A Non-Metabolic Model of Acifluorfen Activity

Duke, Stephen O.; Kenyon, William H.

doi:10.1515/znc-1987-7-812

Cited by 24 publications

(13 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The absorption spectrum of PPIX, with peaks in the blue, green, and red spectral regions, fits the published action spectra for these herbicides (11,12,31,32). Duke and Kenyon (7) argued that the toxic oxygen species in NDPE action is singlet oxygen and Haworth and Hess (15) recently demonstrated that singlet oxygen is the active toxic oxygen species in NDPE action. After dark incubation with the herbicide, the temperature independence of the light-induced photodestruction indicates that a photodynamic dye is responsible for the activity (17).…”

supporting

confidence: 66%

“…We previously speculated that yellow tissues are more sensitive to photobleaching herbicides than are green tissues because they lack the photosynthetic reducing capacity to generate protectants (6,7). To support this hypothesis, we have shown that a smaller concentration of PPIX in the tissue is correlated with a particular herbicidal effect in yellow (tentoxin-treated) than in green tissues (Fig.…”

Section: Discussionmentioning

confidence: 74%

See 1 more Smart Citation

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Becerril¹,

Duke²

1989

Plant Physiol.

Self Cite

128

View full text Add to dashboard Cite

Several laboratories have demonstrated recently that photobleaching herbicides such as acifluorfen and oxadiazon cause accumulation of protoporphyrin IX (PPIX), a photodynamic pigment capable of herbicidal activity. We investigated, in acifluorfen-treated tissues, the in vivo stability of PPIX, the kinefics of accumulation, and the correlation between concentration of PPIX and herbicidal damage. During a 20 hour dark period, PPIX levels rose from barely detectable concentrations to 1 to 2 nanomoles per 50 cucumber (Cucumis sativus L.) cotyledon discs treated with 10 micromolar acifluorfen. When placed in 500 micromoles per square meter per second PAR, PPIX levels decayed logarithmically, with an initial half-life of about 2.5 hours. PPIX levels at each time after exposure to light correlated positively with the cellular damage that occurred during the following 1 hour in both green and yellow (tentoxin-treated) cucumber cotyledon tissues. PPIX levels in discs incubated for 20 hours in darkness correlated positively with the acifluorfen concentration in which they were incubated. In cucumber, the level of herbicidal damage caused by several p-nitrodiphenyl ether herbicides, a p-chlorodiphenylether herbicide, and oxadiazon correlated positively with the amount of PPIX induced to accumulate by each of the herbicide treatments. Similar results were obtained with acifluorfen-treated pigweed and velvetleaf primary leaf tissues. In cucumber, PPIX levels increased within 15 and 30 minutes after exposure of discs to 10 micromolar acifluorfen in the dark and light, respectively. These data strengthen the view that PPIX is responsible for all or a major part of the photobleaching activity of acifluorfen and related herbicides.The cause of the photobleaching activity of NDPE2 herbicides has been a continuing mystery (1,20). Recent reports (8, 19, 21, 23-26, 30, 36) phyrin synthesis strongly inhibit the activity of the herbicide. PPIX presumably acts as a photodynamic pigment, generating singlet oxygen in the presence of light and molecular oxygen. The absorption spectrum of PPIX, with peaks in the blue, green, and red spectral regions, fits the published action spectra for these herbicides (11,12,31,32). Duke and Kenyon (7) argued that the toxic oxygen species in NDPE action is singlet oxygen and Haworth and Hess (15) recently demonstrated that singlet oxygen is the active toxic oxygen species in NDPE action. After dark incubation with the herbicide, the temperature independence of the light-induced photodestruction indicates that a photodynamic dye is responsible for the activity (17). If exposed to metabolic inhibitors, such as respiratory inhibitors, during the dark incubation period, the activity of NDPE herbicides is strongly reduced upon exposure to light (9, 22). Photobleaching NDPE, cyclic imide, and oxadiazole herbicides inhibit Chl synthesis (13,34,35). Furthermore, there is good evidence that photosynthetic light reactions are not required for activity of these herbicides (6, 9, 12, 15) or accumulation ...

show abstract

supporting

confidence: 66%

Section: Discussionmentioning

confidence: 74%

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Becerril¹,

Duke²

1989

Plant Physiol.

Self Cite

128

View full text Add to dashboard Cite

show abstract

“…In the presence of light and molecular oxygen, singlet oxygen is generated and membrane lipids undergo lipid peroxidation chain reactions, resulting in rapid cellular disruption. This scheme is entirely consistent with all available data, including the rapid appearance of Proto IX (11,13), the apparent appearance of porphyrins in the plasma membrane (5,24), and the rapid loss of plasma membane integrity (15,62,63) in treated cells.…”

Section: The Unique Mechanism Of Protox Inhibitorssupporting

confidence: 89%

Protoporphyrinogen Oxidase as the Optimal Herbicide Site in the Porphyrin Pathway

Duke

Ub²,

et al. 1994

Porphyric Pesticides

Self Cite

View full text Add to dashboard Cite

Herbicide discovery efforts have yielded a large number of excellent herbicides that target the porphyrin pathway. Protoporphyrinogen oxidase (Protox) is the only molecular site inhibited by the commercially available members of this herbicide class. We hypothesize that this site of action is much better for herbicidal activity than other sites of the porphyrin pathway because of the location of herbicide-susceptible Protox within the cell (the plastid envelope and the mitochondrion), the existence of a herbicide-resistant form of the enzyme in the plasma membrane (which rapidly causes accumulation of protoporphyrin IX when plastid Protox is inhibited), and two chemical features of the substrate (its relatively low lipophilicity and its non-planar macrocycle). Although enzymes of the porphyrin pathway beyond Protox can be inhibited to cause the accumulation of phytotoxic levels of porphyrins, these sites do not share the unique properties of Protox. As a result, the number of active analogues that effectively inhibit these enzymes in vivo is much smaller than for Protox, and the amount of herbicide needed for effective herbicidal action is relatively higher.Thousands of herbicides have been patented that apparently exert their phytotoxicity through induced accumulation of phototoxic porphyrins (I, 2). All of those for which the molecular site of action is known are inhibitors of protoporphyrinogen oxidase (Protox), the last enzyme common to the synthesis of both chlorophyll and heme in green plants (J, 3-8). Theoretically, inhibition of any enzyme of the porphyrin pathway ( Figure 1; see Figure 1 of Chapter 1 for structures of intermediates) past porphobilinogen deaminase (uroporphyrinogen III cosynthase) would result in the accumulation of a photodynamic porphyrin. Sites in the 0097-6156/94/0559-0191$08.00/0

show abstract

“…In 1989, chlorimuron, a sulfonylurea, and ima zaquin, an imidazolinone, were applied to over 50% of the soybean acreage in Mississippi for POST broadleaf weed control 4 . These herbicides inhibit acetolactate synthase (ALS) 5 , also known as acetohydroxyacid syn-thase, the first common enzyme in the biosynthetic pathway of the branched chain amino acids valine, leucine, and isoleucine (1,2,8). The systemic action of these herbicides inhibits growth and causes eventual death of susceptible weeds such as common cocklebur, pigweeds (Amaranthus spp.…”

Section: Introductionmentioning

confidence: 99%

Interactions of Diphenylether Herbicides with Chlorimuron and Imazaquin

Wesley

Shaw²

1992

Weed technol.

View full text Add to dashboard Cite

Field experiment were conducted to determine interactions of chlorimuron or imazaquin with fomesafen, lactofen, or acifluorfen on three-leaf and eight-leaf common cocklebur, hemp sesbania, pitted morningglory, and prickly sida. Antagonism was the most common interaction with common cocklebur, and was most severe with chlorimuron combined with fomesafen or acifluorfen, whereas lactofen did not antagonize common cocklebur control. Reductions in control were greater when low rates of chlorimuron were used. On three-leaf prickly sida, control synergistically increased when imazaquin was combined with fomesafen or acifluorfen, but the majority of these combinations were additive on eight-leaf prickly sida. Three-leaf pitted morningglory control synergistically increased when 36 g ai ha–1imazaquin was combined with 210 g ai ha–1fomesafen or 110 or 220 g ai ha–1lactofen. With eight-leaf pitted morningglory, synergism occurred when 2 g ai ha–1chlorimuron was combined with the high rate of any diphenylether herbicide tested, and when 36 g ha–1imazaquin was combined with 110 g ha–1lactofen or 210 g ai ha–1acifluorfen; however, at higher rates of chlorimuron or imazaquin, several antagonistic interactions occurred. Hemp sesbania was controlled over 90% by all combinations, and no interactions occurred.

show abstract

A Non-Metabolic Model of Acifluorfen Activity

Cited by 24 publications

References 5 publications

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Protoporphyrin IX Content Correlates with Activity of Photobleaching Herbicides

Protoporphyrinogen Oxidase as the Optimal Herbicide Site in the Porphyrin Pathway

Interactions of Diphenylether Herbicides with Chlorimuron and Imazaquin

Contact Info

Product

Resources

About