The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Tracy M Sterling - One of the best experts on this subject based on the ideXlab platform.
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effect of Picloram on resistant and susceptible yellow starthistle centaurea solstitialis the role of ethylene
Weed Science, 1998Co-Authors: Robert P Sabba, Tracy M Sterling, Norm K LowndsAbstract:Norm K. Lownds Department of Horticulture, Michigan State University, East Lansing, MI 48824; lownds@pilot.msu.edu The noxious weed yellow starthistle is commonly controlled by the auxinic herbicide Picloram. Induction of ethylene synthesis, epinasty, and reduction in shoot growth are typical symptoms of Picloram treatment. Picloram did not induce ethylene evolution in the resistant accession RDW-1, though it caused a 250% increase in ethylene evolution in the susceptible wildtype SCI-1. The ethylene synthesis inhibitor aminoethoxyvinylglycine reduced the amount of ethylene induced by Picloram in SCI-1 to control levels, but only reduced epinasty by 20% after 6 d. Aminoethoxyvinylglycine did not affect the reduction in shoot weight caused by Picloram. The ethylene-releasing compound ethephon induced only a small amount of epinasty and had little effect on shoot weight in either accession. These results suggest that ethylene induced by Picloram in wildtype plants plays only a minor role in the herbicidal effects of Picloram. Furthermore, the resistance of the RDW-1 accession is not due to the lack of ethylene biosynthesis following Picloram application to this accession.
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physiological characterization of Picloram resistance in yellow starthistle
Pesticide Biochemistry and Physiology, 1996Co-Authors: E P Fuerst, Norman K Lownds, Tracy M Sterling, M A Norman, Timothy S Prather, G P Irzyk, Y Wu, Robert H CallihanAbstract:Abstract A yellow starthistle ( Centaurea solstitialis L.) accession from a site near Dayton, Washington is resistant to Picloram applied to roots and/or leaves. The level of resistance to Picloram varied among experiments, ranging from 3- to 35-fold, depending on the site(s) of application and growth conditions. Whole-plant studies indicated cross-resistance of the resistant accession (R), relative to the susceptible accession (S), to clopyralid, fluroxypyr, and dicamba, but not to triclopyr or 2,4-D. Resistance to root- or foliar-applied Picloram was not due to differential metabolism of Picloram. Uptake of foliar-applied Picloram was reduced by half in R compared to S, 72 hr after treatment. Root uptake and acropetal translocation of Picloram were reduced in R compared to S. This reduced acropetal translocation showed specificity for Picloram since transpiration and acropetal translocation of atrazine were similar in R and S. Picloram-induced ethylene production by foliar-applied Picloram was up to 20-fold greater in S than R, indicating that the herbicidal activity of Picloram in R is blocked at, or prior to, the ethylene-induction response. Picloram induced de novo synthesis of several proteins in S but not R, and of a 19-kDa protein in R but not S. Possible mechanisms of resistance are discussed, including reduced Picloram affinity for an auxin-binding site on the plasmalemma, and alterations in the signal transduction process.
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Environmental effects on Picloram uptake and ethylene production by broom snakeweed.
Journal of Range Management, 1996Co-Authors: Tracy M Sterling, Norman K Lownds, Leigh W. MurrayAbstract:Broom snakeweed [Gutierrezia sarothrae (Pursh) Britt. R therefore, it appears that changes in uptake and physiological sensitivity as measured by Picloram-induced ethylene production are not the only factors controlling differential sensitivity to Picloram.
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Picloram uptake translocation and efficacy in relation to water status of russian knapweed acroptilon repens
Weed Science, 1995Co-Authors: Robert G Morrison, Norman K Lownds, Tracy M SterlingAbstract:Picloram uptake, translocation, and efficacy were studied using greenhouse-grown Russian knapweed plants. Uptake of 14C-Picloram, applied as discrete droplets to adaxial leaf surfaces of well-watered plants, averaged less than 10% of that applied. Most uptake occurred within 30 min of application. Uptake increased linearly with external Picloram concentrations from 6.2 to 74.5 mM and was pro- portional to Picloram concentration. Only about 10% of absorbed Picloram was translocated out of the treated leaf of well-watered plants within 96 h, with approximately equal acropetal and basipetal translocation. Water stress before, at the time of, and after Picloram application did not affect Picloram uptake, but reduced total translocation and in- creased the relative amount translocated basipetally. Water stress also reduced Picloram efficacy. Although Silwett L-77 increased Picloram uptake into Russian knapweed leaves, it did not increase efficacy under water stress conditions. No- menclature: Picloram, 4-amino-3,5,6-trichloro-2-pyridine- carboxylic acid; Russian knapweed, Acroptilon repens L. #3
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Picloram Absorption by Broom Snakeweed (Gutierrezia sarothrae) Leaf Tissue
Weed Science, 1992Co-Authors: Tracy M Sterling, Norman K LowndsAbstract:Foliar absorption of Picloram by broom snakeweed, a rangeland shrub, was investigated. Picloram uptake into leaf, axillary bud, and stem tissues was similar. In addition, Picloram uptake by leaf tissue from greenhouse- and field-grown broom snakeweed did not differ. Picloram accumulated rapidly and absorption saturated between 15 min and 1 h of application; no further absorption occurred through 72 h with maximum uptake ca. 15% of applied Picloram. Picloram content increased linearly with increasing external Picloram concentration, implying that movement of the herbicide across the cuticle is via diffusion. Absorption was dependent on relative humidity and temperature with the greatest uptake at 94% relative humidity and 35 C, respectively. Absorption was pH dependent; Picloram absorption was greatest at pH 4 and least at pH 8. In addition, Picloram absorption was less at pH 3 compared to pH 4. These results provide evidence that Picloram is absorbed across the cuticle via simple diffusion and absorption is dependent on environmental conditions and solution pH at and following application.
Robert H Callihan - One of the best experts on this subject based on the ideXlab platform.
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physiological characterization of Picloram resistance in yellow starthistle
Pesticide Biochemistry and Physiology, 1996Co-Authors: E P Fuerst, Norman K Lownds, Tracy M Sterling, M A Norman, Timothy S Prather, G P Irzyk, Y Wu, Robert H CallihanAbstract:Abstract A yellow starthistle ( Centaurea solstitialis L.) accession from a site near Dayton, Washington is resistant to Picloram applied to roots and/or leaves. The level of resistance to Picloram varied among experiments, ranging from 3- to 35-fold, depending on the site(s) of application and growth conditions. Whole-plant studies indicated cross-resistance of the resistant accession (R), relative to the susceptible accession (S), to clopyralid, fluroxypyr, and dicamba, but not to triclopyr or 2,4-D. Resistance to root- or foliar-applied Picloram was not due to differential metabolism of Picloram. Uptake of foliar-applied Picloram was reduced by half in R compared to S, 72 hr after treatment. Root uptake and acropetal translocation of Picloram were reduced in R compared to S. This reduced acropetal translocation showed specificity for Picloram since transpiration and acropetal translocation of atrazine were similar in R and S. Picloram-induced ethylene production by foliar-applied Picloram was up to 20-fold greater in S than R, indicating that the herbicidal activity of Picloram in R is blocked at, or prior to, the ethylene-induction response. Picloram induced de novo synthesis of several proteins in S but not R, and of a 19-kDa protein in R but not S. Possible mechanisms of resistance are discussed, including reduced Picloram affinity for an auxin-binding site on the plasmalemma, and alterations in the signal transduction process.
Norman K Lownds - One of the best experts on this subject based on the ideXlab platform.
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physiological characterization of Picloram resistance in yellow starthistle
Pesticide Biochemistry and Physiology, 1996Co-Authors: E P Fuerst, Norman K Lownds, Tracy M Sterling, M A Norman, Timothy S Prather, G P Irzyk, Y Wu, Robert H CallihanAbstract:Abstract A yellow starthistle ( Centaurea solstitialis L.) accession from a site near Dayton, Washington is resistant to Picloram applied to roots and/or leaves. The level of resistance to Picloram varied among experiments, ranging from 3- to 35-fold, depending on the site(s) of application and growth conditions. Whole-plant studies indicated cross-resistance of the resistant accession (R), relative to the susceptible accession (S), to clopyralid, fluroxypyr, and dicamba, but not to triclopyr or 2,4-D. Resistance to root- or foliar-applied Picloram was not due to differential metabolism of Picloram. Uptake of foliar-applied Picloram was reduced by half in R compared to S, 72 hr after treatment. Root uptake and acropetal translocation of Picloram were reduced in R compared to S. This reduced acropetal translocation showed specificity for Picloram since transpiration and acropetal translocation of atrazine were similar in R and S. Picloram-induced ethylene production by foliar-applied Picloram was up to 20-fold greater in S than R, indicating that the herbicidal activity of Picloram in R is blocked at, or prior to, the ethylene-induction response. Picloram induced de novo synthesis of several proteins in S but not R, and of a 19-kDa protein in R but not S. Possible mechanisms of resistance are discussed, including reduced Picloram affinity for an auxin-binding site on the plasmalemma, and alterations in the signal transduction process.
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Environmental effects on Picloram uptake and ethylene production by broom snakeweed.
Journal of Range Management, 1996Co-Authors: Tracy M Sterling, Norman K Lownds, Leigh W. MurrayAbstract:Broom snakeweed [Gutierrezia sarothrae (Pursh) Britt. R therefore, it appears that changes in uptake and physiological sensitivity as measured by Picloram-induced ethylene production are not the only factors controlling differential sensitivity to Picloram.
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Picloram uptake translocation and efficacy in relation to water status of russian knapweed acroptilon repens
Weed Science, 1995Co-Authors: Robert G Morrison, Norman K Lownds, Tracy M SterlingAbstract:Picloram uptake, translocation, and efficacy were studied using greenhouse-grown Russian knapweed plants. Uptake of 14C-Picloram, applied as discrete droplets to adaxial leaf surfaces of well-watered plants, averaged less than 10% of that applied. Most uptake occurred within 30 min of application. Uptake increased linearly with external Picloram concentrations from 6.2 to 74.5 mM and was pro- portional to Picloram concentration. Only about 10% of absorbed Picloram was translocated out of the treated leaf of well-watered plants within 96 h, with approximately equal acropetal and basipetal translocation. Water stress before, at the time of, and after Picloram application did not affect Picloram uptake, but reduced total translocation and in- creased the relative amount translocated basipetally. Water stress also reduced Picloram efficacy. Although Silwett L-77 increased Picloram uptake into Russian knapweed leaves, it did not increase efficacy under water stress conditions. No- menclature: Picloram, 4-amino-3,5,6-trichloro-2-pyridine- carboxylic acid; Russian knapweed, Acroptilon repens L. #3
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Picloram Absorption by Broom Snakeweed (Gutierrezia sarothrae) Leaf Tissue
Weed Science, 1992Co-Authors: Tracy M Sterling, Norman K LowndsAbstract:Foliar absorption of Picloram by broom snakeweed, a rangeland shrub, was investigated. Picloram uptake into leaf, axillary bud, and stem tissues was similar. In addition, Picloram uptake by leaf tissue from greenhouse- and field-grown broom snakeweed did not differ. Picloram accumulated rapidly and absorption saturated between 15 min and 1 h of application; no further absorption occurred through 72 h with maximum uptake ca. 15% of applied Picloram. Picloram content increased linearly with increasing external Picloram concentration, implying that movement of the herbicide across the cuticle is via diffusion. Absorption was dependent on relative humidity and temperature with the greatest uptake at 94% relative humidity and 35 C, respectively. Absorption was pH dependent; Picloram absorption was greatest at pH 4 and least at pH 8. In addition, Picloram absorption was less at pH 3 compared to pH 4. These results provide evidence that Picloram is absorbed across the cuticle via simple diffusion and absorption is dependent on environmental conditions and solution pH at and following application.
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Picloram-INDUCED ETHYLENE PRODUCTION BY BROOM SNAKEWEED
Hortscience, 1990Co-Authors: Norman K Lownds, Tracy M SterlingAbstract:Broom snakeweed [Gutierrezia sarothrae (Pursh) Britt. & Rusby] is a suffrutescent shrub that is a problem in rangeland production areas because it interferes with forage growth and is potentially dangerous to livestock. Picloram, an auxin-like herbicide, is used for broom snakeweed control. Picloram-induced ethylene production may be important to its efficacy, therefore, studies were conducted to characterize ethylene production and phytotoxicity. Picloram, applied as individual drops, induced a linear increase in ethylene production (r= 0.738***) between 0 and 72 hr after treatment. When plants were sprayed with 0.125, 0.25 and 0.50 lb ae/A, ethylene production increased linearly through 120 hr then leveled off and began to decrease for all three concentrations. The highest rate of ethylene production was induced by 0.25 lb ae/A followed by 0.50 and 0.125, respectively. Epinasty was evident 24 hr after treatment and chlorosis 3 to 4 days after treatment. Both were more severe with increasing Picloram concentration. It appears that Picloram-induced ethylene production is an important component in Picloram activity.
Alessandra Ferreira Ribas - One of the best experts on this subject based on the ideXlab platform.
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Optimization of somatic embryogenesis and in vitro plant regeneration of Urochloa species using Picloram
In Vitro Cellular & Developmental Biology - Plant, 2015Co-Authors: Luciana Midori Takamori, Nelson Barbosa Machado Neto, Luiz Gonzaga Esteves Vieira, Alessandra Ferreira RibasAbstract:The establishment of an efficient methodology for regeneration in Urochloa spp. via somatic embryogenesis is an essential component of genetic engineering technology. The aim of this study was to evaluate different concentrations of growth regulators on callus induction, somatic embryogenesis, and plant regeneration of Urochloa spp. using mature seeds as the initial explant. Firstly, different concentrations (1, 2, 4, and 8 mg/L) of 2,4-D or Picloram were tested using U. brizantha cv. Marandu. In a second step, the above concentrations of Picloram were also used to evaluate its effect on the morphogenetic potential in different genotypes: U. brizantha cvs. Xaraés and Piatã, U. decumbens cv. Basilisk, U. humidicola cv. Llanero, and U. ruziziensis cv. Ruziziensis. There was no significant difference between concentrations of 2,4-D or Picloram for the production of primary calluses in U. brizantha cv. Marandu, ranging from 58.5 to 69.2%. However, embryogenic calluses induced under Picloram showed higher percentage of shoot formation after transferring to MS medium with 2 mg/L BA. A higher number of shoots were produced in mature seed cultures of U. decumbens cv. Basilisk and U. brizantha cvs. Marandu and Xaraés supplemented with 1 mg/L Picloram. No albino plants were regenerated using Picloram. The successful regeneration of green and morphologically normal plants opens the possibility of using this protocol to obtain transgenic plants in Urochloa spp.
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optimization of somatic embryogenesis and in vitro plant regeneration of urochloa species using Picloram
In Vitro Cellular & Developmental Biology – Plant, 2015Co-Authors: Luciana Midori Takamori, Luiz Gonzaga Esteves Vieira, Nelson Barbosa Machado Neto, Alessandra Ferreira RibasAbstract:The establishment of an efficient methodology for regeneration in Urochloa spp. via somatic embryogenesis is an essential component of genetic engineering technology. The aim of this study was to evaluate different concentrations of growth regulators on callus induction, somatic embryogenesis, and plant regeneration of Urochloa spp. using mature seeds as the initial explant. Firstly, different concentrations (1, 2, 4, and 8 mg/L) of 2,4-D or Picloram were tested using U. brizantha cv. Marandu. In a second step, the above concentrations of Picloram were also used to evaluate its effect on the morphogenetic potential in different genotypes: U. brizantha cvs. Xaraes and Piata, U. decumbens cv. Basilisk, U. humidicola cv. Llanero, and U. ruziziensis cv. Ruziziensis. There was no significant difference between concentrations of 2,4-D or Picloram for the production of primary calluses in U. brizantha cv. Marandu, ranging from 58.5 to 69.2%. However, embryogenic calluses induced under Picloram showed higher percentage of shoot formation after transferring to MS medium with 2 mg/L BA. A higher number of shoots were produced in mature seed cultures of U. decumbens cv. Basilisk and U. brizantha cvs. Marandu and Xaraes supplemented with 1 mg/L Picloram. No albino plants were regenerated using Picloram. The successful regeneration of green and morphologically normal plants opens the possibility of using this protocol to obtain transgenic plants in Urochloa spp.
E P Fuerst - One of the best experts on this subject based on the ideXlab platform.
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physiological characterization of Picloram resistance in yellow starthistle
Pesticide Biochemistry and Physiology, 1996Co-Authors: E P Fuerst, Norman K Lownds, Tracy M Sterling, M A Norman, Timothy S Prather, G P Irzyk, Y Wu, Robert H CallihanAbstract:Abstract A yellow starthistle ( Centaurea solstitialis L.) accession from a site near Dayton, Washington is resistant to Picloram applied to roots and/or leaves. The level of resistance to Picloram varied among experiments, ranging from 3- to 35-fold, depending on the site(s) of application and growth conditions. Whole-plant studies indicated cross-resistance of the resistant accession (R), relative to the susceptible accession (S), to clopyralid, fluroxypyr, and dicamba, but not to triclopyr or 2,4-D. Resistance to root- or foliar-applied Picloram was not due to differential metabolism of Picloram. Uptake of foliar-applied Picloram was reduced by half in R compared to S, 72 hr after treatment. Root uptake and acropetal translocation of Picloram were reduced in R compared to S. This reduced acropetal translocation showed specificity for Picloram since transpiration and acropetal translocation of atrazine were similar in R and S. Picloram-induced ethylene production by foliar-applied Picloram was up to 20-fold greater in S than R, indicating that the herbicidal activity of Picloram in R is blocked at, or prior to, the ethylene-induction response. Picloram induced de novo synthesis of several proteins in S but not R, and of a 19-kDa protein in R but not S. Possible mechanisms of resistance are discussed, including reduced Picloram affinity for an auxin-binding site on the plasmalemma, and alterations in the signal transduction process.