Foliar Uptake Research Articles

Uptake of atmospherically deposited cadmium by leaves of vegetables: Subcellular localization by NanoSIMS and potential risks

Atmospherically deposited cadmium (Cd) may accumulate in plants through foliar uptake; however, the foliar uptake, accumulation, and distribution processes of Cd are still under discussion. Atmospherically deposited Cd was simulated using cadmium sulfide (CdS) with various particle sizes and solubility. Water spinach (Ipomoea aquatica Forsk, WS) and pak choi (Brassica chinensis L., PC) leaves were treated with suspensions of CdS nanoparticles (CdSN), which entered the leaves via the stomata. Cd concentrations of WS and PC leaves treated with 125 mg L−1 CdSN reached up to 39.8 and 11.0 mg kg−1, respectively, which are higher than the critical leaf concentration for toxicity. Slight changes were observed in fresh biomass, photosynthetic parameters, lipid peroxidation, and mineral nutrient uptake. Exposure concentration, rather than particle size or solubility, regulated the foliar uptake and accumulation of Cd. Subcellular and the high-resolution secondary ion mass spectrometry (NanoSIMS) results revealed that Cd was majorly stored in the soluble fraction and cell walls, which is an important Cd detoxification mechanism in leaves. The potential health risks associated with consuming CdS-containing vegetables were highlighted. These findings facilitate a better understanding of the fate of atmospheric Cd in plants, which is critical in ensuring food security.

Screening of Leafy Vegetable Varieties with Low Lead and Cadmium Accumulation Based on Foliar Uptake.

Leafy vegetables cultivated in kitchen gardens and suburban areas often accumulate excessive amounts of heavy metals and pose a threat to human health. For this reason, plenty of studies have focused on low accumulation variety screening. However, identifying specific leafy vegetable varieties according to the foliar uptake of air pollution remains to be explored (despite foliar uptake being an important pathway for heavy-metal accumulation). Therefore, in this study, the lead (Pb) and cadmium (Cd) contents, leaf morphology, and particle matter contents were analyzed in a micro-area experiment using 20 common vegetables. The results show that the Pb content in leaves ranged from 0.70 to 3.86 mg kg−1, and the Cd content ranged from 0.21 to 0.99 mg kg−1. Atmospheric particles were clearly scattered on the leaf surface, and the particles were smaller than the stomata. Considering the Pb and Cd contents in the leaves and roots, stomata width-to-length ratio, leaf area size, enrichment factor, and translocation factor, Yidianhongxiancai, Qingxiancai, Baiyuanyexiancai, Nanjingjiangengbai and Sijixiaobaicai were recommended for planting in kitchen gardens and suburban areas as they have low accumulation characteristics. Identifying the influencing factors in the accumulation of heavy metals in vegetables through foliar uptake is important to help plant physiologists/environmentalists/policy makers to select suitable varieties for planting in air-polluted areas and thus reduce their threat to human health.

Foliar water uptake in the needles of Pinus torreyana

The natural habitat of Pinus torreyana, the Torrey pine, is restricted to two locales in coastal Southern California that experience substantial fog and low clouds during the dry months of a Mediterranean climate. In similar semi-arid climate systems that encounter fog or low clouds, many plants can capture atmospheric moisture and are capable of direct foliar water uptake to reduce water stress. In this study, we investigated if the needles of P. torreyana are also capable of direct water uptake. In addition to water immersion, we measured the surface properties along a needle using microdroplets. The droplet contact angle is a measure of surface wettability, and the droplet absorption is a measure of localized foliar water uptake. The results showed that the entire length of the P. torreyana needle, including under the base sheath, is hydrophilic and capable of direct water uptake. The spatial gradients of the wettability and the water uptake along the needle are relatively small. Moreover, the wettability and water uptake increase from young shoots to one-year and two-year old needles. Our results also showed that the decrease in water uptake at higher contact angles can be described by a linear regression. Compared with the leaves of four shrubs in the same habitat, Heteromeles arbutifolia, Malosma laurina, Rhus integrifolia, and Eriodictyon crassifolium, the P. torreyana needles have lower contact angles and higher water uptake rates.

Environmental fate studies with 14C-polyoxyethylene tallow amine (POE-T) to characterize environmental exposure and inform environmental risk assessments

Polyoxyethylene tallow amine (POE-T) is a member of the polyoxyethylene alkylamine (POEA) class of nonionic surfactants and is a component of some glyphosate-based formulations. The presence of POE-T improves foliar uptake of glyphosate in weeds, thereby reducing the amount of glyphosate needed for weed control. To further characterize the environmental fate of POE-T, aerobic soil degradation, hydrolysis, adsorption/desorption, and aerobic aquatic degradation studies were conducted according to U.S. EPA and OECD pesticide regulatory testing guidelines. POE-T labeled with carbon-14 was used in the studies to aid in analysis, assess mineralization to CO2, and allow for mass balance determinations. The aerobic soil half-lives (DT50) for POE-T ranged from 20 to 166 days with DT50 values increasing with increasing soil percent organic carbon (OC). POE-T was hydrolytically stable at pH 4–9. POE-T adsorbed strongly to soil (KFocads = 17,600–114,000) with sorption generally increasing as soil percent OC increased. The aerobic aquatic (water-sediment) system DT50s for POE-T were 14–29 days, with POE-T dissipating from the water column with DT50s of 0.10–0.12 days through metabolism and adsorption to sediment. Based on these results, aquatic organisms are unlikely to be exposed to POE -T in the water column for more than a few hours following waterborne exposure and sediment is a significant sink for POE-T in aquatic systems. However, bioavailability of POE-T in sediment and soil is predicted to be low based on strong adsorption and it is not readily desorbed.

Alcohol Ethoxylates Enhancing the Cuticular Uptake of Lipophilic Epoxiconazole Do Not Increase the Rates of Cuticular Transpiration of Leaf and Fruit Cuticles.

Surfactants are known to enhance the foliar uptake of agrochemicals by plasticizing the transport-limiting barrier of plant cuticles. The effects of two different polydisperse alcohol ethoxylates with a low degree [mean ethoxylation of 5 ethylene oxide units (EOs)] and a high degree (mean ethoxylation of 10 EOs) of ethoxylation on cuticular barrier properties were investigated. The diffusion of the lipophilic organic molecule 14C-epoxiconazole and of polar 3H-water across cuticles isolated from six different plant species was investigated. At low surfactant coverages (10 μg cm-2), the diffusion of water across the cuticles was not affected by the two surfactants. Only at very high surfactant coverages (100-1000 μg cm-2) was the diffusion of water enhanced by the two surfactants between 5- and 50-fold. Unlike that of water, the diffusion of epoxiconazole was significantly enhanced 12-fold at surfactant coverages of 10 and 100 μg cm2 by the surfactant with low ethoxylation (5 EOs), and it decreased to 6-fold at a surfactant coverage of 1000 μg cm-2. The alcohol ethoxylate with a high degree of ethoxylation (10 EOs) only weakly increased the epoxiconazole diffusion. Our results clearly indicate that those surfactants that significantly enhance the uptake of the lipophilic agrochemicals (e.g., epoxiconazole) at a realistic leaf surface coverage of 10 μg cm-2, as is applied in the field, do not interfere with cuticular transpiration as an unwanted negative side effect.

Foliar Uptake of Toxic Metals Bound to Airborne Particulate Matter in an Urban Environment

In this research, the foliar uptake patterns of three toxic metals (Pb, Cd, and Cu) bound to airborne particulate matter (PM) were investigated using two evergreen tree species (Senna siamea and Alstonia scholaris) at six different locations (two residential, traffic, commercial, and industrial) plus one control site in a subtropical urban environment. The concentrations of Pb, Cd, and Cu were measured from foliar dust, leaf, road dust, and soil samples collected from the target sites over two consecutive years. Their temporal variations in leaves were examined at monthly, seasonal, and annual scales. The data were evaluated statistically by One-way Analysis of variance ANOVA and correlation analysis along with enrichment factor (EF). There were significant variations on the monthly as well as the seasonal basis. Accordingly, PM-bound toxic metals in leaves come from an airborne route. In addition, leaves of S. siamea showed a moderately improved accumulation pattern relative to A. scholaris. This study suggests that these plants can be used efficiently as basic tools to assess the pollution and associated behavior of PM-bound toxic metals in an urban environment.

Impact of glyphosate formulations and adjuvants: effects on leaf interaction, metabolism, and control of sourgrass

ABSTRACT: The addition of commercial formulations and adjuvants to a tank mix may result in differences in the wettability on the plant surface, foliar uptake and herbicide efficacy. Thus, the objectives of this study were to evaluate the influence of glyphosate formulations and tank-mixture adjuvants on the contact angle (CA), uptake, metabolism and sourgrass control and the damage to the cuticular microstructure of this species caused by herbicide solutions. For this purpose, assays were carried out in a completely randomized design, and treatments distributed in a 2x5+1 factorial scheme with five replications. Two glyphosate formulations isopropylamine salt (SL) and ammonium salt (WG) combined or not with the adjuvant methylated soybean oil (MSO), mineral oil (MO), ethoxylated alkyl ester (EAE) or polyoxyethylenealkylphenol ether (PAE); and one control (water) were evaluated. CA measurements of the droplets deposited on a sourgrass leaf surface and on the standard surface (parafilm) were obtained using a tensiometer. Herbicide uptake and shikimate accumulation were simultaneously determined by chromatography and spectrometry. The control effect was assessed by observing plant survival dry weight reductions. The glyphosate SL and WG formulations had similar effects on the variables analyzed. However, mixing the adjuvants EAE, MO or MSO with either formulation of herbicide led to greater wettability and more severe damage to the cuticular microstructure, favoring glyphosate uptake and shikimate accumulation. Despite evidence regarding the treatments containing oils/surfactants, the control effect on sourgrass was similar. The combination of glyphosate formulations with such adjuvants is potentially more effective and guarantees satisfactory sourgrass control.

Synergetic effects of tank-mix additives on the foliar uptake of Ca2+ and biological activity of Cu2+ against Venturia inaequalis and Podosphaera leucotricha

Synergetic effects of tank-mix additives on the foliar uptake of Ca2+ and biological activity of Cu2+ against Venturia inaequalis and Podosphaera leucotricha

Influence of posttreatment irrigation timings and herbicide placement on bermudagrass and goosegrass (Eleusine indica) response to low-dose topramezone and metribuzin programs

AbstractImmediate posttreatment irrigation has been proposed as a method to reduce hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] phytotoxicity from topramezone. Immediate irrigation is impractical, because it would take a turfgrass sprayer 10 to 15 min to cover an average golf course fairway or athletic field. There is also insufficient evidence regarding how posttreatment irrigation, immediate or otherwise, influences mature goosegrass [Eleusine indica (L.) Gaertn.] control from topramezone or low-dose topramezone plus metribuzin programs. We sought to investigate bermudagrass and E. indica response to immediate, 15-min, and 30-min posttreatment irrigation compared with no irrigation following topramezone at 12.3 g ae ha−1, the lowest labeled rate, or topramezone at 6.1 g ha−1 plus metribuzin at 210 g ai ha−1. We also evaluated placement of each herbicide and their combination on soil, foliage, and soil plus foliage to help elucidate the mechanisms involved in differential responses between species and herbicide mixtures. Responses were largely dependent on trial due to bermudagrass injury from high-dose topramezone being nearly eliminated by immediate irrigation in one trial and only slightly affected in another. When posttreatment irrigation was postponed for 15 or 30 min, topramezone alone injured bermudagrass unacceptably in both trials. Bermudagrass was injured less by low-dose topramezone plus metribuzin than by high-dose topramezone. All posttreatment irrigation timings reduced E. indica control compared with no posttreatment irrigation. The herbicide placement study suggested that topramezone control of E. indica is highly dependent on foliar uptake and that phytotoxicity of both bermudagrass and E. indica is greater from topramezone than metribuzin. Thus, posttreatment irrigation likely reduces topramezone rate load with a concomitant effect on plant phytotoxicity of both species. Metribuzin reduced 21-d cumulative clipping weight and tiller production of plants, and this may be a mechanism by which it reduces foliar white discoloration from topramezone.

Study on effects of airborne Pb pollution on quality indicators and accumulation in tea plants using Vis-NIR spectroscopy coupled with radial basis function neural network

Tea plants that have a large leaf area mainly suffer from heavy metal accumulation in the above-ground parts through foliar uptake. With the world rapid industrialization, this pollution in tea is considered a crucial challenge due to its potential health risks. The present study proposes an innovative approach based on visible and near-infrared (Vis-NIR) spectroscopy coupled with chemometrics for the characterization of tea chemical indicators under airborne lead stress, which can be performed fast and in situ. The effects of lead stress on chemical indicators and accumulation in leaves of the two tea varieties at different time intervals and levels of treatment were investigated. In addition, changes in cell structure and leaf stomata were monitored during foliar uptake of aerosol particles by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The spectral variation was able to classify the tea samples into the Pb treatment groups through the linear discriminant analysis (LDA) model. Two machine learning techniques, namely, partial least squares (PLS) and radial basis function neural network (RBFNN), were evaluated and compared for building the quantitative determination models. The RBFNN models combined with correlation-based feature selection (CFS) and PLS data compression methods were used to optimize the prediction performance. The results demonstrated that the PLS–RBFNN as a non-linear model outperformed the PLS model and provided the R-value of 0.944, 0.952, 0.881, 0.937, and 0.930 for prediction of MDA, starch, sucrose, fructose, glucose, respectively. It can be concluded that the proposed approach has strong application potential in monitoring the quality and safety of plants under airborne heavy metal stress.

Mechanism of Pb accumulation in Chinese cabbage leaves: Stomata and trichomes regulate foliar uptake of Pb in atmospheric PM2.5

Chinese cabbage (Brassica rapa ssp. pekinensis) is one of the most popular and frequently consumed leafy vegetables. It was found that atmospheric PM2.5-Pb contributes to Pb accumulation in the edible leaves of Chinese cabbage via stomata in North China during haze seasons with high concentrations of fine particulate matter in autumn and winter. However, it is unclear whether both stomata and trichomes co-regulate foliar transfer of PM2.5-Pb from atmospheric deposition to the leaf of Chinese cabbage genotypes with trichomes. Field and hydroponic experiments were conducted to investigate the effects of foliar uptake of PM2.5-Pb on Pb accumulation in leaves using two genotypes of Chinese cabbage, one without trichomes and one with trichomes. It was verified that open stoma is a prominent pathway of foliar PM2.5-Pb transfer in the short-term exposure for 6 h, contributing 74.5% of Pb accumulation in leaves, whereas Pb concentrations in the leaves of with-trichome genotype in the rosette stage were 6.52- and 1.04-fold higher than that of without-trichome genotype in greenhouse and open field, respectively, which suggests that stomata and trichomes co-regulate foliar Pb uptake of from atmospheric PM2.5. Moreover, subcellular Pb in the leaves was distributed in the following order of cytoplasm (53.8%) > cell wall (38.5%)> organelle (7.8%), as confirmed through high-resolution secondary ion mass spectrometry (NanoSIMS). The Leadmium™ Green AM dye manifested that Pb in PM2.5 entered cellular space of trichomes and accumulated in the basal compartment, enhancing foliar Pb uptake in the edible leaves of cabbage. The results of these experiments are evidence that both stomata and trichomes are important pathways in the regulation of foliar Pb uptake and translocation in Chinese cabbage.

Interaction of surfactants with barley leaf surfaces: time-dependent recovery of contact angles is due to foliar uptake of surfactants

Main conclusionTime-dependent contact angle measurements of pure water on barley leaf surfaces allow quantifying the kinetics of surfactant diffusion into the leaf.Barley leaf surfaces were sprayed with three different aqueous concentrations (0.1, 1.0 and 10%) of a monodisperse (tetraethylene glycol monododecyl ether) and a polydisperse alcohol ethoxylate (BrijL4). After 10 min, the surfactant solutions on the leaf surfaces were dry leading to surfactant coverages of 1, 10 and 63 µg cm−2, respectively. The highest surfactant coverage (63 µg cm−2) affected leaf physiology (photosynthesis and water loss) rapidly and irreversibly and leaves were dying within 2–6 h. These effects on leaf physiology did not occur with the lower surfactant coverages (1 and 10 µg cm−2). Directly after spraying of 0.1 and 1.0% surfactant solution and complete drying (10 min), leaf surfaces were fully wettable for pure water and contact angles were 0°. Within 60 min (0.1% surfactant) and 6 h (1.0% surfactant), leaf surfaces were non-wettable again and contact angles of pure water were identical to control leaves. Scanning electron microscopy investigations directly performed after surfactant spraying and drying indicated that leaf surface wax crystallites were partially or fully covered by surfactants. Wax platelets with unaltered microstructure were fully visible again within 2 to 6 h after treatment with 0.1% surfactant solutions. Gas chromatographic analysis showed that surfactant amounts on leaf surfaces continuously disappeared over time. Our results indicate that surfactants, applied at realistic coverages between 1 and 10 µg cm−2 to barley leaf surfaces, leading to total wetting (contact angles of 0°) of leaf surfaces, are rapidly taken up by the leaves. As a consequence, leaf surface non-wettability is fully reappearing. An irreversible damage of the leaf surface fine structure leading to enhanced wetting and increased foliar transpiration seems highly unlikely at low surfactant coverages of 1 µg cm−2.

Surface charge affects foliar uptake, transport and physiological effects of functionalized graphene quantum dots in plants

The present study focused on evaluating the effects of surface charge on foliar uptake, translocation and physiological response of graphene quantum dots (GQDs) in maize (Zea mays L.) plants. Here, maize seedlings were foliar exposed to 10 mg/L GQDs modified with positively charged amino functional groups (NH2-GQDs) and negatively charged hydroxyl functional groups (OH-GQDs) for 8 days, respectively. Positively charged NH2-GQDs adhered on the cuticle layer were approximately 2.1 times more than the negatively charged OH-GQDs due to the electrostatic attraction to plant cell wall with negative charge. Within the initial 5 days, most of the GQDs internalized into the leaves via stomatal opening were efficiently translocated to the vasculature and moved down to the roots. Thereafter, the enlargement of aggregation made the particle sizes approach and even exceed the pipe diameter of vascular bundle, thus limiting the leaf-to-root translocation of GQDs, especially for NH2-GQDs. Compared with positively charged NH2-GQDs, negatively charged OH-GQDs induced stronger inhibitory effect on photosynthesis, higher accumulation of malondialdehyde and stimulation to enzyme activities of superoxide dismutase, catalase, and peroxidase. Overall, our findings provide direct evidence for the influence of surface charge on foliar uptake, translocation, and physiological effects of GQDs in crop plants, and imply that foliar exposure of GQDs negatively impact plant photosynthesis and growth health.

Foliar Uptake of the Potencially Toxic Elements in Garlic Chive Leaves

Contamination of vegetables due to the foliar uptake of atmospheric toxic elements could pose severe health risks. However, the uptake mechanisms of potencially toxic elements (PTEs) from the atmosphere and translocation by plant leaves remain unclear. In this study, carboxylic acid-functionalized water-soluble CdSe/ZnS quantum dot nanoparticles (QD NPs) were used as an experimental particle model of PTEs in the edible plant garlic chive (Allium tuberosum). A droplet of QD NP suspension was deposited to simulate the conditions of raindrops containing metal particles falling on a plant leaf. The 3D spatial distribution of QD NPs in plant leaves was measured using three complementary imaging techniques: synchrotron X-ray microcomputed tomography (micro-CT), nano-CT, and two-photon microscopy (TPM). The TPM and micro-CT results revealed that QD NPs deposited on garlic chive leaves penetrated the plant leaves. Nano-CT images showed that QD NPs are absorbed into mesophyll cells and phloem vessels. The results of TEM and TPM imaging demonstrated that QD NPs penetrate through the leaves and translocate in the direction of the stem. The use of these emerging imaging techniques improved the ability to detect and visualize NPs in a plant leaf. These observations also provide mechanistic insights into foliar metal uptake and their translocation and accumulation.

Global Mercury Assimilation by Vegetation.

Assimilation of mercury (Hg) by vegetation represents one of the largest global environmental Hg mass fluxes. We estimate Hg assimilation by vegetation globally via a bottom-up scaling approach using tissue Hg concentrations synthesized from a comprehensive database multiplied by respective annual biomass production (NPP). As global annual NPP is close to annual vegetation die-off, Hg mass associated with global NPP approximates the transfer of Hg from plants to soils, which represents an estimate of vegetation-mediated atmospheric deposition. Annual vegetation assimilation of Hg from combined atmospheric and soil uptake is estimated at 3062 ± 607 Mg yr-1, which is composed of 2491 ± 551 Mg yr-1 from aboveground tissue uptake and 571 ± 253 Mg yr-1 from root uptake. Assimilation of atmospheric Hg amounts to 2422 ± 483 Mg yr-1 when considering aboveground tissues only. Atmospheric assimilation increases to 2705 ± 504 Mg yr-1 when considering that root Hg may be partially derived from prior foliar uptake and transported internally to roots. Estimated atmospheric Hg assimilation by vegetation is 54-137% larger than the current model and litterfall estimates, largely because of the inclusion of lichens, mosses, and woody tissues in deposition and all global biomes. Belowground, about 50% of root Hg was taken up from soils with currently unknown ecological and biogeochemical consequences.

Foliar water uptake of four shrub species in a semi-arid desert

Dew water plays an important role in supporting biological processes in desert ecosystems. Although some mechanisms underlying how plants survive in water-limited environments have been investigated, the water-use strategies of most desert plants remain unclear. We investigated whether foliar uptake of dew water occurs in four dominant shrub species (Artemisia ordosica, Hedysarum mongolicum, Salix psammophila, and Caragana korshinskii), in the Mu Us Desert of northern China. A fluorescent tracing experiment indicated that all four species absorbed water via leaf trichomes and cuticles, and A. ordosica also absorbed water via the stomata. A dew water exposure experiment and isotopic tracing revealed that water entered the leaves and stems of the four species, thereby enhancing their water potential. The relative contribution of dew water to the total water in the leaves of A. ordosica, H. mongolicum, S. psammophila, and C. korshinskii was 20.0 ± 7.0%, 8.4 ± 6.4%, 7.8 ± 1.9%, 3.1 ± 2.3%, respectively. The results demonstrated that all four species had the capacity to absorb water by their leaves, and the absorbed water could be transported to the stems. Our findings suggest that foliar water uptake may be one of the survival mechanisms by shrubs in the desert environment.

Foliar Uptake and Accumulation of Polycyclic Aromatic Hydrocarbons from Diesel Emissions

Air pollution in settlements has become a continuously growing problem. Traffic, especially emission of diesel-powered vehicles, poses an important health risk. Emitted particles carry a wide range to potentially toxic chemicals, of them polycyclic aromatic hydrocarbons (PAHs) are the most important group of concern. Despite the risk of air pollution, rural gardens are very popular both for food production and for environmental benefit. On the other hand, several mutagenic and/or carcinogenic PAHs have been detected in leafy vegetables grown in impacted areas. In our study, the No. 227 OECD GUIDELINE FOR THE TESTING OF CHEMICALS: Terrestrial Plant Test: Vegetative Vigor Test was followed to assess foliar uptake of PAHs from aqueous extract of diesel aerosol sample. Significant differences were found in the bioaccumulation capacity of the tested vegetables as well as in their bioaccumulation pattern. In general, most vegetables showed good even strong correlation with individual PAHs of the diesel extract. In consistency with other studies, prevalence of 3- and 4-ring PAHs was experienced.

Effect of Soil Degradation and Remediation in Technogenic Barrens on the Uptake of Nutrients and Heavy Metals by Plants in the Kola Subarctic

To assess the state of plants and their response to changes in soil properties, the elemental composition of leaves of widespread and pollution-tolerant species Betula pubescens Ehrh. and Salix caprea L. has been studied near the nonferrous metallurgy enterprises in the Kola Peninsula. The content of nutrients and heavy metals in the leaves of undergrowth on technogenic barrens and remediation sites differing in remediation technologies has been analyzed. According to the results of leaf diagnostics, both species under barren conditions are characterized by a noticeable deficiency of K, Ca, P, and, especially, Mn and Zn. The leaves of both species accumulate Ni, Cu, Co, As, Cr, Fe, Al, Pb, V, and S. Willow leaves contain more Cd, Co, Cr, Ni, Cu, Al, Fe, As, S, Ca, K and less Mn than birch leaves. Chemophytostabilization has little effect, and the covering of contaminated soils with a constructed fertile layer leads to the enrichment of birch and willow leaves with Ca, K, and P. Under conditions of continuing atmospheric emissions and gradual accumulation of bioavailable heavy metals in soils after the remediation, the accumulation of metals in leaves is largely determined by the distance from the pollution source, reflecting the possibility of both root and foliar uptake. The concentrations of Ni and Cu in leaves in 2018 did not decrease compared to 2011. The low, albeit varying, ratios of the contents of heavy metals in undergrowth leaves and in the soil and weak correlation of heavy metal contents in these media indicated that B. pubescens and S. caprea retain their ability to regulate their chemical composition even under extreme conditions of technogenic barrens. At the same time, supporting the protective capabilities of plants via optimizing mineral nutrition and soil acidity in combination with a reduction in atmospheric pollution is a prerequisite for efficient remediation of technogenic territories in the Far North.

Star Polymer Size, Charge Content, and Hydrophobicity Affect their Leaf Uptake and Translocation in Plants.

Determination of how the properties of nanocarriers of agrochemicals affect their uptake and translocation in plants would enable more efficient agent delivery. Here, we synthesized star polymer nanocarriers poly(acrylic acid)-block-poly(2-(methylsulfinyl)ethyl acrylate) (PAA-b-PMSEA) and poly(acrylic acid)-block-poly((2-(methylsulfinyl)ethyl acrylate)-co-(2-(methylthio)ethyl acrylate)) (PAA-b-P(MSEA-co-MTEA)) with well-controlled sizes (from 6 to 35 nm), negative charge content (from 17% to 83% PAA), and hydrophobicity and quantified their leaf uptake, phloem loading, and distribution in tomato (Solanum lycopersicum) plants 3 days after foliar application of 20 μL of a 1g L-1 star polymer solution. In spite of their property differences, ∼30% of the applied star polymers translocated to other plant organs, higher than uptake of conventional foliar applied agrochemicals (<5%). The property differences affected their distribution in the plant. The ∼6 nm star polymers exhibited 3 times higher transport to younger leaves than larger ones, while the ∼35 nm star polymer had over 2 times higher transport to roots than smaller ones, suggesting small star polymers favor symplastic unloading in young leaves, while larger polymers favor apoplastic unloading in roots. For the same sized star polymer, a smaller negative charge content (yielding ζ ∼ -12 mV) enhanced translocation to young leaves and roots, whereas a larger negative charge (ζ < -26 mV) had lower mobility. Hydrophobicity only affected leaf uptake pathways, but not translocation. This study can help design agrochemical nanocarriers for efficient foliar uptake and targeting to desired plant organs, which may decrease agrochemical use and environmental impacts of agriculture.

Studies on foliar uptake of tritiated water on Spinach sp. during light and dark simulated conditions using environmental chamber

Studies on foliar uptake of tritiated water (HTO) on Spinach sp. during light and dark condition was simulated inside the environmental chamber, and an attempt was made to compute CTFWT HTO, Cpfw HTO, Cpcw OBT, Cpfw OBT using basic equations available in IAEA TECDOC1616. The predicted activity was compared with the observed activity. The conversion of tissue-free water tritium (TFWT) to organically bound tritium (OBT) was more in the light condition. The ratio of OBT to TFWT varied from 0.006 to 0.082. The ratio of observed OBT activity (Bq/kg fresh weight) in light to dark conditions varied from 34% to 117%.