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PubMed2003

Production of fertile somatic hybrid plants between Oriental hybrid lily and Liliumxformolongi.

Somatic hybridizations via electrofusion were performed in combinations of Oriental hybrid lilies (cvs. Acapulco and Shirotae) and Liliumxformolongi hort. (cv. Hakucho). Electrofusion-treated protoplasts divided only under nurse culture. The divided protoplasts grew into calli on the culture medium containing picloram, and the calli were then transferred to the hormone-free culture medium for induction of plant regeneration. The regenerants were transferred to a greenhouse, and were grown until the flower stage. In the fusion combinations of Acapulco + Hakucho and Shirotae + Hakucho, four regenerants apparently showed different morphological features compared with their parents. The results of molecular analyses by means of cleaved amplified polymorphic sequences markers and flow cytometry confirmed that these regenerants were somatic hybrid plants. Furthermore, we examined the stability of the morphological features of the hybrids in the next generations. This is the first report to describe the successful realization of Lilium somatic hybridization via protoplast fusion.

Cell Division↗
PubMed1977

Mutagenic and recombinogenic action of pesticides in Aspergillus nidulans.

Thirteen pesticides, aminotriazole, benomyl, captafol, captan, dalapon-Na, dichlorvos, dinobuton, dodine, ioxynil, mecoprop, neburon, picloram and tordon were tested for ability to induce (1) point mutations to 8-azaguanine resistance, (2) mitotic crossing-over, and (3) mitotic non-disjunction and haploidization in Aspergillus nidulans. Tests were performed at three different pHs, i.e. 4.5, 7, 8.2. Three of the pesticides, captan , captafol and dichlorvos induced point mutations; dichlorvos also induced a high frequency of mitotic crossing-over and non-disjunction; benomyl induced a very high frequency of non-disjunction whereas aminotriazole induced weakly both types of somatic segregation.

Aspergillus nidulans↗
PubMed1986

Progress in pesticide exposure studies and future concerns.

A campaign to educate the public regarding the merits of pesticides is necessary if we are to overcome the widespread poor image of pesticides that exists in society today. A comparison of biological monitoring and measurements of pesticide deposition on patches suggests that since only the absorbed dose has any potential for adverse health effects if forced to choose one technique over the other, more emphasis should be placed on biological monitoring. Controlled human pesticide exposure and dermal absorption studies establishing pharmacokinetic data are necessary if scientists and regulatory officials are expected to make knowledgeable worker safety recommendations pertaining to the pesticides being used today. Worker exposure can continue beyond the application day if pesticide-contaminated boots or gloves are used later. Excretion rate of 2,4-D in human urine was not affected by the presence of picloram in the application mixture. Margins of safety guidelines are highly dependent on adoption of appropriate no observed effect levels (NOEL).

Agriculture↗
PubMed2006

Establishing the feasibility of coupled solid-phase extraction-solid-phase derivatization for acidic herbicides.

The significance of this research is that it improves analytical methodology used for organic chemicals in aqueous solutions by establishing the feasibility of heterogeneous chemical derivatization at the liquid-solid interface (i.e., solid-phase reaction or solid-phase derivatization). A solid-phase derivatization method for determining chlorinated herbicide acids was developed. Solid-phase extraction was used to concentrate and retain analytes on sorbents for subsequent solid-phase derivatization. Background interferences were removed from the chromatograms by electronically subtracting the responses of blank, nonfortified analyses from spiked samples. Two extraction sorbents (octadecyl bonded silica and polystyrene-divinylbenzene) and two derivatizing reagents (BF3-MeOH and trimethylsilyldiazomethane) were investigated. Recovery of 13 chlorinated herbicide acids--including pentachlorophenol, dinoseb, and bentazon (having a derivatizable functional group, -OH or -NH, bonded directly to a phenyl group); dicamba, picloram, acifluorfen, 3,5-dichlorobenzoic acid, and dacthal (having a derivatizable functional group, -COOH, bonded directly to a phenyl group); and 2,4-D, 2,4,5-T, dichlorprop, 2,4,5-TP, and 2,4-DB (having a derivatizable functional group, -COOH, bonded directly to a sp3 carbon atom)--was tested. The analytical method developed was proven successful for determining acidic herbicides, except for the dacthal diacid metabolite, in aqueous samples.

Acids↗
PubMed2006

Screening and optimization of the derivatization of polar herbicides with trimethylanilinium hydroxide for GC-MS analysis.

In the present study, a derivatization method for the determination of acidic herbicides has been investigated. This procedure involves the methylation with the quaternary ammonium salt trimethylanilinium hydroxide (TMAH) directly in the gas chromatographic auto-sampler vial for analysis by gas chromatography combined with mass spectrometry. The derivatization reaction has been screened for influential factors and statistically significant parameters. The identified factors, reaction time, temperature and hold-up time were optimized by a complete factorial response surface design and optimal reaction conditions were generated. Finally, the optimized methylation procedure was compared to different alkylation methods and obtained results demonstrated the applicability of derivatization with trimethylanilinium hydroxide. Acidic herbicides used in the study consist of several families of compounds like derivatives of acetic acid (2,4-D and 2,4,5-T), butanoic acid (MCPB), benzoic acid (chloramben, dicamba), phenol (dinoseb and dinoterb), propanoic acid (mecoprop) and other miscellaneous acids such as pyridinecarboxlyic acid (picloram). A reliably working, rapid method for the preparation of methyl compounds is generated with respect to automation for routine analysis.

Diazomethane↗
PubMed2000

Solid-phase extraction of acidic herbicides.

A discussion of solid-phase extraction method development for acidic herbicides is presented that reviews sample matrix modification, extraction sorbent selection, derivatization procedures for gas chromatographic analysis, and clean-up procedures for high-performance liquid chromatographic analysis. Acidic herbicides are families of compounds that include derivatives of phenol (dinoseb, dinoterb and pentachlorophenol), benzoic acid (acifluorfen, chloramben, dicamba, 3,5-dichlorobenzoic acid and dacthal--a dibenzoic acid derivative), acetic acid [2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)], propanoic acid [dichlorprop, fluazifop, haloxyfop, 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP) and silvex], butanoic acid [4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB) and 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB)], and other miscellaneous acids such as pyridinecarboxylic acid (picloram) and thiadiazine dioxide (bentazon).

Chromatography, Gas↗
PubMed1980

Gas chromatographic measurement of volatility of herbicide esters.

The vapour pressures of eleven herbicide esters were calculated from gas chromatographic measurement of relative retention volumes (dibutyl phthalate = 1) on a non-polar SE-30 column. Measurements were made at temperatures from 72 to 182 degrees C, but by assuming that the ratio of the latent heat of vaporization of the ester to that of dibutyl phthalate was independent of temperature, values for vapour pressure could be extrapolated to 25 degrees C. Vapour pressures at 25 degrees C ranged from 2.5.10(-4) mmHg for 2,4-D ethyl ester to 1.9.10(-7) mm Hg for picloram isoocytly ester.

Chromatography, Gas↗
PubMed2000

Decrease in the regeneration potential of long-term cell suspension cultures of Lilium formosanum Wallace and its restoration by the auxin transport inhibitor, 2,3,5-triiodobenzoic acid.

Cell suspension cultures of Lilium formosanum Wallace were initiated from bulb scale-derived calli and subcultured every 2 weeks using a medium containing 5 µM 4-amino-3,5,6-trichloropicolinic acid (picloram). Almost all cell clumps from the suspension cultures developed numerous somatic embryos following their transfer onto a plant growth regulator-free medium, while they vigorously produced shoot buds on media containing 0.5 or 5 µM 6-benzyladenine (BA). The high regeneration potential on a plant growth regulator-free medium was maintained for up to 54 months, but it gradually decreased thereafter, and only a few adventitious shoots and embryos were obtained from 75-month-old cultures. For restoring the regeneration potential of these cultures, various treatments with plant growth regulators were applied, among which about 10-fold increases in the number of regenerated shoot buds were obtained with 0.5 or 5 µM 2,3,5-triiodobenzoic acid (TIBA) in combination with 0.5 or 5 µM BA or N-(1,2,3-thiadiazol-5-yl)-N'-phenylurea (thidiazuron). Only shoot buds were produced from the cell clumps cultured on TIBA-containing media, and these shoot buds developed into complete plantlets after they were excised from the calli and transferred to a plant growth regulator-free medium.

Journal Article↗
PubMed2005

Physiological and biochemical characterization of quinclorac resistance in a false cleavers (Galium spurium L.) biotype.

The physiological and biochemical basis for quinclorac resistance in a false cleavers (Galium spurium L.) biotype was investigated. There was no difference between herbicide resistant (R) and susceptible (S) false cleavers biotypes in response to 2,4-D, clopyralid, glyphosate, glufosinate-ammonium, or bentazon. On the basis of GR(50) (growth reduction of 50%) or LD(50) (lethal dose to 50% of tested plants) values, the R biotype was highly resistant to the acetolactate synthase (ALS) inhibitor, thifensulfuron-methyl (GR(50) resistance ratio R/S = 57), and quinolinecarboxylic acids (quinclorac R/S = 46), resistant to MCPA (R/S = 12), and moderately resistant to the auxinic herbicides picloram (R/S = 3), dicamba (R/S = 3), fluroxypyr (R/S = 3), and triclopyr (R/S = 2). The mechanism of quinclorac resistance was not due to differences in [(14)C]quinclorac absorption, translocation, root exudation, or metabolism. Seventy-two hours after root application of quinclorac, ethylene increased ca. 3-fold in S but not R plants when compared to controls, while ABA increased ca. 14-fold in S as opposed to ca. 3-fold in R plants suggesting an alteration in the auxin signal transduction pathway, or altered target site causes resistance in false cleavers. The R false cleavers biotype may be an excellent model system to further examine the auxin signal transduction pathway and the mechanism of quinclorac and auxinic herbicide action.

Abscisic Acid↗
PubMed1978

Direct selection in vitro for herbicide-resistant mutants of Nicotiana tabacum.

Seven cell lines of Nicotiana tabacum resistant to the herbicide picloram were isolated from cell cultures. In crosses of plants regenerated from four cell lines, resistance was inherited as a single dominant Mendelian allele. Plants could not be regenerated from one cell line, and expression of resistance proved unstable in two others.

Journal Article↗
PubMed2005

Absorption and translocation of 2,4-D in plants of Memora peregrina.

The objective of this work was to evaluate absorption and translocation of the herbicide 2,4-D in plants of Memora peregrina. The herbicide 2,4-D was used alone with the formulation DMA 806 BR and associated with the herbicide picloram in the commercial product Padron. Levels of radioactivity on the treated leaves were determined in sample obtained after washing them with methanol and chloroform at different times after the application of the radiolabelled formulation (1, 2, 4, 8, 24, and 48 h). Translocation was evaluated by cutting plants between stem and root. The parts obtained were: root, stem, leaf treated, leaves above the leaf treated, leaves below the leaf treated, and leaf opposite of the leaf treated. These parts were weighted, dried, ground, burnt, and radioactivity in the samples was determined. The results suggest that the translocation of the radioactive herbicide 2,4-D was insignificant in plants of M. peregrina in the two treatments evaluated. Absorption of 14C 2,4-D in the treatment with DMA 806 BR and the mixture of DMA 806 BR plus Padron had the same behavior. These observations explain the inefficient control obtained with this herbicide in plant species under study.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2001

Auxin herbicides induce H(2)O(2) overproduction and tissue damage in cleavers (Galium aparine L.).

The phytotoxic effects of auxin herbicides, including the quinoline carboxylic acids quinmerac and quinclorac, the benzoic acid dicamba and the pyridine carboxylic acid picloram, were studied in relation to changes in phytohormonal ethylene and abscisic acid (ABA) levels and the production of H(2)O(2) in cleavers (Galium aparine). When plants were root-treated with 10 microM quinmerac, ethylene synthesis was stimulated in the shoot tissue, accompanied by increases in immunoreactive levels of ABA and its precursor xanthoxal. It has been demonstrated that auxin herbicide-stimulated ethylene triggers ABA biosynthesis. The time-course and dose-response of ABA accumulation closely correlated with reductions in stomatal aperture and CO(2) assimilation and increased levels of hydrogen peroxide (H(2)O(2)), deoxyribonuclease (DNase) activity and chlorophyll loss. The latter parameters were used as sensitive indicators for the progression of tissue damage. On a shoot dry weight basis, DNase activity and H(2)O(2) levels increased up to 3-fold, relative to the control. Corresponding effects were obtained using auxin herbicides from the other chemical classes or when ABA was applied exogenously. It is hypothesized, that auxin herbicides stimulate H(2)O(2) generation which contributes to the induction of cell death in Galium leaves. This overproduction of H(2)O(2) could be triggered by the decline of photosynthetic activity, due to ABA-mediated stomatal closure.

Abscisic Acid↗
PubMed1996

Morphogenesis in leaf and single-cell cultures of mature Juniperus oxycedrus.

Single cells were mechanically isolated from leaf-derived callus of mature Juniperus oxycedrus L. These cells divided and gave rise to callus when plated on medium containing growth regulators. Best plating efficiency was obtained on a modified Schenk and Hildebrandt medium supplemented with 0.6 micro M 2,4-dichlorophenoxyacetic acid and 100 mg l(-1) casein hydrolyzate. Although single-cell-derived callus showed poor morphogenic potential, both adventitious shoots and embryogenic tissues differentiated from the callus. We also achieved induction of somatic embryogenesis in leaf explants of mature J. oxycedrus trees cultured in the presence of 6.0 or 10.0 micro M 2,4-dichlorophenoxyacetic acid or picloram. Frequency of embryogenic callus ranged from 6 to 18%; however, under the culture conditions tested, isolated embryos failed to develop into plants.

Journal Article↗
PubMed2006

Mutations in an auxin receptor homolog AFB5 and in SGT1b confer resistance to synthetic picolinate auxins and not to 2,4-dichlorophenoxyacetic acid or indole-3-acetic acid in Arabidopsis.

Although a wide range of structurally diverse small molecules can act as auxins, it is unclear whether all of these compounds act via the same mechanisms that have been characterized for 2,4-dichlorophenoxyacetic acid (2,4-D) and indole-3-acetic acid (IAA). To address this question, we used a novel member of the picolinate class of synthetic auxins that is structurally distinct from 2,4-D to screen for Arabidopsis (Arabidopsis thaliana) mutants that show chemically selective auxin resistance. We identified seven alleles at two distinct genetic loci that conferred significant resistance to picolinate auxins such as picloram, yet had minimal cross-resistance to 2,4-D or IAA. Double mutants had the same level and selectivity of resistance as single mutants. The sites of the mutations were identified by positional mapping as At4g11260 and At5g49980. At5g49980 is previously uncharacterized and encodes auxin signaling F-box protein 5, one of five homologs of TIR1 in the Arabidopsis genome. TIR1 is the recognition component of the Skp1-cullin-F-box complex associated with the ubiquitin-proteasome pathway involved in auxin signaling and has recently been shown to be a receptor for IAA and 2,4-D. At4g11260 encodes the tetratricopeptide protein SGT1b that has also been associated with Skp1-cullin-F-box-mediated ubiquitination in auxin signaling and other pathways. Complementation of mutant lines with their corresponding wild-type genes restored picolinate auxin sensitivity. These results show that chemical specificity in auxin signaling can be conferred by upstream components of the auxin response pathway. They also demonstrate the utility of genetic screens using structurally diverse chemistries to uncover novel pathway components.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1998

Higher activity of an aldehyde oxidase in the auxin-overproducing superroot1 mutant of Arabidopsis thaliana.

Aldehyde oxidase (AO; EC 1.2.3.1) activity was measured in seedlings of wild type or an auxin-overproducing mutant, superroot1 (sur1), of Arabidopsis thaliana. Activity staining for AO after native polyacrylamide gel electrophoresis separation of seedling extracts revealed that there were three major bands with AO activity (AO1-3) in wild-type and mutant seedlings. One of them (AO1) had a higher substrate preference for indole-3-aldehyde. This AO activity was significantly higher in sur1 mutant seedlings than in the wild type. The difference in activity was most apparent 7 d after germination, the same time required for the appearance of the remarkable sur1 phenotype, which includes epinastic cotyledons, elongated hypocotyls, and enhanced root development. Higher activity was observed in the root and hypocotyl region of the mutant seedlings. We also assayed the indole-3-acetaldehyde oxidase activity in extracts by high-performance liquid chromatography detection of indole-3-acetic acid (IAA). The activity was about 5 times higher in the extract of the sur1 seedlings, indicating that AO1 also has a substrate preference for abscisic aldehyde. Treatment of the wild-type seedlings with picloram or IAA caused no significant increase in AO1 activity. This result suggested that the higher activity of AO1 in sur1 mutant seedlings was not induced by IAA accumulation and, thus, strongly supports the possible role of AO1 in IAA biosynthesis in Arabidopsis seedlings.

Aldehyde Oxidase↗
PubMed2000

Auxin-induced ethylene triggers abscisic acid biosynthesis and growth inhibition.

The growth-inhibiting effects of indole-3-acetic acid (IAA) at high concentration and the synthetic auxins 7-chloro-3-methyl-8-quinolinecarboxylic acid (quinmerac), 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 4-amino-3,6, 6-trichloropicolinic acid (picloram), and naphthalene acetic acid, were investigated in cleavers (Galium aparine). When plants were root treated with 0.5 mM IAA, shoot epinasty and inhibition of root and shoot growth developed during 24 h. Concomitantly, 1-aminocyclopropane-1-carboxylic acid (ACC) synthase activity, and ACC and ethylene production were transiently stimulated in the shoot tissue within 2 h, followed by increases in immunoreactive (+)-abscisic acid (ABA) and its precursor xanthoxal (xanthoxin) after 5 h. After 24 h of treatment, levels of xanthoxal and ABA were elevated up to 2- and 24-fold, relative to control, respectively. In plants treated with IAA, 7-chloro-3-methyl-8-quinolinecarboxylic acid, naphthalene acetic acid, 2-methoxy-3,6-dichlorobenzoic acid, and 4-amino-3,6,6-trichloropicolinic acid, levels of ethylene, ACC, and ABA increased in close correlation with inhibition of shoot growth. Aminoethoxyvinyl-glycine and cobalt ions, which inhibit ethylene synthesis, decreased ABA accumulation and growth inhibition, whereas the ethylene-releasing ethephon promoted ABA levels and growth inhibition. In accordance, tomato mutants defective in ethylene perception (never ripe) did not produce the xanthoxal and ABA increases and growth inhibition induced by auxins in wild-type plants. This suggests that auxin-stimulated ethylene triggers ABA accumulation and the consequent growth inhibition. Reduced catabolism most probably did not contribute to ABA increase, as indicated by immunoanalyses of ABA degradation and conjugation products in shoot tissue and by pulse experiments with [(3)H]-ABA in cell suspensions of G. aparine. In contrast, studies using inhibitors of ABA biosynthesis (fluridone, naproxen, and tungstate), ABA-deficient tomato mutants (notabilis, flacca, and sitiens), and quantification of xanthophylls indicate that ABA biosynthesis is influenced, probably through stimulated cleavage of xanthophylls to xanthoxal in shoot tissue.

Abscisic Acid↗
PubMed1970

Quantitative distribution and metabolism of auxin herbicides in roots.

The internal concentrations of four auxin herbicides- 2,4-dichlorophenoxyacetic acid, dicamba, picloram, and naphthaleneacetic acid-were measured in the roots of treated pea seedlings. Intact seedlings were immersed in solutions of labeled herbicides at concentrations sufficient to produce toxic symptoms (inhibition of elongation, radial enlargement, and lateral root proliferation). Measurements of volume and herbicide content of segments taken sequentially along the root showed that an acropetal concentration gradient of each herbicide was established within the root immediately following treatment. Although there was a net loss of herbicide in the following 24 hours, the gradient was maintained. Initially, the concentration of herbicide in the root tips exceeded that in the external medium.In support of the contention that toxic symptoms due to herbicide treatment are caused by the presence of unmetabolized chemical at the site of action, it was found that metabolism was negligible for all herbicides except naphthaleneacetic acid.

Journal Article↗
PubMed1987

Auxin effect on the transmembrane potential difference of wild-type and mutant tobacco protoplasts exhibiting a differential sensitiity to auxin.

The effects of 1-naphthaleneacetic acid (NAA) and other auxin analogs on the transmembrane potential difference (Em) were compared on tobacco protoplasts isolated from two genotypes differing in their sensitivity to auxins. For both types, NAA modifies Em by inducing at low doses a hyperpolarization, the amplitude of which increased with auxin concentration. Above an optimal concentration this hyperpolarization was reduced and even nullified. However, for the mutant type, this electrical response was shifted toward higher NAA concentrations, as its growth response. In the presence of structural analogs of auxin which have been showed to modify the dose-response curve for growth, the Em was altered: the growth-stimulatory molecule (picloram) initiated hyperpolarization, whereas the growth-inhibitory substance (4-bromophenylacetic acid) caused depolarization. These results provide evidence for a specific action of auxin at the membrane level related to its biological activity.

Journal Article↗