Probing Behavior Research Articles

Nutrient supply patterns across the Sandhill Fen reclamation watershed and regional reference fens in Alberta, Canada: An ion exchange membrane study

AbstractUsing Plant Root Simulator (PRS®) probes, we evaluate nutrient supply rates at the Sandhill Fen reclamation watershed across a gradient of increasing water table position and compare observations with three reference fens (a poor, moderate‐rich, and saline fen). Our objectives were threefold: (a) determine the behavior of PRS probes across multiple peatland classes, (b) determine which type of peatland Sandhill Fen is most analogous to in terms of nutrient supply patterns and site chemistry, and (c) attempt to provide a repeatable approach for assessing nutrient supply in peatlands. In terms of porewater chemistry, conditions at Sandhill Fen were quite unique, yet, most comparable to the saline fen. Consistent with porewater analysis, PRS probes had low nitrate supply at all sites, high calcium and magnesium supply at all sites (except the poor fen), and much higher sulfur supply at Sandhill Fen. Site differences in PRS probe measurements were smaller for 20‐ than 2‐day burial periods due to displacement of less strongly held elements (e.g., potassium) on ion exchange membranes. Because long‐term incubations may underrepresent supply rates for weakly held ions due to displacement by divalent ions, we recommend that reclamation assessments over a wide range of fen types should use a relatively short burial period of 1 to 3 days. With few exceptions (sulfate and iron), nutrient supply patterns at Sandhill Fen were quite comparable to the reference fens. For future wetland reclamation performance assessments in the AOSR, PRS probes could serve an important role for evaluating belowground functional components.

Studying Proton Gradients Across the Nuclear Envelope.

The existence of nuclear pore complexes in the nuclear envelope has led to the assumption that ions move freely from the cytosol into the nucleus, and that the molecular mechanisms at the plasma membrane that regulate cytosolic pH also regulate nuclear pH. Furthermore, studies to measure pH in the nucleus have produced contradictory results, since it has been found that the nuclear pH is either similar to the cytosol or more alkaline than the cytosol. However, most studies of nuclear pH have lacked the rigor needed to understand pH regulation in the nucleus. A major problem has been the lack of in situ titrations in the nucleus and cytosol, since the intracellular environment is different in the cytosol and nucleus and the behavior of fluorescent pH probes is different in these environments. Here we present a method that uses the fluorescence of SNARF-1 that labels both cytosol and nucleus. Using ratio imaging microscopy, regions of interest corresponding to the nucleus and cytosol to perform steady-state pH measurements followed by in situ titrations, tocorrectly assign pH in those cellular domains.

Correlation of Leaf Parameters with Incidence of Papaya Ring Spot Virus in Cultivated Papaya and its Wild Relatives

Papaya ring spot virus (PRSV) disease has been the major impediment in papaya cultivation. The disease is transmitted through three aphid vectors and field tolerance towards this disease varies among Carica papaya cultivars as well as within the Vasconcellea genus. Leaf morphological traits are known to have influence on the probing preferences of aphids. Hence, this study was conducted to know whether the leaf parameters could contribute to the incidence of PRSV possibly by influencing the probing or feeding behaviour of aphid vectors. Leaf parameters viz., leaf thickness, leaf epicuticular wax content, presence and type of trichomes, trichome density were correlated with disease incidence at field conditions. The result revealed that leaf thickness along with epicuticular wax content had significant negative correlation with disease incidence. Similarly, trichome density had negative impact on disease incidence at 99.92% significance level. High epicuticular wax content and high trichome density in V. cauliflora and V. cundinamarcensis were found to be negatively associated with low to very low infection indicating that these parameters may have limited the vector transmission significantly.

Correlation of Leaf Parameters with Incidence of Papaya Ring Spot Virus in Cultivated Papaya and its Wild Relatives

Papaya ring spot virus (PRSV) disease has been the major impediment in papaya cultivation. The disease is transmitted through three aphid vectors and field tolerance towards this disease varies among Carica papaya cultivars as well as within the Vasconcellea genus. Leaf morphological traits are known to have influence on the probing preferences of aphids. Hence, this study was conducted to know whether the leaf parameters could contribute to the incidence of PRSV possibly by influencing the probing or feeding behaviour of aphid vectors. Leaf parameters viz., leaf thickness, leaf epicuticular wax content, presence and type of trichomes, trichome density were correlated with disease incidence at field conditions. The result revealed that leaf thickness along with epicuticular wax content had significant negative correlation with disease incidence. Similarly, trichome density had negative impact on disease incidence at 99.92% significance level. High epicuticular wax content and high trichome density in V. cauliflora and V. cundinamarcensis were found to be negatively associated with low to very low infection indicating that these parameters may have limited the vector transmission significantly.

Study of prototropic reactions of indole chalcone derivatives in ground and excited states using absorption and fluorescence spectroscopy

The prototropic behavior of biologically active intramolecular charge transfer (ICT) probes namely, indole chalcone (IC) derivatives in aqueous media of Ho/pH/H_ from −3.03 to 17.95, was studied using absorption and steady-state fluorescence spectroscopy. This study reveals the presence of monocation (MC), neutral (N) and monoanion (MA) prototropic species in ground and excited states. Prototropic equilibrium between the ionic species is found to be dependent on the nature of substituents. These molecules show the formation of MC via protonation of the carbonyl oxygen atom, conversely a predictable deprotonation takes place from the >NH group of indole ring to form the MA in the ground (S0) and the first excited singlet states (S1). The presence of OH and NH2 group enhances the prototropic behavior of these ICT probes leading to the formation of dianion species (DA). The highest occupied molecular orbitals (HOMO), lowest unoccupied molecular orbitals (LUMO) and molecular electrostatic potential (MEP) surfaces were generated from the optimized geometries of IC derivatives obtained using Density Functional Theory (DFT) calculations with restricted hybrid functional B3LYP using 6-31G (d) basis set to account for ICT. The MEP surfaces also show the possible protonation and deportation sites in these molecules. The dissociation constants, pKa and pKa⁎, for all the prototropic equilibria were determined in S0 and S1 states, respectively using different methods such as Henderson-Hasselbalch (HH), Photometric Titration (PT), Fluorimetric Titration (FT) and Förster Cycle (FC). For MC ⇌ N equilibrium, the excited state pKa⁎ values are found to be greater than the ground state pKa values, which suggests a more basic nature of these molecules in the excited state.

The Power of Electropenetrography in Enhancing Our Understanding of Host Plant-Vector Interactions.

The invasive Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae), is the primary vector of the phloem-infecting bacterium, Candidatus Liberibacter asiaticus. Candidatus L. asiaticus is the putative causal agent of Huanglongbing (HLB) disease, a destructive disease of Citrus. While many Citrus species are susceptible to D. citri probing and HLB disease, there are marked behavioral differences in D. citri probing responses and Ca. Liberibacter asiaticus infection severity among Citrus species. Using four mandarin hybrid selections and pummelo plants variably resistant to D. citri probing, oviposition, and survival, we explored probing differences using electropenetrography (EPG), conducted an oviposition and survival study, and determined host plant metabolites using gas-chromatography mass-spectroscopy (GC-MS). We found thirty-seven D. citri probing variables to be significantly different among tested mandarin selections and pummelo, in addition to differential oviposition and survivorship abilities on tested plants. We found sixty-three leaf metabolites with eight being significantly different among tested mandarin selections and pummelo. Detailed analysis of probing behavior, oviposition, survivorship, and host plant metabolite concentrations reveals the complex, layered resistance mechanisms utilized by resistant Citrus against D. citri probing. EPG is a powerful technology for screening Asian citrus psyllid resistant Citrus to elucidate host plant-vector interactions, with an aim to minimize vector probing and eliminate the spread of the bacterial pathogen, Ca. L. asiaticus.

Waveforms From Stylet Probing of the Mosquito Aedes aegypti (Diptera: Culicidae) Measured by AC–DC Electropenetrography

Electropenetrography (EPG) has been used for many years to visualize unseen stylet probing behaviors of plant-feeding piercing-sucking insects, primarily hemipterans. Yet, EPG has not been extensively used with blood-feeding insects. In this study, an AC-DC electropenetrograph with variable input resistors (Ri), i.e., amplifier sensitivities, was used to construct a waveform library for the mosquito arbovirus vector, Aedes aegypti (Linneaus), while feeding on human hands. EPG waveforms representing feeding activities were: 1) electrically characterized, 2) defined by visual observation of biological activities, 3) analyzed for differences in appearance by Ri level and type of applied signal (AC or DC), and 4) quantified. Electrical origins of waveforms were identified from five different Ri levels and AC versus DC. Mosquitoes produced short stylet probes ('bites') that typically contained five waveform families. Behaviors occurred in the following order: surface salivation (waveform family J), stylet penetration through the outer skin (K), penetration of deeper tissues and location of blood vessels/pathway activities (L), active ingestion with engorgement (M), and an unknown behavior that terminated the probe (N). Only K, L, and M were performed by every insect. A kinetogram of conditional probabilities for waveform performance demonstrated plasticity among individuals in L and M, which were alternated. Now that EPG waveforms for mosquito feeding have been defined, EPG can be used as a tool for improved biological understanding of mosquito-borne diseases.

Differential gene expression during substrate probing in larvae of the Caribbean coral Porites astreoides.

The transition from larva to adult is a critical step in the life history strategy of most marine animals. However, the genetic basis of this life history change remains poorly understood in many taxa, including most coral species. Recent evidence suggests that coral planula larvae undergo significant changes at the physiological and molecular levels throughout the development. To investigate this, we characterized differential gene expression (DGE) during the transition from planula to adult polyp in the abundant Caribbean reef‐building coral Porites astreoides, that is from nonprobing to actively substrate‐probing larva, a stage required for colony initiation. This period is crucial for the coral, because it demonstrates preparedness to locate appropriate substrata for settlement based on vital environmental cues. Through RNA‐Seq, we identified 860 differentially expressed holobiont genes between probing and nonprobing larvae (p ≤ .01), the majority of which were upregulated in probing larvae. Surprisingly, differentially expressed genes of endosymbiotic dinoflagellate origin greatly outnumbered coral genes, compared with a nearly 1:1 ratio of coral‐to‐dinoflagellate gene representation in the holobiont transcriptome. This unanticipated result suggests that dinoflagellate endosymbionts may play a significant role in the transition from nonprobing to probing behaviour in dinoflagellate‐rich larvae. Putative holobiont genes were largely involved in protein and nucleotide binding, metabolism and transport. Genes were also linked to environmental sensing and response and integral signalling pathways. Our results thus provide detailed insight into molecular changes prior to larval settlement and highlight the complex physiological and biochemical changes that occur in early transition stages from pelagic to benthic stages in corals, and perhaps more importantly, in their endosymbionts.

Novel Amino-pillar[5]arene as a Fluorescent Probe for Highly Selective Detection of Au3+ Ions.

A novel fluorescent probe, amino-pillar[5]arene (APA), was prepared via a green, effective, and convenient synthetic method, which was characterized by nuclear magnetic resonance (NMR), infrared (IR), and high-resolution mass spectrometry. The fluorescence sensing behavior of the APA probe toward 22 metal ions in aqueous solutions were studied by fluorescence spectroscopy. The results showed that APA could be used as a selective fluorescent probe for the specificity detection of Au3+ ions. Moreover, the detection characteristics were investigated by fluorescence spectral titration, pH effect, fluorescence competitive experiments, Job’s plot analysis, 1H NMR, and IR. The results indicated that detection of Au3+ ions by the APA probe could be achieved in the range of pH 1–13.5 and that other coexisting metal ions did not cause any marked interference. The titration analysis results indicated that the fluorescence intensity decreased as the concentration of Au3+ ions increased, with an excellent correlation (R2 = 0.9942). The detection limit was as low as 7.59 × 10–8 mol·L–1, and the binding ratio of the APA probe with Au3+ ions was 2:1. Therefore, the APA probe has potential applications for detecting Au3+ ions in the environment and in living organisms.

Linker length affects photostability of protein-targeted sensor of cellular microviscosity

Viscosity sensitive fluorophores termed ‘molecular rotors’ represent a convenient and quantitative tool for measuring intracellular viscosity via Fluorescence Lifetime Imaging Microscopy (FLIM). We compare the FLIM performance of two BODIPY-based molecular rotors bound to HaloTag protein expressed in different subcellular locations. While both rotors are able to penetrate live cells and specifically label the desired intracellular location, we found that the rotor with a longer HaloTag protein recognition motif was significantly affected by photo-induced damage when bound to the HaloTag protein, while the other dye showed no changes upon irradiation. Molecular dynamics modelling indicates that the irradiation-induced electron transfer between the BODIPY moiety and the HaloTag protein is a plausible explanation for these photostability issues. Our results demonstrate that binding to the targeted protein may significantly alter the photophysical behaviour of a fluorescent probe and therefore its thorough characterisation in the protein bound form is essential prior to any in vitro and in cellulo applications.

Brief insight into the behavior, activity, and interspecific interactions of urban Trimeresurus (Cryptelytrops) albolabris (Reptilia: Squamata: Viperidae) vipers in Bangkok, Thailand

Green Pit Vipers are a widely distributed, diverse group of snakes which occur across a variety of habitats. Little is known about their natural history in anthropogenically modified environments, and no ecological work has investigated their persistence in cities. We non-invasively photo-monitored White-lipped Green Pit Vipers Trimeresurus (Cryptelytrops) albolabris in the metropolis of Bangkok, Thailand (n = 4 individuals, mean = 2,658 minutes per individual). Subsequently, we preliminarily characterize urban green pit vipers as nocturnal predators, displaying ambush-foraging at night, sheltering during the day, and having limited movement in between temporal periods. We recorded two predation events of vipers capturing and ingesting anuran prey. Vipers infrequently displayed tail undulations (239 minutes total), with one event occurring immediately before a predation event. We also document chemosensory, probing, and mouth-gaping behaviors having occurred exclusively at night. Other vertebrates including birds, frogs, geckos, small mammals, and a cobra were photographed interacting with focal vipers or their immediate surroundings (315 minutes total). Knowledge of organisms in tropical urban environments is scarce, and the persistence of venomous snakes in these unique and challenging habitats requires further study.

Location of TEMPO-PC in Lipid Bilayers: Implications for Fluorescence Quenching.

The characterization of the behavior of lipid-attached spin probes in a bilayer is of fundamental importance for correct interpretation of the results of both EPR and fluorescence studies of protein-membrane interactions. The knowledge of the immersion depth of TEMPO spin probe attached to lipid headgroup in TEMPO-PC is critical for the determination of the transverse location of fluorescence probes attached to proteins and peptides. The question of bilayer penetration of TEMPO moiety in TEMPO-PC has recently came into prominence in two studies of interfacial solvation (Cheng et al. in Biophys J 109:330-339, 2015; Lee et al. in Biophys J 111:2481-2491, 2016). Here, we re-examine the arguments on TEMPO penetration using the cross-validation of MD simulations and depth-dependent fluorescence-quenching experiments, which confirms that TEMPO in TEMPO-PC penetrates below the level of phosphate groups. The proper analysis of fluorescence quenching requires the use of Tempo position below the level of phosphate groups; and failure to do so will result in substantial systematic errors in determining the penetration of the labeled site on a membrane protein.

Solvatochromic Absorbance and Fluorescence Probe Behavior within Ionic Liquid + γ-Butyrolactone Mixture

The co-solvent modified ionic liquid (IL) systems offer favorable physicochemical properties, which render them as suitable solvents for several technological applications. Therefore, it is an utmost need to achieve a full understanding of such systems before their further applications. Here, solvation properties of 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim][BF4], and γ-butyrolactone (GBL) mixture, which is an important binary mixture for several electrochemical applications, are explored by multiprobe spectroscopic and theoretical studies. The Reichardt polarity parameter (ETN) and Kamlet–Taft parameter (α, β, and π*) are determined with several absorbance probes. The unusual synergism in the probe’s response is observed within the [bmim][BF4] and γ-butyrolactone (GBL) mixture. Such type of anomalous behavior is also observed in the response of the following fluorescence probes: 8-anilino-1-naphthalene sulfonate (ANS), 6-propionyl-2-(dimethylamino)naphthalene (PRODAN), and pyrene (Py). This un...

Improving the Consistency of Nanoscale Etching for Atomic Force Microscopy Tomography Applications

The atomic force microscope empowers research into nanoscale structural and functional material properties. Recently, the scope of application has broadened with the arrival of conductance tomography, a technique for mapping current in three-dimensions in electronic devices by gradually removing sample material with the scanning probe. This technique has been valuable in studying resistance switching memories and solar cells, although its broader use has been hindered by a lack of understanding of its reliability and practicality. Implementation can be preclusive, owing to difficulties in characterizing tip-sample interactions and accounting for probe degradation, both of which are crucial factors in process efficacy. This work follows the existing conductance tomography literature, presenting an insight into the repeatability and reliability of the material removal processes. The consistency of processes on a hard oxide and a softer metal are investigated, to understand the critical differences in etching behavior that might affect tomography measurements on heterostructures. Individual probe behavior stabilizes following a wearing-in stage and etching processes are consistent between probes, in particular on oxide. However, process inconsistency increases with applied force on metal. The effects of scan angle, tip speed and feedback gain are therefore explored and their tuning found to improve the spatial consistency of material removal. With these findings, we aim to present a critical study of the implementation of tomography with the atomic force microscope in order to contribute to its methodological development.

Membrane Localization and Lipid Interactions of Common Lipid-Conjugated Fluorescence Probes.

Lateral segregation of lipids in model and biological membranes has been studied intensively in the last decades using a comprehensive set of experimental techniques. Most methods require a probe to report on the biophysical properties of a specific molecule in the lipid bilayer. Because such probes can adversely affect the results of the measurement and perturb the local membrane structure and dynamics, a detailed understanding of probe behavior and its influence on the properties of its direct environment is important. Membrane phase-selective and lipid-mimicking molecules represent common types of probes. Here, we have studied how the fluorescent probes trans-parinaric acid (tPA), diphenylhexatriene (DPH), and 1-oleoyl-2-propionyl[DPH]-sn-glycero-3-phosphocholine (O-DPH-PC) affect the membrane properties of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) bilayers using 2H and 31P NMR spectroscopy in the solid state. In addition, using 2D 1H magic-angle spinning (MAS) nuclear Overhauser enhancement spectroscopy (NOESY) NMR, we have determined the distribution of the probe moieties in the POPC membrane parallel to the membrane normal. We found that the different probes exhibit distinct membrane localizations and distributions, e.g. tPA is located parallel to the membrane normal while DPH predominantly exist in two orientations. Further, tPA was conjugated to sphingomyelin (tPA-SM) as a substitute for the acyl chain in the SM. 1H NOESY NMR was used to probe the interaction of the tPA-SM with cholesterol as dominant in liquid ordered membrane domains in comparison to POPC-cholesterol interaction in membranes composed of ternary lipid mixtures. We could show that tPA-SM exhibited a strong favorable and very temperature-dependent interaction with cholesterol in comparison to POPC. In conclusion, the NMR techniques can explain probe behavior but also be used to measure lipid-specific affinities between different lipid segments and individual molecules in complex bilayers, relevant to understanding nanodomain formation in biological membranes.

Chronopotentiometry as a Sensitive Interfacial Characterisation Tool for Peptide Aptamer Monolayers

AbstractConstant current chronopotentiometry is employed in conjunction with cyclic voltammetry and ac voltammetry to present in‐depth interfacial characterisations of the adsorption behaviour of a peptide affinity probe (Cys‐p53), of a thiolated hepta(ethylene glycol) (t‐OEG) and of mixed monolayers of these at mercury electrodes. The peptide sequence is derived from the interaction site of the protein p53 with the protein Mdm2. The adsorbed Cys‐p53 peptide is catalytically active towards the hydrogen evolution reaction, giving rise to very intense peaks in chronopotentiometry, whereas the oligo(ethylene glycol) is not. This difference enables one to monitor the presence of the peptide within mixed monolayers. It is shown that in the binary layers, the adsorption of t‐OEG is kinetically favoured while Cys‐p53 is thermodynamically more strongly adsorbed.

Effects of biochar amendment to soils on stylet penetration activities by aphid Sitobion avenae and planthopper Laodelphax striatellus on their host plants.

To understand why biochar amendment to soils has a negative effect on sap-feeding insects on their host plants, we used the electrical penetration graph (EPG) technique to examine probing and feeding behaviors of the English grain aphid Sitobion avenae on wheat and the small brown planthopper Laodelphax striatellus on rice; their food plants were cultured in soils receiving different treatments of biochar type (derived from three different types of feedstock: wheat, corn or rice straw) by amendment rate (four levels: 0, 1.5%, 3%, or 5%). In addition, we analyzed the contents of key nutrients in the wheat plant to explore their relevance to aphid feeding activities. Biochar amendment to soils increased the number of events and duration of non-probing and probing-preparation activities while decreasing the duration of stylet penetrations in the phloem sieve by both S. avenae and L. striatellus. The effect varied depending on the biochar amendment rate in S. avenae and on both biochar type and amendment rate in L. striatellus. Biochar amendment decreased the content of sucking stimulatory nitrogen and increased that of sucking inhibitory silicon and potassium in wheat plants; this effect varied with biochar amendment rate and not with biochar type. Biochar amendment can make stylet penetration activities less effective by S. avenae and L. striatellus on their host plants. Ineffective penetration may result from the alteration in the contents of penetration-relevant nutrients in the host plant as a consequence of biochar amendment to soils. © 2019 Society of Chemical Industry.

Developing an RGB - Arduino device for the multi-color recognition, detection and determination of Fe(III), Co(II), Hg(II) and Sn(II) in aqueous media by a terpyridine moiety

A multi cation sensor based on a terpyridine moiety was successfully designed and synthesized. The sensing behavior of the developed probe was monitored via colorimetric and fluorimetric methods using UV–vis and a fluorescence spectral technique. Each metal ion (Fe3+, Co2+, Hg2+, and Sn2+) exhibited a different color, indicating the high selectivity of the developed probe. A hydrogel sensor, prepared for practical utility, displayed the same colors for each ion as the visual detection experiment. Furthermore, an RGB-Arduino multiple chemosensor detecting system was developed to measure the presence of ions such as Fe3+, Co2+, Hg2+, and Sn2+.

Resonance-Size Parameter Relationship and Dynamics of an AFM Subjected to Multimode Excitation and Based on the Modified Couple Stress Theory

The mathematical model of AFM probe subjected to multimode excitation based on the modified couple stress theory is presented. The semianalytical solution of the system is proposed. The transient behavior and response spectrum of AFM probe subjected to multimode excitation are investigated. It is very helpful to predict the nanotopography and surface properties based on the response of multimodes excitation. The effects of the root excitation, size parameter, and interacting distance on the response spectrum and frequency shift are investigated. The resonant frequency relation of the two systems with different size parameters is discovered and expressed in a formula. The natural frequencies predicted via the formula and those determined by the semianalytical method are significantly consistent.

Oxidative stress links response to lead and Acyrthosiphon pisum in Pisum sativum L.

This study demonstrates the impact of lead at hormetic (0.075 mM Pb(NO3)2) and sublethal (0.5 mM Pb(NO3)2) doses on the intensity of oxidative stress in pea seedlings (Pisum sativum L. cv. ‘Cysterski’). Our first objective was to determine how exposure of pea seedlings to Pb alters the plant defence responses to pea aphid (Acyrthosiphon pisum Harris), and whether these responses could indirectly affect A. pisum. The second objective was to investigate the effects of various Pb concentrations in the medium on demographic parameters of pea aphid population and the process of its feeding on edible pea. We found that the dose of Pb sublethal for pea seedlings strongly reduced net reproductive rate and limited the number of A. pisum individuals reaching the phloem. An important defence line of pea seedlings growing on Pb-supplemented medium and next during combinatory effect of the two stressors Pb and A. pisum was a high generation of superoxide anion (O2−). This was accompanied by a considerable reduction in superoxide dismutase (SOD) activity, and a decrease in the level of Mn2+ ions. A the same time, weak activity of Mn-SOD was detected in the roots of the seedlings exposed to the sublethal dose of Pb and during Pb and aphid interaction. Apart from the marked increase in O2−, an increase in semiquinone radicals occurred, especially in the roots of the seedlings treated with the sublethal dose of Pb and both infested and non-infested with aphids. Also, hydrogen peroxide (H2O2) generation markedly intensified in aphid-infested leaves. It reached the highest level 24 h post infestation (hpi), mainly in the cell wall of leaf epidermis. This may be related to the function of H2O2 as a signalling molecule that triggers defence mechanisms. The activity of peroxidase (POX), an important enzyme involved in scavenging H2O2, was also high at 24 hpi and at subsequent time points. Moreover, the contents of thiobarbituric acid reactive substances (TBARS), products of lipid peroxidation, rose but to a small degree thanks to an efficient antioxidant system. Total antioxidant capacity (TAC) dependent on the pool of fast antioxidants, both in infested and non-infested and leaves was higher than in the control. In conclusion, the reaction of pea seedlings to low and sublethal doses of Pb and then A. pisum infestation differed substantially and depended on a direct contact of the stress factor with the organ (Pb with roots and A. pisum with leaves). The probing behavior of A. pisum also depended on Pb concentration in the plant tissues.