Herbicide Chlorsulfuron Decreases Assimilate Transport Out of Treated Leaves of Field Pennycress (Thlaspi arvense L.) Seedlings

Abstract

Treatment of field pennycress (Thiaspi arvense L.) leaves with the herbicide chlorsulfuron resulted in a decrease in the export of assimilate. Twelve hours after a spot application of 1 microgram, assimilate translocation was 70% of that in control leaves. In excised leaves treated with chlorsulfuron the total amounts of sugars and free amino acids were 150 and 170%, respectively, of the amounts in control leaves, 30 hours after herbicide treatment. The amount of sucrose was 247% of that in control leaves. The increase in the concentration of sucrose in the chlorsulfurontreated leaves, combined with the absence of an effect of chlorsulfuron on carbon dioxide fixation, suggests that the decrease in assimilate transport is not due to an effect on the synthesis of assimilates, but rather to an effect on their movement out of the leaves. Supplying branched-chain amino acids to the field pennycress seedlings prior to the application of chlorsulfuron prevented the occurrence of the effects described.dose was translocated out of treated leaves of several species in a 24-h period. Export of less than 5% of the absorbed chlorsulfuron in 24 h has been reported for Canada thistle and perennial sow thistle (Sonchus arvensis) (8) The limited phloem mobility of chlorsulfuron cannot be, explained in terms of the ability of plant tissue to accumulate the herbicide (6, 7) but, instead, is attributed to an effect on assimilate translocation. The objective of the research described in this paper was to understand the effect of chlorsulfuron on the translocation of assimilates out of treated leaf tissue of field pennycress (Thlaspi arvense L.) seedlings. In addition, the rates of uptake and of translocation of the herbicide and the extent of its metabolism were determined. MATERIALS AND METHODSThe herbicidal action of a chemical arises from its ability to interact with a plant in such a manner as to inhibit or disturb its growth. This interaction usually involves the inhibition of a process essential to growth. The sulfonylurea herbicide chlorsulfuron4 inhibits the growth of susceptible plants by inhibiting the enzyme ALS, an enzyme common to the biosynthesis of the branched-chain amino acids L-valine, L-leucine, L-isoleucine (4).In

Phloem Transport of d,l-Glufosinate and Acetyl-l-Glufosinate in Glufosinate-Resistant and -Susceptible Brassica napus

“…This occurs as a consequence of the deregulation of carbon metabolism and increased carbon flow into the shikimate pathway following the inhibition of 5-enolpyruvylshikimate-3-phosphate synthase, the herbicide target site (Steinrü cken and Amrhein, 1980;Gougler and Geiger, 1984;Geiger et al, 1986Geiger et al, , 1987. Chlorsulfuron, on the other hand, does not reduce carbon fixation or hexose/Suc synthesis, but prevents Suc loading in source leaf tissue (Bestman et al, 1990;Devine et al, 1990;Hall and Devine, 1993). Therefore, the phloem mobility of chlorsulfuron was considerably greater in an Arabidopsis mutant with a resistant form of acetolactate synthase (the herbicide target site [Ray, 1984]) than in a susceptible biotype (Hall and Devine, 1993).…”

Plasmodesmata: Symplastic Transport of Herbicides Within the Plant

“…It would be incorrect to assume that a relatively large organic molecule, such as an herbicide, would prefer to cross two cell walls and two plasma membranes instead of being carried by a continuous cytoplasmic tube between cells in the same domain. Another study describes the application of 10 droplets of chlorsulfuron on the third definitive leaf of a seedling of field pennycress (Thlaspi arvense) with five definitive leaves (Bestman et al, 1990). Chlorsulfuron is an herbicide that belongs to the group of sulfonylurea, inhibitor of the enzyme acetolactate synthase (ALS), involved in the synthesis of branched-chain amino acid valine, leucine, and isoleucine (Leite et al, 1998).…”

Amino acid content and biomass productivity of selected weed species as an indicator of their response to herbicide stress

“…For example, S h i m et al [13] reported an increase in free amino acid content with an increasing dose of azimsulfuron and explained it by the reactivation of metabolic pathways leading to the introduction of compounds that had been received from amino acid degradation. B e s t m a n et al [14] also proved an increase in free amino acid content after chlorsulfuron application as a result of secondary transformation of amino acids and proteins in plants. Amino acid content may also be affected by environmental stress, i.e.…”