 In many instances, however, the maximum benefit from these valu.. able research tools is not realized. Too often, for example, the sole approach used by plant scientists is that of gross autoradiography. That technique, although put to excellent use in the past (Arnon et al., 1940;Boyd, 1955; Colwell, 1942;Crafts, 1953Crafts, , 1956 and variously improved in more recent herbicidal studies (Pallas and Crafts, 1957; Yamaguchi and Crafts, 1958), permits only semiquantitative interpretation of results, and does not characterize the translocated radioactive substance(s) either as the original herbicide or some degradation products thereof. Moreover, when counting is done, the data are usually expressed in relative rather than absolute terms. Results are often more meaningful if several approaches are used concurrently.In recent studies on the absorption, distribution, and metabolism of 2,2-dichloropropionic acid (dalapon) in relation to phytotoxicity, the techniques of (a) autoradiography, (b) extraction and fractionation, (c) counting, and (d) paper partition cochromatography were effectively combined. This combination of techniques permits the determination of distributional patterns and, to some extent, the metabolic fate of translocated herbicides, both qualitatively and quantitatively.

Absorption, distribution, & metabolism of 2,2-dichloropropionic acid in relation to phytotoxicity. II. Distribution & metabolic fate of dalapon in plants.

“…The general techniques and materials employed in these studies have been described (8,9). Radioautography, counting, extraction and fractionation.…”

“…In all short term experiments (3 days or less), in which expressed plant sap was chromatographed directly, only dalapon (Rf 0.4-0.6) or dalapon plus impurities present in the treatment solution were found. Also, by the liquid extraction of corn leaf disks with water or ethanol 3 hours after treatment (6,9) Also, the counts obtained from an aliquot (multiplied by a factor and subtracted from the total activity added) yielded the amount of dalapon held in or on plant material. Furthermore, any that remained with the plant residue after exhaustive washing with several hundred volumes of water was presumed to be metabolically incorporated in a non-diffusible constituent.…”

“…1 filter paper by use of a micropipette. After equilibration, the chromatograms were developed one-dimensionally overnight using n-butanol and 1.5 N ammonium hydroxide (6,9,25).…”

Formulation of Dalapon to Reduce Soil Contamination

“…Under many conditions 2 days would seem to be a reasonable allowance for evaporation of spray residues. The response of test plants to the sodium salt of dalapon, which is essentially non-volatile (Foy 1960), could serve as a basis of comparison of herbicidal efFects.…”