Translocation and Metabolism of Picloram and 2,4‐D in Populus tremula

Abstract

Translocation and metabolism of 4‐amino‐3,5,6‐trichloropicolinic acid (picloram) and 2,4‐dichlorophenoxyacetic acid (2,4‐D) in small plants of aspen (Populus tremula L.) were studied. In most experiments 14C‐carboxyl‐labelled herbicides were used. Considerable quantities of both herbicides were retained in the treated leaf. Translocation was mainly upwards into the growing shoot tip. Only minute quantities were found in the roots. Injection of the herbicides through a cut stem surface increased the translocation into the roots very little. One of the reasons for the limited downward translocation is considered to be a ready transfer of the herbicides between the phloem and the xylem. Both herbicides were incorporated into complexes from which the active herbicides could be released. However, this complex formation can only partly account for the retention of the herbicides in the treated leaves. The differences in metabolism found between 2,4‐D and picloram cannot explain the considerable difference in toxicity between the compounds.

Picloram metabolism in leafy spurge: isolation and identification of glucose and gentiobiose conjugates

“…Root-absorbed [14C]picloram was rapidly translocated to the foliar tissues and metabolized to polar products (Table I). Similar patterns of picloram root absorption, acropetal transport, and metabolism have been reported in other plant species (Hall and Vanden Born, 1988;Hallmén, 1975;Eliasson and Hallmén, 1973;Isensee et al, 1971; Gaudiel and Vanden Born, 1979; Sharma and Vanden Born, 1973a,b). Two days after the initiation of the pulsed root treatment, >90% of the absorbed 14C was present in stem and leaf tissues; 30% was present as methanol-soluble metabolites; and only trace amounts were associated with the methanol-insoluble residue fraction.…”

“…Metabolism studies in a variety of sensitive and tolerant plants have shown that picloram forms water-soluble complexes that can be hydrolyzed to yield picloram (Hall and Vanden Bom, 1988; Hallmén, 1974Hallmén, ,1975Sharma and VandenBorn, 1973a; Hallmén and Eliasson, 1972; Eliasson and Hallmén, 1973;Kudaikina et al, 1981a). Recent picloram metabolism studies have identified acid-labile 7V-glucoside and alkali-labile glucose ester conjugates in sunflower and other plants (Chkanikov et al, 1983;Kudaikina et al, 1981a).…”

Comparison of extraction/hydrolysis procedures for the determination of acidic herbicides in plants: residues of mecoprop in barley following postemergence application

“…In one approach, the plant tissue is subjected to extended hydrolysis followed by partitioning of the "free" acidic herbicide into an organic phase (Bjerke et al, 1967;Cessna, 1980;Bristol et al, 1982;Frank et al, 1983;Galoux et al, 1983;Smith, 1984;Smith et al, 1986;Steinwandter, 1989). The other approach involves extracting the free acidic herbicide plus any conjugates directly into an organic phase and then effecting hydrolysis (Hamilton et al, 1971;Buckland et al, 1973;Feung et al, 1973;Beynon et al, 1974;Shimabukuro et al, 1979;Eronen et al, 1979;Scheel and Sandermann, 1981).…”

“…Acidic herbicides, such as mecoprop [(±)-2-(4-chloro-2-methylphenoxy)propanoic acid; Chow et al, 1971], 2,4-D [(2,4-dichlorophenoxy)acetic acid ;Feung et al, 1973], dichlorprop [(±)-2-(2,4-dichlorophenoxy)propanoic acid ;Lokke, 1975], diclofop [(±)-2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid; Jacobson and Shimabukuro, 1984], picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid; Eliasson and Hallmén, 1973), and benzoylprop [JV-benzoyl-IV-(3,4-dichlorophenyl)-DL-alanine; Beynon et ed., 1974], are known to form conjugates with plant substituents. The site of conjugation is the carboxyl moiety and generally involves the formation of an amido linkage by reaction with amino acids/proteins and/or an ester linkage by reaction with sugars.…”