Uptake,distribution and metabolic fate of 3H-triforine in plants. II. Long-term experiments

Uptake of ³H-triforine by tomato and barley seedlings from soil with a high organic matter content was much less efficient than from aqueous suspensions, even though the period of exposure was much longer—at least 1 week (“long-term treatment”) vs 1 day (“short-term treatment”). After transplanting to fresh soil, part of the label in the roots was lost probably by desorption. Distribution of label in tomato shoots was as irregular as after short-term treatment; label was virtually confined to the leaves which expanded before about 14 days after cessation of the treatment. In shoots of barley seedlings which were pretreated in an aqueous suspension of ³H-triforine for 1 day before being subjected to a long-term soil treatment, almost all radioactivity present could be ascribed to uptake during the pretreatment phase. The distribution pattern strongly resembled that obtained after short-term treatment, hardly any label being found in leaves which unfolded after the pretreatment phase. Rates of conversion of ³H-triforine in barley shoots depended to some extent on whether or not seedlings were transplanted to fresh soil after 1 week.     

Selectivity of 2,4-D in Solanum ptycanthum Dun. and Lycopersicon esculentum Mill.

In controlled environmental studies, a marked difference was observed between the growth pattern of tomato and eastern black nightshade plants that received doses of 2,4-D ranging from 28 to 952 g a.e. ha^?1. The highest dose of 2,4-D reduced the dry weight of eastern black nightshade and tomato by approximately 15 and 50%, respectively, when compared with controls. Although the height of both species was reduced by all doses of 2,4-D, eastern black nightshade plants produced secondary shoots, which compensated for any potential loss in dry weight that otherwise may have occurred. Tomato plants did not produce secondary shoots. After application of ¹⁴C-2,4-D to tomato and eastern black nightshade, the pattern of ¹⁴C absorption and translocation was similar in both plant species. However, there was significantly more radioactivity recovered in tomato (72%) than in eastern black nightshade (52%) plants, 72 h after treatment. Assay radioactivity in the nutrient solution of hydroponically grown plants indicated that 7·0 and 27·9% of the applied radioactivity was exuded from the roots of tomato and eastern black nightshade, respectively, within 72 h after treatment. Assay of plant extracts by thin layer chromatography revealed that the amount of radioactivity that remained as unaltered 2,4-D was 73 and 49% in tomato and eastern black nightshade, respectively, 72 h after treatment. Thus the greater tolerance of eastern black nightshade appeared to be due to greater rates of 2,4-D metabolism and/or greater rates of herbicide elimination by root exudation.     

Absorption and translocation of 14C-3,6-dichloropicolinic acid in Cirsium arvense (L.) Scop.

Experiments were conducted in a growth cabinet to investigate the absorption and translocation of ¹⁴C-3, 6-dichloropicolinic acid by Cirsium arvense (L.) Scop. (Canada thistle, creeping thistle), a sensitive species. Applications were made, either to the middle four leaves of 12-cm-tall vegetative plants grown under low (40%) and/or high (>95%) relative humidity (r.h.), or to four upper or lower leaves of 30-cm-tall flowering plants grown under low r.h. Following application to vegetative plants, absorption and translocation of ¹⁴C-3,6-dichloropicolinic acid was rapid and was approximately doubled by high r.h. High r.h. increased the amount of radioactivity retained by the treated leaves or translocated to the shoots but did not affect greatly the amount retained in the roots. The herbicide was highly mobile, with over half of that absorbed, translocated out of the treated leaves after two days. The apex accumulated most of the radioactivity, while approximately 8% was recovered from the roots. The absorption and translocation patterns were similar to those reported in the literature for picloram in C. arvense. Absorption of 3,6-dichloropicolinic acid was greater in vegetative than in flowering C. arvense plants, and placement of herbicide on lower leaves tended to decrease the amount of radioactivity recovered from shoot apex and increase the amount recovered from the roots. Approximately 15% of the applied radioactivity could not be recovered from treated plants by 2 days after treatment.     

Distribution and loss of phorate residues in the foliage of broad bean plants following root uptake of 14C-labelled phorate

¹⁴C-Methylene labelled phorate was added to nutrient solutions supplying the roots of young broad bean plants and after 24 h absorption, fresh nutrient was substituted. The radiolabel accumulated at the leaf margins was initially associated with solvent-soluble toxic metabolites. Radiolabel extracted from foliage which developed after the treatment was mainly in water-soluble form. The maximum concentration of toxic material occurred in the marginal areas of the leaves after 5 or 6 days and in the central portions after 2 days. The concentrations declined to half of their peak values in 4–6 days from leaf-margin tissue and in 2 days from the central tissues. Water-soluble label did not accumulate to any significant extent. Most was found in the marginal areas but concentrations built up slowly reaching a maximum after about 2 weeks, declining slowly thereafter.     

Deamination of metribuzin in tolerant and susceptible soybean (Glycine max) cultivars

The deamination of metribuzin was studied in vitro in peroxisomes isolated from the leaves of soybean cultivars which were either metribuzin tolerant, intermediate, or sensitive. The deamination rate observed with peroxisomes from tolerant leaves was about twice the rate observed with peroxisomes from sensitive leaves. The intermediate group was also intermediate with respect to the in-vitro deamination rate. Tolerant and sensitive intact soybean plants were pulse-labeled with [¹⁴C]metribuzin via the roots for 5 h. The extractable radioactivity in roots, stems and leaves was measured and separated into metabolites after the 5 h pulse and after an additional 24 h growth in water. The level of DA (deaminated metribuzin) was always significantly higher in the stems and leaves of tolerant soybean plants (4.8–10.0% of the extracted radioactivity) than in sensitive stems and leaves (1.8–2.9%). Conjugates were rapidly formed in tolerant as well as in sensitive soybean tissues. More conjugates were found in the tolerant cultivars, especially after the 5 + 24 h incubation time. Labeled [¹⁴C]DA fed to soybean plants via the roots was conjugated two to four times faster than [¹⁴C]metribuzin. Tolerant soybean tissue conjugated [¹⁴C] DA two to three times faster than sensitive tissue. The results are interpreted as showing that, in tolerant soybean plants, metribuzin is metabolized via deamination and subsequent conjugation, in addition to the well-known direct conjugation of metribuzin parent compound.     

Metribuzin metabolism as the basis for tolerance in barley (Hordeum vulgare L.)*

Metabolism of ¹⁴C-5 (ring)-metribuzin was studied in Steptoe (tolerant) and Morex (susceptible) barley (Hordeum vulgare L.) cultivars, 1, 4, and 8 days following a single application to roots. Both cultivars contained similar ether-soluble metribuzin metabolites and five water-soluble metabolites. Water-soluble compounds increased from 12 to 53% of the total ¹⁴C recovered for Steptoe and 5–17% for Morex between 1 day and 8 days, respectively, whereas the percentage of ether-soluble metabolites decreased. Ninhydrin reacting compounds were the major water-soluble metabolites in the leaf blades 8 days after treatment. On a d.p.m. mg^?1 dry weight basis, Steptoe leaves had five times more water-soluble material than Morex leaves and half the quantity of ether-soluble compounds. Metribuzin comprised 83 and 89% of the ether-soluble compounds in leaves of Morex and Steptoe, respectively, at 8 days. Terminal radioactivity comprised between 19% and 26% of total radioactivity for both cultivars as early as 1 day after application, with little change over 8 days. Rapid metabolism of metribuzin to non-phytotoxic water-soluble conjugates and terminal residues was the major mechanism responsible for the differential tolerance between these two barley cultivars.     

Magnesium oxide nanoparticles induce systemic resistance in tomato against bacterial wilt disease

Bacterial wilt is a serious problem affecting many important food crops. Recent studies have indicated that treatment with biotic or abiotic stress factors may increase the resistance of plants to bacterial infection. This study investigated the effects of magnesium oxide nanoparticles (MgO NP) on disease resistance in tomato plants against Ralstonia solanacearum, as well as its antibacterial activity. The roots of tomato seedlings were inoculated with R. solanacearum and then immediately treated with MgO NP; the treated plants showed very little inhibition of bacterial wilt. In contrast, when roots were drenched with a MgO NP suspension prior to inoculation with the pathogen, the incidence of disease was significantly reduced. Rapid generation of reactive oxygen species such as O₂^?˙ radicals was observed in tomato roots treated with MgO NP. Further O₂^?˙ was rapidly generated when tomato plant extracts or polyphenols were added to the MgO NP suspension, suggesting that the generation of O₂^?˙ in tomato roots might be due to a reaction between MgO NP and polyphenols present in the roots. Salicylic acid‐inducible PR1, jasmonic acid‐inducible LoxA, ethylene‐inducible Osm, and systemic resistance‐related GluA were up‐regulated in both the roots and hypocotyls of tomato plants after treatment of the plant roots with MgO NP. Histochemical analyses showed that β‐1,3‐glucanase and tyloses accumulated in the xylem and apoplast of pith tissues of the hypocotyls after MgO NP treatment. These results indicate that MgO NP induces systemic resistance in tomato plants against R. solanacearum.     

Effect of chlorfenprop-methyl, flamprop-isopropyl and benzoylprop-ethyl on 14C2 fixation in Avena fatua L., Triticum aestivum L. and Hordeum vulgare L.

The effect of chlorfenprop-methyl, flampropisopropyl and benzoylprop-ethyl on ¹⁴CO₂ fixation was followed in wild oat (Avena fatua L.), barley (Hordeum vulgare L., cv. Ametyst), and wheat (Triticum aestivum L., cv. Mironovská). Experimental plants were exposed to a ¹⁴CO₂-enriched atmosphere in a special apparatus 2 h, 1, 3, and 9 days after the herbicide treatment. Chlorfenprop-methyl already inhibited ¹⁴CO₂ fixation in wild oat plants 2 h after the treatment. ¹⁴C-metabolite transport to the roots was strongly decreased. Both ¹⁴CO₂ fixation and ¹⁴C-metabolite level in the roots were significantly depressed in A. fatua when compared with untreated plants at the last sampling time. ¹⁴C incorporation into starch was inhibited from the first day after treatment, and on day 9 was lowered more than ten fold in treated plants. Flamprop-isopropyl inhibited ¹⁴CO₂ fixation in wild oat plants from day 3 after treatment, but benzoylprop-ethyl not until day 9. Both herbicides also decreased ¹⁴C incorporation into starch in A. fatua. Chlorfenprop-methyl also slightly decreased ¹⁴CO₂ fixation in barley on day 9. However, assimilate transport into the roots and ¹⁴C incorporation into starch were not affected. Flamprop-isopropyl inhibited ¹⁴CO₂ fixation in barley plants only on the first day after treatment, and assimilate transport was also reduced. By contrast, no differences from untreated plants were found at the end of the experiment. Benzoylprop-ethyl did not decrease either ¹⁴CO2 fixation or assimilate transport to the roots in wheat, but it inhibited starch synthesis. Atrazine depressed ¹⁴CO₂ fixation in wild oat plants by 91%, in wheat plants by 99% compared with untreated plants. Assimilate transport into the roots was also strongly inhibited. In contrast to atrazine, the effect of chlorfenprop-methyl, flamprop-isopropyl, and benzoylprop-ethyl on CO₂ fixation seems to be secondary.     

Laboratory and greenhouse evaluation of a new systemic fungicide,N,N'-bis-(1-formamido-2,2,2-trichloroethyl)-piperazine (CELA W 524)

The new systemic fungicide N,N'-bis-(1-formamido-2,2,2-trichloroethyl)-piperazine (CELA W 524) was shown to display a moderate to distinct fungitoxic activity in vitro towards several pathogenic and non-pathogenic fungi. Depending on the inert ingredients present², the available formulations proved to be either rather phytotoxic or virtually non-phytotoxic. Pre-infectional spraying with the non-phytotoxic formulation provided complete protection of barley, bean, cucumber, pea and tomato plants against barley powdery mildew, bean rust, cucumber powdery mildew and cucumber scab, pea powdery mildew and tomato leaf mould, respectively. some suppression of disease symptoms —although only at high concentrations of CELA W 524 — was observed in the case of leaf spot in pea plants. Upon post-infectional treatment disease control was less pronounced, although powdery mildew diseases and tomato leaf mould were effectively suppressed. When applied via the roots CELA W 524 proved to be systemically active, successfully protecting barley plants against powdery mildew, and cucumber plants against powdery mildew and cucumber scab.Samenvatting Het nieuwe systemische fungicide CELA W 524 (C. H. Boehringer Sohn, Ingelheim am Rhein, Duitsland) bleek een matige tot duidelijke fungitoxische werking in vitro te vertonen tegenover verschillende pathogene en niet-pathogene schimmels. Eén van de beschikbare formuleringen bleek vrij sterk fytotoxisch, de andere was nagenoeg niet fytotoxisch. Bespuiting vóór inoculatie met de niet-fytotoxische formulering resulteerde in volledige bescherming van gerst, bonen, komkommers, erwten en tomaten tegen respectievelijk gerstemeeldauw, boneroest, komkommermeeldauw en vruchtvuur, erwtemeeldauw en bladvlekkenziekte bij tomaat. Enige onderdrukking van ziektesymptomen trad ook op bij erwten, geïnoculeerd metAscochyta pisi, tenminste, wanneer hoge concentraties van CELA W 524 werden gebruikt. Bij bespuiting na inoculatie was het effect geringer, hoewel meeldauwziekten en bladvlekkenziekte bij tomaat toch doeltreffend bestreden werden. Toegediend via de wortels bleek CELA W 524 systemisch actief; het beschermde aldus gerst tegen meeldauw en komkommers tegen meeldauw en vruchtvuur.     

Studies on the colonization of axenically grown tomato plants by a GFP-tagged strain of Clavibacter michiganensis subsp. michiganensis

In this study, colonization and disease development of axenically-grown tomato plants by Clavibacter michiganensis subsp. michiganensis (Cmm), the causative agent of bacterial wilt and canker, was investigated. For this, a spontaneous rifampicin resistant strain of Cmm was tagged with a marker that expressed a green fluorescent protein (GFP) in a stable way and which possessed a similar virulence to the parental strain. In vitro plants were drop-inoculated at the stem base and the population dynamics was determined by dilution pour-plating in a selective medium. At 3 h after inoculation, Cmm was already present in low densities in roots, stems and leaves. At 16 dpi, Cmm was found throughout the entire plant in high densities of ca. 10¹⁰ cfu g^?1. Symptoms developed in the in vitro plants typical for Cmm, such as canker, wilting and growth reduction. The presence of Cmm in vascular and parenchymatic tissue of in vitro tomato plants was confirmed by epifluorescence stereo- and confocal laser scanning microscopy. This study showed that in vitro tomato plants can be effectively used for detailed studies on interactions between Cmm and its host, in particular if a GFP-tagged strain of the pathogen is used.     

Persistence and translocation of a benzothiadiazole derivative in tomato plants in relation to systemic acquired resistance against Pseudomonas syringae pv tomato

A reproducible and accurate procedure, based on HPLC analysis, has been developed to determine simultaneously acibenzolar‐S‐methyl (CGA 245 704) and its acid derivative (CGA 210 007) in tomato leaves. The limit of detection and quantification of the method are 0.015 and 0.15 mg litre^?1 for CGA 245 704 and 0.030 and 0.30 mg litre^?1 for CGA 210 007. In tomato plants treated with 250 µM CGA 245 704, it was found that the inducer rapidly translocates from treated leaves (cotyledons, 1st and 2nd) to untreated leaves (3rd to 5th), with the maximum translocation (40% of the total quantity found) occurring 8 h after the treatment. CGA 245 704 residues decreased as time elapsed in both treated and untreated tomato leaves, reaching negligible values 72 h after treatment. The acid derivative, CGA 210 007, was formed in tomato plants as early as 2 h after CGA 245 704 treatment, albeit only in the treated leaves. CGA 210 007 residues decreased in treated tomato leaves with a trend similar to that observed for CGA 245 704. Treatment of tomato plants with CGA 245 704 or CGA 210 007 at 250 µM systemically protected the plants against Pseudomonas syringae pv tomato attacks, the causal agent of bacterial speak disease. Evidence of this were reductions in the degree of infection, the bacterial lesion diameter and the bacterial growth in planta. Since neither CGA 245 704 nor CGA 210 007 inhibited bacterial growth in vitro and the protection against bacterial speak of tomato was observed when the two compounds were completely degraded, the protection must be due to the activation of the plant's defence mechanisms. © 2001 Society of Chemical Industry     

Studies in phytotoxicity III. Changes in the levels of some keto-acids in plants treated with a phytotoxic pesticide

In attempts to develop more rapid tests for phytotoxicity before the appearance of visual symptoms, the levels of pyruvic and a-oxo-glutaric acids were determined in leaves of dwarf bean (Phaseolus vulgaris) before and after treatment with a toxicant (lime sulphur). Efforts were also directed towards demonstrating the recovery of the initial photosynthetic processes by exposing plants to radio-active labelled carbon dioxide at various intervals after treatment and then measuring the quantities of radioactivity incorporated into the two acids.     

THE BASIS OF THE DIFFERENTIAL PHYTOTOXICITY OF 4-HYDROXY-3,5-DI-IODOBENZONITRlLE*

Summary. Entry of ioxynil-¹⁴C into portions of leaves was greater with mustard than with barley or pea and was unrelated to stomatal density. Measurement of ioxynil content of sprayed plants showed that by increasing the concentration of ioxynil and adding a surfactant, almost as much ioxynil could be made to enter barley as entered mustard from a lower concentration without surfactant. Auto radiographs showed that a limited amount of ¹⁴C was translocated to a small extent in plants following localized application of ioxynil-¹⁴C. An experiment comparing leaf removal by cutting with destruction of equivalent leaf areas by ioxynil treatment suggested a greater translocated effect of ioxynil with mustard than with pea or barley. Les principes de la phytotoxicité différentielle du 4-hydroxy-3,5-di-iodobetZonitrile II. Absorption et migration     

Studies on the selectivity of alloxydim-sodium in plants

Alloxydim-sodium, methyl 3-[1-(allyloxyimino)butyl]-4-hydroxy-6,6-dimethyl-2-oxocyclohex-3-enecarboxylate sodium salt, is a selective herbicide which controls grass weeds in a wide range of broad-leaf crops. Spray retention, tested at two growth stages, was generally greater for the broad-leaf crops (cotton, sugarbeet, flax, beans and peas) than for wild oat (Avena fatua L.), blackgrass (Alopecurus myosuroides Huds), barley and couch grass [Agropyron repens (L.) Beauv.], and did not contribute to selectivity between susceptible and tolerant species. Broad-leaf crops tolerated 2820 g alloxydim-sodium ha^?1, three times the recommended rate used to control annual grasses. Differential uptake and translocation were not factors contributing to selectivity. In wild oat, blackgrass and sugarbeet, uptake and translocation of ¹⁴C continued during a period of 14 days after treatment with [¹⁴C]alloxydim-sodium. Translocation in susceptible and tolerant species was predominately symplastic. Over 40% of the applied ¹⁴C was eliminated from treated wild oat, blackgrass and sugarbeet plants within 7 days, due to degradation and volatilisation. A greater proportion of the methanol-soluble radioactivity extracted from leaves and roots was present as water-soluble polar metabolites in sugarbeet, than in wild oats, 7 days after treatment. The proportion of unaltered alloxydim in the organo-soluble fraction of a methanol extract was greater in wild oat than in sugarbeet. Differential metabolism appears to be one of the factors contributing to alloxydim-sodium selectivity between sugarbeet and wild oat.     

Joint action of Cochliobolus lunatus and atrazine on Echinochloa crus-galli (L.) Beauv.

The potential of the endemic fungus Cochliobolus lunatus as a biological control agent against Echinochloa crus-galli was investigated. Under appropriate conditions the fungus produced leaf necrosis on E. crus-galli resulting in death of young seedlings. However, plants with more than two leaves mostly recovered after some time. Bean, barley, maize, oat, rye, tomato and wheat were highly resistant to the fungus. In experiments in a climate room or in a glasshouse E. crus-galli with more than two leaves could effectively be controlled by C. lunatus in combination with a sub-lethal dosage of atrazine as low as 2.5 mg m^?2 due to a positive interaction between fungus and herbicide.     

QuEChERS-高效液相色谱法分析6-苄氨基腺嘌呤和吡唑醚菌酯在番茄植株和土壤中的残留动态

为了探究根部处理剂6-苄氨基腺嘌呤(6-BA)和吡唑醚菌酯在植物-土壤间的分布规律,以番茄为试材,建立了测定番茄根、叶及根围土壤中2种化合物的QuEChERS-高效液相色谱法,并采用该方法研究了两者在番茄体内和根围土壤中28 d内的含量变化。结果表明:6-BA与吡唑醚菌酯在番茄根、叶和根围土壤中的回收率在82%~107%之间,定量限在0.03~0.09 mg/kg之间;经番茄苗蘸根处理后12 h^28 d,在根围土壤中未检测到6-BA,而在番茄叶和根中均有检出(0.043~2.0 mg/kg),表明6-BA可被根部快速吸收,并传导至叶片,在番茄各部位中的含量为侧叶>根部>顶叶;6-BA在番茄根部和叶片中消解较快,处理7~10 d后低于检出限;吡唑醚菌酯可扩散至根围土壤中,大部分被根部吸收并维持在较高含量水平(1.2~3.0mg/kg)达28 d以上;根部的吡唑醚菌酯可转移至叶片,并以较低含量水平(0.11~0.78 mg/kg)保留4~6 d。研究结果为番茄根、叶及土壤中6-BA和吡唑醚菌酯的残留分析提供了方法,并为评价该根部处理剂的应用效果提供了必要数据。     

Indian peanut clump virus (IPCV) infection on wheat and barley: symptoms, yield loss and transmission through seed

Wheat and barley crops were shown to be susceptible to Indian peanut clump virus (IPCV) under field conditions. In wheat, the Hyderabad isolate of IPCV (IPCV-H) induced symptoms resembling the rosette caused by soil-borne wheat mosaic virus, and these were apparent only three weeks after emergence. Early-infected plants were severely stunted and dark green, with chlorotic streaks on the youngest leaves, which turned necrotic as the plants aged; most of these plants died. Late-infected plants were also stunted and were conspicuous in the field because of their dark green appearance as a result of delayed maturity. The virus was detected by ELISA and nucleic acid hybridization in all plants with symptoms. These plants usually produced fewer tillers than healthy ones. Spikes were malformed, often did not emerge from the flag leaf, and they contained few, shrivelled seeds. Grain yield was decreased, on average, by 58%. In barley, IPCV-H caused severe stunting and general leaf chlorosis. As the plants aged, the leaves became necrotic and the few infected plants that reached maturity produced small spikes. IPCV-H antigens were detected by ELISA in every wheat seed from infected plants and the virus was transmitted through wheat seed at a frequency of 0.5–1.3%. Storage at 4°C for more than a year did not affect seed transmission frequency. The virus was detected in leaves and roots of seed-transmitted plants. Seed transmission was not detected in barley. The Durgapura isolate (IPCV-D) was detected in wheat crops (cv. RR-21) at 3 different locations in Rajasthan State, India. Infected plants showed reduced growth without any overt symptoms.     

Uptake and fate of triticonazole applied as seed treatment to spring wheat (Triticum aestivum L.)

Following seed treatment of wheat (Triticum aestivum L.) with ¹⁴C-labelled triticonazole at a dose of 1·8 g kg^-1 seed, the uptake of radioactivity by shoots and roots was investigated from the two- to three-leaf stage up to the beginning of the booting phase, 80 days after sowing. Triticonazole equivalents taken up by wheat plants reached 5·7% and 14·6% of the applied dose in the shoots and the roots, respectively. Between the two- to three-leaf stage and the beginning of the booting phase, the concentration of triticonazole equivalents in the shoots decreased from 2·5 to 0·15 μg g^-1 fresh weight. This was attributed to uptake of triticonazole by roots not keeping pace with shoot growth and increased retention in the roots of triticonazole taken up. The main factor limiting the uptake of triticonazole by the roots may be the rapid growth of the uptake-active apical root parts out of the dressing zone which had formed in the soil. Distribution of triticonazole equivalents taken up by the main shoot showed a decreasing concentration gradient from the oldest to the youngest leaf. An increase in the seed treatment dose was investigated as a way to increase the concentration of triticonazole in the shoots, but its influence remained limited. © 1998 SCI     

Metabolic fate of bioxone in cotton

The metabolic fate of the ¹⁴C-labeled herbicide, 2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione (bioxone), in cotton (Gossypium hirsutum L. “Acala 4-42-77”) was studied using thin-layer chromatography, autoradiography, and counting. Bioxone-¹⁴C was readily metabolized by cotton tissue to 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU) and 1-(3,4-dichlorophenyl)urea (DCPU). Leaf discs metabolized bioxone-¹⁴C rapidly; 12 hr posttreatment, 65% of the ¹⁴C in methanol extracts was in forms other than intact herbicide. Excised leaves treated through the petiole with either heterocyclic ring-labeled or phenyl ring-labeled herbicide contained little bioxone-¹⁴C after 1 day; DCPMU was formed early then decreased with time. DCPU accounted for 55–70% of the ¹⁴C in excised leaves 3 days posttreatment. In intact plants treated via the roots, the herbicide was rapidly metabolized in the roots to DCPMU and DCPU; little or no intact herbicide was translocated to the leaves. Little radioactivity accumulated in the roots with time; the radioactivity in the leaves accounted for 80–90% of the methanol-soluble ¹⁴C 47 days posttreatment. Most of the ¹⁴C in the leaves was recovered as DCPU (50–60%) and unidentified polar metabolite(s) which remained at the origin of the thin-layer plates (30–40%). The percentage of radioactivity which remained in cotton residue after methanol extraction increased with time. Digestion of the plant residues with the proteolytic enzyme pronase indicated that some of the nonextractable ¹⁴C may be DCPMU and DCPU complexed with proteins. Similar metabolic patterns were noted after treatment with either heterocyclic ring-labeled or phenyl ring-labeled bioxone-¹⁴C. Generally, bioxone was metabolized to DCPMU which in turn was demethylated to DCPU. The herbicide and DCPMU were 20 times as toxic as DCPU to oat (Avena sativa L.), a susceptible species.     

Effect of triadimefon and triadimenol on growth of various plant species as well as on gibberellin content and sterol metabolism in shoots of barley seedlings

The fungicides triadimefon and triadimenol markedly reduced growth of coleoptiles, primary leaves, and roots of barley seedlings when grown for 7 days in petri dishes in the dark. The addition of gibberellins (A₁, A₃, A₄, A₇, A₉) alleviated growth retardation of primary leaves and coleoptiles induced by the fungicides. While fungicide-induced growth retardation of the shoots was partly relieved by kinetin, IAA did not show an alleviating activity. Triadimefon and triadimenol also substantially retarded the elongation of shoots of tomato and cotton plants and simultaneous application of GA₃ nullified the retardation. The fungicides only slightly interfered with both α-amylase production of intact germinating barley seed and the GA₃-induced α-amylase synthesis in barley endosperm. On the other hand, extracts of triadimefon- and triadimenol-treated shoot tissue of 10- to 12-day-old barley plants contained substantially lower gibberellin-like activity than control shoots. Both compounds also interfered in sterol metabolism of shoots of barley seedlings when compared to control plants, treatment resulted in lower amounts and altered proportions of C-4,4-desmethyl sterols. While both fungicides inhibited synthesis of C-4,4-desmethyl sterol fraction, sterols possessing C-4 and C-14-methyl groups were accumulated. It is assumed that triadimefon and triadimenol interfere in gibberellin and sterol biosynthesis in barley seedlings by inhibiting oxidative demethylation reactions.