Absorption of 2,4-Dichlorophenoxyacetic Acid and 3-(<i>p</i>-Chlorophenyl)-1, 1-dimethylurea (Monuron) by Barley Roots

Donaldson, T. W.; Bayer, D. E.; Leonard, O. A.

doi:10.1104/pp.52.6.638

Cited by 39 publications

(37 citation statements)

References 18 publications

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“…With the exception of 2,4-D (6,18), herbicides have seldom been reported to require a carrier-mediated transport system for uptake across the plasmalemma. Recent evidence from our laboratories suggested that paraquat is taken up by maize (Zea mays L. cv 3377 Pioneer) root epidermal and cortical cells via a protein-mediated system.…”

mentioning

confidence: 99%

Transport Interactions between Paraquat and Polyamines in Roots of Intact Maize Seedlings

Hart¹,

DiTomaso²,

Linscott³

et al. 1992

Plant Physiol.

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Interactions between absorption of paraquat and the polyamines putrescine, cadaverine, and spermine in roots of intact maize (Zea mays L. cv 3377 Pioneer) seedlings were examined. Concentrationdependent kinetics for paraquat and putrescine influx were similar and both kinetic curves could be resolved into a linear and a saturable component. The linear component was previously shown to represent cell wall/membrane binding. The saturable components for paraquat and putrescine uptake, which represent influx across the plasmalemma, had Km values of 98 and 120 micromolar, respectively, and Vmax values of 445 and 456 nanomoles per gram fresh weight per hour, respectively. Lineweaver-Burk transformation of the saturable component of paraquat influx in the presence of varying concentrations of putrescine indicated that the diamine competitively inhibited the saturable component of paraquat uptake. Reciprocal experiments similarly demonstrated that paraquat competitively inhibited the saturable component of putrescine uptake. Competitive inhibition of both paraquat and putrescine influx could also be demonstrated with the diamine cadaverine, which has a charge distribution similar to that of paraquat and putrescine. In contrast, the larger, tetravalent polyamine spermine appeared to noncompetitively inhibit the influx of paraquat and putrescine. These results strongly suggest that paraquat enters maize root cells via a carrier system that normally functions in the transport of diamines with a charge distribution similar to that of paraquat.Paraquat is a widely used postmergence contact herbicide that acts by accepting electrons from PSI of chloroplast membranes (3). To reach its site of action following foliar application, paraquat must be capable of crossing the plasmalemma (as well as the chloroplast envelope). In aqueous solution, however, paraquat exists as a divalent cation and is therefore unlikely to passively diffuse across the lipid bilayer of plant cell membranes. Until recently (11), however, little evidence has been reported for a paraquat transport mechanism in plant cell membranes.With the exception of 2,4-D (6, 18), herbicides have seldom been reported to require a carrier-mediated transport system for uptake across the plasmalemma. Recent evidence from our laboratories suggested that paraquat is taken up by maize (Zea mays L. cv 3377 Pioneer) root epidermal and cortical cells via a protein-mediated system. This is based primarily on concentration-dependent kinetic studies of paraquat absorption. In these studies, we demonstrated that paraquat influx across the plasmalemma is via a saturable system with a Km of 90 tiM and a Vmax of 458 nmol g-1 fresh weight h-1 (11).Paraquat uptake in animal tissues has also been reported to be mediated by a saturable system with a Km of 40 to 80 AM (17,21) and Vmax of 300 to 600 nmol g-' fresh weight h-1 (15,17). In contrast with our data from maize roots, influx into animal cells was reported to be sensitive to respiratory inhibitors such as cyanide and rotenone ...

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mentioning

confidence: 99%

Transport Interactions between Paraquat and Polyamines in Roots of Intact Maize Seedlings

Hart¹,

DiTomaso²,

Linscott³

et al. 1992

Plant Physiol.

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“…The Absorption in Live and Dead Tissue. The experimental approach used in this research was similar to that described by Peterson and Edgington (20) 429 Bq nmolt') were prepared in solutions of distilled water:ethanol (9:1, v/v) so that the final herbicide concentration, when 10 Ml of these solutions was added to 3.0 ml buffer, was 1.0 uM. The 14C content of the solutions was measured by taking a 50-Ml aliquot at specified time intervals (including t = 0, immediately after the herbicide was added) and assaying for 14C by LSS.…”

mentioning

confidence: 99%

Uptake and Accumulation of the Herbicides Chlorsulfuron and Clopyralid in Excised Pea Root Tissue

Devine¹,

Bestman²,

Born³

1987

Plant Physiol.

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The herbicides chlorsulfuron and clopyralid were taken up rapidly by excised pea root tissue and accumulated in the tissue to concentrations ten and four times those in the external medium, respectively. Uptake was related linearly to external herbicide concentration over a wide concentration range, implying that transport across the membrane is by nonfacilitated diffusion. Uptake of both compounds was influenced by pH, with greatest uptake at low pH. The pH dependence of uptake suggests that the herbicides (both of which are weak acids) are transported across the plasma membrane in the undissociated form, and accumulate in the cytoplasm by an ion trap mechanism. Most of the absorbed herbicide effluxed from the tissue when it was transferred to herbicide-free buffer, indicating that the accumulation was not due to irreversible binding. Consequently, both herbicides remain available for transfer to the phloem. These results can explain the high reported phloem mobility of clopyralid in intact plants. The low phloem mobility of chlorsulfuron must be accounted for by factors that override its ability to accumulate in the symplast.There has been considerable interest in recent years in the mechanisms by which plant growth regulating chemicals, both natural and synthetic, move across cell membranes. In the case of naturally occurring compounds this interest has been directed towards determining the way(s) in which concentrations of these compounds, at both the tissue and cellular levels, are regulated by the plant. Results indicate that endogenous plant growthregulating chemicals are transported across membranes by both nonfacilitated and carrier-mediated processes (1, 17). Endogenous control of the latter process presumably plays a role in regulating internal concentrations.Herbicide uptake into plant tissue has been studied primarily in relation to the subsequent translocation of the herbicides. Herbicide entry and retention in the symplast are prerequisites for phloem transport (19,26), and the relationship between phloem transport and physicochemical properties of herbicides has been the focus of much attention recently (6,19 429 Bq nmolt') were prepared in solutions of distilled water:ethanol (9:1, v/v) so that the final herbicide concentration, when 10 Ml of these solutions was added to 3.0 ml buffer, was 1.0 uM. The 14C content of the solutions was measured by taking a 50-Ml aliquot at specified time intervals (including t = 0, immediately after the herbicide was added) and assaying for 14C by LSS. Absorption was calculated by correcting the 14C data for the fraction of total solution assayed, with appropriate adjustment for the change in solution volume, and was expressed as picomoles of herbicide absorbed/100 mg root tissue.

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“…In the case of passive physical absorption, the Q 10 value should be low, normally around 1.0 (26,33). Theoretically, a solute must be neutrally charged and lipid-soluble in order to diffuse passively across a membrane.…”

Section: Discussionmentioning

confidence: 99%

“…10/(T2ϪT1) (K 2 and K 1 represent the absorption rate at temperature T 2 and T 1 , respectively) (26). The pH dependence of uptake of p-OHBG was determined by incubation of 1 ml of protoplasts in uptake reaction mixtures containing 10 mM MES-Tris of pH 4, 5, 5.5, 6, 7, and 8.…”

Section: Methodsmentioning

confidence: 99%

Characterization of Glucosinolate Uptake by Leaf Protoplasts of Brassica napus

Chen¹,

Halkier²

2000

Journal of Biological Chemistry

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The uptake of radiolabeled p-hydroxybenzylglucosinolate (p-OHBG) by protoplasts isolated from leaves of Brassica napus was detected using silicone oil filtration technique. The uptake was pH-dependent with higher uptake rates at acidic pH. Imposition of a pH gradient (internal alkaline) across the plasma membrane resulted in a rapid uptake of p-OHBG, which was inhibited in the presence of carbonyl cyanide m-chlorophenylhydrazone, indicating that the uptake is dependent on a proton motive force. Dissipation of the internal positive membrane potential generated a small influx as compared with that seen for pH gradient (⌬pH). Kinetic studies demonstrated the presence of two uptake systems, a saturable and a linear component. The saturable kinetics indicated carrier-mediated translocation with a K m of 1.0 mM and a V max of 28.7 nmol/l/h. The linear component had very low substrate affinity. The carriermediated transport had a temperature coefficient (Q 10 ) of 1.8 ؎ 0.2 in the temperature range from 4 -30°C. The uptake was against a concentration gradient and was sensitive to protonophores, uncouplers, H ؉ -ATPase inhibitors, and the sulfhydryl group modifier p-chloromercuriphenylsulfonic acid. The carrier-mediated uptake system had high specificity for glucosinolates because glucosinolate degradation products, amino acids, sugars, or glutathione conjugates did not compete for p-OHBG uptake. Glucosinolates with different side chains were equally good competitors of p-OHBG uptake, which indicates that the uptake system has low specificity for the glucosinolate side chains. Our data provide the first evidence of an active transport of glucosinolates by a proton-coupled symporter in the plasma membrane of rape leaves.Glucosinolates are amino acid-derived natural plant products containing a thioglucose and a sulfonated oxime. Glucosinolates are present in the Capparales order, including the family Brassicaceae, whose many cultivars have provided mankind with a source of condiments, vegetables, forage crops, and the economically important crop oilseed rape (Brassica napus L.). Glucosinolates are hydrolyzed by specific thioglucosidases, called myrosinases, to produce a wide range of degradation products, typically isothiocyanates, nitriles, and thiocyanates, with different biological activities. The glucosinolate/myrosinase system is believed to play a role in plant-pest interaction. The degradation products serve as attractants for insect specialists and as repellents for generalist herbivores, insects, and microorganisms (for review see Ref. 1).Glucosinolates are present in all parts of the plant. The level of glucosinolates varies in different tissues at different developmental stages (2, 3) and is affected by external factors such as growth conditions (4, 5), wounding (6), fungal infection (7), actual and simulated insect damage (6,8), and other forms of stress (9). Generally, high levels of biosynthesis are found in young leaves (10, 11), shoots, and silique walls (12); however, the high content of glucosinolates in...

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Absorption of 2,4-Dichlorophenoxyacetic Acid and 3-(p-Chlorophenyl)-1, 1-dimethylurea (Monuron) by Barley Roots

Cited by 39 publications

References 18 publications

Transport Interactions between Paraquat and Polyamines in Roots of Intact Maize Seedlings

Transport Interactions between Paraquat and Polyamines in Roots of Intact Maize Seedlings

Uptake and Accumulation of the Herbicides Chlorsulfuron and Clopyralid in Excised Pea Root Tissue

Characterization of Glucosinolate Uptake by Leaf Protoplasts of Brassica napus

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