Hyperaccumulator Research Articles

Heavy Metal Accumulation Trends for Tsunga, Tomatoes and Rape in Soils from Two Provinces of Zimbabwe

Tomatoes, tsunga (mustard) and rape were sampled from Mashonaland East and Central provinces of Zimbabwe. Aim was to assess hyper accumulative tendency of these towards heavy metals (Cd, Cu, Co, Cr, Ni, and Pb). Most of these heavy metals were noted to be of anthropogenic origin. Co, Mn and Cr were noted to be naturally inherent in Mushimbo, Mutoko soils. Heavy metal levels in irrigation water were within internationally acceptable ranges according to ATSDR. There was no direct reflection of level dependency between the water and plants studied. Bioaccumulation of cadmium and lead levels occurred in all vegetables despite low levels in the soil environment. High heavy metal levels in arable land as compared to virgin land proves contamination at play and also the anthropogenic origin. It was concluded that different vegetables accrue different heavy metals at different rates under the same environment. It was recommended to do more investigations on factors that determine absorption and hyper accumulation tendency of heavy metals in plants. This data could be used as a basis for recommending what crops to grow and in specific areas hence promote food safety in addition to food security for the nation.

Symplasmic and transmembrane zinc transport is modulated by cadmium in the Cd/Zn hyperaccumulator Sedum alfredii

This study investigated the influence of Cd (25 µM) on Zn accumulation in a hyperaccumulating (HE) and a non-hyperaccumulating (NHE) ecotype of Sedum alfredii Hance at short-term supply of replete (Zn5, 5 µM) and excess (Zn400, 400 µM) Zn. Cd inhibited Zn accumulation in both ecotypes, especially under Zn400, in organs with active metal sequestration, i.e. roots of NHE and shoots of HE. Direct biochemical Cd/Zn competition at the metal-protein interaction and changes in transporter gene expression contributed to the observed accumulation patterns in the roots. Specifically, in HE, Cd stimulated SaZIP4 and SaPCR2 under Zn5, but downregulated SaIRT1 and SaZIP4 under Zn400. However, Cd downregulated related transporter genes, except for SaNRAMP1, in NHE, irrespective of Zn. Cadmium stimulated casparian strip (CSs) development in NHE, as part of the defense response, while it had a subtle effect on the (CS) in HE. Moreover, Cd delayed the initiation of the suberin lamellae (SL) in HE, but stimulated SL deposition in NHE under both Zn5 or Zn400. Changes in suberization were mainly ascribed to suberin-biosynthesis-related genes and hormonal signaling. Altogether, Cd regulated Zn accumulation mainly via symplasmic and transmembrane transport in HE, while Cd inhibited both symplasmic and apoplasmic Zn transport in NHE.

Phytotoxicity Assay of Cu, Pb and Zn on Launaea cornuta and Sporobolus jacquemontii Grown in Heavy Metal contaminated soil

In this paper, a phytotoxicity assay is used to assess the harmfulness and tolerance of L. cornuta and S. jacquemontii in phytoremediation of heavy metal-contaminated soils. The effects of Pb, Cu, and Zn concentrations in the soil on the number of leaves generated, root and shoot growth, and tolerance indices of the investigated plant species were analyzed. The experimental plants were grown in soil with 0, 100, 300, 600, 1500, 2000, 2500, and 3000 mg/kg dry soil weight (DW for Pb, Cu, and Zn). Sample preparation and laboratory analysis followed the standard methods. Data were analyzed with one-way analysis of variance (ANOVA) using GraphPad Instat 3.1 software. The growth mean of different treatments was compared using Duncan’s Multiple Range Test at p < 0.05. Plants grown in soil containing more than 300/kg DW metal contents exhibited a significant effect on the growth of the root and shoot. Concentrations lower than 300 did not show any significant effects. At 1500 mg/kgDW, the numbers and sizes of leaves decreased very significantly, while at 2000 mg/kgDW both plants failed to survive. The toxic effects of the metals on biomass production showed inhibition in the following trend: Zn>Cu>Pb. The results suggest that hyper accumulator plants can also be affected by metals in the soils on which they grow. Therefore, the application of L. cornuta and S. jacquemontii as phytoremediation plants at higher metal soil concentrations requires the application of soil amendments to minimize the toxicity effect of metal on the plants.

Efficiencies of Heavy Metal Hyper-accumulation Plants as Potential Land Remediators for Heavy Metal Polluted Soils

The purpose of this study was to determine which hyper accumulator plant is more efficient for phytoremediation of heavy metals in a heavy metal polluted soil. The plants used were Sunflower (Helianthus annuus), Asiatic dayflower (Commelina communis), Guinea grass (Panicum maximum), Bahama grass (Cynodon dactylon), and Vertiver grass (Chrysopogon zizanioides). Heavy metals such as Pb, Zn, Cu, Cd, Ag and Hg were impregnated in the soil samples and analyzed using atomic absorption spectrophotometer (AAS). The plants were planted in the heavy metal polluted soil and harvested after 75 days to determine the percentage concentration of the heavy metals in the root and shoot of the plants. The result showed that heavy metals were hyper-accumulated in the roots and shoots of the plants at the end of the investigation. The heavy metals with a percentage concentration above 50 % can be used as a phytoremediator of that particular metal in a polluted soil. It was discovered that the best hyperaccumulator plants for Pb is the Sunflower, for Zn and Cd is the Bahama grass, for Cu and Ag is the Vertiver grass whilst, for Hg is the Guinea grass.

Phytoremediation method and Brassica family: Removal of chromium, cadmium and lead accumulation with broccoli (Brassica oleracea var. italica)

Phytoremediation is the most cost effective and applicable technique to clean contaminated soils. The study was carried out in controlled conditions. Cadmium was applied as only cadmium (30 mgkg−1), and together with a chelator as Cd (30 mgkg−1) + EDTA, in triplicates. Chromium was applied as only chromium (10 mg/kg−1), and together with a chelator as Cr (10 mgkg−1) + EDTA. Similarly, lead was applied as only lead (100 mgkg−1), and together with a chelator as Pb (100 mgkg−1) + EDTA. The highest root and shoot dry weights were detected in lead and chromium applied pots. The highest lead, cadmium and chromium concentrations in the shoot of broccoli (Brassica oleracea var.italica) were found to be 14.0 mgkg−1, 6.67 mg kg-1and, 5.17 mg kg−1, respectively, in the chelated applications. The order of accumulation in the root was Cr > Pb > Cd. Broccoli was shown to be effective in phytoextraction of Pb Chromium was especially accumulated in the roots of broccoli which indicated that this plant was successful for phytostabilization of Cr. Broccoli can be employed for both phytostabilization and phytoextraction of cadmium. The results revealed that broccoli played a role in the remediation of lead, chromium and cadmium heavy metals as a hyper accumulator plant.

Phytoremediation potential of a few hydrophytic medicinal plants: A review

Environmental pollution is one of the explicit challenges faced globally. Pollution by heavy metal contamination is a threat to the environment and is of critical concern. Rapid industrialization and urbanization have escalated the contamination rates by heavy metals. This rapid increase resulted in different health problems inducing toxicity and damaging the proper functioning of the brain, lungs, kidney, liver, blood composition, and other vital organs. Plants have evolved particular and very efficient mechanisms to obtain essential micronutrient metals from the environment and accumulate them up to a threshold of 10-15ppm. However, certain plants categorized as "Hyper accumulators," can take up toxic metal ions at levels beyond this limit. As a result, animals and people may suffer negative impacts from bio accumulating harmful heavy metals in the biota of riverine habitats. The "life-blood of the biosphere" is water and hence these heavy metals impact the ecological well-being of aquatic systems and animal species. Water dissolves various organic and inorganic substances and environmental toxins since it is a universal solvent. Thus, it highlights the significance of ecological restoration and phytoremediation. Phytoremediation is a technology that uses plants to degrade, assimilate, metabolize, or detoxify metal and organic chemical contamination. About five phytoremediation technologies have often been employed for soil decontamination by plants: phytostabilisation, phytodegradation, rhizofiltration, phytoextraction, and phytovolatilization. Articles from databases like PubMed and Scopus were reviewed to explore the potential plants for phytoremediation. Hydrophytes can be selected over other terrestrial plants because of their enhanced capability to accumulate almost 1450-fold the concentration of heavy metals in water. Another advantage of aquatic plants' rapid growth rate is increased biomass production, high pollutant uptake ability, and more pronounced purification because of their direct contact with water. They are also helpful in regulating oxygen levels and the food cycle by acting as a food source for small fish. In addition, some widely used aquatic medicinal plants such as Ceratophyllum demersum, Potamogeton pectinatus, Pistia stratiotes, Nelumbo nucifera, Pontederia crassipes & Bacopa monnieri were discussed. This review explores the phytoremediation potential of hydrophytic medicinal plants and through an insight to recreate and restore our ecosystem.

Soil-Plant-Ni-As: Four-Fold Interactions – Modest Blessing from Total Disguise

As an essential plant nutrient, deficiency of nickel (Ni) can cause metabolic and enzymatic disorder in plants; however an excess amount of this element can also be proven deadly for a plant. To examine the critical level of Ni tolerance two plant species, Kalmi (Ipomoea aquatica) and Red Amaranthus (Amaranthus cruentus) were selected where Red Amaranthus (Amaranthus cruentus) was verified as a hyper accumulator of Ni. In this diverse experimental set up, arsenic (As) was applied with irrigation water and increased doses of Ni was observed to put antagonistic effect on availability as well as plant uptake of As. The results from such a complex and diverse four-fold interaction can be concluded as a little blessing of remediation of As toxicity from a disguise of Ni toxicity.

Comparative Transcriptome Analysis Unveils the Molecular Mechanism Underlying Sepal Colour Changes under Acidic pH Substratum in Hydrangea macrophylla

The hydrangea (Hydrangea macrophylla (Thunb). Ser.), an ornamental plant, has good marketing potential and is known for its capacity to change the colour of its inflorescence depending on the pH of the cultivation media. The molecular mechanisms causing these changes are still uncertain. In the present study, transcriptome and targeted metabolic profiling were used to identify molecular changes in the RNAome of hydrangea plants cultured at two different pH levels. De novo assembly yielded 186,477 unigenes. Transcriptomic datasets provided a comprehensive and systemic overview of the dynamic networks of the gene expression underlying flower colour formation in hydrangeas. Weighted analyses of gene co-expression network identified candidate genes and hub genes from the modules linked closely to the hyper accumulation of Al3+ during different stages of flower development. F3'5'H, ANS, FLS, CHS, UA3GT, CHI, DFR, and F3H were enhanced significantly in the modules. In addition, MYB, bHLH, PAL6, PAL9, and WD40 were identified as hub genes. Thus, a hypothesis elucidating the colour change in the flowers of Al3+-treated plants was established. This study identified many potential key regulators of flower pigmentation, providing novel insights into the molecular networks in hydrangea flowers.

Gradient Matters: Designing Binarized Neural Networks via Enhanced Information-Flow.

Binarized neural networks (BNNs) have drawn significant attention in recent years, owing to great potential in reducing computation and storage consumption. While it is attractive, traditional BNNs usually suffer from slow convergence speed and dramatical accuracy-degradation on large-scale classification datasets. To minimize the gap between BNNs and deep neural networks (DNNs), we propose a new framework of designing BNNs, dubbed Hyper-BinaryNet, from the aspect of enhanced information-flow. Our contributions are threefold: 1) Considering the capacity-limitation in the backward pass, we propose an 1-bit convolution module named HyperConv. By exploiting the capacity of auxiliary neural networks, BNNs gain better performance on large-scale image classification task. 2) Considering the slow convergence speed in BNNs, we rethink the gradient accumulation mechanism and propose a hyper accumulation technique. By accumulating gradients in multiple variables rather than one as before, the gradient paths for each weight increase, which escapes BNNs from the gradient bottleneck problem during training. 3) Considering the ill-posed optimization problem, a novel gradient estimation warmup strategy, dubbed STE-Warmup, is developed. This strategy prevents BNNs from the unstable optimization process by progressively transferring neural networks from 32-bit to 1-bit. We conduct evaluations with variant architectures on three public datasets: CIFAR-10/100 and ImageNet. Compared with state-of-the-art BNNs, Hyper-BinaryNet shows faster convergence speed and outperforms existing BNNs by a large margin.

Effects of Lead, Copper and Cadmium on Bioaccumulation and Translocation Factors and Biosynthesis of Photosynthetic Pigments in Vicia faba L. (Broad Beans) at Different Stages of Growth

Trace elements in the environmental media contribute to toxicities of different types. Their presence in the arable pedosphere is a human-health risk factor. This study focused on Vicia faba represented by two Tunisian varieties of bean (Mamdouh) and faba bean (Badii). The objective was to analyze the effects of lead, copper and cadmium on their growth, chlorophyll-content and carotenoids-content, as well as the bioaccumulation and translocation factor, at different stages of growth. For each metal, the concentrations the plants were subjected to were 6, 0.3 and 0.03 mg/L of the metal in the compound for lead nitrate, copper nitrate and cadmium acetate, respectively. The analysis was carried out using an atomic absorption spectrophotometer (ICP-MS), encompassing all the parts of the plant. The authors detected a perceptible decrease in the fresh weight of roots and shoots, as well as a drop in the chlorophyll and carotenoid, for all the three heavy metals. Cadmium turned out to be the most toxic of the three metals and copper (which is incidentally an essential micronutrient for plant growth) the least. As far as the bioaccumulation factor was concerned, bean and faba bean exhibited different behaviours, both with regard to the growth stages and the heavy metal absorbed. During the vegetative growth stage, both were accumulators of all the three heavy metals (a translocation factor less than unity). However, in the flowering stage, faba bean was a hyper-accumulator of copper (TF > 1); while the bean plants accumulated a lot of lead in the pods-stage (TF > 1). It is worthwhile to pose new research questions and try to answer them in this study, if legumes are accumulator or hyper accumulator plants in which stage and in where organ accumulate more HMs.

Preliminary studies on trace metal accumulation by aquatic weed Salvinia molesta and its implication in Phytoremediation

Water, sediment sample and specimens of free-floating aquatic macrophyte, Salvinia molesta were collected from a Lake situated in North Goa to assess trace metal (Mn, Ni, Zn and Pb) accumulation by selected aquatic weed. The concentration of trace metals from water, sediment and S. molesta was determined using atomic absorption spectroscopy. Studies revealed that concentration of metals in water was less as compared to sediments. Brown fronds of Salvinia accumulated more concentration of trace metal as compared to green shoots. Metal accumulation in brown fronds in pre monsoon was as (Mn 3.32.ppm; Ni-0.04 ppm; Zn - 3.62ppm; Pb-BDL) while in green shoots (Mn 1.20ppm; Ni-BDL; Zn - 1.02ppm; Pb-BDL); in monsoon season the metal concentration in brown frond was (Mn 3.04.ppm; Ni-0.07 ppm; Zn – 1.93ppm; Pb-BDL) and in green shoot ( Mn 0.62ppm; Ni-BDL; Zn - 0.30 ppm; Pb-BDL); whereas in post monsoon metal concentration in brown frond was recorded as (Mn 4.75ppm; Ni-0.55 ppm; Zn - 0.25ppm; Pb-0.39ppm) and in green shoot- (Mn 1.10.ppm; Ni-0.12 ppm; Zn - 0.10ppm ; Pb-0.10ppm). Bioaccumulation and Translocation factors for metal accumulation and translocation were above 1. Study revealed that S. molesta is hyper accumulator of above trace metals therefore suitable for phytoremediation.

Identification of Vehicular Emission Hyper Accumulator And Its Subsequent Use as Phytoremediation

Effects of vehicular emission on two plants Amaranthus spinosus Linn. and Croton bonplandianum Baill, collected from polluted site and from relatively less polluted site/control site of Kolkata city of West Bengal, India was studied. Photosynthetic pigment content, proline content, phosphatase activity and Hill activity, heavy metal contents and their relevance to be used as phytoremediators was investigated. Decrease in pigment content and increase in proline content and phosphatase activity was observed in the plants from polluted areas. Micromorphological studies revealed the effect of automobile emission on epidermal cells and stomatal size on both the experimental plants. Data indicated that between the two plants, A. spinosus was more susceptible and C. bonplandianum was more tolerant to vehicular pollution. Bangladesh J. Bot. 51(2): 207-216, 2022 (June)

Assessment of Total Hydrocarbon Soil Content of <i>Rhizophora mangle</i> and <i>Nypa fruticans</i> at Onne and Eagle Island

The assessment of total hydrocarbon soil (THC) content of <i>Rhizophora mangle</i> and <i>Nypa fruticans</i> was investigated. Plant part of the studied plants (leaves, root, and stem) were collected from the studied forest. In each study area a 20 x 20m plot was delineated. Within each plot 10 trees were sampled randomly using stratified systematic analyzed sampling method. For the soil analysis, fresh samples were collected insitu with a soil augur weighed and placed in a sterile polythene bags and sent to laboratory, each location 3 replicates from each sampling plot were used for both locations. leaves, pieces of root and stem of red mangrove were harvested similar techniques were adopted for Nypa palm and placed in the cooler and taken to the laboratory for analysis. The collected samples were analyzed for THC in plant parts, THC and physicochemical parameters for soil and water. The result generated showed a significant variation of THC accumulation was more in root of <i>Nypa fruticans</i> than <i>Rhizophora mangle</i> roots. The leaves and bark of <i>Rhizophora Mangle</i> accumulated high concentration of THC. This study showed that higher productivity and litter fall in <i>Rhizophora mangle</i> is a mechanism to counter the effect of total hydrocarbon pollution in a polluted rain forest environment. <i>Rhizophora mangle</i> could be referred also as hyper accumulator due to its ability in accumulating the high amount of THC in leaves.

Accumulation of Heavy Metals in Agricultural Crops and Ecological Series of Crops Placement

The accumulation of toxic elements in vegetables and melons grown in agriculture, Brassica rapa - turnip, Solanum lycopersicum - tomato, Citrullus lanatus - watermelon, Capsicum annuum - bell pepper, Daucus carota - carrots, Cucurbita pepo - pumpkin, Cucumis melo - melon, and also Prunus armeniaca - apricot from fruit trees were analyzed. The excess of maximum allowable concentrations in agricultural crops of the element As by 1.65-1.75, Cd - 1.6-2.3, Cr -1.2-2.35, Cu -1.6-3.3, Ni - 1.16-3.53, Pb - 1.54-3.08, Al - 1.36-3.5, Sb - 2.0-33, Se - 1.1-3.3 times was established. The maximum allowable concentration of mercury in vegetables and melons was equal to 0.02 mg/kg, and in the chosen plants this indicator was close to the maximum allowable concentration (MAC). An ecological series of vegetable and melon crops (tomatoes → pumpkin → turnips → bell peppers → melons → watermelons → carrots) has been developed for their placement on fields contaminated with heavy metals Se, As, Pb, Cd, Zn, included in the first class in terms of the degree of danger to human health, while Ni, Cu, Cr metals were from the second class, and metal Mn from the third class. Agricultural crops in the ecological series are placed in inverse proportion to the regularities of the hyper accumulation of heavy metals in them.

Assessing the bioconcentration of heavy metals in Nypa Palm (Nypa fruticans (Wurmb) from selected mangrove forests in Rivers State, Nigeria

The bioconcentration of Pb, Zn, Cd, Cr and Ni in tissues of Nypa palm (Nypa fruticans) was investigated during wet and dry seasons from selected mangrove forests, using the randomized complete block design. Soil and plant samples were randomly collected from plant dominated growth stations and analyzed for heavy metal content using the Perkin Elmer Analysts 200 Atomic Absorption Spectrophotometer (AAS). The results obtained showed the bio-transfer factors of heavy metals at wet season as Pb (1.08mg/kg), Zn (1.42 mg/kg), Cd (6.14 mg/kg), Cr (0.56 mg/kg) Ni (0.90 mg/kg) and dry season as Pb (0.86 mg/kg), Zn (1.15 mg/kg), Cd (5.44 mg/kg), Cr (0.66 mg/kg), Ni (1.12 mg/kg). The result further showed the bio-translocation factors of the metals at wet seasons as Pb (0.59 mg/kg), Zn (0.76 mg/kg), Cd (3.25 mg/kg), Cr (0.22 mg/kg), Ni (0.54 mg/kg) and dry season as Pb (0.64 mg/kg), Zn (1.03 mg/kg) Cd (3.07 mg/kg), Cr (0.24 mg/kg), Ni (0.61 mg/kg) respectively. Findings indicate the study plant as a hyper accumulator of Ni, Cd and Zn, and non-hyper accumulator of Cr and Pb. It is thus recommended that N. fruticans be utilized for phytoremediation of Ni, Cd and Zn in polluted mangrove ecosystem.

Effects of alkaline fertilizer and rice cultivation (Oryza sativa L.) on remediation of soils polluted with cadmium (Cd)

Objective: The objective of this study was to develop a simple and feasible methodology which makes possible restoration of soils polluted by cadmium using two types of fertilizers (alkaline and conventional), and the technique of phytoremediation (low rice variety, and hyper accumulator of cadmium). Methodology and results: Its application mode was experimented at Guangdong Provincial Research Center for Environmentally Friendly Fertilizer Engineering Technology in Guangzhou, republic of china. The experiment was carried out in a greenhouse, with an average daytime temperature of 25.5°C, in the city of Guangzhou (China). Polyethylene pots with an inner diameter of 25 cm and a height of 25 cm were each filled with 5 kg of air-dried soil and passed through a 1cmx1cm mesh of a sieve. Four factors were studied, soil contamination level (soil contaminated with Cd, soil with low Cd contamination), pH of the fertilizer (high, pH = 9.5, normal pH 5.8), dosage of the fertilizer applied (low level, medium level, high level) and low Cd accumulating rice variety (Xiangwanxian 12) and hyper Cd accumulating rice (Yuzhenxiang). Soil samples taken from a depth of 0 to 30 cm were delivered to the laboratory for analyses. Results obtained showed that the soil pH was higher with the treatment of alkaline fertilizer compared to that of normal fertilizer. The pH in the soil contaminated with Cd was 5.80 (alkaline fertilizer applied), higher than that of 5.74 (normal fertilizer applied), alkaline fertilizer improve pH soil, cure Cd pollution, bring to rice specific nutrients, at specific moment that rice need to growth and achieve the effect of inhibiting soil pollution, more in hyper accumulation rice than that low accumulation one. Conclusion and application of results: The results should be helpful in determining appropriate amounts of alkaline fertilizer rice farmers should use to return farm land to productive food crop use, beyond that it was thought cane would be helpful in cadmium uptake from soil. Some rice farmers were reluctant to follow this transition and insisted on growing their rice for survival, alkaline fertilizers can better stop soil pollution and increase the soil pH value. The application of alkaline fertilizer achieves the effect of "controlling Cd pollution with fertilizer". Key words: alkaline fertilizer, pH, Cd, normal pH fertilizer, accumulation

Evaluation of Heavy Metal Phytoextraction Potential of Rhizophora Racemosa in Niger Delta Mangrove Forest, Rivers State, Nigeria

The bio transfer and bio translocation factors of heavy metals in the tissues of Rhizophora racemose was evaluated in this study. Soil, roots and shoot samples of the study plant were randomly collected from Kono, Bomu, Ogu and Borokiri mangrove forests at wet and dry seasons, digested and analyzed for heavy metals using standard laboratory methods. The laboratory results of field samples were further subjected to bio transfer and bio translocation factors analysis. Findings on wet season bio transfer factor revealed the concentrations of Cr (0.36mg/kg), Ni (0.86 mg/kg), Cd (2.86 mg/kg), Pb (1.17 mg/kg) and Zn (1.85 mg/kg), while dry season showed Cr (0.36mg/kg), Ni (0.55 mg/kg), Cd (1.24 mg/kg), Pb (2.72 mg/kg) and Zn (1.99 mg/kg). The bio translocation factor results for wet season indicated the concentrations of Cr (0.51mg/kg), Ni (1.47 mg/kg), Cd (1.02 mg/kg), Pb (1.48 mg/kg) and Zn (0.88 mg/kg), while dry season result revealed Cr (0.41mg/kg), Ni (0.65 mg/kg), Cd (1.24 mg/kg), Pb (1.50 mg/kg) and Zn (0.81 mg/kg). This study therefore classifies Rhizophora racemose as a hyper accumulator of Pb and Cd in shoot tissues and non-hyper accumulator of Cr, Ni and Zn in root tissues. Beside other uses, the plant has shown high affinity for the accumulation of heavy metals and thus can be used for phytoremediation. Keywords: Phytoextraction, mangrove, heavy metals, evaluation, bio-transfer, bio-translocation DOI: 10.7176/JNSR/12-14-03 Publication date: July 31 st 2021

Low nitrogen availability inhibits the phosphorus starvation response in maize (Zea mays ssp. mays L.)

BackgroundNitrogen (N) and phosphorus (P) are macronutrients essential for crop growth and productivity. In cultivated fields, N and P levels are rarely sufficient, contributing to the gap between realized and potential production. Fertilizer application increases nutrient availability, but is not available to all farmers, nor are current rates of application sustainable or environmentally desirable. Transcriptomic studies of cereal crops have revealed dramatic responses to either low N or low P single stress treatments. In the field, however, levels of both N and P may be suboptimal. The interaction between N and P starvation responses remains to be fully characterized.ResultsWe characterized growth and root and leaf transcriptomes of young maize plants under nutrient replete, low N, low P or combined low NP conditions. We identified 1555 genes to respond to our nutrient treatments, in one or both tissues. A large group of genes, including many classical P starvation response genes, were regulated antagonistically between low N and P conditions. An additional experiment over a range of N availability indicated that a mild reduction in N levels was sufficient to repress the low P induction of P starvation genes. Although expression of P transporter genes was repressed under low N or low NP, we confirmed earlier reports of P hyper accumulation under N limitation.ConclusionsTranscriptional responses to low N or P were distinct, with few genes responding in a similar way to the two single stress treatments. In combined NP stress, the low N response dominated, and the P starvation response was largely suppressed. A mild reduction in N availability was sufficient to repress the induction of P starvation associated genes. We conclude that activation of the transcriptional response to P starvation in maize is contingent on N availability.

Garlic (Allium sativum) based interplanting alters the heavy metals absorption and bacterial diversity in neighboring plants

Heavy metals are naturally occurring elements that have a high atomic weight and let out in the environment by agriculture, industry, mining and therapeutic expertise and thrilling amassing of these elements pollutes the environment. In this study we have investigated the potential of garlic interplanting in promoting hyper accumulation and absorption of heavy metals to provide a basis for phytoremediation of polluted land. Monoculture and inter-plantation of garlic were conducted to investigate the absorption of cadmium and lead contamination in the land. A group of experiments with single planting (monoculture) of Lolium perenne, Conyza canadensis and Pteris vittata as accumulators were used. The results have shown that garlic has a potential as a hyper accumulate and absorb heavy metals. It was found that the accumulation of Cd and Pb was much higher with inter-planting. Garlic boosts up the absorption of heavy metals in Lolium perenne of Cd 66% and Pb 44% respectively. The Inter-planting of garlic with Pteris vittata promotes the Cd 26% and Pb 15%. While the maximum accumulation of Lead 87% and Cadmium 77% occurred in Conyza canadensis herb plant. The bacterial diversity in the soil was analyzed for each experimental soil and was found that the Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes, and Planctomycetes were commonly abundant in both single planting (monoculture) of ryegrass and interplanting ryegrass with garlic habitats. Variances were observed in the bacterial floral composition of single (monoculture) and intercropping (interplant) soils. Relative abundance of bacterial taxa revealed that the proportion of Proteobacteria, Acidobacteria, and Actinobacteria in the inter-planting group was slightly higher, while Firmicutes and Planctomycetes were low. This study provides the evidence to control the heavy metals contaminated soils with weed species. Growth promotion and heavy metal uptake of neighboring plants proved the specific plant-plant and plant-microbial associations with garlic plants. This inter-planting strategy can be used to improve heavy metal absorption.

Effect of endophytic-assisted phytoremediation on plant growth and chromium (Cr) toxicity reduction in contaminated soil

This study focused on phytoremediation of chromium (Cr) through endophytic bacteria. Four endophytic bacteria i.e. Pseudomonas putida (CEN2), Pseudomonas aeruginosa (CEN3), Acinetobacter baumanni (CEN4), and Pseudomonas aeruginosa (CEN5) were selected for phytoremediation experiments to investigate its effects on plant growth and Cr uptake. Phytoremediation experiment was carried out by using one hyper accumulator (Brassica napus) and one non-hyper accumulator plant (Coriandrum sativum), grown in agricultural soil amended with three different concentrations 50 ppm, 100 ppm and 200 ppm of Cr for 60 days. In Brassica napus, endophytic consortia showed maximum root, shoot elongation and vigour index at all concentrations. In Coriandrum sativum CEN5 strain showed maximum root, shoot length and vigour index. Brassica napus with consortia produced maximum fresh and dry biomass as compared to the control treatments. Therefore, endophytic-assisted phytoremediation could be a promising tool for mitigating heavy metals toxicity from polluted soil without any negative effects on plant growth.