Effects of picloram on the synthesis of soluble plant proteins as determined by gel electrophoresis

Changes in soluble proteins synthesized in soybean (Glycine max L.), safflower (Carthamus tinctorius L.), radish (Raphanus sativus L.), and barley (Hordeum vulgare L.) treated with either growth promotive or inhibitory concentrations of picloram (4-amino-3,5,6-trichloropicolinic acid) were determined by polyacrylamide gel electrophoresis and isoelectric focusing. A special gel mixture was developed which provided resolution of protein bands superior to that obtained by standard gel electrophoresis. Growth promotive concentrations of picloram caused both qualitative and quantitative alterations in the band patterns of soluble proteins of safflower, radish, and barley roots and shoots. Isoelectric focusing was applied for the separation and identification of soluble protein fractions from soybean and barley roots and shoots treated primarily with growth inhibitory concentrations of picloram (except for barley shoot tissues). More than 35 clear bands were distinguishable in a typical gel electrophoretogram for either soybean or barley tissue (4-day-old plants). Approximate pI values of the bands from barley root protein were determined from a pH gradient diagram. Protein band patterns of picloram-treated samples were changed qualitatively and quantitatively, in comparison with controls, mostly in the range above pI 6, and predominantly in the neutral and basic protein regions. Band patterns for 96-hr root samples treated with growth inhibitory concentrations of picloram were more similar to those from 48-hr (soybean) or 55-hr (barley) than 96-hr control seedlings. A quantitative decrease in intensity of a band which had the same pI value as that of RNase was noticed in both the treated samples and 2- or 3-day-old control seedlings.     

An energy-dependent efflux mechanism for fenarimol in a wild-type strain and fenarimol-resistant mutants of Aspergillus nidulans

Uptake of [¹⁴C]fenarimol (30 μM) by mycelium of wild-type Aspergillus nidulans was characterized by a rapid initial accumulation during the first 10 min of incubation with the fungicide and a subsequent gradual release with time. Uptake appeared to be the result of influx and efflux. Influx of fenarimol could not be inhibited by low temperature, anaerobiosis, starvation of mycelium, or incubation with several respiratory inhibitors and is, therefore, a passive process. Under identical test conditions efflux activity was severely inhibited and should, therefore, be regarded as an energy-dependent mechanism. After prolonged incubation (90 min) an equilibrium between influx and efflux was established, resulting in an energy-dependent permeability barrier, since uptake could instantaneously be enhanced by addition of oligomycin or N,N′-dicyclohexylcarbodiimide. It also indicates that efflux activity is inducible; this hypothesis is supported by the observation that pretreatment of mycelium with unlabeled fungicide prevented subsequent uptake of [¹⁴C]fenarimol. Uptake by fenarimol-resistant mutants J146, M193, and R264 of A. nidulans, all possessing the imaB gene for resistance, was relatively low and almost constant in time. In this case, uptake appeared to be considerably enhanced by low temperature, anaerobiosis, starvation of mycelium, and incubation with respiratory inhibitors. Low uptake by these mutants is ascribed to a higher energy-dependent efflux activity for fenarimol compared with the wild-type strain. Upon inhibition of the barrier activity, net uptake resulted from remaining passive influx, which in that case may be as high as in the wild-type strain. The results suggest that both wild-type and fenarimol-resistant mutants possess an energy-dependent efflux mechanism with different efficiencies to excrete fenarimol and probably other chemicals to which cross-resistance or collateral sensitivity is present.     

Laboratory resistance to dicarboximides and ergosterol biosynthesis inhibitors in Penicillium expansum

Samenvatting Isolaten vanPenicillium expansum werden geselecteerd op moutagar met een dicarboximide (iprodion, procymidon, vinchlozolin) of een ergosterol biosynthese remmer (fenarimol, fenapanil, imazalil, prochloraz). De verkregen isolaten vertoonden alleen kruisresistentie tegen fungiciden behorende tot dezelfde groep van middelen. Deze kruisresistentie kon ook in dompelproeven met geïnoculeerde appels worden aangetoond. Alle getoetste isolaten bezaten in mengpopulaties van gevoelige en resistente isolaten op appels een relatief laag competitief vermogen.     

Uptake and translocation of non-ionised pesticides in the emergent aquatic plant parrot feather Myriophyllum aquaticum

The uptake of four (14)C-labelled non-ionised compounds, the methyl carbamoyloxime insecticide/nematicide oxamyl and three model phenylureas, from solution by rooted stems of the aquatic plant parrot feather [Myriophyllum aquaticum (Vell.) Verdc], together with translocation to the emergent shoots, was measured over periods of 24 and 48 h. Uptake into the submerged tissues of roots and stem base could be ascribed to two processes: movement into the aqueous phase of cells and then partitioning onto the plant solids. This latter process was related to lipophilicity (as measured by the l-octanol/water partition coefficient, K(ow)) and gave rise to high uptake rates of the most lipophilic compounds. Translocation to shoots was passive and was optimal at log K(ow) approximately 1.8, at which the efficiency of translocation of compound was about 40% of that of water. This optimum log K(ow) was identical to that observed previously in barley, although the translocation efficiency was somewhat less in parrot feather. Solvation parameters were applied to model uptake and translocation of a set of ten compounds by barley with the particular objective of understanding why translocation efficiency is lower at log K(ow) > 1.8.     

Entry of pesticides into the plant symplast as measured by their loss from an ambient solution

A method was developed to determine the extent of penetration of substances into the plant symplast. The known apoplastic dye trisodium 3-hydroxy-5,8,10-pyrenetri-sulphonate (PTS) and various systemic pesticides were studied using potato tuber tissue. The dye penetrated only 5% of the volume of living tissue while those pesticides which display an apoplastic pattern of transport in plants penetrated the entire tissue volume. The pesticides diffused freely out of the tissue when it was transferred to fresh medium. It is proposed that the term euapoplastic be used to describe chemicals that behave like the dye, and that the term pseudoapoplastic be used to describe chemicals that behave like atrazine, carbendazim, carboxin and diuron. 2,4-D, which displays a symplastic transport pattern in the plant, was concentrated by the tissue and did not diffuse out freely. It appears that the property which allows a pesticide to be transported in the symplast is not its ability to penetrate the plasmalemma but rather its ability to be retained by the symplast after entry.     

A comparison of the translocation within plants of pyroxychlor and a 6-amino analogue

The uptake and translocation within tomato plants of pyroxychlor (2 chloro-6-methoxy-4-(trichloromethyl) pyridine) and the 6-amino analogue were compared. Both fungicides were transported symplastically but the amino analogue was more efficiently taken up by foliage with much less loss by volatilization from leaf surfaces. Pyroxychlor was taken up more efficiently by root treatment than the amino analogue but the latter was more readily transported to above-ground parts of plants. The uptake of both fungicides appears to be passive, based on temperature studies, and differences between analogues may be due to relative lipophilicity. Uptake and efflux studies with potato tuber tissue confirmed passive accumulation against a concentration gradient by cells. The concentration against a gradient was less and the release from tissue more complete with the amino analogue which is logically correlated with its more ambimobile pattern of transport.     

Phloem translocation of non-ionised chemicals in Ricinus communis

Techniques using R. communis were modified to enable the movement of chemicals in phloem and the factors controlling their distribution in the plant to be described quantitatively. The non-ionised chemicals tested, aminotriazole, O-methylcarbamoyloximes (including aldoxycarb and oxamyl) and phenylureas, spanning a range of lipophilicity of log K_OW= ?0.87 to +2.27, all freely entered the phloem. However, only the more polar compounds were retained sufficiently in the phloem to be transported over long distances, indicating that polar compounds cross cell membranes more slowly than compounds of intermediate lipophilicity; these findings substantiate the ‘intermediate permeability hypothesis’ of phloem translocation of xenobiotics. However, the amount of chemical reaching or retained in the sink tissues, especially in the root, was small even for the chemicals that were translocated best in the phloem.     

Adsorption of systemic pesticides on ground stems and in the apoplastic pathway of stems,as related to lignification and lipophilicity of the pesticides

The adsorption of five systemic fungicides (carbendazim, triadimefon, nuarimol, triarimol, and fenarimol) and one herbicide (fluometuron) on ground stems and in the apoplastic pathway of excised pepper, cotton, and bean stems was studied. Adsorption on ground and water extracted stems, as well as retention in the apoplast of excised stems, increased with the 1-octanol/water partition coefficients of the pesticides. Methylation of ground stems increased their adsorption capacity (carbendazim excluded), while extraction with organic solvents did not affect it. Woody stems adsorbed more of the pesticides than herbaceous ones. Binding of pesticides in the apoplastic pathway of stems seems to be related to their degree of lignification and to the lipophilicity of the pesticides.     

Differential accumulation of fenarimol by a wild-type isolate and fenarimol-resistant isolates of Penicillium italicum

Accumulation of [¹⁴C] fenarimol by mycelium ofPenicillium italicum was studied with isolates having varying levels of laboratory resistance to fenarimol. All resistant isolates tested showed a significantly lower accumulation than the wild-type isolate.Various metabolic inhibitors enhanced accumulation to relatively high levels in both wildtype and resistant isolates. it indicates that accumulation is governed by two processes viz. a non-mediated influx and an energy-dependent efflux. A relatively high fenarimol efflux in resistant isolates probably accounts for low accumulation and for fenarimol resistance. One of the inhibitors which annihilated fenarimol efflux and enhanced fenarimol accumulation was sodium orthovanadate. The synergistic action of fenarimol and orthovanadate to both wildtype and resistant isolates in crossed-paper strip bioassays is probably related to the effect of the latter compound on fenarimol accumulation. Synergistic action between the chemicals in control ofPenicillium decay of oranges could not be detected.Samenvatting De accumulatie van [¹⁴C]fenarimol door mycelium vanPenicillium italicum werd bestudeerd bij isolaten met een uiteenlopende graad van laboratorium-resistentie tegen fenarimol. Alle getoetste resistente isolaten vertoonden een lagere opname dan de wild-stam.Verschillende antimetabolieten verhoogden de accumulatie tot relatief hoge waarden die voor gevoelige en resistente isolaten ongeveer gelijk waren. Deze waarneming duidt erop dat accumulatie wordt bepaald door twee processen: nonmediated influx en energie-afhankelijke efflux. Een hogere fenarimol efflux in resistente isolaten vormt waarschijnlijk de verklaring voor de lagere accumulatie en voor het resistentiemechanisme. Een van de remmers die de fenarimolefflux te niet doet, en de accumulatie van fenarimol verhoogt, is natriumorthovanadaat. De synergistische werking van fenarimol en orthovanadaat tegen zowel wild-type als resistente isolaten in crossed-paper strip biotoetsen houdt waarschijnlijk verband met het effect van laatstgenoemde stof op de accumulatie van fenarimol. Synergistische werking van deze verbindingen bij de bestrijding vanPenicillium-rot op sinaasappels werd niet waargenomen.     

吲哚乙酸引导下三唑醇在大豆植株中的传导与积累研究初报

将吲哚乙酸与三唑醇发生酯化反应后生成的吲哚乙酸三唑醇酯 ,在0.5 mmol/L浓度下水培和喷雾处理6~8叶期大豆植株,同时以相同浓度的三唑醇及其与吲哚乙酸的混合物为对照,色谱法测定不同时间植株不同部位吲哚乙酸三唑醇酯和三唑醇的含量。结果表明,与对照相比,吲哚乙酸三唑醇酯在大豆中具有明显的双向传导和向根部积累的特点。喷雾处理后,在12~60 h之间内吸量和根部积累量均出现最大值。     

Effects of phthalimide fungicides on the accumulation of fenarimol by Aspergillus nidulans

Phthalimide fungicides (captafol, captan and folpet) enhanced the accumulation of fenarimol by the mycelium of a wild-type strain and a fenarimol-resistant strain of Aspergillus nidulans. The accumulation is ascribed to inhibition of active efflux of fenarimol from the mycelium. It is assumed that the synergistic action observed between the phthalimide fungicides and fenarimol with respect to fungitoxicity, was caused by the increased accumulation of fenarimol.     

In vitro inhibition of α-amylase and protease by nematocides in Cicer arietinum L

The in vitro effects of four systemic nematocides, i.e., aldicarb, carbofuran, oxamyl, and phorate, on the α-amylase and protease activities in Cicer arietinum has been revealed. All four nematocides markedly inhibited the activities of both the enzymes, with a general tendency of increased inhibition with corresponding increase in the concentrations of the nematocides. There was complete inhibition of α-amylase activity by the highest concentration (500 μM) of aldicarb and carbofuran, while oxamyl at the same concentration showed the same effects on protease activity. The lowest concentration (10 μM) was almost ineffective.     

Interaction between saflufenacil and imazethapyr in red rice (Oryza ssp.) and hemp sesbania (Sesbania exaltata) as affected by light intensity

BACKGROUND: Saflufenacil is a broadleaf herbicide for preplant burndown and pre‐emergence applications in various crops. This study was established to evaluate the absorption and translocation of saflufenacil in hemp sesbania and imazethapyr in red rice as a function of their post‐emergence interaction and light intensity. RESULTS: Imazethapyr plus saflufenacil provided a greater uptake (30%) and translocation (35%) of ¹⁴C‐imazethapyr than imazethapyr alone. In the section above treated leaf (ATL), a higher percentage of the absorbed imazethapyr (23%) was quantified in the imazethapyr plus saflufenacil treatment after 168 h. Faster basipetal movement of imazethapyr was identified under higher light availability. Absorption of ¹⁴C‐saflufenacil ranged from approximately 40 to 60% among herbicide and light intensity treatments. At 12 and 24 h after treatment (HAT) a greater percentage (15–20%) of the absorbed saflufenacil was quantified above the treated leaf at the two lower light intensities. Similar trends were observed for basipetal movement of saflufenacil. CONCLUSION: Saflufenacil enhanced absorption, overall translocation and acropetal movement of imazethapyr in the TX4 red rice. Basipetal movement of imazethapyr was faster under higher light intensities. Overall, imazethapyr improved absorption of saflufenacil in hemp sesbania plants. Reduction in light intensity resulted in greater translocation of saflufenacil, promoting acropetal and basipetal distribution at the two lower light intensity treatments. Copyright © 2011 Society of Chemical Industry     

Measured and simulated behaviour of oxamyl in fallow soils

The movement and breakdown of the insecticide and nematicide oxamyl was monitored in fallow sandy loam soils under field conditions. Using measurements of rainfall and evaporation from a water surface, the water flow in soil was simulated by a computer model, and the results were compared with the measured soil-moisture profiles. The model was extended to simulate the behaviour of oxamyl, using laboratory data for adsorption and rates of degradation in soil. The model generally underestimated oxamyl movement in the first month, whereas it tended to overestimate later movement. The rate of breakdown of oxamyl, as affected by soil type, temperature and soil-moisture content, was fairly well described. After about 2 months only small amounts of oxamyl remained. Accumulation of oxamyl near the soil surface in dry periods was overestimated, indicating deficiencies in the modelling procedure under these conditions.     

A non-destructive method for testing two components of the behaviour of soil-applied agricultural chemicals over a long period

BACKGROUND: Owing to the complexity of soil composition, accurate predictions of both apoplastic systemicity of lipophilic xenobiotics and their leaching from the soil are made difficult. Therefore, a non‐destructive method to assess directly these two components of the spatial behaviour of soil‐applied phytochemicals is needed. RESULTS: The plant selected was a dwarf tomato, which can exude an abundant apoplastic fluid through large stomata for several months. The feasibility and reliability of the method were assayed using three triazoles exhibiting different log D values. HPLC‐MS analyses indicated that triadimenol (log D = 2.97) was clearly the most mobile compound within the apoplast, especially its diastereoisomer A. Propiconazole (log D = 3.65) and penconazole (log D = 4.64) exhibited a similar low systemicity. The data remained the same when the three fungicides were applied together on the soil. Long time‐course studies (1.5 months) of penconazole behaviour indicated that, in contrast to leaching, which decrease sharply, root‐to‐shoot translocation remained almost unchanged during the whole experiment, in spite of the high lipophilicity of this fungicide. CONCLUSION: This method must contribute to a better knowledge of the behaviour of commercial soil‐applied phytochemicals. It can also be used to screen new xenobiotics within strategies to satisfy environmental requirements. Copyright © 2011 Society of Chemical Industry     

Visualisation of the uptake of two model xenobiotics into bean leaves by confocal laser scanning microscopy: diffusion pathways and implication in phloem translocation

The diffusion of two fluorescent dyes, Oregon Green 488 (Oregon Green) and Rhodamine B into the leaves of broad bean (Vicia faba L) plants was studied to simulate the foliar uptake process of pesticides. The uptake rate of these model xenobiotics into bean foliage was measured using a standard leaf surface wash-off method. Diffusion into leaf tissues was visualised in vivo by confocal laser scanning microscopy (CLSM). The moderately lipophilic dye (Rhodamine B) showed faster uptake than the hydrophilic one (Oregon Green), despite the former being a larger molecule. While no distinct channels or domains for preferential entry of any of the dyes could be detected in the cuticle layer by CLSM, two different diffusion patterns were identified for the movement of these two dyes after traversing the cuticle. Upon desorption from the cuticle, Rhodamine B diffused extensively into the vacuole of the epidermal cells. Further transport of this dye from the epidermal cells to the mesophyll cells was not observed. In contrast, Oregon Green was found in the epidermal cell walls and cytoplasm, and was also present in the mesophyll cells. Examination of the petioles of the treated leaves revealed that, once absorbed, Oregon Green moved readily out of the treated leaf, whereas Rhodamine B did not show any phloem translocation. It is proposed that these two different diffusion characters may be responsible for the contrasting phloem mobility of the two xenobiotics. The results are discussed in relation to the current knowledge on the uptake, translocation and efficacy of pesticides as influenced by their properties.     

A nonlinear, dynamic, simulation model for transport, and whole plant allocation of systemic xenobiotics following foliar application. IV: Physicochemical properties requirements for optimum absorption and translocation

The relationship between the physicochemical properties (molar volume, partition coefficient, and dissociation constant) of slow-acting systemic postemergence xenobiotics and their uptake and translocation to the sites of action was investigated using the nonlinear, dynamic simulation model ERMESSE. When the pK_a was held constant at 4.0, the model enables the prediction of the uptake of a systemic xenobiotic as a function of its partition coefficient and molar volume. The model also considered the effects of the physicochemical properties of a systemic xenobiotic on its long-distance translocation within the vascular tissues. For instance, when the log K_ow and pK_a were held constant at 1.5 and 6.0, respectively, the model predicted a higher translocation rate (55%) for molecules with a small (e.g., MV = 100 cm³ mol⁻¹) as opposed to a large (e.g., MV = 300 cm³ mol⁻¹, 33%) molar volume. In addition, the theoretical predictions from the ERMESSE model showed that any xenobiotic with a molar volume not exceeding 300 cm³ mol⁻¹ could provide an uptake ?50% and a translocation rate ?25% when its log K_ow is between −0.5 and 2.5 and its pK_a is between 0.0 and 8.0.     

Some studies on the systemic activity of the thiophanate fungicides in plants

Three closely related fungicides, thiophanate (NF 35), thiophanate methyl (NF 44) and NF 48 have been found to be active against a wide range of diseases including the powdery mildews of apple, cucumber and barley; apple and pear scab and grey mould of soft fruit. This paper deals with the preliminary experiments to compare their relative mobilities and biological persistence in crop plants, using the powdery mildews as indicator infections. NF 44 and NF 48 in particular showed a high degree of systemic activity by root uptake and persistence of action against barley and cucumber mildew but very little systemic activity against apple mildew on potted rootstocks. They have also displayed trans-laminar and localised movement towards the leaf apex in sprayed cucumber and barley leaves but movement was not so marked in sprayed apple leaves. NF 48 was also active as a seed dressing against loose smut of barley.     

THE EFFECT OF SIMAZINE ON THE PHOTOFIXATION OF CO2 AND ON TRANSLOCATION OF ASSIMILATES IN NORWAY SPRUCE (PICEA ABIES)

Summary. A method of exposing seedlings of Norway spruce (Picea abies (L.) Karst.) to ¹⁴CO₂ is described. Within the 1st hr alter ¹⁴CO₂ exposure, no translocation of the ¹⁴C out of the treated branch could be observed. After a 24-hr period, however, the ¹⁴C in dormant seedlings had been translocated basipetally to part of the root system only, with no lateral diffusion of the ¹⁴C-compounds in the stem. About a week after exposure, both symplastic and apoplastic patterns of translocation had caused a more uniform distribution of ¹⁴C. In seedlings at active internode elongation, the translocation patterns were fundamentally identical to those in dormant seedlings, but the active shoot growth had led to a more uniform distribution of the ¹⁴C.
Simazine at 20 ppm had apparently stimulated both the photofixation of ¹⁴CO₂ and the rate of translocation of the ¹⁴C-assimilates. At 30 ppm, however, simazine had blocked the translocation of nutrients to the roots. On the other hand, the ¹⁴CO₂ uptake was not influenced. The simazine incubation had apparently no influence on the synthesis of cationic photosynthate.     

Resistance to fenarimol in Nectria haematococca var. cucurbitae

Genetic work with 51 fenarimol-selected strains of Nectria haematococca var. cucurbitae identified a polygenic system for resistance with at least nine chromosomal loci involved. The mutant genes, designated fen-1 to fen-9, gave low levels of resistance to fenarimol and to three other C-14 demethylation inhibiting (DMI) fungicides, namely triforine, imazalil, and triadimenol. Haploid strains carrying two fen mutations exhibit higher levels of resistance, indicating additivity of gene effects. All fen mutations appear to be pleiotropic, having more or less adverse effects on growth, sporulation, spore germination, pathogenicity, and tolerance of somewhat high temperatures. Accumulation of fenarimol in resistant strains was lower than in the wild type, suggesting that fen mutations code for a common resistance mechanism based on a permeability barrier. Various inhibitors of energy generation increased the accumulation level, indicating that accumulation is energy dependent and may be the result of passive influx and energy-dependent efflux. Lower accumulation in resistant strains is probably the result of increased efflux, as has been found with other fungi. A double mutant carrying the mutations fen-7 and fen-9 showed lower accumulation of fenarimol than a strain carrying the fen-7 only, indicating additivity of effects in this regard also.