Movement Of Paraquat Research Articles

14 C-paraquat Efflux Assay in Arabidopsis Mesophyll Protoplasts.

Weeds compete with crops for growth resources, causing tremendous yield losses. Paraquat is one of the three most common non-selective herbicides. To study the mechanisms of paraquat resistance, we need to trace the movement of paraquat in plants and within the cell. 14 C is a radioactive carbon isotope widely used to trace substances of interest in various biological studies, especially in transport analyses. Here, we describe a detailed protocol using 14 C-paraquat to demonstrate paraquat efflux in Arabidopsis protoplasts.

Nitrogen fertilizer programs following rice exposure to a sub-lethal concentration of paraquat

AbstractOff-target paraquat movement to rice has become a major problem in recent years for rice producers in the midsouthern United States. Nitrogen (N) fertilizer is applied to rice in greater quantity and frequency than all other nutrients to optimize rice yield. Two separate field studies were conducted from 2015 to 2018 in Stoneville, MS, to assess whether starter N fertilizer can aid rice recovery from exposure to a sub-lethal concentration of paraquat and to evaluate rice response to different N fertilizer management strategies following exposure to a sub-lethal concentration of paraquat. In both studies, paraquat treatments consisted of paraquat at 0 and 84 g ai ha–1 applied to rice in the two- to three-leaf (EPOST) growth stage. In the starter fertilizer study, N fertilizer at 24 kg ha–1 as ammonium sulfate (AMS) was applied to rice at spiking- to one-leaf (VEPOST), two- to three-leaf (EPOST), or three- to four-leaf (MPOST) growth stages before and after paraquat treatment. In the N fertilizer timing study, N fertilizer at 168 kg N ha–1 was applied in a single four-leaf to one-tiller (LPOST) application or two-, three-, and two four-way split applications. Despite starter N fertilizer applications, paraquat injured rice ≥41%, reduced height 57%, reduced dry weight prior to flooding 77%, delayed maturity 10 d, reduced dry weight at maturity 33%, and reduced rough rice yield 35% in the starter fertilizer study. Similarly, in the N fertilizer timing study, paraquat injured rice ≥45%, reduced height 14%, delayed maturity 10 d, reduced dry weight at maturity 44%, and reduced rough rice yield 50% for all N fertilizer management strategies. Both studies indicate that severe complications in growth and development can occur from rice exposure to a sub-lethal concentration of paraquat. In both studies, manipulation of N fertilizer management did not facilitate rice recovery from early-season exposure to paraquat.

Penggunaan Metode Bioassay untuk Mendeteksi Pergerakan Herbisida Pascatumbuh Paraquat dan 2,4-D dalam Tanah

A simple and cheap method to detect herbicide residue in soil and water is urgently needed as the quantity and frequency of herbicide usage is steadily increasing in Indonesia which raises concern about the effects of herbicide residue in soil and water. This study is the third step from a series of studies aim to develop bioassay technique to detect the present and quantity of herbicides in soil and water. In this study, bioassay was used to detect movement of paraquat and 2,4-D herbicides in soil. Study was carried out using soil column method. Treatments were arranged factorially in a completely randomized block design with 3 replicates. Two ultisol soil types: Podsolik Merah Kuning (PMK) and Latosol Coklat (LC) and 2 post emergence herbicides: paraquat and 2,4-D, were tested. To calculate the amount of herbicide using bioassay, each standard curve for paraquat and 2,4-D were developed. Using these standard curves, the amount of paraquat and 2,4-D was calculated based on the growth rate of caisim as indicator plant. Results showed that bioassay method can be utilized to detect herbicide movement in soil. The amount and the rate of herbicide movement were determined by soil and herbicide types. In PMK, paraquat reached the depth of 20-30 cm at 2 weeks after application (WAA), however, after that the amount of paraquat found was very limited. In LC, the movement of paraquat was more limited compared to its movement in PMK. Paraquat reached soil depth of 10-20 cm at 2 WAA, afterward paraquat was only detected in soil depth of 0-10 cm. Similar pattern was observed for 2,4-D which reached soil depth of 30-40 cm at 1 WAA in PMK. In LC, 2,4-D movement was more limited. At 2 WAA, 2,4-D in LC reached soil depth of 30-40 cm in limited amount and after 12 WAA the herbicide was detected only at soil depth of 0-10 cm.

Physiological Responses ofRehmannia glutinosato Paraquat and Its Tolerance Mechanisms

Rehmannia glutinosawas extremely tolerant to paraquat at the levels of leaf disk and chloroplast. The tolerance level ofR. glutinosawas much greater at the level of leaf disk than at the level of chloroplast, indicating that the tolerance factor(s) are mainly located external to the chloroplast envelope. Possible tolerance mechanisms ofR. glutinosato paraquat were examined in comparison with paraquat-susceptible corn and soybean. Epicuticular wax and cuticle contents did not correspond to differential paraquat effects on the three plant species. Cuticular penetration of paraquat was almost the same in the three plant species. Autoradiography experiments with [14C]paraquat indicated that the paraquat absorption and translocation inR. glutinosaleaves were not restricted. In addition, the time- and the concentration-dependent paraquat accumulation into the vacuole ofR. glutinosawas found to be very similar to those of corn and soybean. However, paraquat binding to the cell wall was greater inR. glutinosathan in corn and soybean, presumably resulting in the reduction of paraquat movement to its site of action inR. glutinosa.The levels of lipid peroxidation in the thylakoid membrane caused by paraquat were found to be almost the same in the three plant species, suggesting that altered site of action is not a mechanism of paraquat tolerance inR. glutinosa. The activities of protective enzymes of superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase in the stromal extracts were all higher inR. glutinosathan in corn and soybean. However, the enhanced activities of the protective enzymes are not likely to account for the paraquat tolerance ofR. glutinosa, since the activities did not correlate with the differential paraquat effects on the three plant species. Thin-layer chromatographic analysis of leaf extracts revealed that paraquat metabolism occurred in intact leaves ofR. glutinosa,but not in the chloroplast. Our results suggest that paraquat can be metabolized by unknown factor(s) in the cytosol, not in the chloroplast, ofR. glutinosaleaves. Collectively, it can be concluded that the tolerance ofR. glutinosato paraquat might mostly be due to the consequence of paraquat metabolism outside of the chloroplast, although paraquat binding to the cell wall is also likely to confer the tolerance to some extent.

Resistance to paraquat in Hordeum glaucum is temperature dependent and not associated with enhanced apoplasmic binding

SummaryResponse to paraquat was investigated in two Hordeum glaucum Steud. (wall barley) biotypes grown at warm (30^C) and cool (15^C) temperatures. Paraquat‐resistant (R) plants were nearly seven‐fold more tolerant when grown at 15^C than when grown at 3CPC. In contrast, there was a tendency for susceptible (S) plants to be more tolerant when grown at the higher temperature. The difference in response between the two biotypes grown at 30^ and 15^C increased from 3‐ to >40‐fold. Forty‐eight hours after foliar application, 62% less radiolabelled paraquat had translocated basipetally in the R compared with the S biotype. In addition, 26% more herbicide was retained within the treated zone of R compared with S plants. Thus, paraquat movement was restricted in the R biotype. It has been postulated that reduced mobility of the herbicide in the R plants is due to enhanced apoplasmic binding. In this study, paraquat binding to the cell walls and its release into the external solution was investigated in roots of R and S biotypes of H. glaucum grown under warm or cool conditions. No significant differences between the two biotypes were measured at either growth temperature. We propose that the mechanism of resistance to paraquat may involve a temperature‐dependent alteration in symplasmic transport of the herbicide.

Differential Movement of Paraquat in Resistant and Sensitive Biotypes of Conyza

Previous indirect evidence indicates that paraquat resistance in hairy fleabane ( Conyza bonariensis [L.] Cronq.) is correlated with restricted movement in the resistant (R) biotype. Experiments were conducted to further characterize the mobility of paraquat (1,1′-dimethyl-4-4′bipyridinium ion) in R and sensitive (S) biotypes of Conyza. The lateral movement of [ 14C]paraquat from the point of application on he adaxial surface of intact leaves incubated in darkness was significantly restricted in the R relative to the S biotype. This restricted movement of paraquat may result from a mechanism of sequestration that conveys resistance to the R biotype. Autoradiographs of treated, intact leaves as well as leaf disks floated in an aqueous solution containing [ 14C]paraquat (dark incubation) revealed a distinctive pattern of black spots very similar to the density and distribution of unicellular and multicellular leaf hairs (trichomes). Paraquat accumulated in trichomes on the abaxial surface of leaf disks of both biotypes even though this surface was not in direct contact with the incubation solution. Microautoradiography and paradermal sectioning studies were conducted following the treatment of the adaxial surface of intact leaves of both biotypes with [ 14C]paraquat for 4 hr in darkness. Analyses of the data indicated a 10- to 100-fold increase in the amount of paraquat associated with trichomes (relative to other leaf cells) on the adaxial and abaxial leaf surfaces of both biotypes. It is unlikely that the accumulation of paraquat in abaxial trichomes within 4 hr after treatment can occur solely by diffusion. A 20% increase in the density of multicellular trichomes was observed in leaves of the R biotype. This small increase may contribute slightly to the 100-fold level of resistance typically observed in intact leaves of the R biotype. These data further support the hypothesis that paraquat resistance in Conyza is correlated with restricted movement (sequestration) in the R biotype.

Sequestration and Oxygen Radical Detoxification as Mechanisms of Paraquat Resistance

Evidence in the literature has generally supported either of two paraquat resistance mechanisms: an increase in activity of oxygen radical-scavenging enzymes in resistant plants which affords protection from active oxygen species formed by paraquat; and sequestration of paraquat away from its site of action in the chloroplast. Evidence for the first model relies primarily on measurement of increased enzyme activity and cross-resistance to other oxygen radical-generating stresses in resistant plants. The sequestration model is supported by data showing decreased translocation of paraquat and absence of paraquat injury in plant systems that do not have increased levels of protective enzymes. An alteration in paraquat transport at one of several plant cell membranes could confer resistance by modifying movement of paraquat into the compartment bounded by that membrane. Properties of the plasmalemma, chloroplast envelope, and tonoplast that may be important to paraquat transport are discussed and data supporting or discounting specific membrane alterations in resistant plants are presented. Finally, the possibility that both mechanisms may work in concert is addressed.

Compartmentation Analysis of Paraquat Fluxes in Maize Roots as a Means of Estimating the Rate of Vacuolar Accumulation and Translocation to Shoots.

Efflux analysis conducted after five loading periods of various lengths (2, 6, 12, 18, or 24 h) was used to investigate uptake, compartmentation, and translocation of [14C]paraquat in maize (Zea mays L.) seedlings. The time course for net paraquat uptake (paraquat concentration in uptake solution = 25[mu]M) into maize roots was linear (56.7 nmol g-1 root fresh weight h-1) for 24 h. Estimates of changes in paraquat content in the vacuole, cytoplasm, and cell wall after 2-, 6-, 12-, 18-, and 24-h loading periods indicated that the cell wall saturated rapidly, whereas accumulation of paraquat into the vacuole increased linearly (12.4 nmol g-1 root fresh weight h-1) over 24 h. In contrast to vacuolar accumulation, cytoplasmic paraquat content appeared to approach saturation. The half-time for paraquat efflux from the cell wall (16.6 min [plus or minus] 1.2 SD) and cytoplasm (58.8 min [plus or minus] 8.9 SD remained relatively constant regardless of the length of the loading period, whereas the half-time for efflux from the vacuole was considerably longer and increased linearly with increased loading time (6.1-18.7 h). The time course for paraquat translocation to the shoot was linear within a 24-h exposure to radiolabeled herbicide, but translocation did not begin until 5 h after initiation of treatment. The experimental approach used in these experiments provides a valuable method for examining the movement of paraquat in maize seedlings. Results indicate that the herbicide slowly accumulates in the vacuole of root cells but is also translocated to the shoot.

Movement of paraquat in resistant and susceptible biotypes of Erigeron philadelphicus and E. canadensis

Paraquat (1,1′‐dimethyl‐4,4′‐bipyridinium) resistant biotypes of Erigeron philadelphicus and E. canadensis, from fields where paraquat had been used for weed control, showed more than 100 times higher resistance than the susceptible biotype of both plants. Excised leaves of the susceptible biotypes wilted when supplied with more than 5 μM paraquatat at the cut ends, but those from the resistant biotypes did not wilt even at 500 μM. Autoradiographs indicated that (14CH3)‐paraquat taken up through the cut ends was rapidly distributed through the vascular system in leaves of the susceptible biotype, but was barely translocated in leaves of the resistant biotype. The amount of paraquat taken up during 48 h in the resistant biotype was 0.5% of that in the susceptible biotype in light. This difference in paraquat movement may be correlated with paraquat resistance in Erigeron.

Suitability of the Contact Herbicide Paraquat as a Simulator of Mexican Bean Beetle (Coleoptera: Coccinellidae) Defoliation Under Greenhouse Conditions

Under greenhouse conditions, the contact herbicide paraquat was compared with manual and Epilachna varivestis Mulsant defoliation of soybean plants. After 14 or 28 days of posttreatment growth, there were no significant height or dry-weight differences between plants defoliated with any of these three methods, even though experimental sensitivity (eight replications) was great enough to detect both height and dry-weight differences between control and defoliated plants. At the highest concentration used, there were two observations of possible paraquat movement and damage to untreated leaves. As paraquat concentration was decreased, the extent of lesion expansion beyond the treated area decreased significantly. The use of paraquat at an appropriate concentration (e.g., 14.6 µg/ml) may adequately simulate insect defoliation, because the herbicide: completely defoliated the treated leaf area but with minimum necrosis beyond the treated margin; had no additional effect son overall plant growth (height or weight); and did not interfere with vegetative phenology or flower initiation.

Surfactants and the uptake and movement of paraquat in plants

AbstractSurfactants are still considered to be agents which either increase spray coverage of leaves with herbicidal solutions and/or increase herbicide penetration into the leaves. Experiments where the method of application largely eliminates leaf wetting as a factor in paraquat uptake show that this is an over‐simplification. Its efficiency in the plant is influenced by penetration and most of all by the degree of movement down the plant into untreated leaves. Results on the uptake, movement and biological activity of paraquat are reported using cocksfoot and wheat. A relation is found between paraquat movement and the hydrophilic nature of the surfactant. It moves most when the number of ethylene oxide residues is less than six and it is minimal when the number is 10 to 15. Leaf penetration, however, is at a maximum when movement under the influence of surfactant is least. Partition studies in which surfactants are distributed between leaf wax and water are described. There is a direct correlation between the degree of partition of the surfactant into the wax and the degree of movement of paraquat in cocksfoot and wheat. Surfactants are essential components of a paraquat formulation to wet the leaf surface and increase penetration but, when the surfactant also penetrates into the leaf, it reduces the mobility of paraquat and hence its efficiency.

Changes in the microbial populations of a reservoir treated with the herbicide paraquat

Submerged angiosperms were completely eradicated from a fishing reservoir by the application of 1·0 mg 1 −1 paraquat, but the subsequent growth of the macrophytic alga, Chara sp., was resistant to a second application of the herbicide. Some changes in the microbial populations of the reservoir over the period of study were consistent with the movement of paraquat within the system and others with the death of the plants. Numbers of arbitrarily classified “paraquat resistant” micro-organisms increased in the water and mud immediately after both herbicide applications and after the first application a reduction in total viable heterotroph counts was observed. Accompanying the death of the angiosperms there were increases in the counts of viable heterotrophs and some exoenzyme producers in the mud and water but after the second application of paraquat, when there was no plant death, these micro-organisms showed little response.

Uptake and movement of paraquat in cocksfoot and wheat as influenced by surfactants

AbstractSurfactants are used to increase the efficiency of herbicide formulations mainly because they wet out leaf surfaces, thereby stabilising and increasing the contact area of droplets on the surface. Herbicide penetration through the cuticle may also be facilitated.The work described eliminates effects on wetting and contact area in order to study the effect of surfactants on the penetration and movement of paraquat in cocksfoot. Surfactants were various types of alcohols and amine oxides condensed with 2 to 30 moles of ethylene oxide used at 0.1 to 0.5%. An adult leaf of cocksfoot (Dactylis glomerata) was immersed briefly to constant area in paraquat solutions containing surfactant and uptake and movement of paraquat is recorded.Uptake was little affected by differences in surfactant structure except where surface activity was low and solutions failed to wet out the leaf surface. Percentage movement with 0.5% surfactant was often less than that with 0.1% and a high ethylene oxide content also reduced percentage movement. Paraquat activity was influenced by both the degree of uptake and movement, but movement was the greater influence.Amine oxide surfactants reduced movement less than those based on alcohols. The action of surfactants is discussed in terms of a hydrophobic/hydrophilic balance in the surfactant molecule.

The movement of paraquat as influenced by the partition coefficient of surfactants between water and leaf wax

Abstract“Lissapol” NX and “Lubrol” L, used to improve the uptake of paraquat into plants were found in earlier work to reduce its movement. Several series of surfactants with widely varying solubilities in water were partitioned between cabbage wax and water. A marked correlation was found between the effect of surfactants on the movement of paraquat and the amount of surfactant partitioning into the wax.It is concluded that although surfactants increase the uptake of paraquat into leaves, this increase is offset by reduced movement following penetration of surfactants into leaf tissue. Surfactant partition into wax reduces the degree of penetration, but there is no evidence how surfactants in leaf tissue reduce movement.

Tracer Studies by14C-labeled Herbicides, DMSO, and Surfactant

Primary leaves of 17-day-old-bean(Phaseolus vulgarisL. ‘Black Valentine’) were treated with14C-labeled dimethylsulfoxide (DMSO), 3,6-dichloro-o-anisic acid (dicamba), 1,1′-dimethyl-4,4′-dipyridinium salt (paraquat), and 2-chloro-4-(ethylamino)-6-(isopropylamino-s-triazine (atrazine). Each herbicide was tested alone, and in combination with 30% DMSO, 0.25% Tween 80 (nonionic surfactant containing polyoxyethylene sorbitan monooleate), or both. DMSO at concentrations of 25% or more caused varying degrees of acute toxicity. However, a small amount of radioactive carbon generally was distributed throughout the plant 5 days after application of DMSO-14C, as determined by autoradiography and counting. Tween 80 enhanced whereas DMSO had little effect on the absorption and translocation of dicamba, a phloem-mobile herbicide. The contact toxicity and apoplastic movement of paraquat was increased with DMSO. Tween 80 enhanced eight-fold and DMSO, two-fold, the foliar uptake and (apoplastic) movement of atrazine within the treated leaves.

Pesticide Mobility in Soils I. Parameters of Thin‐Layer Chromatography

AbstractPesticide movement was studied using the recently developed soil thin‐layer chromatographic (TLC) method (Science 162:562, 1968). Thin layers of soil, the adsorbent phase, are developed with water using techniques analogous to conventional TLC.Mobility, expressed as RF values for frontal movement, was insensitive to these parameters: removal of coarse or medium sand, movement distance, soil layer thickness, temperature, and sample size (0.3 to 50 µg). Water flux was modified by physical, soil amendment (inorganic and organic additives), and solvent amendment methods. Increased flux may slightly increase mobility of pesticides. The mobilities of 2,4‐D and atrazine decreased markedly in > 0.5M NaCl solution, whereas some movement of paraquat then occurred. Distance to the wetting front on soil TLC plates was linearly related to the square root of time.Three methods of visualizing radioactive pesticide movement were compared: autoradiography, radiochromatogram scanning, and zonal extraction.

Effects of Paraquat and Light Regime on Quackgrass Growth

We applied 1,1′-dimethyl-4,4′-bipyridinium ion (paraquat) to quackgrass (Agropyron repens L. Beauv.) at different stages of growth and subjected these treated plants to different light regimes. After paraquat and light treatment, foliage was removed and the reduction in regrowth was measured as evidence of paraquat movement and its effect on the regenerative potential of the rhizomes. Paraquat or a toxic metabolite moved in quantity from point of leaf application. Sufficient basipetal movement occurred in both the dark and light to significantly affect regrowth. As quackgrass plants matured and developed more foliage, the effect of paraquat treatment increased (i.e., the regrowth capacity of the plants and the regenerative ability of their rhizome buds decreased). A period of darkness (24 hr) after paraquat application and before exposure of treated plants to light did not affect numbers of plants killed but did decrease rate of regrowth. Treated quackgrass foliage showed extensive paraquat injury when placed in light for 48 to 72 hr after treatment; but only parts of treated leaves were killed. Leaving treated foliage intact greatly increased the number of plants killed.

THE SYNERGISTIC ACTION OF HERBICIDE COMBINATIONS CONTAINING PARAQUAT ON AGROPYRON REPENS (L.) BEAUV.*

Summary. Herbicide combinations containing paraquat were synergistic and provided control of established Agropyron repens (L.) Beauv. (quackgrass) sods for the entire growing season. Paraquat applied at 0–5 lb/ac with simazine or diuron at 4–0 lb/ac was more phytotoxic than either herbicide applied singly and the enhanced activity was more than additive. This synergism was not due to increased absorption or translocation of either herbicide in aerial portions of the plant. Paraquat applied to the shoot increased the susceptibility of quackgrass to simazine action through the soil. Pre‐treatment of quackgrass with aminotriazole or amitrole‐T at 10 lb/ac 7 days before paraquat application at 0–5 lb/ac provided increased toxicity over that obtained when the two herbicides were applied together or singly. Subsequent studies indicated that aminotriazole applications prior to shoot destruction by either paraquat or clipping resulted in more chronic aminotriazole toxicity. Using methyl‐14C‐paraquat it was found that aminotriazole pre‐loading also increased the movement of paraquat in and out of the treated leaf. This increase was even more pronounced with amitrole‐T. When the two herbicides were applied together, antagonism in absorption and translocation occurred. Action synergique de combinaisons d'herbicides comprenant du paraquat sur Agropyron repens (L.) Beauv.

THE MOVEMENT OF PARAQUAT IN PLANTS

Summary. A qualitative study of the movement of the herbicide paraquat from droplets applied to leaves of tomato plants, using 14C‐methyl‐labelled and 14C‐ring‐labelled paraquat dichloride and di(methylsulphate), has shown that it moves in the xylem with the transpiration stream. The chemical is as well transported from young leaves as from mature ones, and will move through a steam‐ringed petiole. The enhancement of the amount of paraquat transported from the treated leaves which occurs when treated plants are kept in darkness for a period following treatment and then exposed to light, is probably due to the greater movement into the xylem through undamaged tissue which can occur in the dark. Once the chemical has been absorbed into treated leaves, light‐induced damage is required for significant movement through the rest of the plant to take place, but the damage then inhibits further entry of paraquat into the xylem. The movement of paraquat in broad bean and maize is essentially similar, though the enhancement of movement by a period of darkness after application is much less marked.La migration du paraquat dans les plantes

ABSORPTION AND TRANSLOCATION OF RADIOACTIVE HERBICIDES IN SUBMERSED AND EMERSED AQUATIC WEEDS*

Summary. Absorption and translocation of labelled herbicides by a submersed weed, waterstargrass (Heteranthera dubia (Jacq.) MacM.) were studied. Autoradiographs showed that simazine (or the labelled carbon atom) and 2,4‐D‐butoxyethyl ester moved both from roots to shoots and from shoots to roots. Ametryne, prometryne, fenac and 2,4‐D (acid) moved to a slight extent from shoot to root, but no movement from root to shoot could be detected in the autoradiographs. However, counting data indicated that small amounts of these four compounds, not recorded on autoradiographs, may move from root to shoot. Radioassay did not detect diquat or paraquat movement to the roots or to the upper portions of the shoots, but the autoradiograph of one plant receiving a root application of paraquat showed slight movement into the lower portion of the stem.Absorption and translocation of labelled herbicides by an emersed weed, alligatorweed (Alternanthera philoxeroides (Mart.) Griseb.), were also studied. Darkening of film indicated that relative mobility of root‐applied herbicides was as follows: ametryne = fenac = prometryne = simazine>diquat = paraquat> 2,4‐D (acid) = 2,4‐D‐butoxyethyl ester. There was little movement of foliage‐applied simazine, ametryne and prometryne. There was slight downward movement of foliage‐applied fenac, diquat and paraquat, and considerable downward movement of 2,4‐D (acid) and 2,4‐D‐butoxyethyl ester, which accumulated in the nodal regions of the stem.Radiolabelled phosphorus moved in both directions in both plants and there was more movement in an upward direction in both species.Absorption et migration d'herbicides radio‐actifs dans des mauvaises herbes aquatiques immergées et émergentes