Concentrations Of Picloram Research Articles

Picloram Absorption by Broom Snakeweed (Gutierrezia sarothrae) Leaf Tissue

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.

PICLORAM-INDUCED ETHYLENE PRODUCTION BY BROOM SNAKEWEED

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.

Influence of phytohormones, carbohydrates, aminoacids, growth supplements and antibiotics on somatic embryogenesis and plant differentiation in finger millet

Cultured caryopses of finger millet (Eleusine coracana GAERTN) produced callus from shoot apices or mesocotyls depending upon the concentration of picloram and combination of cytokinins in MS basal medium. On subsequent subcultures, numerous somatic embryos differentiated from the callus on MS medium supplemented with picloram and kinetin. The embryos germinated into complete plants on medium devoid of phytohormones. When different carbohydrates were tested, basal medium containing glucose and sucrose produced the highest frequency of germinating somatic embryos. Supplementation of MS basal medium with a variety of aminoacids, osmotic agents and growth supplements had an adverse effect on the germination of embryos. Incorporation of different antibiotics such as carbenicillin, cefotaxime and streptomycin sulfate enhanced plant differentiation from somatic embryos. Cytological analysis of regenerated plants showed normal diploid chromosome number in their root tips.

Ontogeny of Somatic Embryos of Vigna aconitifolia, Vigna mungo and Vigna radiata

Callus cultures were initiated from immature cotyledons of Vigna aconitifolia, V. mungo and V. radiata on MS medium supplemented with NAA, picloram or 2, 4-D. On transfer to L-6 liquid medium supplemented with low concentrations of picloram, GA3 and cytokinins, large number of somatic embryos differentiated from the callus. The cells destined to become somatic embryos divided to form spherical or filamentous proembryos. From the filamentous proembryo, the embryo proper developed either at single or multiple sites. Development of somatic embryos from multiple sites resulted in several embryos connected by a common suspensor at the radicle end. Continued divisions of the proembryos led to globular, heart shaped and dicotyledonary stages of somatic embryogenesis. The somatic embryos of V. mungo and V. aconitifolia differentiated into tiny plantlets at low frequency (1%) in liquid suspension cultures supplemented with zeatin, picloram and GA3.

Absorption and Translocation of Picloram by Lindheimer Pricklypear (Opuntia lindheimeri)

Removing the epicuticular wax from mature pads (cladophylls) of Lindheimer pricklypear increased picloram absorption by four- to sixfold in the laboratory, while the addition of surfactant had little effect on absorption. Absorption decreased with increasing pH of the picloram solution, indicating that picloram diffused through the cuticle as the undissociated molecule. Picloram entered detached pads at the areoles more readily than through the surrounding cuticle. In the glasshouse, whole plants consisting of an old, mature pad supporting a young, growing pad absorbed picloram very slowly whether picloam was applied as a spray to old or young pads or to the soil. About 90 and 80% of the applied picloram remained on the waxy surface of old and new pads, respectively, and about 2% of the applied picloram was recovered from within the epicuticular wax after 30 days. Picloram concentrations within pads treated in the glasshouse were greater when the herbicide was applied to new pads (4.6 μg/g) than old pads (1.9 μg/g) after 30 days. More picloram was translocated basipetally from treated new pads to untreated old pads than in the opposite direction, but concentrations in untreated pads were low (<1 μg/g). Little picloram was absorbed by roots, compared to pads, and little was translocated into or out of roots. These results conflict with the view that the effectiveness of picloram for pricklypear control is attributable to extensive root uptake and acropetal transport. However, observations of plants 6 months after treatment indicated that soil applications were more effective than sprays in the glasshouse.

Picloram Release from Leafy Spurge (Euphorbia esula) Roots in the Field

Picloram release by leafy spurge roots, as affected by picloram rate, plant growth stage, and time intervals after treatment, was quantified under field conditions. Picloram was pipe-wick applied to leafy spurge in the vegetative, flowering, and seed-filling growth stages. Percent leafy spurge control was evaluated and picloram residues were determined in soil samples from 0- to 13-, 13- to 26-, and 26- to 39-cm depths taken 1, 2, and 3 weeks after treatment. Leafy spurge was controlled (frequently >85%) by all picloram concentrations applied, although control tended to increase as solution concentration increased. Picloram release from roots was greater from plants treated in the flowering and seed-filling stages than from plants in the vegetative stage. Picloram release from roots generally was correlated with application rate, averaging 490, 820, and 1420 ppbw in soil for the 30, 60, and 120 g ae/L application rates, respectively. Picloram release from roots occurred rapidly with 86% of the picloram detected in the 0- to 13-cm soil depth present by 1 week after treatment. Picloram was detected at all soil depths sampled, but over 84% was in the upper 13 cm and 8% was in both the 13- to 26- and 26- to 39-cm depths. Leafy spurge shoots emerged through a 7.5- and 15-cm depth of picloram-treated soil at concentrations up to 1000 ppbw within 14 to 21 days after the untreated control. Picloram soil residue had little effect on leafy spurge root growth.

Induction of somatic embryogenesis in leaf-derived callus of Vicia narbonensis L.

A method for the induction of somatic embryogenesis in callus cultures, using explants from mature leaves of Vicia narbonensis L., is described. Callus developed on a solid medium (Murashige and Skoog 1962), which was supplemented with low concentrations of picloram and benzylaminopurine. Subsequent culture was carried out in different liquid media (culture length four months). The gradual reduction of auxin and cytokinin concentrations, and the addition of glutamine and pyridoxal·HCl were favourable. Somatic embryos appeared on solid media without phytohormones.

Survey for Picloram in North Dakota Groundwater

Wells and streams in 10 North Dakota counties were surveyed for picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), the major herbicide used to control leafy spurge (Euphorbia esulaL. # EPHES). Three rivers and 144 wells were sampled in 1985. Picloram concentration ranged from <0.1 to 12.4 ppb in the water from five wells in five counties and from <0.1 to 6 ppb in two rivers. An additional 44 wells were sampled in 1986; they were located within 2 km of the five wells where picloram was detected in 1985. Picloram concentrations in 1986 ranged from non-detectable to 6.7 ppb in the original contaminated wells and was 0.97 ppb in water from one of the additional 44 wells. Picloram concentration in the river water was lower in 1986 than in 1985 but was detected farther downstream. All contaminated wells were within 1.5 km of an area treated for leafy spurge, but picloram had been spilled accidentally or misapplied near all but one of the wells. The concentrations detected were at least 100 times below suggested tolerance levels for water.

Somatic embryogenesis in avocado (Persea americana Mill.) in vitro

A tissue culture procedure was developed for the regeneration of somatic embryos from callus cultures of the avocado,Persea americana. Immature zygotic embryos, 0.6–0.8 mm long, were used as original explants. Addition of 0.1 mg/l picloram (4-amino-3,5,6-trichloropicolinic acid) to culture medium appeared critical for callus initiation. Development of somatic embryos was accomplished in picloram concentrations of 0.01 to 0.1 ml/l. A few well developed embryos produced green shoots. Attempts to induce a higher incidence of germination were unsuccessful.

Concentration of 2,4,5-T, Triclopyr, Picloram, and Clopyralid in Honey Mesquite (Prosopis glandulosa) Stems

Triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), and clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were applied to honey mesquite (Prosopis glandulosaTorr. # PRCJG) on seven different dates about every 3 weeks from May to September in 1980 and 1981. Concentrations of 2,4,5-T or triclopyr in stem tissue were usually less than 2 μg/g fresh weight regardless of date of application. Concentrations of picloram and clopyralid were as high as 11 and 22 μg/g fresh weight, respectively, in upper stem phloem at some dates of application. Higher concentrations of all herbicides were detected in upper stem phloem than in the upper stem xylem or basal stem phloem or xylem. More herbicide tended to be detected in stems when herbicides were applied early (May and June) than late (August and September) in the season. Concentrations of triclopyr and picloram recovered from honey mesquite stems were about 25% greater at 3 than at 30 days after treatment, whereas concentrations of 2,4,5-T and clopyralid were about 50% greater at 3 than at 30 days after application.

SIMULATION OF HERBICIDE CONCENTRATIONS IN STORMFLOW FROM FORESTED WATERSHEDS1

SummaryThe breakpoint rainfall hydrology and pesticide options of the field scale model CREAMS (Chemicals, Runoff, and Erosion from Agricultural Management Systems) were used to predict average concentrations of hexazinone [3 cyclohexyl‐6‐(dimethyl‐amino)‐1‐methyl‐1,3,5‐triazine‐2,4(1H,3H)‐dione] in stormflow from four forested watersheds in the upper Piedmont region of Georgia. Predicted concentrations were compared with measured concentrations recorded over a 13‐month period. CREAMS accurately predicted hexazinone concetrations in the initial stormflow events which also contained the highest concentrations. The model underestimated the hexazinone concentrations in stormflow two months and greater following pesticide application. In a companion study, the daily rainfall option of the CREAMS model was used to evaluate the reltive risk associated with the maximum expected concentration of hexazinone, bromacil (5‐bromo‐3 sec‐butyl‐6 methyuracil), picloram (4‐amino‐3,5,6 trichloropicolinic acid), dicamba (3,6‐dichloro‐0‐anisic acid), and triclopyr {[(3,5,6‐trichloro‐2‐pyridinyl)oxy] acetic acid} in stormflow from small forested watersheds. The model predicted the following order of potential residue appearance in stormflow: bromacil>triclopyr>hexazinone>picloram>dicamba. Subsurface movement of residues via interflow and deep leaching losses are not simulated by the version of CREAMS used in these studies.

Application of Herbicides on Rangelands by a Carpeted Roller: Control of Goldenweeds (Isocomaspp.) and False Broomweed (Ericameria austrotexana)

Solutions containing 24 or 120 g ae/L of amine or salt formulations of glyphosate [N-(phosphonomethyl) glycine], triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, and picloram (4-amino-3,5,6-trichloropicolinic acid) were applied to small shrubs with a carpeted roller. Glyphosate reduced the live canopy cover of false broomweed (Ericameria austrotexanaM.C. Johnston) by 83 to 87% at one site but only by 37 to 58% at another location. The lower concentration of picloram reduced false broomweed cover by at least 92%, and the higher concentration completely controlled the weed at both study sites. Effectiveness of triclopyr was usually intermediate between glyphosate and picloram. Removing a scraper designed to abrade stems prior to herbicide deposition reduced the effectiveness of picloram but not other herbicides. The herbicides reduced canopy cover of common goldenweed [Isocoma coronopifolia(Gray) Greene ♯3IOCCO] by 92 to 100%. Common goldenweed was also controlled by 2,4-D [(2,4-dichlorophenoxy)acetic acid] amine applied with the carpeted roller. In glasshouse experiments, 1.2 to 60 g ae/L of 2,4-D amine reduced live canopy dry weight of common goldenweed by 73 to 88% at 5 months after application with a carpeted roller.

Dissipation of Picloram in Storm Runoff

AbstractThe extent of progressive decrease in concentration of the herbicide picloram (4‐amino‐3,5,6‐trichloropicolinic acid) in intermittent streamflow was determined during runoff‐producing storms. Maximum concentrations of picloram were 48 and 250 mg/m3 in initial runoff water leaving a sprayed 8‐ha area in 1978 and 1979. Concentration decreased with distance from the treated area in proportion to the size of adjacent, untreated watershed subunits, which contributed runoff water to streamflow. Picloram concentrations usually decreased with each successive runoff event; an exception occurred when unusually large quantities of runoff (8.7 cm) diluted concentrations to levels less than those observed in the succeeding event (1.4 cm runoff). About 6% of the applied picloram left the treated area during a period of 1 month when conditions were especially conducive to transport of the herbicice in surface runoff water.Rapid dilution of picloram was observed after direct introduction of the herbicide near the upper end of a larger stream during rising stage of flow. Maximum concentrations at 90, 1170, and 5400 m downstream from the point of introduction of 1270 g of picloram were 13 720, 470, and 5 mg/m3, respectively. The calculated quantity of picloram which was detected at the 5400‐m sampling point in streamflow was only 0.13% of that introduced. Mixing of water during streamflow and additions of uncontaminated water along the channel apparently reduced picloram concentration to below that detectable by gas chromatography.

Induction of somatic embryos in pea, Pisum sativum L.

Using low concentrations of picloram (0.06 mg/l), embryoids were formed on the surface of leaf-derived callus of pea, Pisum sativum L. (c.v. Dippes Gelbe Victoria) upon transfer to liquid medium. After some days in culture, embryoids spontaneously separated from the calli, and developed into torpedo-shaped embryos, which were transferred to solid medium. In a second series of experiments, embryos were also formed by mutant 489C and a genetic line of Pisum arvense, which additionally exhibited embryogenesis also from epicotyl-derived callus. Some of the embryos showed root formation, but no shoot morphogenesis occurred. In a limited number of cases, an additional root was formed in the apparent shoot apical region after 2–5 days.

PICLORAM RESIDUE LEVELS FOR THE CONTROL OF LEAFY SPURGE REGROWTH

The persistence of picloram was measured in the soil following a single application of 2.24 kg/ha and four consecutive annual applications of 0.56 kg/ha for the control of leafy spurge. The concentration of picloram in the surface 7.5 cm of soil decreased from 820 ppb immediately following the application of 2.24 kg/ha to range between 17 and 52 ppb in the third year after treatment. Picloram residues ranged between 45 and 165 ppb during each of the 4-yr periods of annual applications of 0.56 kg/ha. The critical level of picloram that must remain in the soil to prevent leafy spurge re-establishment from seed is about 50 ppb.

Infrared Spectroscopy of Picloram Interactions with Al(III)-, Fe(III)-, and Cu(II)-Saturated and Hydrous Oxide-Coated Montmorillonite

AbstractThin clay films prepared from aqueous suspensions of the potassium or sodium salt of picloram (4-amino-3,5,6-trichloropicolinic acid) with Al-, Fe-, or Cu-saturated montmorillonite or with montmorillonite coated with hydrous oxides of Al, Fe, or Cu were examined in an air-dry condition by infrared (IR) techniques to elucidate possible modes of interaction between picloram and the mineral surfaces. Deuteration was used to confirm band assignments of picloram and its salts prior to interaction with montmorillonite. Picloram interactions with Al- and Fe-saturated montmorillonite and with montmorillonite coated with hydrous oxides of Al and Fe were concentration dependent. At high picloram concentrations similarities with the IR spectrum of potassium picloram indicated that much of the picloram was present in the salt form. As the concentration of picloram was reduced below that equivalent to 1 meq/g clay, the IR spectrum indicated the presence of the monomeric acid on the mineral surface. The spectrum of picloram on montmorillonite with a coating of copper hydrous oxide was similar to that of a Cu-picloram complex indicating coordination type bonding. The spectrum of picloram with Cu-saturated montmorillonite did not correspond to any of the other spectra of picloram examined. The interaction of picloram with montmorillonite coated with a hydrous oxide coating of Cu and with Cu-saturated montmorillonite were independent of picloram concentration in the range 2.20-0.44 meq/g clay.

Picloram in Water and Soil from a Semiarid Pinyon‐Juniper Watershed

AbstractA mixture of picloram (4‐amino‐3,5,6‐trichloropicolinic acid) at 2.8 kg acid equivalent (ae)/ha and 2,4‐D [(2,4‐dichlorophenoxy) acetic acid] at 5.6 kg acid equivalent/ha was aerially applied onto 113 ha of a 146‐ha pinyon‐juniper watershed [Juniperus osteosperma (Torr.) Little and Pinus edulis Engelm., respectively] in north‐central Arizona. Picloram residues in runoff water and soil were monitored. Picloram was detected in runoff water leaving the treated area for 30.5 months after application. The highest concentration, 320 ppbw, was in the initial runoff after treatment. A total of 1.1% of the picloram applied left the treated area in runoff water. Picloram was not detected farther than 5.6 km downstream. The picloram concentration was relatively constant during runoff events unless water from snow melt or from an untreated area mixed with the runoff from the treated area. Less picloram came from an area with individually treated trees than from an area with broadcast application. Dip (grab), single‐stage flood, or splitter‐box water samples all gave comparable picloram contents from the same location with the same runoff event. Picloram was detected in the soils for 44 months, mainly below the 45‐cm depth down to bedrock at 122 cm.

Genotypic Responses to Auxins in Tissue Cultures of Phaseolus

AbstractResponses of seven Phaseolus genotypes to the four auxins picloram, 2,4‐D, NAA and 1AA, in tissue cultures, were examined. Callus growth was promoted by picloram and the range of effective concentrations for most genotypes was broad. The auxin 2,4‐D also enhanced callus growth, but the range of optimal concentrations was markedly narrower than that of picloram. NAA when supplied at relatively high concentrations gave good growth. IAA was ineffective in supporting callus growth. The differences in 2,4‐D concentrations required for optimal growth and the differential responses to low concentrations (0.04–1.25 μM) of picloram between several genotypes tested were large. These genotypic variations in auxin responses were repeatable and may thus reflect genetic differences.

Effect of Picloram on Organogenesis in Detached Leaves ofEcheveria elegansBgr.

The effect of picloram (4-amino-3,5,6-trichloropicolinic acid) on regeneration of detached leaves ofEcheveria elegansBgr. was studied. Picloram stimulated callus production at all concentrations. Low concentrations of 1 to 15 ppmw picloram did not affect shoot organogenesis and the same, however, stimulated rhizogenesis. Inhibition of both root- and shoot-organogenesis was noticeable at concentrations below 20 ppmw and above. Roots increased in number at all picloram concentrations below 40 ppmw, the maximum number being at concentration of 15 to 20 ppmw of the herbicide. Observations indicated that root elongation was considerably suppressed. Picloram-induced callus contained mature parenchyma cells devoid of contents and considerable amount of tissue disruption was noticed. Irregular vascular differentiation and obliteration of tissues particularly in the region of tracheary elements, were obvious. Although normal apical organization was lacking in root primordia and in arrested short roots, these elongated normally into mature roots when they were transferred to water, thus indicating that apical meristems were not severely affected by picloram.

Ammonium Sulfate Enhancement of Picloram Absorption by Detached Leaves

Ammonium sulfate increased the magnitude and rate of14C-picloram (4-amino-3,5,6-trichloropicolinic acid) absorption in detached strawberry guava (Psidium cattleianumSabine) leaves. Absorption of14C-picloram with or without ammonium sulfate leveled off at 6 to 12 hr. The magnitude of the ammonium sulfate-induced increase in14C-picloram absorption was not affected by picloram concentration in the range 250 to 2000 ppmw, or by leaf age. The absorption of14C-picloram was increased by 0.1, 0.5, 1.0, and 10% ammonium sulfate; 0.01% had no effect. Increased14C-picloram absorption resulted from adding the ammonium salts of sulfate, nitrate, chloride, or dibasic phosphate, but ammonium sulfate was the only one of six sulfate salts to increase picloram absorption. A pH adjustment of the external solution from 6 to 4 increased picloram absorption, whereas a pH change from 6 to 8 had no effect. Both ammonium dibasic phosphate at a solution pH of 7.7 and ammonium monobasic phosphate at pH 4.6 increased picloram absorption, whereas potassium dibasic phosphate at pH 9.5 had no effect, and potassium monobasic phosphate at pH 4.6 did increase absorption.