Shoot Uptake Research Articles

Root and Shoot Uptake of Synthesized Nano Zno and Its Impact on Differences in Bio-Availability During Exposure In Aqueous Suspension

The proposed study highlights on the synthesis of Zinc oxide nanoparticles using chemical and green methods. In the field of nanotechnology Green synthesis is an eco-friendly development. The synthesis of ZnO is carried out using leaf extract of Azadirachta indica (neem) as a reducing agent. The synthesised products were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDAX). The present work is to investigate the effect of chemical and green synthesized zinc oxide nanoparticles on germination and growth of Lycopersicon esculentum (tomato) using petriplate seed germination method. The impact of concentration of applied ZnO nanoparticles via green synthesis and chemical methods were analyzed. It was observed that the growth of Seedling is maximum for green synthesized zinc oxide nanoparticles at appropriate concentration over chemically synthesized zinc oxide nanoparticles, bulk ZnO and control. Hence the green method is found to be more effective.

Comparative assessment of Indian mustard (Brassica juncea L.) genotypes for phytoremediation of Cd and Pb contaminated soils

Heavy metal removal by phytoremediation bears a great potential to decontaminate soils and Brassica juncea L. (Indian mustard) seems to be a possible candidate species for this purpose. A field experiment was conducted to compare the efficiency of eighty Indian mustard cultivars for phytoextraction of cadmium (Cd) and lead (Pb) from bimetal contaminated soil. Our results indicated that total Cd and Pb concentrations in the shoots and roots were in the range of 2.43 ± 0.00 to 0.31 ± 0.02 mg/kg and 2.94 ± 0.05 to 0.44 ± 0.03 mg/kg and 5.33 ± 0.76 to 0.47 ± 0.20 mg/kg and 3.78 ± 0.06 to 0.16 ± 0.08 mg/kg. Significant differences based on the translocation factors indicated that root-to-shoot transfer is higher for Pb (3.87 ± 0.12 to 0.48 ± 0.03) than Cd (3.38 ± 0.05 to 0.22 ± 0.01). Furthermore, significant correlations between dry weights, Cd and Pb concentrations and uptake in both shoots and roots were observed, but translocation factor showed a negative correlation with roots, but not in shoots. Among 80 genotypes of Indian mustard IM-25, IM-13 and IM-65 for Cd and IM-79, IM-24 and IM-32 for Pb seems to perform well for phytoextraction. The results of the field experiment suggest that certain Brassica juncea L. cultivars are suitable for removal of Cd and Pb in low to moderately contaminated soils.

Earthworm activities weaken the immobilizing effect of biochar as amendment for metal polluted soils

The effect of earthworms on the immobilization of heavy metals by biochar was investigated using 4-week soil pot experiments. Our results showed that both sludge and rice husk biochars applied to Cd, Pb and Zn contaminated soils significantly reduced the bioavailability of those heavy metals in soils, and their concentrations in soil pore water. The Cd and Pb concentrations in pakchoi shoots were decreased by 10.8%–11.7% and 21.5%–26.5%, respectively, in biochar treatments alone. Biochar and earthworm treatments, alone or in combination, can significantly increase pakchoi growth. However, compared with biochar-treated alone, applying earthworms into pots with biochar treatments significantly reduced soil pH by 0.1–0.19 units, increased the Cd, Pb and Zn concentrations in soil pore water, their bioavailability and total uptake in shoots. Additionally, earthworms weaken the immobilization effect of biochar on heavy metals. The results of principal component analysis and correlation analysis showed that earthworm treatment was the main cause of soil pH reduction, and soil pH was significantly negatively correlated with the bioavailable Cd, Pb and Zn concentrations in the soil. Furthermore, the effect of the earthworm digestive system (casts) on bioavailable Cd, Pb and Zn concentrations could not explain their changes in the soil. In addition, the application of biochar had no significant effect on the survival and heavy metal enrichment of earthworm. Therefore, the effect of earthworms must be considered in the process of Cd, Pb and Zn contaminated farmland soil remediation using biochar.

Lead Phytostabilization and Cationic Micronutrient Uptake by Maize as Influenced by Pb Levels and Application of Low Molecular Weight Organic Acids

ABSTRACTPhytoremediation is a promising technique to clean up toxic heavy metals including lead (Pb). A greenhouse trial was conducted to evaluate the effectiveness of citric, succinic, malonic and oxalic acids on micronutrient uptake and phytoremediation of Pb contaminated soil by maize under different Pb levels. Mean root and shoot dry weights of maize decreased with increasing Pb levels. At the lowest Pb level, application of citric and oxalic acids caused increase effects on root and shoot dry weight, respectively, as compared to the absence of organic acid. As Pb levels increased, micronutrient uptake in maize shoot decreased. Among the studied organic acids, only the application of oxalic acid increased uptake of all micronutrients in maize shoot as compared to control at the lowest Pb level. Mean root and shoot Pb concentration and uptake and also uptake index noticeably increased at the highest Pb level. All tested acids increased Pb concentration and uptake in maize root. At the highest Pb level, organic acids, except for citric acid, significantly increased shoot Pb uptake and uptake index as compared to the absence of organic acid. Translocation factors less than 1, demonstrated that most of Pb taken up by maize accumulated in root as compared to shoot. According to results reported herein, application of malonic, succinic and oxalic acids is a good strategy to enhance phytostabilization potential of Pb by maize in pb-polluted soils.

Enhanced Ni phytoextraction by effectiveness of chemical and biological amendments in sunflower plant grown in Ni-polluted soils

ABSTRACTA greenhouse study was conducted as a completely randomised design in a factorial arrangement to assess how inoculation of AMF (arbuscular mycorrhizal fungus) and application of EDTA (ethylenediaminetetracetic acid) as biological and chemical amendments can affect the Ni (nickel) phytoremediation in Ni-polluted soils using sunflower plant. The results showed that the inoculation of AMF increased root colonisation while applying EDTA and high level of Ni decreased it. Microbial incubation has a positive effect on both shoot and root dry yields; however, co-application of Ni and EDTA demoted the growth rate. Shoot nutrients uptake of plants decreased as Ni levels increased. In inoculated plants, shoot uptake of Zn, Fe and Mn was higher in all Ni levels than non-inoculated plants. Ni uptake in plant shoots and roots increased with applying both AMF and EDTA. However, the mean Ni concentration and uptake in inoculated plants along with applying EDTA are higher in sunflower shoots than in roots. As Ni levels increased, Ni extraction and uptake efficiencies increased; it can be concluded co-application of EDTA and AMF was effective in increasing phytoextraction potential of sunflower plants in Ni-contaminated sites. This study highlights that AMF could be suitable for cleaning Ni-polluted areas and it could significantly contribute to phytoremediation technology.

Zinc oxide nanoparticles alleviate drought-induced alterations in sorghum performance, nutrient acquisition, and grain fortification

Drought is a major environmental event affecting crop productivity and nutritional quality, and potentially, human nutrition. This study evaluated drought effects on performance and nutrient acquisition and distribution in sorghum; and whether ZnO nanoparticles (ZnO-NPs) might alleviate such effects. Soil was amended with ZnO-NPs at 1, 3, and 5 mg Zn/kg, and drought was imposed 4 weeks after seed germination by maintaining the soil at 40% of field moisture capacity. Flag leaf and grain head emergence were delayed 6–17 days by drought, but the delays were reduced to 4–5 days by ZnO-NPs. Drought significantly (p < 0.05) reduced (76%) grain yield; however, ZnO-NP amendment under drought improved grain (22–183%) yield. Drought inhibited grain nitrogen (N) translocation (57%) and total (root, shoot and grain) N acquisition (22%). However, ZnO-NPs (5 mg/kg) improved (84%) grain N translocation relative to the drought control and restored total N levels to the non-drought condition. Shoot uptake of phosphorus (P) was promoted (39%) by drought, while grain P translocation was inhibited (63%); however, ZnO-NPs lowered total P acquisition under drought by 11–23%. Drought impeded shoot uptake (45%), grain translocation (71%) and total acquisition (41%) of potassium (K). ZnO-NP amendment (5 mg/kg) to drought-affected plants improved total K acquisition (16–30%) and grain K (123%), relative to the drought control. Drought lowered (32%) average grain Zn concentration; however, ZnO-NP amendments improved (94%) grain Zn under drought. This study represents the first evidence of mitigation of drought stress in full-term plants solely by exposure to ZnO-NPs in soil. The ability of ZnO-NPs to accelerate plant development, promote yield, fortify edible grains with critically essential nutrients such as Zn, and improve N acquisition under drought stress has strong implications for increasing cropping systems resilience, sustaining human/animal food/feed and nutrition security, and reducing nutrient losses and environmental pollution associated with N-fertilizers.

Rice straw biochar and phosphorus inputs have more positive effects on the yield and nutrient uptake of Lolium multiflorum than arbuscular mycorrhizal fungi in acidic Cd-contaminated soils

The purpose of the study was to examine biochar amendment, phosphorus (P) fertilizer and arbuscular mycorrhizal fungi (AMF) on the yield, nutrient and cadmium (Cd) absorption of Lolium multiflorum in acidic soil. It was shown that mycorrhizal inoculation had no positive influence on the plant shoot biomass and the contents of nitrogen (N), P, potassium (K), calcium (Ca) and magnesium (Mg) in plants at all biochar and P level treatments. Irrespective of mycorrhizal inoculation and P level, biochar amendments markedly elevated the soil available P and K uptake in plant tissues. In contrast, biochar significantly decreased the translocation factor of plants, soil exchangeable Cd, and acid and neutral phosphatase activities, regardless of the mycorrhizal inoculation and P fertilizer. Without P fertilization, biochar amendments significantly promoted shoot P content, while biochar amendments significantly reduced shoot P content when P fertilizer was applied. Without biochar application, P fertilizer application significantly promoted the biomass and N uptake of shoots in both AMF inoculation treatments, while P fertilizer increased these only in the presence of biochar and mycorrhizal inoculation. The increased N content induced by the biochar amendment elevated the shoot N:P ratio and alleviated the N deficiency with P fertilizer input. Thus, we concluded that the addition of biochar and P fertilizer showed more positive effects on the promotion of growth and nutrient uptake of L. multiflorum than AMF grown in acidic Cd-contaminated soils.

Phytostabilization of Zn and Cd in Mine Soil Using Corn in Combination with Biochars and Manure-Based Compost

Mining activities could produce a large volume of spoils, waste rocks, and tailings, which are usually deposited at the surface and become a source of metal pollution. Phytostabilization of the mine spoils could limit the spread of these heavy metals. Phytostabilization can be enhanced by using soil amendments such as manure-based biochars capable of immobilizing metal(loid)s when combined with plant species that are tolerant of high levels of contaminants while simultaneously improving properties of mine soils. However, the use of manure-based biochars and other organic amendments for mine spoil remediation are still unclear. In this greenhouse study, we evaluated the interactive effect of biochar additions (BA) with or without the manure-based compost (MBC) on the shoots biomass (SBY), roots biomass (RBY), uptake, and bioconcentration factor (BCF) of Zn and Cd in corn (Zea mays L.) grown in mine soil. Biochar additions consisting of beef cattle manure (BCM); poultry litter (PL); and lodge pole pine (LPP) were applied at 0, 2.5, and 5.0% (w/w) in combination with different rates (0, 2.5, and 5.0%, w/w) of MBC, respectively. Shoots and roots uptake of Cd and Zn were significantly affected by BA, MBC, and the interaction of BA and MBC. Corn plants that received 2.5% PL and 2.5% BCM had the greatest Cd and Zn shoot uptake, respectively. Corn plants with 5% BCM had the greatest Cd and Zn root uptake. When averaged across BA, the greatest BCF for Cd in the shoot of 92.3 was from the application of BCM and the least BCF was from the application of PL (72.8). Our results suggest that the incorporation of biochar enhanced phytostabilization of Cd and Zn with concentrations of water-soluble Cd and Zn lowest in soils amended with manure-based biochars while improving the biomass productivity of corn. Overall, the phytostabilization technique and biochar additions have the potential to be combined in the remediation of heavy metals polluted soils.

Gene identification and transcriptome analysis of low cadmium accumulation rice mutant (lcd1) in response to cadmium stress using MutMap and RNA-seq

BackgroundCadmium (Cd) is a widespread toxic heavy metal pollutant in agricultural soil, and Cd accumulation in rice grains is a major intake source of Cd for Asian populations that adversely affect human health. However, the molecular mechanism underlying Cd uptake, translocation and accumulation has not been fully understood in rice plants.ResultsIn this study, a mutant displaying extremely low Cd accumulation (lcd1) in rice plant and grain was generated by EMS mutagenesis from indica rice cultivar 9311 seeds. The candidate SNPs associated with low Cd accumulation phenotype in the lcd1 mutant were identified by MutMap and the transcriptome changes between lcd1 and WT under Cd exposure were analyzed by RNA-seq. The lcd1 mutant had lower Cd uptake and accumulation in rice root and shoot, as well as less growth inhibition compared with WT in the presence of 5 μM Cd. Genetic analysis showed that lcd1 was a single locus recessive mutation. The SNP responsible for low Cd accumulation in the lcd1 mutant located at position 8,887,787 on chromosome 7, corresponding to the seventh exon of OsNRAMP5. This SNP led to a Pro236Leu amino acid substitution in the highly conserved region of OsNRAMP5 in the lcd1 mutant. A total of 1208 genes were differentially expressed between lcd1 and WT roots under Cd exposure, and DEGs were enriched in transmembrane transport process GO term. Increased OsHMA3 expression probably adds to the effect of OsNRAMP5 mutation to account for the significant decreases in Cd accumulation in rice plant and grain of the lcd1 mutant.ConclusionsAn extremely low Cd mutant lcd1 was isolated and identified using MutMap and RNA-seq. A Pro236Leu amino acid substitution in the highly conserved region of OsNRAMP5 is likely responsible for low Cd accumulation in the lcd1 mutant. This work provides more insight into the mechanism of Cd uptake and accumulation in rice, and will be helpful for developing low Cd accumulation rice by marker-assisted breeding.

Effect of Vermicompost and Compound inorganic Fertilizer on Soil Phosphate Availability and Yield of Potatoes (Solanum tuberosum L.) Grown in Andisols

Potatoes (Solanum tuberosum L.) which are comonly grown in the highland with Andisols require organic and inorganic fertilizers to maintain soil health and increase yield. The purpose of field experiment was to obtain information on the effect of vermicompost with and without NPK fertilizer on soil acidity, soil phosphor (P) availability and P uptake in potatoes shoot; as well as yield and quality of tuber. The experimental design was a randomized block design with eight treatments and three replication. The treatment consisted of a combination of vermicompost doses (5 and 10 t/ha) with NPK fertilizer doses (0; 0.5 t/ha and 1 t/ha). The two control treatments were 1) without fertilizer and 2) the method of fertilizing local farmers included 10 t /ha chicken manure and 1 t/ha NPK fertilizer. This experiment verified that vermicompost and NPK fertilizer increased plant height as well as soil P availability and acidity compared to those of control. Vermicompost has not yet substitute chicken manure to obtain the same tuber production although the percentage of marketable tuber was quite similar. Keywords : Andisols, NPK Fertilizer, Phosphorus, Potato, Vermicompost.

Rice OsHAK16 functions in potassium uptake and translocation in shoot, maintaining potassium homeostasis and salt tolerance.

OsHAK16 mediates K uptake and root-to-shoot translocation in a broad range of external K concentrations, thereby contributing to the maintenance of K homeostasis and salt tolerance in the rice shoot. The HAK/KUP/KT transporters have been widely associated with potassium (K) transport across membranes in both microbes and plants. Here, we report the physiological function of OsHAK16, a member belonging to the HAK/KUP/KT family in rice (Oryza sativa L.). Transcriptional expression of OsHAK16 was up-regulated by K deficiency or salt stress. OsHAK16 is localized at the plasma membrane. OsHAK16 knockout (KO) dramatically reduced root K net uptake rate and growth at both 0.1mM and 1mM K supplies, while OsHAK16 overexpression (OX) increased total K uptake and growth only at 0.1mM K level. OsHAK16-KO decreased the rate of rubidium (Rb) uptake and translocation compared to WT at both 0.2mM and 1mM Rb levels. OsHAK16 disruption decreased while its overexpression increased K concentration in root slightly but in shoot remarkably. The relative distribution of total K between shoot and root decreased by 30% in OsHAK16-KO lines and increased by 30% in its OX lines compared to WT. OsHAK16-KO diminished K uptake and K/Na ratio, while OsHAK16-OX improved K uptake and translocation from root to shoot, resulting in increased sensitivity and tolerance to salt stress, respectively. Expression of OsHAK16 enhanced the growth of high salt-sensitive yeast mutant by increasing its K but no Na content. Taking all these together, we conclude that OsHAK16 plays crucial roles in maintaining K homeostasis and salt tolerance in rice shoot.

Ameliorative Effects of Biochar on Rapeseed (Brassica napus L.) Growth and Heavy Metal Immobilization in Soil Irrigated with Untreated Wastewater

Untreated wastewater carries substantial amount of heavy metals and causes potential ecological risks to the environment, food quality, and soil health. The pot study was established to evaluate the effectiveness of woodchip-derived biochar (BC) on rapeseed biomass, photosynthetic pigments, antioxidant enzyme activities, such as peroxidase (POD), ascorbate peroxidase (APX), polyphenol peroxidase (PPO), catalase enzyme (CAT), and heavy metal-induced phytotoxicity under untreated domestic (DWW) and industrial (IWW) wastewater irrigation. Biochar was applied at three levels (0, 1, and 2%) combined with DWW and IWW treatments. Wastewater analysis indicated higher heavy metal concentrations than the safer limits set by FAO. Results revealed that DWW and IWW treatments without biochar incorporation adversely affected the rapeseed growth performance, photosynthetic pigments, and antioxidative defense system. Compared with DWW and IWW treatments, BC at 2% rate significantly enhanced shoot fresh biomass (41% and 72%), root fresh biomass (34% and 62%), total chlorophyll (79% and 85%), total pigments (77% and 108%), carotenoids (74% and 94%), and lycopene concentration (43% and 61%), respectively. In addition, BC also improved the antioxidant enzymes activities by reducing the heavy metal-induced oxidative stress in rapeseed leaves. Similarly, AB-DTPA extractable Cd was decreased by (44% and 26%), Pb (51% and 54%), Ni (59% and 56%), and Cu (45% and 41%) in soil when BC was applied at 2% application rate along with DWW and IWW treatments and thereby reduced their uptake in shoots and roots of rapeseed. Therefore, BC can be considered an efficient strategy to ameliorate the hazardous effects of untreated DWW and IWW wastewater and to enhance rapeseed biomass, physiological attributes, and antioxidant enzyme activities.

Inoculation With Piriformospora indica Is More Efficient in Wild-Type Rice Than in Transgenic Rice Over-Expressing the Vacuolar H+-PPase.

Achieving food security in a context of environmental sustainability is one of the main challenges of the XXI century. Two competing strategies to achieve this goal are the use of genetically modified plants and the use of plant growth promoting microorganisms (PGPMs). However, few studies assess the response of genetically modified plants to PGPMs. The aim of this study was to compare the response of over-expressing the vacuolar H+-PPase (AVP) and wild-type rice types to the endophytic fungus; Piriformospora indica. Oryza sativa plants (WT and AVP) were inoculated with P. indica and 30 days later, morphological, ecophysiological and bioenergetic parameters, and nutrient content were assessed. AVP and WT plant heights were strongly influenced by inoculation with P. indica, which also promoted increases in fresh and dry matter of shoot in both genotypes. This may be related with the stimulatory effect of P. indica on ecophysiological parameters, especially photosynthetic rate, stomatal conductance, intrinsic water use efficiency and carboxylation efficiency. However, there were differences between the genotypes concerning the physiological mechanisms leading to biomass increment. In WT plants, inoculation with P. indica stimulated all H+ pumps. However, in inoculated AVP plants, H+-PPase was stimulated, but P- and V-ATPases were inhibited. Fungal inoculation enhanced nutrient uptake in both shoots and roots of WT and AVP plants, compared to uninoculated plants; but among inoculated genotypes, the nutrient uptake was lower in AVP than in WT plants. These results clearly demonstrate that the symbiosis between P. indica and AVP plants did not benefit those plants, which may be related to the inefficient colonization of this fungus on the transgenic plants, demonstrating an incompatibility of this symbiosis, which needs to be further studied.

Chelate-assisted phytoextraction of lead using Fagopyrum esculentum: laboratory vs. field experiments

The development of more sustainable remediation techniques has been receiving greater attention, as an alternative to soil excavation plan in urban gardens. An in situ phytoextraction experiment with buckwheat (Fagopyrum esculentum) was performed with a 5 mmol kg−1 citric acid (CA) application. Joint experiments under laboratory conditions were conducted using various cultivars of F. esculentum in two soils with a Pb contamination of either geogenic or anthropogenic origin and various chelate concentrations. Results show that a minimum dose of 50 mmol kg−1 of CA is required to lower soil pH and raise the concentration of mobile Pb–CaCl2 for both soils. Consequently, Pb shoot uptake is increased from 6.3 to 8.9 times depending on soil type. Phytoextraction efficiency is found to be 1.3 to 2.0 times higher in the anthropogenic contaminated soil than in the soil with geogenic Pb. A scale effect has also been identified since Pb root accumulation under laboratory conditions was 2.4 times higher than in the field experiment. Despite an increase in the Pb extraction rate with CA, buckwheat appears to lack the efficiency needed to remove Pb in moderately contaminated soils. The calculated remediation period would last 166 years to remove the mobile Pb fraction.

Zinc Uptake, Translocation, and Remobilization in Winter Wheat as Affected by Soil Application of Zn Fertilizer.

Effect of zinc (Zn) application to soil on root growth and Zn uptake and translocation in winter wheat are poorly understood. This study evaluated the effect of soil Zn fertilization (0, 2.3, 5.7, 11.4, 22.7, 34.1 kg of Zn ha−1) on root growth and distribution, crop Zn uptake, root-to-shoot translocation of Zn, and remobilization of Zn from shoot to grain. Results of this study revealed that Zn application ≤11.4 kg ha−1 significantly increased root dry weight, root length density, and root surface area within 0–30 cm soil depth and higher rates of Zn application caused slight decreases in these root parameters. Shoot biomass and shoot Zn accumulation increased as Zn application rate increased mainly because of improved matching of root growth and enhanced availability of Zn in the topsoil layer. Post-anthesis Zn uptake by shoot increased and translocation of Zn from root to shoot decreased as rate of Zn application increased. The degree to which Zn accumulation in grain resulted from pre-anthesis remobilization vs. post-anthesis shoot uptake depended on Zn availability in soil; post-anthesis shoot uptake dominated at DTPA-Zn concentrations >7.15 mg kg−1, and pre-anthesis remobilization dominated at lower soil Zn levels. In conclusion, Zn uptake, translocation and remobilization to grain were affected by root growth and its matching with the availability of soil Zn. The results suggest that soils similar to the study soil should be fertilized to 30 cm depth with about 11.4 kg ha−1 Zn in order to obtain high yield and grain Zn concentration of wheat.

Effects of Soil-Applied Materials on the Dry Weight and Boron Uptake of Maize Shoots (Zea Mays L.) Under High Boron Conditions

ABSTRACTHigh concentrations of boron (B) in the soil, reduces plant growth, crops’ yield and quality. Regarding such problem, synergistic and antagonistic relations between the nutrients can be used to ameliorate the B toxicity. Therefore, a greenhouse experiment was conducted to evaluate effects of soil-applied zinc (Zn), nitrogen (N), calcium (Ca), lime (CaCO3), potassium (K), humic acid (HA), and humus on the dry weight and B uptake of maize shoots (Zea mays L.) under high-B containing soil conditions. Increasing doses of B (0, 2.5, 5, and 10 mg kg−1 B) were applied to soil as borax (Na2B4O710H2O), and boric acid (H3BO3). Positive correlations were found between B doses and the uptake amounts (r = 0.934**; – 0.964**). However, the correlations between the dry weight and B doses (r = −0.314**; – r = −0.495**) and between the dry weight and the uptake amounts (r = −0.294*; – r = −0.497**) were negative. Among the materials, Zn and humus exhibited positive correlations with dry weight values (r = 0.249*; r = 0.525**), and an effective increase (p < 0.01) in the dry weight amounts of maize shoots was observed under toxic B conditions.

Phytoremediation of Heavy Metal-Contaminated Soil by Switchgrass: A Comparative Study Utilizing Different Composts and Coir Fiber on Pollution Remediation, Plant Productivity, and Nutrient Leaching

We investigated the effects of organic amendments (thermophilic compost, vermicompost, and coconut coir) on the bioavailability of trace heavy metals of Zn, Cd, Pb, Co, and Ni from heavy metal-spiked soils under laboratory conditions. To test switchgrass (Panicum virgatum) as a potential crop for phytoremediation of heavy metal from soil, we investigated whether the addition of organic amendments promoted switchgrass growth, and consequently, uptake of metals. Compost is a valuable soil amendment that supplies nutrients for plant establishment and growth, which is beneficial for phytoremediation. However, excess application of compost can result in nutrient leaching, which has adverse effects on water quality. We tested the nutrient leaching potential of the different organic amendments to identify trade-offs between phytoremediation and water quality. Results showed that the amendments decreased the amount of bioavailable metals in the soils. Organic amendments increased soil pH, electrical conductivity (EC), and soil nutrient status. Switchgrass shoot and root biomass was significantly greater in the amended soils compared to the non-amended control. Amended treatments showed detectable levels of heavy metal uptake in switchgrass shoots, while the control treatment did not produce enough switchgrass biomass to measure uptake. Switchgrass uptake of certain heavy metals, and concentrations of some leachate nutrients significantly differed among the amended treatments. By improving soil properties and plant productivity and reducing heavy metal solubility that can otherwise hamper plant survival, organic amendments can greatly enhance phytoremediation in heavy metal-contaminated soils.

Eutrophication triggers the shift of nutrient absorption pathway of submerged macrophytes: Implications for the phytoremediation of eutrophic waters

Ecologically restoring eutrophic water bodies by using submerged macrophytes is an economical, effective and sustainable technology worldwide. However, current understanding on the nutrient absorption pathway of submerged macrophytes in freshwater ecosystems, especially under different trophic states, is still limited. In this study, two strategically designed systems were established to form isolated units for preventing nutrient exchange amongst Potamogeton crispus, water column and sediments. Results showed that, in oligotrophic state, P. crispus mainly relied on their roots to absorb nutrients from sediments for maintaining stable growth, with the maximum average height, fresh weight and relative growth rate of 12.85 cm, 4.86 g ind−1 and 0.062, respectively. However, the eutrophic conditions (TN of 4 mg L−1 and TP of 0.3 mg L−1) triggered the shift of the nutrient absorption pathway from the roots to the shoots to some extent, that is, the shoots of P. crispus gradually became a remarkable pathway to directly absorb nutrients from the water column. Approximately 49.85% and 18.35% of total nitrogen (TN) and total phosphorus (TP) from overlying water were allocated to the shoots of P. crispus, but had no effects on the growth, photosynthesis and ecological stoichiometric differences (p > 0.05). Sediments acting as a nitrogen (N) source supported nearly 11.56% of TN for shoot uptake and simultaneously received around 13.33% of TP subsidy from the overlying water. The no longer sole dependence of submerged macrophytes on their root system to absorb N and phosphorus nutrients indicated that the ability of shoots to absorb nutrients increased with the gradual increase in nutrients in water column. These findings imply that the large specific surface area of shoots is beneficial for restoring eutrophic waters.

Influence of P Sources and Rhizobium Inoculation on Growth and Yield of Soybean Genotypes on Ferric Lixisols of Northern Guinea Savanna Zone of Ghana

ABSTRACTSoybean is becoming an important cash crop in northern Ghana. Yet the yields are low due to use of low yielding varieties and limited use of inputs. Greenhouse and field experiments were carried out to evaluate the effects of two phosphorus (P) sources and Rhizobium inoculation on growth, nodulation, P uptake, and yield of three soybean genotypes on Ferric Lixisols of the Guinea savanna zone of Ghana. The P sources were triple superphosphate (TSP) and Morocco phosphate rock (MPR), while the genotypes were TGx 1448-2E, TGx 1904-6F, and TGx 1955-4F. The greenhouse experiment was conducted at the University of Ghana, Legon in a completely randomized design. The field experiment which was carried out in the Upper East region of Ghana was laid out in a split-split plot design with four replicates. In both the greenhouse and field experiments, application of TSP at 30 kg P ha−1 resulted in significantly higher growth and P uptake in shoot compared with MPR and control. Soybean genotypes showed significant differences in growth, nutrient uptake, and grain yield in both the greenhouse and the field experiments. Rhizobium inoculation increased nodule number and dry weight but did not increase grain yield. The genotype TGx 1955-4F appears to show greater potential for increasing productivity of soybean in low P soils in northern Ghana.

The Use of Agrobacterium sp.I3 and Compost as Chelator Combined by NPK Fertilizer and Mendong Plant (Fimbristylis sp.) in Bioremediation of Paddy Soil Contaminated by Lead (Pb)

Industrial waste supplies contains heavy metals such as Pb which will cause pollution in paddy fields. Remediation of paddy soil contaminated by Pb heavy metal must be done by simple, environmental friendly, cheap and sustainable technology, that is bioremediation. The purpose of this study was to study the effectiveness of bioremediation using Agrobacterium sp. I3 and compost as chelator combined by Mendong plant and NPK fertilizer, and learn the ability of Mendong in uptaking metal soil Pb. This was field experimental research, had a factorial patern, using Completly Randomized Block Design as the base design, with three factors: (1) NPK fertilizers (P0: no NPK fertilizers, P1: with NPK fertilizers), (2) Chelator (K0: no chelator; K1: with chelator Agrobacterium sp. I3 ; K2: with chelator compost); and (3) Plant (T0: without plant; T1: with Mendong plant). The results showed that Agrobacterium sp. I3 and compost were increasing Pb uptake in shoot, but decreasing Pb uptake in root. Mendong plant has highly ability in uptaking soil Pb, so decreased soil Pb, and effective as the phytoremediator. NPK fertilizer increased plant growth so increased Pb uptaken by plant. The highest Pb uptake was in treatment combination of NPK fertilizer + Mendong plant: 80.916 µg, followed by NPK fertilizer + Agrobacterium sp. I3 + Mendong Plant: 76.363 µg. The highest decreased of soil Pb (42.41%) was found in treatment combination of compost + Mendong Plant. Key words: Agrobacterium sp.I3, compost, Fimbristylis sp, Pb, phytoremediation