Non-toxic orange carbon dots stimulate photosynthesis and CO2 assimilation in hydroponically cultivated green beans (Phaseolus vulgaris).

Continuous increasing leaf photosynthesis may enhance plant yield. As an evolutionary property, plants use less photosynthetic capacity than is theoretically possible. Plant nanobionics is a bioengineering field that improves plant functions using nanoparticles. We applied orange carbon dots (o-CDs) onto the foliage of green beans (Phaseolus vulgaris ) grown in hydroponics to improve their photosynthetic performance and CO2 assimilation. Photosynthesis parameters, photosynthetic pigments content, total phenolic content (TPC) and antioxidative activity (TAA) were measured. Results show that photosynthetic pigments remained unchanged, while photosynthesis was improved. Both o-CDs concentrations decreased TPC and TAA. The light response curve showed higher CO2 assimilation at both o-CDs concentrations, particularly at lower light intensity. Correlation analysis confirmed increased CO2 binding and assimilation at 1mg L-1 . This study demonstrated the potential of using o-CDs as a safe biostimulator through photosynthesis increase and CO2 assimilation without toxic effects on plants. This may stimulate yield increase that paves the way for their agricultural application.

Breaking the myth of healthy food production in rural areas: cases studied in Vojvodina Province (Serbia).

The aim of the present study was to analyze the chemical composition of parsley, parsnip, carrot, and celeriac cultivated at different localities (urban, or suburban/village). The concentrations of heavy metals (cadmium, nickel, chromium) and essential elements (potassium, sodium, calcium, phosphorus) in edible plant parts were determined. Human health risks associated with chronic consumption of potentially contaminated vegetables were assessed through the use of hazard quotients. The concentrations of heavy metals and essential elements in the edible parts of the tested plants varied among plant species, cultivation locality and plant organ (leaf/root). Carrots showed the lowest levels of cadmium, nickel, and chromium accumulation, while the highest concentrations were measured for parsley leaves, with respect to average values. Metal pollution index values obtained for cities were lower than those obtained for some villages and a suburban settlement. The hazard quotient revealed the highest values for cadmium. Positive Pearson's correlation between chromium and nickel was found in many cases. Principal component analysis indicated differences in plants ability to accumulate certain nutrients and pollutants, while sample diversification was closely related to growth site properties. We sincerely hope that the present study will inspire similar investigations in other developing countries, as well as in the Western Balkans region, to obtain broader insight into vegetable food safety and local human health risk. Considering that food quality and safety are major concerns, our results should inform the relevant government authorities and provide a foundation for implementation of a system of controls over cultivation processes and vegetable quality in Serbia.

The Anatomical Basis of Heavy Metal Responses in Legumes and Their Impact on Plant-Rhizosphere Interactions.

Rapid industrialization, urbanization, and mine tailings runoff are the main sources of heavy metal contamination of agricultural land, which has become one of the major constraints to crop growth and productivity. Finding appropriate solutions to protect plants and agricultural land from heavy metal pollution/harmful effects is important for sustainable development. Phytoremediation and plant growth-promoting rhizobacteria (PGPR) are promising methods for this purpose, which both heavily rely on an appropriate understanding of the anatomical structure of plants. Specialized anatomical features, such as those of epidermis and endodermis and changes in the root vascular tissue, are often associated with heavy metal tolerance in legumes. This review emphasizes the uptake and transport of heavy metals by legume plants that can be used to enhance soil detoxification by phytoremediation processes. Moreover, the review also focuses on the role of rhizospheric organisms in the facilitation of heavy metal uptake, the various mechanisms of enhancing the availability of heavy metals in the rhizosphere, the genetic diversity, and the microbial genera involved in these processes. The information presented here can be exploited for improving the growth and productivity of legume plants in metal-prone soils.

Should I GROW or should I SLOW: A meta-analysis of fast-growing tree-species grown in cadmium perturbed environment.

Variations in soil chemical composition may lead to disturbances in plant growth and survival. Which strategies of biomass allocation fast-growing species acquire to overcome the disturbances in the rhizosphere remains an open research challenge. We conducted a series of greenhouse pot experiments to collect enough experimental evidence to elucidate the answer. A tiered analytical approach was applied to collected data to fingerprint both the intraspecies and interspecies differences. We investigated the biomass allocation patterns in Robinia pseudoacacia L., Populus × euramericana, Populus deltoides, Salix alba, Salix matsudana Koidz., and Salix viminalis L. (18 fast-growing genotypes in total) under cadmium-free and cadmium-perturbed soil conditions. Further, we explored the intraspecific and interspecific differences between tested plants and looked for different strategies employed under perturbed conditions. We show that fast-growing species tend to strengthen their roots toward the Cd triggered perturbances in the rhizosphere and allocate more biomass to that plant organ/part. Intraspecies analyses pointed to differences in resource use efficiency and acquisition strategy based on specific leaf area, pointing toward P. deltoides genotypes PE19/66 and PD3, and S. alba B44 as strong, fast-growing oriented genotypes. Others exhibited more or less a conservative resource use and acquisition strategy under perturbed conditions. Our study highlights the intraspecies and interspecies specificity of fast-growing species to Cd occurrence in the rhizosphere. Association of growth traits and Cd-related traits tested with structural equation model highlighted the shoots bioconcentration index as a proxy-trait which directly interplay with the functional traits performance and modify the biomass shift.

Photosynthesis Enhancement in Maize via Nontoxic Orange Carbon Dots.

The sustained increase in leaf photosynthesis may increase crop yield. Due to many limitations, plants use much less photosynthetic capacity than is theoretically possible. Plant nanobionics investigates nanoparticle application in living plants, which improves certain plant functions. We synthesized and tested nontoxic orange carbon dots (o-CDs) for the photosynthetic efficiency increase in maize (Zea mays L.). We applied o-CDs foliarly or by adding to the growth solution. The photosynthetic parameters and content of photosynthetic pigments were recorded. The total phenolic content (TPC) and total antioxidant activity (TAA) were measured to monitor the plant antioxidant response to o-CDs. The photosynthetic parameters' values were higher for foliar than for solution application. The 1 mg/L o-CDs applied foliarly and 5 mg/L in solution increased photosynthetic parameters in leaves. The o-CDs raised photosynthetic pigments. The TAA and TPC results indicate reduced antioxidant activity in the plant organs more exposed to o-CDs, depending on the way of application.

Health assessment of medicinal herbs, celery and parsley related to cadmium soil pollution-potentially toxic elements (PTEs) accumulation, tolerance capacity and antioxidative response.

Celery and parsley are recognized as medicinal herbs and nutraceutical vegetables due to their valuable pharmacological properties and numerous health benefits. However, in recent years, soil loadings with various PTEs have become a serious concern across the world, leading to plants pollution, which can consequently diminish their quality and safety for human consumption. Therefore, we attempted to quantify quality and safety of celery and parsley grown in Cd polluted soil. We examined the presence of PTEs: As, Cu, Fe, Mn, Ni, Cu and Cd in soil and selected herbs, as well as their physiological responses to different Cd exposures (control-without Cd addition, 3 and 6 µg/g Cd of dry soil). Following elevation of Cd in plants, both species showed increasing trend of As, Pb and Cu in plants, which overcome safe limits, with exception for Cu. Further, celery showed strong phytoextraction ability (99.9 µg/g Cd of dry weight) with high potential to tolerate Cd due to the efficient antioxidative machinery. Besides that herbs pollution was evident on the basis of target hazard quotients (HQ), hazard index (HI) and cancerogenic risk (CR), revealing that chronic consumption of contaminated herbs can consequently endanger human health. HI was greater than 1, while CR exceeded safe limits in treated plants, with exception for As. In the point of view of toxicology and food safety, growing of medicinal plants should be strictly regulated and distinguished based on the purpose of growing, and further herbs usage.

Assessment of phytostabilization potential of two Salix L. clones based on the effects of heavy metals on the root anatomical traits.

Willow species (Salix L.) are a useful tool for assessing phytostabilization of the sites polluted by heavy metals. Phytostabilization potential of two willow genotypes (Salix alba L. clone '68/53/1' and Salix nigra Marshall clone '0408') has been evaluated in a 45-day hydroponic experiment, using stem cuttings (diameter 12 to 14 mm, length 20 cm) exposed to two concentrations (10-4 M and 10-5 M) of individually applied Cd, Ni, and Pb. Metals were diluted in 25% Hoagland's solution, in forms of CdCl2·H2O, NiSO4·6H2O, and Pb-EDTA. The control group of cuttings was grown in 25% Hoagland's solution without heavy metals. High Cd concentrations in willow roots, 8637 mg/kg (clone '68/53/1') and 6728 mg/kg of dry weight (clone '0408'), have indicated a high phytostabilization potential. However, detailed analyses of cross-sectional area of the root cortex and the central cylinder revealed that the excess concentration of Cd led to a significant reduction of measured anatomical root's traits of clone '68/53/1' in comparison with the control samples. Excessive concentration of Ni and Pb in nutrient solution increased the values of quantitatively measured root's traits of clone '0408', implying stimulatory effects of the applied concentrations. Concentration of 10-4 M of each metal had more negative effects on the roots' anatomical traits, notably on parenchymal and exodermal cells and vessels. Deposits of metals were observed in root tissues. Clone '0408' demonstrated an increased tolerance to heavy metals, which could potentially make this clone useful in phytostabilization.

Citric acid as soil amendment in cadmium removal by Salix viminalis L., alterations on biometric attributes and photosynthesis.

During the past decade, the target in cleaning polluted sites is an application of chelating agents, such as citric acid (CA), which is proposed as a good candidate in the promotion of phytoremediation. Among heavy metals, cadmium (Cd) is one of the most common and dangerous elements, which strongly disturbs morphophysiological properties in plants. A pot experiment was assessed to evaluate the influence of CA in Cd phytoremediation in alkaline soil by Salix viminalis (clone SV068). The effects of CA on Cd bioavailability, mobility, and distribution in plants, various morphometric measurements, and physiological performances as photosynthesis, transpiration, water use efficiency, and pigment content were tested. The highest Cd accumulation was evident after 60 days of growing, in plants subjected to combined treatment of CA with a higher dose of Cd. Application of CA showed a beneficial effect in maintaining the photosynthetic rate as well as gas exchange capacity in willows grown in Cd-contaminated soil. Furthermore, CA slightly increased plant growth and biomass production, depending on applied Cd dose and harvest period. A chelating agent like CA showed strong influence in plant response to combat Cd toxicity.

Heavy metal accumulation in vegetable species and health risk assessment in Serbia.

Continuous monitoring of heavy metal content in vegetables is of high priority for population nutrition control, as well as risk assessment for human health. The chemical composition of plants is a reliable indicator of their contamination by hazardous substances accumulated in the environment as a consequence of inadequately applied agro-technology. The main goal of this study was to examine the quality of vegetables that reach consumer markets as a function of growth location. Samples of 11 of the most common vegetable species used in the human diet were collected during a 4-year survey. Vegetables originated from local farm producers who cultivated them at different locations in Vojvodina Province, Serbia. Many vegetable samples contained disturbingly high levels of the investigated metals: cadmium, lead, nickel, and chromium. The plant species with the highest Cd accumulation was spinach, where Cd leaves exceeded the maximum permissible concentrations (MPCs) in more than half of the analyzed samples from different localities (54%). Pb concentrations in spinach were also higher than MPC values (according to Serbian law 3.0 µg/g) in 46% of all analyzed samples. Results showed that Cr levels in all tested vegetable species were below MPC values recommended by the FAO/WHO organization. The largest chromium accumulator was spinach, with average values of 2.3 µg/g, followed by beetroot and parsnips with an average concentration of 1.4 µg/g. The highest average content of Ni in all analyzed vegetable species was also recorded in spinach leaves, with an average value of 2.2 µg/g, followed by broccoli (1.7 µg/g) and tomatoes (1.5 µg/g).

Drought Impact Is Alleviated in Sugar Beets (Beta vulgaris L.) by Foliar Application of Fullerenol Nanoparticles.

Over the past few years, significant efforts have been made to decrease the effects of drought stress on plant productivity and quality. We propose that fullerenol nanoparticles (FNPs, molecular formula C60(OH)24) may help alleviate drought stress by serving as an additional intercellular water supply. Specifically, FNPs are able to penetrate plant leaf and root tissues, where they bind water in various cell compartments. This hydroscopic activity suggests that FNPs could be beneficial in plants. The aim of the present study was to analyse the influence of FNPs on sugar beet plants exposed to drought stress. Our results indicate that intracellular water metabolism can be modified by foliar application of FNPs in drought exposed plants. Drought stress induced a significant increase in the compatible osmolyte proline in both the leaves and roots of control plants, but not in FNP treated plants. These results indicate that FNPs could act as intracellular binders of water, creating an additional water reserve, and enabling adaptation to drought stress. Moreover, analysis of plant antioxidant enzyme activities (CAT, APx and GPx), MDA and GSH content indicate that fullerenol foliar application could have some beneficial effect on alleviating oxidative effects of drought stress, depending on the concentration of nanoparticles applied. Although further studies are necessary to elucidate the biochemical impact of FNPs on plants; the present results could directly impact agricultural practice, where available water supplies are often a limiting factor in plant bioproductivity.

Hydroponic screening of black locust families for heavy metal tolerance and accumulation.

Present work examines phytoextraction potential of four black locust families (half-sibs 54, 56, 115, and 135) grown hydroponically. Plants were treated with 6 ppm of cadmium (Cd), 100 ppm of nickel (Ni), and 40 ppm of lead (Pb) added in Hoagland nutrient solution, accompanying with simultaneously applied all three metals. Responses to metals exposure among families were different, ranging from severe to slight reduction of root and shoot biomass production of treated plants. Calculated tolerance indices are indicating tested families as highly tolerant (Ti > 60). Family 135 had the lowest tolerance index, pointing that it was highly susceptible to applied metals. Comparing photosynthetic activities of tested families it has been noticed that they were highly sensitive to stress induced by heavy metals. Net photosynthetic rate of nickel treated plants was the most affected by applied concentration. Cadmium and nickel concentrations in stems and leaves of black locust families exceeded 100 mg Cd kg(-1) and 1000 mg Ni kg(-1), in both single and multipollution context. On the contrary, accumulation of lead in above ground biomass was highly affected by multipollution treatment. Tf and BCF significantly varied between investigated treatments and families of black locust. Concerning obtained results of heavy metals accumulation and tolerance of black locust families can be concluded that tested families might be a promising tool for phytoextraction purposes, but it takes to be further confirmed in field trials.