Effects Of Diquat Research Articles

Effects of diquat and fomesafen applied alone and in combination with a nonylphenol polyethoxylate adjuvant on Lemna minor in aquatic indoor microcosms

The influence of tank-mix adjuvants on pesticide toxicity remains largely unknown. Agral ® 90, a nonylphenol polyethoxylated tank-mix adjuvant, has been used with diquat (bipyridylium herbicide) and fomesafen (diphenyl-ether herbicide) in aquatic indoor microcosms in order to compare the toxicity of the single compounds and of binary herbicide–adjuvant mixtures to Lemna minor. Twenty-four microcosms were used and treatments were performed with substances alone or with herbicide–adjuvant binary mixtures, at two concentrations levels (44.4 and 222.2 μg/L for the herbicides, and 100 and 500 μg/L for Agral 90). Toxicity was assessed weekly for 1 month through growth measurements, as inferred from the relative frond number (RFN) and relative frond area (RFA). Concentrations of diquat and fomesafen in water and sediments were measured weekly. The herbicides showed very different behaviour in microcosms, with a rapid disappearance of diquat from the aqueous phase whereas fomesafen levels remained almost constant over time. Diquat strongly inhibited the growth of L. minor whereas fomesafen had no effect on plant growth. Presence of the adjuvant only slightly reduced the effect of the lowest concentration of diquat, probably as a result of dispersion of the herbicide at the water surface. It is concluded that tank-mix adjuvant designed to improve herbicide efficiency in the terrestrial environment did not have any effect on aquatic plants when applied to the aquatic environment.

Effects of the mixture of diquat and a nonylphenol polyethoxylate adjuvant on fecundity and progeny early performances of the pond snail Lymnaea stagnalis in laboratory bioassays and microcosms

Effects of the bipyridylium herbicide diquat and tank-mix adjuvant Agral ®90 were investigated on various life history traits of the freshwater pulmonate snail Lymnaea stagnalis. Trait expression was measured in simple laboratory bioassays on small size groups of snails, and under more complex, indoor microcosm conditions, on larger groups of snails. Microcosms were provided with sediment, plants, and fish, thus allowing a more complex level of intra and inter-specific interactions to develop. Treatments were performed with substances alone or in mixture, at concentrations ranging from 4.4 to 222.2 μg l −1 for diquat, and from 10 to 500 μg l −1 for Agral 90, under a fixed ratio design. Adult growth was negatively affected by diquat and its mixture with Agral 90 both at the highest concentrations (222.2 and 500 μg l −1, respectively). Fecundity expressed differently in bioassays and microcosms, but no effect of the chemicals could be observed on this trait. Progeny development was impaired by 222.2 μg l −1 diquat and its mixture with 500 μg l −1 Agral 90, as reflected by longer development time and reduced hatching rate of clutches laid by the exposed animals, as compared to the controls. Hatching data suggested that diquat bioavailability was lower in microcosms than under bioassay conditions. Consistently, chemical analysis showed that diquat disappeared more rapidly from the water in microcosms than in bioassays. Moreover, the differential expression of several life history traits under bioassays and microcosms conditions was probably also influenced by the level of intraspecific interaction, which differed among the systems. When significant, the effect of diquat was attenuated by the presence of Agral 90, indicating antagonistic interaction between the two substances. Such a deviation from additivity was partly validated statistically.

Effects of diquat on pigment-protein complexes of thylakoid membranes in soybean and maize plants

Soybean (Glycine max Merrill) and maize (Zea mays L.) plants were exposed for 5 to 48 h to the herbicide diquat under white light (WL) or far-red radiation (FR) (photon fluence rate of 30 µmol m-2 s-1). The WL enhanced diquat effect on chlorophyll content in soybean plants, while FR had the same effects on maize plants. After 5 h, diquat increased the content of polypeptides bound to light-harvesting proteins in both plants.

Diquat increases cysteine proteinase inhibitors greatly in rat plasma and tissues.

Biochemical and gross pathological effects of diquat were studied with special attention to cysteine proteinase inhibitor level which was often increased in acute and chronic disorder. Diquat was fed continuously to rats at the dose of 1000 ppm in the diet. After 10 days, anorexia and severe diarrhea were observed but epistaxis and hypokinesia were not apparent. The rats were killed after feeding the diet for 13.5 days and plasma components such as acute phase reactant proteins and some vitamins which act as antioxidants were examined. The results showed that alpha-cysteine proteinase inhibitor (alpha-CPI) increased to 9-fold and vitamin C radical increased to 1.6-fold, whereas alpha 1 proteinase inhibitor (alpha 1-PI) decreased to 0.9-fold and vitamins C and E were the same as the control. Among three components of alpha-CPI, the T kininogen level in intoxicated rat plasma was about 20-fold, whereas the high molecular weight kininogen level was about 2-fold of the control. Diquat also enhanced the cysteine proteinase inhibitor (CPI) level to 20-fold in kidney and to 7- to 10-fold in the other organs. The large increment of T kininogen in these organs was also confirmed immunologically. The kidney showed a granular degeneration and its weight increased to 1.2-fold of control. The other organs showed neither gross pathological alteration nor weight change, compared with the control. The diquat distribution was highest in spleen and next highest in kidney among several organs. These results were compared with those caused by paraquat.

Diquat- and acetaminophen-induced alterations of biliary efflux of iron in rats

The effects of diquat on the biliary efflux of nonheme iron in rats were studied as a means of examining the possible effects of diquat metabolism on hepatocellular iron metabolism and the association of altered iron metabolism with the initiation of acute hepatic necrosis. Administration of hepatotoxic doses (0.1 mol/kg) of diquat to male Fischer-344 rats increased biliary iron concentrations from 6 μM to more than 15 μM. However, increases in biliary efflux of iron were not observed during the first 60 min following exposure to diquat, despite the rapid increases in biliary glutathione disulfide concentrations, which increased maximally within 40 min. Biliary efflux of iron was not altered by diquat in Sprague-Dawley rats, which are resistant to hepatic necrosis in response to diquat, despite the marked oxidant stress responses observed in these animals. Conversely, hepatotoxic doses of acetaminophen (1500 mg/kg) caused significant decreases in biliary iron efflux. The rapid decreases in biliary iron caused by acetaminophen and the delay in diquat-induced iron efflux suggested the possibility that some fraction of the biliary iron was being excreted as reversibly formed GS-Fe 2+ chelates, with inhibition of export by glutathione disulfide (GSSG) in the case of diquat, or by 3-(glutathion- S-yl)acetaminophen (GS-AAP) in the case of the acetaminophen-treated animals. However, 50–200 mg/kg doses of acetaminophen showed little effect on biliary iron excretion despite producing biliary GS-AAP conjugate concentrations almost 1000 times the 6μM concentrations of iron, which would not appear to support the hypothesis of excretion of GS-Fe 2+ chelates. The data demonstrate a significant effect of diquat on hepatic iron metabolism in Fischer-344 rats, and the possible importance of this iron redistribution to reactive oxygen-mediated cell damage in vivo is indicated by the absence of similar responses in diquat-treated Sprague-Dawley rats.

Biliary Excretion of Lysosomal Enzymes, Iron, and Oxidized Protein in Fischer-344 and Sprague-Dawley Rats and the Effects of Diquat and Acetaminophen

Administration of hepatotoxic doses of diquat to male Fischer-344 rats increases biliary excretion of nonheme iron, whereas comparably hepatotoxic doses of acetaminophen decrease biliary export of iron. The effects of acetaminophen and diquat on the activities in bile of representative lysosomal enzymes, β-N-acetylglucosaminidase (β-NAG) and β-glucuronidase (β-GLUC) were examined as a means of assessing the possible role of lysosomal exocytosis in the effects of these hepatotoxins on biliary excretion of iron. In pentobarbital-anesthetized male Fischer-344 rats, diquat at 0.1 mmol/kg increased the biliary export of biliary β-NAG and β-GLUC, in conjunction with similar increases in iron. Sprague-Dawley rats, which are resistant to diquat-induced hepatic necrosis despite showing marked oxidant stress responses, showed no increases in biliary efflux of iron, β-NAG, or β-GLUC in response to diquat. Conversely, acetaminophen at doses of 400 or 1500 mg/kg markedly decreased biliary concentrations and efflux rates of β-NAG and β-GLUC in Fischer-344 rats in parallel with decreases in biliary iron, suggesting that the hepatotoxin-induced effects on biliary iron excretion may be mediated through effects on lysosomal exocytosis. Both acetaminophen and diquat increased total protein content of bile in both strains of rats; however, the proteins excreted after administration of diquat to Fischer-344 rats showed marked increases in contents of protein carbonyls, as assayed with 2,4-dinitrophenylhydrazine, whereas biliary proteins in acetaminophen-treated animals were not more oxidized than in controls. Sprague-Dawley rats given diquat showed no increase in the biliary excretion of protein carbonyls, despite the increased excretion of glutathione disulfide observed in these animals. The significant increases in biliary excretion of protein carbonyls by the diquat-treated Fischer-344 rats suggest oxidation of cellular proteins catalyzed by chemically reactive iron chelates and the excretion of at least some of the oxidized proteins to the bile, possibly through lysosomal exocytosis. The effects of acetaminophen on biliary protein excretion do not appear to involve oxidation.

Effects of diquat on freshwater microbial communities

A static microcosm system was used to evaluate effects of the herbicide diquat (0.3–30 mg/L) on the structure and function of naturally derived microbial communities on polyurethane foam substrates. Microbial communities were exposed to a single application of diquat and were monitored for 21 days. Effects on community structure included changes in algal cell density at diquat concentrations ⩾0.3 mg/L (after an initial decrease in net productivity), bacterial cell density (1 mg/L diquat), and increased biomass accumulation (10 and 30 mg/L diquat). The species richness of protozoa was reduced at diquat concentrations >0.3 mg/L; protozoan species composition was progressively more dissimilar with diquat treatment. Effects on community function included inhibition of net productivity and community respiration (10 and 30 mg/L diquat), and decreased enzyme activities [alkaline phosphatase (1, 10, and 30 mg/L diquat), electron transport system (⩾0.3 mg/L diquat), and β-glucosidase (⩾0.3 mg/L diquat)]. Both photosynthetic and nonphotosynthetic organisms were affected by diquat. Most structural and functional responses were sensitive indicators of stress. Estimated chronic toxicity values ranged from 0.3 mg/L (day 3) to 5.5 mg/L (day 21). Most microbial responses indicated that microbial community structure and function did not recover within the 21-day exposure period.

Comparison of the ecological effects of diquat on laboratory multi species and outdoor freshwater systems

Comparison of the ecological effects of diquat on laboratory multi species and outdoor freshwater systems

Lethal effects of diquat and paraquat on developing frog embryos and 15-day-old tadpoles, Rana pipiens.

Lethal effects of diquat and paraquat on developing frog embryos and 15-day-old tadpoles, Rana pipiens.

Effect of diquat on cell growth and macromolecule synthesis in cultured pneumocytes.

The effects of diquat (DQ) on cell growth and macromolecule synthesis were investigated in cultured rat, feline and human. pneumocytes. DQ at 10(-3) M and 10 (-5) M showed time- and dose-dependent inhibition of cell growth for 7 days. The incorporation of 3H-thymidine, 3H-uridine and 14C-leucine into DNA, RNA and protein was reduced to 0-47% by 10(-3) M of DQ, and that of 14C-leucine into protein of A-549 cells was reduced to 67% by 10(-5) M of DQ. Among the cells examined, A-549 cells derived from human lung were the most resistant to the inhibitory effects of DQ on cell growth and macromolecule synthesis. On the other hand, human lung embryonic fibroblast cells and L-2 cells derived from rat lung were the most sensitive to the toxicity of DQ. These results indicate that the inhibitory effects of DQ on cell growth and on macromolecule synthesis are dependent on the concentrations of DQ administrated, and that species differences in the sensitivity to DQ toxicity may exist.

Ethylene application in agriculture. 1. 2-Chloroethylphosphonic acid as potato haulm desiccant

2-Chloroethylphosphonic acid (CEPA) was applied, as a foliar spray in the form of Ethrel, to potato plants (var. Uran). The effects on water loss, chlorophyll degradation, and on the growth potential of tubers from the treated plants, were studied and compared with the effects of diquat.

The Effects of the Dipyridyl Diquat on the Metabolism of Chlorella Vulgaris

The effects of diquat, in the light, on chlorophyll bleaching and the fine structure of the cells of O. vUlgaris (211-11h) have been studied. Diquat causes bleaching of chlorophyll when the cells are illuminated in water or phosphate or bicarbonate buffer. Using cultures of uniform cell size it is shown that diquat causes considerable damage to cell membranes in less than 10 hr of illumination, but that inhibition of both photosynthesis and respiration precede any damage to the plastids visible under the electron microscope.

The Effeots of the Dipyridyl Diquat on the Metabolism of Chlorella Vulgaris I. Gas Exchange in the Light

The effects of diquat on gas exchange in illuminated C. vUlgaris have been studied by manometric procedures. Estimates of dark oxygen uptake were made by transfer of treated cells to darkness. Analysis of the results indicates that on adding diquat to C. vUlgariB there is a rapid fall in the rate of apparent photosynthesis. This is due to an immediate and large increase in dark metabolism (C02 and O2 exchange) accompanied by irreversible inhibition of real photosynthesis firstly, then of respiration. At some unspecified stage a light-dependent oxygen uptake begins, rises to a maximum rate, and declines to a low value, continuing after the inhibition of respiration. These results are discussed in relation to the known effects of diquat on plastid reactions and to the hypothesis that in illuminated green tissue diquat produces a toxic substance which damages both the photosynthetic and respiratory apparatus.

The influence of darkness on the uptake and movement of diquat and paraquat in tomatoes, sugar beet and potatoes

SUMMARYUptake of diquat and paraquat was doubled and occasionally quadrupled when tomatoes were darkened after treatment. The increase was not directly related to the duration of darkness because, after a time, uptake decreased. Three possible explanations for this decrease are considered, namely: diquat exudation from the leaves, downward movement into the roots and the complexing of diquat in plant tissue. Evidence was against exudation from leaves and downward movement into the roots.Diquat activity also depends on its degree of movement in the plant but the possible influence of other factors is discussed when treatments are made in the afternoon or in the morning after a period of reduced light intensity.In a CO2‐free atmosphere, uptake and activity increased in light and were comparable to those in darkness. Uptake is therefore not impeded by phyto‐toxic effects of diquat but possibly by the presence of a high concentration of solutes or by photosynthetic intermediates.

Effects of Diquat on Bluegills and their Food Organisms

Effects of Diquat on Bluegills and their Food Organisms