Accumulation In Maize Research Articles

Imbalance of redox homeostasis and antioxidant defense status in maize under chromium (VI) stress

The present study assesses the toxicity of hexavalent chromium [Cr(VI)] on maize (Zea mays L.) seedlings. Three different levels of Cr stress [50, 100 and 200 mg/l CrO3] were imposed and maize seedling growth performances were monitored at 2d and 4d. Modulation of antioxidant genes expression, metabolites, membrane damage, in vivo ROS detection, foliar H2O2 and proline accumulation were studied in detail to get an overview of Cr stress response of maize. Prime stress responses included marked reduction in plant height and biomass, loss of root cell viability with decreased APX-1, Cu/Zn SOD and DHAR expression and high accumulation of Cr in roots with little translocation to shoots. Higher uptake of Evans blue by Cr challenged roots indicates loss of root cells viability. In vivo detection of superoxides and H2O2 as dark blue and deep brown spots in stressed leaves supported with CM-H2DCFDA and DHE staining of roots strongly suggest severe oxidative burst under Cr stress. Marked decline in MDAR and DHAR expression in 200 mg/l Cr challenged leaves at 4d with non-significant change in AsA/DHA ratio indicate futile recycling of ascorbate pool which might lead to disturbance in redox homeostasis. Isolated increase in GR expression coupled with high GSH/GSSG do not seem to prevent cells from oxidative damages, as evident from high foliar MDA level in Cr challenged seedlings. Moreover, enhanced proline accumulation in maize leaves does not give much protection against Cr stress. Over all, this study facilitates our understanding of the plant’s adaptive mechanisms to Cr stress.

Maize phenylalanine ammonia-lyases contribute to resistance to Sugarcane mosaic virus infection, mostlikely throughpositive regulation of salicylic acid accumulation.

Summary Sugarcane mosaic virus (SCMV) is a pathogen of worldwide importance that causes dwarf mosaic disease on maize (Zea mays). Until now, few maize genes/proteins have been shown to be involved in resistance to SCMV. In this study, we characterized the role of maize phenylalanine ammonia‐lyases (ZmPALs) in accumulation of the defence signal salicylic acid (SA) and in resistance to virus infection. SCMV infection significantly increased SA accumulation and expression of SA‐responsive pathogenesis‐related protein genes (PRs). Interestingly, exogenous SA treatment decreased SCMV accumulation and enhanced resistance. Both reverse transcription‐coupled quantitative PCR and RNA‐Seq data confirmed that expression levels of at least four ZmPAL genes were significantly up‐regulated upon SCMV infection. Knockdown of ZmPAL expression led to enhanced SCMV infection symptom severity and virus multiplication, and simultaneously resulted in decreased SA accumulation and PR gene expression. Intriguingly, application of exogenous SA to SCMV‐infected ZmPAL‐silenced maize plants decreased SCMV accumulation, showing that ZmPALs are required for SA‐mediated resistance to SCMV infection. In addition, lignin measurements and metabolomic analysis showed that ZmPALs are also involved in SCMV‐induced lignin accumulation and synthesis of other secondary metabolites via the phenylpropanoid pathway. In summary, our results indicate that ZmPALs are required for SA accumulation in maize and are involved in resistance to virus infection by limiting virus accumulation and moderating symptom severity.

Environmental and genetic effects on cadmium accumulation capacity and yield of maize

Maize (Zea mays) is an economic crop suitable for use in phytoremediation in low to moderately cadmium (Cd)-contaminated soils due to its ability to accumulate high concentration of Cd in parts of maize that are not used in human diet. The aim of this study was to test Cd content in nine female parents of the commercial maize hybrids (C1 = ♀2-48; C2 = ♀1767/99; C3 = ♀87-24; C4 = ♀135-88, C5 = ♀84-28; C6 = ♀84-44; C7 = ♀438-95; C8 = ♀30-8; C9 = ♀B-73) grown under field conditions in two soils (B1: eutric cambisol, B2: stagnosol) during three growing seasons (A1: 2006, A2: 2007, A3: 2008). The stationary trial was conducted in four replicates. The ear-leaves at flowering and grain at maturity were taken for chemical analysis. The average quantities of leaf-Cd were 0.081, 0.088 and 0.143 mg per kg of dry matter for A1, A2 and A3, 0.089 and 0.118, for B1 and B2, respectively. Grain-Cd was below the threshold (< 0.02 mg/kg). Five Cd-inefficient genotypes (C3, C5, C6, C7 and C9) had low leaf-Cd (average 0.049 mg/kg), while this content was about 6-times higher (average 0.299 mg/kg) in Cd-efficient genotype C4. The yield among the years ranged from 2.36 to 4.31 t/ha. Maize grown on B2 had about 26% lower yield than on B1. Five genotypes (C1, C2, C8 and C9) achieved yields less than 3.50 t/ha (mean 3.15 t/ha), while in two genotypes (C3 and C5) yields were above 4.00 t/ha (mean 4.14 t/ha). Very strong correlations (r) of leaf-Cd status among years (ranged from 0.52 to 0.77) confirmed high genetic effect on the capability of Cd accumulation in maize. However, correlations between Cd content and yield were low (ranged from –0.17 to 0.06). Cd-efficient C4 female parent could be used for development of maize hybrids suitable for phytoremediation, while Cd-inefficient female parents for hybrids could be suitable as forage maize crop contributing to the lower Cd input into food chain.

Effects of a prothioconazole- and tebuconazole-based fungicide on Aspergillus flavus development under laboratory and field conditions

Aspergillus flavus is a fungal pathogen of crops including maize and is frequently associated with the accumulation of aflatoxin, which presents a concern for human and animal health. In maize, good agricultural practices can only partially reduce Aspergillus occurrence, and biological control through atoxigenic strains decreases aflatoxin content, but increasing mold decreases kernel quality. The control of Aspergillus infections by chemicals is not authorized in maize, but recently in Italy, some sterol-biosynthesis inhibitors obtained an emergency authorization for use against Fusarium infections. Therefore, it could be interesting to determine if these inhibitors could also be useful against A. flavus. A mixture of prothioconazole and tebuconazole was tested in vitro on toxigenic and atoxigenic strains and on populations with respect to conidial germination, germinal potential and fungal growth. The fungicide mixture inhibited fungal growth, with a higher effect on toxigenic strains than on atoxigenic strains. All considered parameters were significantly reduced for monoconidial strains at doses lower than those recommended for field application for straw cereals; however, under-dosing should be avoided since it increases aflatoxin production. Field trials under natural infection conditions revealed the efficacy of the fungicide treatment on the reduction of both Aspergillus occurrence and aflatoxin accumulation in maize. In a context in which the sustainable use of pesticides can be guaranteed, our findings support the inclusion of azole-based fungicides in a multiple-strategy approach to control Aspergillus infections in maize.

Assessment of conservation agriculture and intercropping practices for enhanced productivity and profitability in maize (Zea mays)

A field experiment was conducted to study the effect of tillage and intercropping on yield, net returns and weed density in maize (Zea mays L.) at ICAR-Indian Agricultural Research Institute, New Delhi during 2010, 2011 and 2012. The experiment was conducted in split-plot design with three replications. In main plots, tillage systems, viz. conventional tillage (CT), CT + residues at 3 t/ha, zero-tillage (ZT) and ZT+ residues at 3 t/ha were taken. In sub plots, intercropping systems such as sole maize, sole groundnut, maize + groundnut (1:1) and maize + groundnut (1:2) were taken. The results indicated that ZT + residue at 3 t/ha recorded the highest dry matter (DM) accumulation in maize at all the growth stages except 30 DAS followed by CT + residue at 3 t/ha over the years. The yield attributes such as number of gain rows/cob and number of grains/grain row were recorded highest in ZT + residue at 3 t/ha followed by CT + residue at 3 t/ha. The residue retention at 3 t/ha in ZT enhanced 25.3-28.9% grain yield in maize compared to CT over the years. ZT + residue at 3 t/ha recorded the highest net returns (49.8 × 103 /ha) and B:C ratios (1.7) in maize. In 2010, weed population of broad-leaved weed (BLWs), narrow-leaved weed (NLWs) and total was recorded highest in ZT + residue at 3 t/ha. However, the population of BLWs and total increased in CT compared to ZT at the end of the study period. The intercropped system, viz. maize + groundnut in 1:1 and 1:2 recorded the lowest DM accumulation than the sole maize over the years. The number of grain rows/cob and number of grains/ grain row were recorded highest in sole maize compared to intercropped maize. However, higher grain yield and net returns was found in maize + groundnut in 1:1 and 1:2 than sole maize. The intercropped maize + groundnut in 1:1 and 1:2 recorded the lowest population of BLWs, NLWs and total during the years.

Combined application of arbuscular mycorrhizal fungi and steel slag improves plant growth and reduces Cd, Pb accumulation in Zea mays

Little attention has been paid to the combined use of arbuscular mycorrhizal fungus (AMF) and steel slag (SS) for ameliorating heavy metal polluted soils. A greenhouse pot experiment was conducted to study the effects of SS and AMF−Funneliformis mosseae (Fm), Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on plant growth and Cd, Pb uptake by maize grown in soils added with 5 mg Cd kg−1 and 300 mg Pb kg−1 soil. The combined usage of AMF and SS (AMF + SS) promoted maize growth, and Gv + SS had the most obvious effect. Meanwhile, single SS addition and AMF + SS decreased Cd, Pb concentrations in maize, and the greater reductions were found in combined utilization, and the lowest Cd, Pb concentrations of maize appeared in Gv + SS. Single SS amendment and AMF + SS enhanced soil pH and decreased soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd, Pb concentrations. Furthermore, alone and combined usage of AMF and SS increased contents of soil total glomalin. Our research indicated a synergistic effect between AMF and SS on enhancing plant growth and reducing Cd, Pb accumulation in maize, and Gv + SS exerted the most pronounced effect. This work suggests that AMF inoculation in combination with SS addition may be a potential method for not only phytostabilization of Pb-Cd-contaminated soil but maize safety production.

Lipids as Key Markers in Maize Response to Fumonisin Accumulation.

The present field study offers new insights into the role played by plant lipid pathways in the modulation of fumonisin accumulation in maize. Untargeted metabolomics was applied to better understand the multifactorial plant-pathogen-interaction mechanisms, including host resistance. Our results showed a significant influence from the hybrid genotype and the environmental growing conditions on fumonisin accumulation. A total of 25 significant metabolites have been identified, with glycerophospholipid and linoleic acid metabolism as the main pathways affected by the plant-pathogen interactions. This evidence highlighted the crucial role played by lipid signaling as an integrated part of the complex regulatory network in plants.

Alleviation of cadmium accumulation in maize (Zea mays L.) by foliar spray of zinc oxide nanoparticles and biochar to contaminated soil

Due to the increase in area of cadmium (Cd)-contaminated soils worldwide, effective measures are necessary to minimize the Cd accumulation in cereals including maize (Zea mays L.) plant. A study was therefore performed to explore the effectiveness of foliar spray of zinc oxide (ZnO) nanoparticle (NPs) alone (0, 50, 75, 100 mg/L) or combined with soil application of biochar (1.0% w/w) on biomass, antioxidant enzyme activity and Cd concentrations in maize plants grown on a Cd-contaminated soil. The results depicted that ZnO NPs alone or in combination with biochar improved the height of maize plants, number of leaves, shoot and roots dry biomass, chlorophyll concentrations and gas exchange attributes. All the amendments reduced the electrolyte leakage, malondialdehyde, and hydrogen peroxide contents while improved the activities of antioxidant enzymes in leaf and roots of maize over the control. The application of 50, 75 and 100 mg/L ZnO NPs reduced the Cd contents in shoots by about 12%, 23, and 61%, and in roots by 18%, 33%, and 53%, respectively, over the control. The Cd concentrations in shoot decreased by 15%, 28%, and 68% and in roots by 14%, 35, and 55% after biochar combined with foliar spray of 50, 75 and 100 mg/L ZnO NPs, respectively. All the amendments improved the Zn concentrations in maize shoots and roots whereas reduced the soil bioavailable Cd. Overall, biochar combined with foliar spray of ZnO NPs could be recommended for safely growing the crops on Cd-contaminated soils.

Increased biomass accumulation in maize grown in mixed nitrogen supply is mediated by auxin synthesis.

The use of mixed nitrate and ammonium as a nitrogen source can improve plant growth. Here, we used metabolomics and transcriptomics to study the underlying mechanisms. Maize plants were grown hydroponically in the presence of three forms of nitrogen (nitrate alone, 75%/25% nitrate/ammonium, and ammonium alone). Plants grown with mixed nitrogen had a higher photosynthetic rate than those supplied only with nitrate, and had the highest leaf area and shoot and root biomass among the three nitrogen treatments. In shoot and root, the concentration of nitrogenous compounds (ammonium, glutamine, and asparagine) and carbohydrates (sucrose, glucose, and fructose) in plants with a mixed nitrogen supply was higher than that with nitrate supply, but lower than that with ammonium supply. The activity of the related enzymes (glutamate synthase, asparagine synthase, phosphoenolpyruvate carboxylase, invertase, and ADP-glucose pyrophosphorylase) changed accordingly. Specifically, the mixed nitrogen source enhanced auxin synthesis via the shikimic acid pathway, as indicated by the higher levels of phosphoenolpyruvate and tryptophan compared with the other two treatments. The expression of corresponding genes involving auxin synthesis and response was up-regulated. Supply of only ammonium resulted in high levels of glutamine and asparagine, starch, and trehalose hexaphosphate. We conclude that, in addition to increased photosynthesis, mixed nitrogen supply enhances leaf growth via increasing auxin synthesis to build a large sink for carbon and nitrogen utilization, which, in turn, facilitates further carbon assimilation and nitrogen uptake.

Aflatoxin in maize: a review of the early literature from "moldy-corn toxicosis" to the genetics of aflatoxin accumulation resistance.

Aflatoxin is a potent toxin produced by Aspergillus flavus Link:Fr, an opportunistic ear-rot pathogen of maize (Zea mays L. subsp. Mays). Prior to the discovery of aflatoxin, A. flavus was considered a minor pathogen and was not a priority for maize breeders or pathologists. Aflatoxin was discovered in England in 1961 following an epidemic in poultry. By the early 1970s, surveys of agricultural commodities in the USA found that maize produced in the Southeast was especially vulnerable to aflatoxin contamination. Aflatoxin contamination was initially treated as a post-harvest issue, but pre-harvest contamination was proven by 1975. Pre-harvest contamination meant that genetically based host-plant resistance was a possible solution. The potential magnitude of the problem became apparent in 1977 when the southeastern US maize crop suffered epidemic aflatoxin contamination. The first experiment demonstrating the heritability of host-plant resistance to aflatoxin accumulation was published in 1978. These events combined to make breeding for reduced aflatoxin contamination both a high priority and a rational breeding objective. This review surveys the early scientific literature in order to place research on the genetics of aflatoxin accumulation in maize into historical context. It tells the story of how multi-disciplinary research began with veterinary diseases of unknown etiology and resulted in host-plant resistance to a previously minor plant pathogen becoming a central public sector breeding objective.

Integrated agronomic practice increases maize grain yield and nitrogen use efficiency under various soil fertility conditions

Crop yield potential can be increased through the use of appropriate agronomic practices. Integrated agronomic practice (IAP) is an effective way to increase maize (Zea mays L.) grain yield and nitrogen use efficiency (NUE); however, the physiological processes associated with gains in yield potential obtained from IAP, particularly the different under various soil fertility conditions, remain poorly understood. An IAP strategy including optimal planting density, split fertilizer application, and subsoiling tillage was evaluated over two growing seasons to determine whether the effects of IAP on maize yield and NUE differ under different levels of soil fertility. Compared to farmers' practices (FP), IAP increased maize grain yield in 2013 and 2014 by 25% and 28%, respectively, in low soil fertility (LSF) fields and by 36% and 37%, respectively, in high soil fertility (HSF) fields. The large yield gap was attributed mainly to greater dry matter (DM) and N accumulation with IAP than with FP owing to increased leaf area index (LAI) and DM accumulation rate, which were promoted by greater soil mineral N content (Nmin) and root length. Post-silking DM and N accumulation were also greater with IAP than with FP under HSF conditions, accounting for 60% and 43%, respectively, of total biomass and N accumulation; however, no significant differences were found for post-silking DM and N accumulation between IAP and FP under LSF conditions. Thus, the increase in grain yield with IAP was greater under HSF than under LSF. Because of greater grain yield and N uptake, IAP significantly increased N partial factor productivity, agronomic N efficiency, N recovery efficiency, and physiological efficiency of applied N compared to FP, particularly in the HSF fields. These results indicate that considerable further increases in yield and NUE can be obtained by increasing effective soil N content and maize root length to promote post-silking N and DM accumulation in maize planted at high plant density, especially in fields with low soil fertility.

Inheritance and genotype by environment analyses of resistance to Fusarium verticillioides and fumonisin contamination in maize F1 hybrids

Fusarium ear rot (FER) and fumonisin accumulation in maize, caused by Fusarium verticillioides, can lead to lower grain quality, crop yield reduction and mycotoxicosis of humans and livestock. The best approach to control this fungus is through the development of resistant maize varieties, however, no immune cultivars are available with commercial cultivars ranging from susceptible to moderately resistant. Therefore, this study evaluated F1 maize hybrids, generated from inbred lines resistant to FER/fumonisins and Aspergillus flavus/aflatoxins, for improved resistance to F. verticillioides infection and fumonisin contamination. Diallel analysis was performed to understand the inheritance of resistance to F. verticillioides/fumonisins. Consequently, maize inbred lines resistant to F. verticillioides/fumonisins under South African conditions and lines resistant to Aspergillus flavus under Kenyan conditions were crossed to produce 18 hybrids. Hybrids and parental lines were planted in replicated field trials at three localities in South Africa. Artificially inoculated trials were conducted with disease severity, F. verticillioides target DNA and total fumonisin concentrations determined by visual assessment, quantitative PCR and liquid chromatography tandem mass spectrometry, respectively. Hybrids R119W × CKL05015, CML 495 × CKL05015 and CKL05015 × R119W were the most resistant to FER severity, F. verticillioides colonisation and fumonisin contamination, respectively. The resistance levels of hybrids did not differ significantly from their parental inbred lines, except for specific hybrids in certain test environments. General combining ability and specific combining ability were significant (P ≤ 0.05) for all three parameters evaluated. Kenyan inbred lines CKL05015 and CML 495 were good general combiners for resistance to fumonisin contamination. Specific combinability estimates showed that CKL05015 × R119W was the best hybrid combination for resistance to FER severity, F. verticillioides colonisation and fumonisin contamination. Additive gene effects were predominant in the inheritance of resistance in this set of hybrids. Parental inbred line performance was indicative of F1 hybrids performance. This study provided fundamental information on the maize lines evaluated that would be useful to breeders in the development of F. verticillioides/fumonisin-resistant cultivars.

Heterotic affinity and combining ability of exotic maize inbred lines for resistance to aflatoxin accumulation

Aflatoxin accumulation in maize (Zea mays L.) kernels is a serious economic and health problem that reduces grain quality and nutritional values and causes death to livestock and humans. Understanding the genetic parameters and heterotic responses of exotic maize inbred lines can facilitate their use for developing aflatoxin resistant parents of hybrids in Africa. This study was designed to (1) determine the heterotic affinities of aflatoxin resistant exotic lines, (2) identify exotic inbreds with good combining ability, and (3) determine the mode of inheritance of resistance to aflatoxin contamination in these lines. A line × tester mating design was used to determine combining ability of 12 yellow and 13 white inbreds and classify them into heterotic groups. The inbreds were crossed to two adapted testers representing two African heterotic groups and the resulting testcrosses along with hybrid checks were evaluated in separate trials at two locations for 2 years in Nigeria. General combining ability (GCA) effects were more important than specific combining ability effects for aflatoxin and grain yield. Among 15 exotic inbred lines having negative GCA effects for aflatoxin and 13 with positive GCA effects for grain yield, six combined the two desired traits. Five white and six yellow endosperm testcrosses were found to be good specific combiners for the two desired traits. The exotic lines with negative GCA effects for aflatoxin accumulation will be used as donor parents to develop backcross populations for generating new inbred lines with much higher levels of resistance to aflatoxin accumulation.

Impact of surfactant and dissolved organic matter on uptake of atrazine in maize and its mobility in soil

The purposes of this study were to investigate the activation and transport of atrazine in the presence of dissolved organic matter (DOM) and the surfactant (Triton X-100) and to understand interactions between DOM, Triton X-100, and atrazine. Uncontaminated soils collected from Nanjing, China, along with DOM extracted from rice straw and Triton X-100 (TX-100), were used in the study. The sorption and desorption experiments were carried out using the standard batch equilibration analysis. Soil column leaching was conducted with soil samples packed into PVC columns. Soil thin-layer chromatography was performed using soil and water mixture spread on a 0.5–0.7-mm-thick layer over 20 × 10-cm glass plates. Atrazine accumulation in maize was determined by planting maize in plastic pots (1 L) containing 1 kg soil mixed with 1.0 mg kg−1 atrazine. Soils were watered with different solutions, with the relative water content of 60%. Using batch experiment and soil thin-layer chromatography, application of DOM and surfactant reduced sorption and increased desorption of atrazine in soil. In column experiment, DOM and surfactant significantly promoted the mobility of atrazine in soil and the total concentration of atrazine in leachate of the soil column. Accumulation of atrazine in both maize roots and shoots increased with the elevated concentration of surfactant, whereas the content of atrazine declined with the increase of the DOM concentration. Dissolved organic matter and TX-100 affected the partitioning and transport of atrazine in soil–water and soil–plant ecosystems.

Biostimulant Potential of Humic Acids Extracted From an Amendment Obtained via Combination of Olive Mill Wastewaters (OMW) and a Pre-treated Organic Material Derived From Municipal Solid Waste (MSW).

Olive mill wastewaters (OMW) contain significant levels of phenolic compounds with antimicrobial/phytotoxic activity and high amounts of undecomposed organic matter that may exert negative effects on soil biology. Among OMW detoxification techniques, those focusing on oxidative degradation of phenolic compounds are relevant. The composting (bio-oxidation) process in particular, exploits exothermic oxidation reactions by microorganisms to transform the organic matrix of OMW into an amendment biologically stable and feasible to use in agriculture. This process consists of an active phase during which organic compounds are rapidly decomposed, and a curing phase characterized by a slow breakdown of the remaining materials with the formation of humic substances (HS) as by-products. In this study, bio-oxidation of OMW was performed using a pre-treated organic material derived from municipal solid waste (MSW). The obtained amendment (OMWF) was stable and in accordance with the legislative parameters of mixed organic amendments. HS were then extracted from OMWF and MSW (control amendment, Amd-C), and differences in structural properties of their humic acid (HA) fraction were highlighted via spectroscopy (Fourier Transform Infrared) and Dynamic Light Scattering. To assay a potential use of HA as biostimulants for crops, 12-day old Zea Mays L. plants were supplied with HA at 0.5 mg and 1 mg C L-1 for 2 days. HA from both amendments increased plant growth, but HA from OMWF was more effective at both dosages (plus 35–37%). Also, HA from OMWF enhanced both nitrogen assimilation and glycolysis by increasing the activity of nitrate reductase (∼1.8–1.9 fold), phosphoglucose isomerase (PGI) (∼1.8–2 fold) and pyruvate kinase (PK) (∼1.5–1.8 fold), while HA from Amd-C targeted glycolysis preferentially. HA from OMWF, however, significantly stimulated plant nutrition only at lower dosage, perhaps because certain undetermined compounds from detoxified OMW and incorporated in HA altered the root membrane permeability, thus preventing the increase of nutrient uptake. Conversely, HA from Amd-C increased nutrient accumulation in maize at both dosages. In conclusion, our results indicate that the amendment obtained via OMW composting using MSW had a reduced pollution load in terms of phenolic compounds, and HA extracted from OMWF could be used as valuable biostimulants during maize cultivation.

Effects of N application rate on N remobilization and accumulation in maize (Zea mays L.) and estimating of vegetative N remobilization using hyperspectral measurements

Hyperspectral data are useful for the nondestructive and timely monitoring of the physiological status and photosynthetic performance of crops. The objectives of the present study were (i) to analyze the effect of N application rate on the post-silking N uptake and vegetative N remobilization status and (ii) to indicate the optimum vegetation index (VI) for the assessment of the N remobilization status in maize. Two field experiments were conducted with five N treatments with varying rates and three maize (Zea mays L.) cultivars in 2016 and 2017, and time-course hyperspectral measurements were taken of collected plant samples. The present study considered the following three approaches: commonly used vegetation indices, novel indices of all possible two-band combinations as either simple ratios (SR) or normalized differences (ND) and spectral differences between the periods 63 and 75 (or 90) day after sowing (DAS). The commonly used VIs, such as the Green normalized difference vegetation index (GNDVI) at 75 DAS and Green model (G-M) at 90 DAS, were successfully used to assess the leaf N remobilization. The VIs computed with all possible two-band combinations ranging from 350 to 1350 nm were related to vegetative N remobilization. The results show that novel indices, such as SR (764 nm/716 nm), SR (762 nm/700 nm), ND (756 nm/550 nm) and ND (900 nm/750 nm), were successfully used to assess leaf N remobilization during the filling stage but were not suitable for monitoring culm N remobilization. Moreover, the spectral differences (i.e., between reflectance at 940 and 799 nm) between the corresponding 63 and 75 (90) DAS could stably estimate leaf N remobilization (R2 > 0.47, RMSE < 6.59, RE (%) < 20.7%). The idea of using remote sensing to calculate leaf N remobilization was feasible because the method calculates nitrogen uptake during critical periods and thus quantifies N deficiency and N management.

Soil amendment with compost and crop growth stages influenced heavy metal uptake and distribution in maize crop grown on lead-acid battery waste contaminated soil

Heavy metal contamination of agricultural soils poses serious risk to human health through food chain. Immobilization technique to reduce metal bioaccumulation in plant tissues is being promoted. Field experiment was carried out on heavy metal contaminated site to test for the efficacy of different organic amendments (Mexican sunflower compost (MSC) and Cassava peel compost (CPC) applied at 0, 20 and 40 t/ha) and inorganic fertilizer (NPK; 20:10:10 at 100 kg Nitrogen /ha) in metal immobilization and uptake by maize crop at different growing stages (one, two month(s) after planting (1MAP, 2MAP) and at harvesting). Compost amendments generally reduced heavy metal accumulation in maize crop unlike NPK and control where high metal toxicity led to plant death at 2MAP. Pb was highly accumulated at every growing stage followed by Cd while Cr concentration was below the detection limit at harvesting. Bioaccumulation and transfer factors were found to depend on maize growing stage with higher accumulation at 1MAP. Percentage Pb accumulation in the shoot was more at 1MAP but reversed at 2MAP and harvesting with higher accumulation in the root. Application of MSC and CPC at 20 and 40 t/ha reduced Pb accumulation in maize by 37.8–64.7% compared with control and the reduction at harvesting was more significant than those recorded at 1MAP and 2MAP, The study concluded that compost reduced heavy metals accumulation in maize crop and that metal accumulation depends on maize growth stage.

&lt;b&gt;Chromium accumulation in maize and cowpea after successive applications of composted tannery sludge

Chromium (Cr) accumulation in soil and plants has been reported after successive applications of tannery sludge, which is a matter of concern because Cr can promote environmental contamination and affect the food chain. In this study, we evaluated the growth of and Cr accumulation in maize and cowpea after seven years of consecutive applications of composted tannery sludge (CTS) under field conditions. The experiment consisted of application of CTS at five levels: 0 (control), 2.5, 5, 10, and 20 Mg ha -1 (dry basis). The growth of and Cr accumulation in maize and cowpea were evaluated at 75 and 65 days after plant emergence, respectively. CTS application increased the shoot biomass of maize and cowpea. Accumulation of Cr was similar for both plant species, with higher accumulation in roots. However, Cr accumulation in grains differed as the CTS doses increased; cowpea accumulated more Cr while maize did not accumulate more Cr in grains with higher CTS doses. In conclusion, application of CTS led to higher growth of maize and cowpea plants, and both species exhibited similar Cr accumulation in roots and shoots.

Effect of different forms of N fertilizers on the hyperaccumulator Solanum nigrum L. and maize in intercropping mode under Cd stress.

In the present study, we investigated the effects of different forms of nitrogen fertilizers on the hyperaccumulator Solanum nigrum L. and maize in intercropping mode under cadmium (Cd) stress and explored the physiological response mechanism. This research lays the foundation for the appropriate use of nitrogen (N) fertilizer, reduced costs of ecological restoration, and phytoremediation of environmental pollution by using this intercropping system. The main greenhouse pot experiment was conducted using 1.92 mg kg−1 Cd-contaminated soil. NH4+–N fertilizer and NO3−–N fertilizer treatments were performed along with no nitrogen fertilizer treatment as the control. The results indicate that intercropping could decrease the Cd uptake of maize compared with maize monocropping, but the biomass of maize would decrease under the intercropping mode. The application of N fertilizer to the maize–S. nigrum intercropping system could increase the total biomass of maize and S. nigrum. Compared with the NO3−–N fertilizer treatment, the Cd content of stem, leaf and grain tissues of S. nigrum significantly increased by 9.43%, 22.2%, and 8.33%, respectively, under the NH4+–N fertilizer treatment. The bioconcentration and translocation factors of S. nigrum significantly increased by 11.1% and 15.3%. Moreover, the Cd content of stem, leaf, and grain tissues of maize decreased by 26.5%, 21.2%, and 21.4%, respectively. The bioconcentration and translocation factors of maize significantly decreased by 38.8% and 46.7%. The application of N fertilizers promoted the accumulation of Cd in maize roots, while Cd content decreased in maize shoots. Compared with NO3−–N fertilizer, NH4+–N fertilizer can improve Cd accumulation in various S. nigrum tissues under intercropping, which could reduce Cd accumulation in maize under intercropping. Therefore, the application of NH4+–N fertilizer is recommended for satisfactory bioremediation when using the Cd-hyperaccumulator S. nigrum and for supporting the safe production of maize in Cd-contaminated soil, thus enabling the goal of simultaneous agricultural production and remediation.

Heavy Metal Accumulation in Maize (&amp;lt;i&amp;gt;Zea mays&amp;lt;/i&amp;gt; L.) Grown on Chromated Copper Arsenate (CCA) Contaminated Soil Amended with Treated Composted Sewage Biosolid

A pot experiment was conducted to investigate the heavy metal accumulation in maize (Zea mays L.) plant grown in chromated copper arsenate (CCA) soil amended with treated composted sewage biosolid. The initial concentrations of chromium, copper, arsenate in the CCA soil and sewage biosolid were determined by atomic absorption spectrophotometer. These were found to be, in CCA soil: 365.8 ± 6.18, 109.22 ± 14.04, 28.22 ± 3.8 and in sewage biosolid: 35 ± 1.06, 1.0 ± 0.02, 0 mg·kg-1 respectively. The concentration of Cr, Cu and As determined in both the roots and shoots generally decreased with increase in percentage amendment concentration and number of days (20 and 40 days after planting). At 20 days, the total metal concentration ranges in roots were As (5.54 ± 0.03 - 6.69 ± 1.14), Cr (9.59 ± 0.02 - 13.22 ± 0.03), Cu (2.28 ± 0.06 - 4.53 ± 0.37) mg·kg-1 while at 40 days the values were As (5.60 ± 0.19 - 6.08 ± 0.01), Cr (9.47 ± 0.04 - 10.95 ± 0.09), Cu (3.94 ± 0.19 - 4.64 ± 0.07) mg·kg-1. For the shoot system, the concentrations of the metals at 20 days were As (5.28 ± 0.03 - 5.90 ± 0.13), Cr (9.30 ± 0.05 - 10.07 ± 0.06), Cu (3.64 ± 0.12 - 4.72 ± 0.15) mg/kg while at 40 days the values obtained were As (5.28 ± 0.03 - 5.9 ± 0.13), Cr (9.69 ± 0.14 - 10.07 ± 0.03), Cu (2.94 ± 0.72 - 4.53 ± 0.03) mg·kg-1. The roots accumulated the three heavy metals more than the shoot system at all treatments used. Concentration of arsenic, chromium and copper in the plants decreased with increasing percentage amendments. The results suggest relatively low bioavailability of the three metals in CCA soil treated with high percentages of sewage biosolid as an amendment.