Physico-chemical factors determining the phloem translocation of benzoic acids

A series of ¹⁴C-labelled benzoic acids, chosen to permit assessment of the role of pK_a and lipophilicity in determining movement in plants of these herbicide analogues, was synthesised and their phloem translocation investigated. Following application of substituted benzoic acids to castor bean, Ricinus communis L., by injection into the petioles, the compounds of intermediate lipophilicity (2-fluoro-, 4-chloro- and 3,4-dichlorobenzoic acids) gave highest concentrations in phloem exudates; 4-methyl-2,3,5,6-tetrafluoro- and pentafluorobenzoic acids were less well translocated, perhaps because their pK_a values are much less than those of the other benzoic acids studied. The polar 4-ureidobenzoic acid and the lipophilic 3-(4-methylphenoxy)benzoic acid were much less efficiently translocated in phloem. These results are similar to those previously obtained for phenoxyacetic acids, and provide further support for the role of ionisation in the accumulation and retention of chemicals in phloem sieve tubes.     

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 kinetic model of fumigant sorption by grain using batch experimental data

BACKGROUND: Most fumigants are adsorbed by grain at differing rates depending on the fumigant or grain type. Sorption can reduce the concentrations of fumigation doses to sublethal levels before grain has been disinfested. A model to predict fumigant losses due to sorption in industrial scenarios is needed. RESULTS: This work reviews the kinetics of grain fumigant sorption and develops a new alternative model based upon key factors established from the literature and batch experimental results. The novel model accounts for linear mass transfer within the grain, irreversible 'binding' and linear partitioning of the fumigant to the grain. Model coefficients were estimated by minimizing the sum of squared residuals between model predictions and experimental data. The model was compared with other options including diffusion into spheres, and results for methyl bromide and phosphine are provided. CONCLUSION: The model describes the transient changes of fumigant concentrations in both the intergranular air and grain. It provides the capacity to predict fumigant concentrations throughout grain stacks for a wide range of scenarios of industrial importance.     

Calibration and evaluation of an electronic sensor for rainfall kinetic energy

ABSTRACT A novel sensor for measuring the kinetic energy of impacting raindrops, developed based on a soil-mass erosion sensor, was tested in the laboratory, with a rain simulator, and in the field. Drop impactions on the sensor-consisting of a piezoelectric crystal and associated electronics-produce an electrical charge that equals a fixed amount of energy. Calibration of the sensor was done in the laboratory using water drops of known diameter impacting with known velocity, and thus, with known kinetic energy. The relationship between pulse-count output of the sensor minus the background pulse counts when no drops were impacting (O; per min) and kinetic energy flux density (i.e., power [P; mJ cm(-2) min(-1)]) was found to be described by the formula P; = (0.204 + 0.065 . O)(0.67). The measurement threshold was 0.34 mJ cm(-2) min(-1). Using the sensor, generated rains with intensities of 23 to 48 mm/h were found to have powers of 0.4 to 2.2 mJ cm(-2) min(-1). In 2 years of field testing, 85 individual rain episodes were monitored, with mean intensities ranging from 0.1 to 42 mm/h. These rains had mean powers ranging from 0 to 5 mJ cm(-2) min(-1), and the highest power for a 5-min sampling period was 10 mJ cm(-2) min(-1). Both power and intensity varied greatly over time within rain episodes, and there was considerable variation in power at any given rain intensity, emphasizing the importance of measuring rather than simply predicting power. Although there was no known true power measurements for the generated or natural rains, estimates were realistic based on theoretical calculations, assuming that the gamma distribution represents raindrop sizes. The sensor is important in assessing the risk of rain splash dispersal of plant pathogens.     

小麦抗赤霉病3B-QTL和6B-QTL的遗传互作模式分析

为明确来自抗赤霉病的小麦品种望水白的2个主效抗扩展3B-QTL和6B-QTL的抗性遗传和互作模式,基于分子标记辅助选择方法,构建了回交分离群体,以病小穗数(NDS)和病轴长(LDR)为鉴定指标,采用单花滴注接种法对携带3B-QTL和6B-QTL的BC_3F_1、BC_3F_2、BC_3F_3世代以及抗感对照进行了抗赤霉病扩展的表型鉴定和评价。结果表明,3B-QTL和6B-QTL在烟农19和矮抗58不同的背景中,杂合基因型与纯合望水白基因型之间的NDS和LDR差异显著;携带3B-QTL和6B-QTL株系的抗扩展性与只含有单个3B-QTL的株系无显著差异,但显著高于只携带单个6B-QTL株系的抗性,抗感分离比经卡方检验符合4∶3∶9的分离比例,遵循2个独立孟德尔遗传因子控制的隐性遗传模式,且3B-QTL隐性上位于6B-QTL。研究表明,望水白的3B-QTL和6B-QTL抗扩展效应强且稳定,可以作为抗赤霉病基因资源在育种实践中充分利用。     

Role of social structure in establishment of an invasive large mammal after translocation

Background

Data on the movement behavior of translocated wild pigs is needed to develop appropriate response strategies for containing and eliminating new source populations following translocation events. We conducted experimental trials to compare the home range establishment and space-use metrics, including the number of days and distance traveled before becoming range residents, for wild pigs translocated with their social group and individually.

Results

We found wild pigs translocated with their social group made less extensive movements away from the release location and established a stable home range ~5 days faster than those translocated individually. We also examined how habitat quality impacted the home range sizes of translocated wild pigs and found wild pigs maintained larger ranges in areas with higher proportion of low-quality habitat.

Conclusion

Collectively, our findings suggest translocations of invasive wild pigs have a greater probability of establishing a viable population near the release site when habitat quality is high and when released with members of their social unit compared to individuals moved independent of their social group or to low-quality habitat. However, all wild pigs translocated in our study made extensive movements from their release location, highlighting the potential for single translocation events of either individuals or groups to have far-reaching consequences within a much broader landscape beyond the location where they are released. These results highlight the challenges associated with containing populations in areas where illegal introduction of wild pigs occurs, and the need for rapid response once releases are identified. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

The interaction of insecticide synergists with nonenzymatic model oxidation systems

Insecticide synergists such as the 1,3-benzodioxoles, the 1,2,3-benzothiadiazoles and the phenyl-2-propynyl ethers inhibit the epoxidation of aldrin to dieldrin by a modified Fenton's reagent (H₂O₂, Fe²⁺, EDTA and bovine serum albumin). Inhibition appears to result from the ability of the synergists to compete with aldrin for the OH· radicals generated by the system, and as a result of this interaction the synergists are themselves chemically modified. In the case of the 1,3-benzodioxoles the reaction results in the formation of the corresponding catechols and the rate at which this occurs correlates favorably with the ability of the synergist to inhibit aldrin epoxidation in the system. Although a number of nonenzymatic systems generating radical species other than OH· are also capable of aldrin epoxidation, these are not affected by the presence of insecticide synergists and the synergists are not themselves modified by these systems. The possible relevance of these results to the mode of action of synergists is discussed.     

Synthesis and phloem mobility of acidic derivatives of the fungicide fenpiclonil

A series of derivatives of the phenylpyrrole fungicide fenpiclonil was synthesized in which a carboxyl group was present at various sites of this non-phloem-mobile molecule. Using the Kleier model, all these acidic analogues were predicted to be moderately phloem-mobile, especially the N-substituted derivatives. One of these latter molecules, N-carboxymethyl-3-cyano-4-(2,3-dichlorophenyl)pyrrole, exhibited some fungicidal activity on the pathogenic fungus Eutypa lata, and was then tested as a phloem-mobile pesticide in the Ricinus system. The compound was indeed mobile in the sieve tubes and was not degraded to fenpiclonil in the phloem sap under our experimental conditions. Its concentration in the sap was closely correlated to the percentage of the undissociated form of the molecule in the external medium, and was similar under acidic conditions (external pH 4.6-5.0) to that of the herbicide glyphosate.     

A preliminary report on the occurrence of bacteria-like organisms in both phloem and xylem tissues of stuntedMelaleuca armilaris plants

A disease ofMelaleuca armilaris (Myrtaceae) plants, belonging to the yellows group of diseases, is described from Israel. The disease was associated with bacteria-like organisms (BLO) occurring in growing tips. The BLO were observed in both xylem and phloem tissues. Electron microscope observations demonstrated that the overall number of cells invaded by BLO in winter, when seen best, was relatively small. BLO diameter was 400 to 650 nm and length was 950 to 1400 nm.     

A review of foliar absorption and translocation of 2,4-D and 2,4,5-T

This review is restricted to an examination of the literature on the environmental and chemical factors that affect foliar absorption and translocation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichloro-phenoxyacetic acid (2,4,5-T) by plants. Most of the papers covered by this review have been published since 1965. Earlier works have been reviewed elsewhere by other authors (Currier & Dybing, 1959; Sargent, 1965; Franke, 1967; Robertson & Kirkwood, 1969; Hull, 1970). Often absorption and translocation of herbicides are considered together; here the two will be considered separately wherever possible.     

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.     

吩嗪-1-羧酸双酰肼衍生物的合成、杀菌活性及韧皮部的输导性研究

天然产物吩嗪-1-羧酸（PCA,申嗪霉素）及其衍生物吩嗪-1-甲酰肼具有独特的化学结构和优良的杀菌等生物活性,但均没有韧皮部输导性。本文以具有抑菌活性的吩嗪-1-羧酸和具有韧皮部输导性的马来酰肼为先导化合物,将马来酰肼中的双酰肼结构引入到吩嗪-1-羧酸中,设计、合成了17个新化合物,其结构均经过核磁共振氢谱、高分辨质谱及X-射线单晶衍射分析确证。初步生物活性测试表明:大部分目标化合物在50 mg/L下对水稻纹枯病菌Thanatephorus cucumeris表现出中等偏上的抑制活性,其中化合物6m的抑制率达92%。但输导性研究结果显示,目标化合物没有明显的韧皮部输导性。     

A bio-economic model of long-run Striga control with an application to subsistence farming in Mali

A bio-economic model of Striga control is developed and applied to Mali's Mourdiah Zone. Various constraints are added, and optimal production practices identified based on Striga infestation levels, rainfall levels, and economic parameters. Model optimization suggests efforts to suppress Striga with nitrogen applications are both expensive and risky. The efficacy of hand-pulling Striga in reducing the Striga seedbank depends on Striga infestation levels and climatic conditions, as does the profitability of hiring labour to expand cultivated acreage. Under all climatic conditions and infestation levels considered, millet in a pure stand generated greater expected net returns than a millet - groundnut or millet - cowpea association. Under conditions of low rainfall, the model suggests planting millet at a density of 0.5 hills m^?2. With average or higher rainfall, the model suggests planting millet at a density of 3.5 hills m^?2. Estimates of Striga-induced net revenue losses also vary with climatic conditions, ranging from 6% to 85%. Model results are encouraged to be used as a guide in the design and evaluation of research and extension programmes aimed at identifying long-run Striga control strategies and promoting their adoption.     

Tissue analysis and hemolymph translocation of [14C]chlorpyrifos sorbed from treated surfaces by American cockroaches

Using radiotracer methodology and dissection techniques it was demonstrated that [¹⁴]chlorpyrifos and/or its ¹⁴C-labeled metabolite(s) concentrated mainly in the gut tissues and malpighian tubules of American cockroaches, Periplaneta americana (Linnaeus), following sorption from a treated surface. Significantly lower (P ≤ 0.10) amounts of ¹⁴C were present in testes samples and no radioactive material was detected in brain tissue. After 41.5–48 hr of exposure of adult male American cockroaches to sublethal concentrations of [¹⁴C]chlorpyrifos, radioactivity was detected in the hemolymph of all cockroaches tested. The hemolymph accounted for 30.83% of the total sorbed ¹⁴C. A parabiotic experiment confirmed translocation of chlorpyrifos and/or its ¹⁴C-labeled metabolite(s) in hemolymph.     

A new derivative of fipronil: Effect of adding a glycinyl group to the 5-amine of pyrazole on phloem mobility and insecticidal activity

Glycinyl fipronil, a new fipronil derivative with 5-amine acylated by glycine, was synthesized. The phloem mobility of the synthesized derivative was higher that of the parent compound in intact soybean seedling and its insecticidal activity against the 3rd instar larvae of Plutella xylostella was comparable with that of fipronil.     

A new derivative of fipronil: Effect of adding a glycinyl group to the 5-amine of pyrazole on phloem mobility and insecticidal activity

Glycinyl fipronil, a new fipronil derivative with 5-amine acylated by glycine, was synthesized. The phloem mobility of the synthesized derivative was higher that of the parent compound in intact soybean seedling and its insecticidal activity against the 3rd instar larvae of Plutella xylostella was comparable with that of fipronil.     

Aspergillus flavus-secreted proteins during an in vivo fungal-cotton carpel tissue interaction

Cotton bolls (Gossypium hirsutum) were inoculated with Aspergillus flavus to investigate extracellular hydrolases produced during infection. Fungal proteins from the infection site were isolated and analyzed by SDS-PAGE. Protein bands were excised and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We identified several proteins including an exoglucanase 1 precursor (AFL2G_03805), a hypothetical protein similar to rhamnogalacturonan lyase A (AFL2G_05136), and a hypothetical protein similar to pectate lyase A (AFL2G_05954). We also matched three peptides to an oryzin precursor protein (AFL2G_01995). Our findings support the conclusion that glucanase, pectinolytic, and proteolytic proteins are important for fungal maceration of cotton carpel tissue during infection.     

三个小麦-簇毛麦易位系抗条锈性遗传及基因间关系分析

采用8个我国当前流行的条锈菌生理小种(菌系)对三个易位系进行抗锈性评价,并用CYR30、CYR31、Su-4和单孢菌系CYR32-6对三个易位系与感病品种铭贤169配制的F1、BC,1F1和F2代株系以及三个易位系之间双列杂交的F2株系进行遗传分析和等位性分析.结果表明:三个易位系是优秀的小麦抗条锈病资源;V9128-1对CYR30、CYR32-6和Su-4的抗病性由1对显性基因控制,对CYR31的抗病性由1显1隐2对基因独立控制,V9128-3对四个菌系的抗病性均由1对显性基因控制,V3对CYR32-6和Su-4的抗病性均由2对显性基因互补作用控制,对CYR31的抗病性由1显1隐2对基因独立控制或由1对显性基因控制;V9128-1与V9128-3对CYR31、CYR32-6和Su-4有相同或紧密连锁的抗病基因,且对CYR30、CYR32-6和Su-4的抗病基因与V3都不同.但与V3含有相同或紧密连锁的抗CYR31基因.