Treated Maize Seedlings Research Articles

Plant Growth Ameliorating and Rhizosphere Competent Native Acinetobacter pittii Strain F2 5 from the Rhizosphere of Zea mays L.

Background: Acinetobacter is an aerobic gram negative, non-spore forming, oxidase negative, catalase positive, non-motile encapsulated coccobacilli. They are ubiquitous in nature mostly isolated from soil, water, food, sewage, animal and human skin, marine water and rhizosphere of maize and wheat. The present study was focused on isolation and characterization of a native strain of rhizospheric Acinetobacter for plant growth promoting ability through different microbiological and morphometric parameters under greenhouse conditions. Methods: Rhizosphere soil samples were collected from maize fields and processed as per the standard microbiological procedure. The morphology was reconfirmed through scanning electron microscopy. DNA extraction was performed by using al. Two sets of primers (universal and specific for H. pylori) were used to amplify the 16S ribosomal gene. Sanger sequencing was applied and the resulted sequences were matched with the sequences of the National Center for Biotechnology Information (NCBI) nucleotide database. The evolutionary aspects were analyzed using MEGA7 software. Result: The strain exhibited plant growth promoting attributes of ammonia generation, inorganic and organic phosphate solubilization 1-aminocyclopropane-1-carboxylate deaminase activity. The strain was identified as Acinetobacter pittii through 16S rRNA sequencing and was designated as Acinetobacter pittii strain F2 5 with the accession number KM677194. Scanning electron microscopy was carried out to reconfirm the morphology of the strain. Under laboratory and green house conditions the strain improved the shoot and root length and its biomass of the treated maize seedlings as compared to the uninoculated control underscoring the plant growth potential of these strains in sustainable agricultural practices.

Alkamides: a new class of plant growth regulators linked to humic acid bioactivity

BackgroundThe use of humic substances as plant biostimulants has been increasingly attracting farmers and stunning researchers. The ability of these substances to enhance root growth by changing root architecture is often linked to their hormonal activities, such as auxin effects and nitric oxide production. Humeomics accesses the molecular constituents of humic substances, revealing the importance of alkyl components because of their conformations and chemical activities. Here, we describe the alkamides present in humic acids and compare their bioactivities using plasma membrane H+-ATPase activity level as a biochemical marker.MethodsHumic acids isolated from vermicompost were analyzed using 13C and 15N nuclear magnetic resonance spectroscopy. The unbound fraction was extracted with ethyl acetate and submitted to gas chromatography coupled to mass spectrometry to detect the presence of N-isopropyldecanamide. We synthesized N-isopropyldecanamide and treated maize seedlings for 7 and 15 days with different concentrations. The root growth and plasma membrane H+-ATPase activity were monitored. Nitric oxide accumulation in the lateral roots was imaged using 4,5-diaminofluorescein diacetate. The results were compared with those obtained for seedlings treated with humic acids isolated from vermicompost.ResultsThe amide functional group produced the only nitrogen signal in the 15N humic acid resonance spectrum and similar alkamide moieties were found in the unbound humic extract through comparisons using gas chromatography coupled to mass spectrometry. The synthesis of N-isopropyldecanamide had few steps and produced a high yield (86%). The effects of N-isopropyldecanamide on root growth were concentration dependent. High concentrations (10−4 M) enhanced root growth after 15 day of diminishing shoot biomass. However, low concentrations (10−8 M and 10−6 M) promoted root growth at 7 and 15 days, similar to the humic acid-induced plasma membrane H+-ATPase activity. Both N-isopropyldecanamide and humic acids enhanced nitric oxide accumulation during lateral root emergence.ConclusionWe described for the first time the effects of N-isopropyldecanamide on the plasma membrane H+-ATPase activity in maize seedling roots and compared its effects with those caused by humic acids. N-Isopropyldecanamide was detected in the unbound fraction of the humic supramolecular assembly, indicating that the putative hormone-like effects of these substances result also from the presence of this new class of plant regulators, in addition to other molecules.

Triacontanol Alleviated Nickel Toxicity in Maize Seedling by Controlling Its Uptake and Enhancing Antioxidant System

Triacontanol (TRIA) role in improving growth, physiological activities and tolerance against abiotic stresses has been reported. Yet, the mechanism by which TRIA executes its effects remains elusive. This work therefore studied the possible role of TRIA exogenous application in counteracting the adverse effects of nickel (Ni) treated maize seedlings. Maize seedlings (15-day-old) were grown in washed sand irrigated with nutrient solution provided with 100 μM NiCl2. Two concentrations of TRIA (25 and 50 µM) were applied twice as a foliar spray for Ni-stressed seedlings. Shoot and root growth attributes, Ni content, and antioxidant defence systems of maize seedlings were determined. Ni treatment reduced the shoot and root length and biomass, causing necrosis of the old leaves,greater reduction was shown in the roots. The shoot and root length was negatively correlated with their Ni content, which was consistent with their content of H2O2, but not with their malondialdehyde (MDA) content. As the roots had the greatest Ni content, maximum peroxidase (PX) and glutathione reductase (GR) activity as well as the highest ascorbic acid (ASA) and reduced glutathione (GSH) content were observed in the roots. The Ni-induced deleterious effects were alleviated by foliar application of TRIA concentrations. Also, TRIA treatment minimized root Ni content, whereas it maintained the shoots unharmed by Ni. Such mitigative effects of TRIA are explained by its key role in enhancing antioxidant capacity (expressed as IC50), increased PX and ascorbate oxidase (AO) activity, GSH, and total phenolic contents.

In-Cold Exposure to Z-3-Hexenal Provides Protection Against Ongoing Cold Stress in Zea mays.

Green leaf volatiles (GLVs), which have mostly been described as providers of protection against insect herbivory and necrotrophic pathogen infections, were recently shown to provide significant fortification against cold stress damage. It was further demonstrated that cold-damaged maize seedlings released a significant amount of GLVs, in particular, Z-3-hexenal (Z-3-HAL). Here, we report that the in-cold treatment of maize seedlings with Z-3-HAL significantly improved cold stress resistance. The transcripts for cold-protective genes were also significantly increased in the Z-3-HAL treated maize seedlings over those found in only cold stressed plants. Consequently, the maize seedlings treated with HAL during cold showed a significantly increased structural integrity, significantly less damage, and increased growth after cold stress, relative to the non-HAL treated maize seedlings. Together, these results demonstrate the protective effect of in-cold treatment with HAL against cold damage, and suggest that the perception of these compounds during cold episodes significantly improves resistance against this abiotic stress.

Effects of rhizobial nod factors (Lipo chitooligosaccharide) on seedling growth of maize (Zea mays L.) under salt stress

Effects of nod factors (lipo chitooligosaccharide) on seedling growth of maize under salt stress have been studied. The study was framed with seed priming using lipo chitooligosaccharide (LCO) a nod factor @ 4 ml/kg of seeds and without priming on maize seedling growth which was exposed to different levels of salinity (0, 2, 4, 6, 8 and 10 dS/m). Salinity negatively influenced the seedling growth of maize. However nod factor treated maize seedlings had relatively higher germination percentage, root length, shoot length, reducing sugars and amylase activity. Correlation analysis revealed positive relationships between seedling growth parameters. Thus, seed priming with nod factor (4 ml/kg) improved the resistance to salinity at seedling stage. NaCl concentrations restricted amylase enzyme activity and reducing sugar content in the germinating seeds. Priming of nod factor/LCO mitigated the restricted effects of salinity on amylase activity and reducing sugars.

Application of Brassinosteroid Mimetics Improves Growth and Tolerance of Maize to Nicosulfuron Toxicity

Pesticide residues, especially for herbicides, often damage crops, except for weeds, which results in reduced production or even death in agriculture. Brassinosteroids (BRs) can alleviate the injury from pesticide stress and enhance the growth of plants. However, the roles of low-cost BR mimetics in alleviation and protection from herbicide (nicosulfuron, NSF) stress in maize remain unclear. To investigate the effects of brassinosteroid mimetics on the growth of NSF-stressed plants, we treated maize seedlings with bikinin and brazide at 10 µM prior to NSF treatment, and epibrassinolide (EBL) as a positive control. The NSF treatment dramatically reduced the height, root length, and biomass of maize, and significantly influenced photosynthetic activity and pigments. Accumulation of reactive oxygen species (ROS) and membrane lipid peroxidation, enhanced activity of antioxidant, and detoxification-related enzymes were also observed under NSF stress. As compared to NSF-induced plants, foliar application of bikinin and brazide significantly increased biomass, photosynthesis, and antioxidant enzymes activities and decreased the ROS levels by more than 32.3%, the similar effects as EBL. The glutathione content genes (GST1, ABC-2, ALS1) involved in detoxification in the BR mimetics + NSF-treated plants were higher than those of NSF alone. Reduced levels of NSF residues by more than 55% after 3 days were observed as a result of BR mimetics pretreatment. In summary, our results present a new pattern of roles of BR mimetics, which display the potential protection of plants under pesticide stress.

Changes based on oxidative stress in metolachlor and atrazine treated maize seedlings

Changes based on oxidative stress in metolachlor and atrazine treated maize seedlings

Glutathione-induced alleviation of cadmium toxicity in Zea mays

Glutathione (GSH) is known to alleviate cadmium (Cd) stress in many plant species. However, the comprehensive mechanisms responsible for this effect in maize are still need more investigation. Here, a combination of physiological and molecular approaches was utilized in GSH-Cd treated maize seedlings, which revealed that GSH reversed the adverse effects of Cd, as reflected by plant growth, plant hormones, vacuole, stoma development, gene expression, etc. Plant growth, root cell viability, photosynthetic capacity, redox equilibrium, and cell ultrastructure recovery following GSH treatment, coupled with the strong up-regulation of Cd tolerance-related genes (e.g., phytochelatin synthetase-like protein, MYB and WRKY transcription factors, and CYP450), demonstrated the efficient activation of cellular defense against Cd toxicity. The addition of GSH significantly elevated GSH/GSSG ratio and the activity of γ-glutamylcysteine synthetase in both shoots and roots and markedly reduced Cd concentration in shoots. Ethylene emission rate and abscisic acid (ABA) content were significantly reduced after GSH application in the presence of Cd, except ABA content in leaves. These findings highlighted the significance of GSH in alleviating Cd-stress in maize and indicate a promising strategy for safe food production.

Hydrogen-rich water induces aluminum tolerance in maize seedlings by enhancing antioxidant capacities and nutrient homeostasis

The ameliorative effect of H2 on aluminum (Al)-induced stress remains poorly understood. We treated maize seedlings with Al and hydrogen-rich water (HRW) to determine the roles of H2 in the alleviation of Al toxicity. Our results demonstrated that Al stress triggered damage to the photosynthetic apparatus, plant growth inhibition, and reactive oxygen species (ROS) production, and boosted lipid peroxidation. However, the addition of HRW at 75% saturation markedly alleviated Al toxicity symptoms through the promotion of root elongation. These responses were related to the significantly increased activities of typical antioxidant enzymes (CAT, APX, SOD, and POD). In vivo imaging of plasma membrane integrity, lipid peroxidation, and the level of ROS provided further evidence that HRW could improve Al tolerance. Our results also indicate that 100% HRW mitigated Al toxicity less than 75% HRW. Moreover, different concentrations of HRW significantly improved photosynthesis and increased nutrient uptake. We conclude that exogenous H2 supplementation could enhance Al tolerance by reestablishing redox homeostasis and maintaining nutrient homeostasis.

Exogenous γ-aminobutyric Acid (GABA) Application Improved Early Growth, Net Photosynthesis, and Associated Physio-Biochemical Events in Maize.

γ-aminobutyric acid (GABA) is an endogenous signaling molecule and involved in growth regulations and plant development, however, a little information is available on the consequences of exogenous GABA application on growth, development, and associated physio-biochemical processes in maize. The present study examined the GABA-induced regulations in early growth, net photosynthetic rate, gas exchange, osmoregulation, and enzymatic activities in three maize cultivars, i.e., Yuecainuo 6, Zhengtian 68, and Yuecainuo 2. Two levels of GABA, i.e., 0 mg L-1 and 50 mg L-1, in solution form, with total application volume of 100 ml per pot containing 15 maize seedlings were exogenously applied. Results revealed that exogenous GABA application improved seedling growth in terms of seedling length and biomass accumulation in all maize cultivars at both 3 and 7 days after treatment (DAT). It also promoted net photosynthesis and variably affected gas exchange attributes, i.e., stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr), as well as leaves SPAD value. Furthermore, lipid peroxidation [in terms of malondialdehyde (MDA)] under GABA treated maize seedlings were also remained variable; however, osmolyte accumulation (protein and proline) and activities of anti-oxidants enzymes, i.e., super-oxide dismutase and peroxidase were also affected differently at both 3 and 7 DAT in all maize cultivars. Furthermore, enzymes involved in nitrogen metabolism, e.g., nitrate reductase and glutamine synthetase were improved. These results suggest the involvement of GABA in various physio-metablical mechanisms which might lead to improvement in morphological growth of maize. In future, research is still needed at molecular and genetic levels to unravel the involvement of GABA-mediated regulations in growth and its associated physio-biochemical mechanisms.

Effects of decaying leaf litter and inorganic fertilizer on growth and development of maize (Zea mays L.)

The effects of decaying leaf litter of Tithonia diversifolia and Vernonia amygdalina as organic fertilizer, inorganic fertilizer (NPK 15-15-15) and their combination effects on the growth and development of maize were studied in a screen house. Twenty-four experimental bags filled with 20 kg of loamy soil were laid out in a completely randomized design with six treatments and four replications for each treatment which included: 250 g of decaying leaves of T. diversifolia as mulch (T1), 250 g of decaying leaves of V. amygdalina (T2), 1.52 g of NPK (inorganic) fertilizer (T3), a mixture of 250 g of decaying leaves of T. diversifolia and 1.52 g of NPK 15-15-15 fertilizer (T4), a mixture of V. amygdalina and 1.52 g of NPK 15-15-15 fertilizer (T5) and control (T6). The significant growth as well as maize yields were obtained from T3 treated maize seedlings, and this was closely followed by T4 treated seedlings. The study showed that the decaying leaf litter as an organic fertilizer in maize production in a screen house conditions did not give better yield than NPK treatment alone.

Determination of genotoxic effects of boron and zinc on Zea mays using protein and random amplification of polymorphic DNA analyses.

In this research, we aimed to determine genotoxic effects of boron (B) and zinc (Zn) on Zea mays by using total soluble protein content and random amplification of polymorphic DNA (RAPD) analyses. For the RAPD analysis, 16 RAPD primers were found to produce unique polymorphic band profiles on treated maize seedlings. With increased Zn and B concentrations, increased polymorphism rate was observed, while genomic template stability and total soluble protein content decreased. The treatment with Zn was more effective than that of B groups on the levels of total proteins. The obtained results from this study revealed that the total soluble protein levels and RAPD profiles were performed as endpoints of genotoxicity and these analyses can offer useful biomarker assays for the evaluation of genotoxic effects on Zn and B polluted plants.

Minor effects of two elicitors of insect and pathogen resistance on volatile emissions and parasitism of Spodoptera frugiperda in Mexican maize fields

Synthetic elicitors can be used to induce resistance in plants against pathogens and arthropod herbivores. Such compounds may also change the emission of herbivore-induced plant volatiles, which serve as important cues for parasitic wasps to locate their hosts. Therefore, the use of elicitors in the field may affect biological control of insect pests. To test this, we treated maize seedlings growing in a subtropical field in Mexico with methyl jasmonate (MeJA), an elicitor of defense responses against many insects, and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), an elicitor of resistance against certain pathogens. Volatile emission, herbivore infestation, pathogen infection, and plant performance (growth and grain yield) of treated and untreated maize plants were measured. Application of BTH slightly reduced volatile emission in maize, while MeJA increased the emission compared to control treatments. Despite the apparent changes in volatile emissions, the elicitor application did not consistently affect infestation by Spodoptera frugiperda larvae, the main insect pest found on the maize seedlings, and had only marginal effects on parasitism rates. Similarly, there were no treatment effects on infestation by other herbivores and pathogens. Results for the six replications that stretched over one summer and one winter season were highly variable, with parasitism rates and the species composition of the parasitoids differing significantly between seasons. This variability, as well as the severe biotic and abiotic stresses on young seedlings might explain why we measured only slight effects of elicitor application on pest incidence and biological control in this specific field study. Indeed, an additional field experiment under milder and more standardized conditions revealed that BTH induced significant resistance against Bipolaris maydis, a major pathogen in the experimental maize fields. Similar affects can be expected for herbivory and parasitism rates.

Relations between carbohydrate accumulation in leaves, sucrose phosphate synthase activity and photoassimilate transport in chilling treated maize seedlings

Sucrose and starch concentration, sucrose phosphate synthase (SPS) activity in leaves, and long distance transport were studied in maize seedlings treated with moderate chilling (14 °C/12 °C - day/night).

Diversion of Oviposition by Atherigona soccata (Diptera: Muscidae) to Nonhost Maize with Sorghum Seedling Extract

The oviposition responses of Atherigona soccata Rondani, commonly known as the sorghum shootfly to seedlings of maize, which is not a host plant, that had been sprayed with acetone extracts of sorghum seedlings were investigated. Sorghum cultivars susceptible to the shootfly(CSH-1), resistant (IS 2122, IS 2123, and IS 2205), and wild sorghum, Sorghum arundinaceum (Desv.), were used. The possibility also was investigated of diverting shootfly egg laying in the field to maize sprayed with sorghum seedling extract. All of these extracts elicited significantly greater oviposition (67–91%) on treated maize seedlings than (9–33%) on untreated controls. Oviposition stimulant activity of CSH-1 extract decreased as the extracted plants grew older. The results suggest that a chemical oviposition stimulant is perhaps widespread among cultivated and wild sorghums, and it may serve as a kairomone in host finding and egg laying by the shootfly. In the field, maize seedlings sprayed with sorghum seedling extract served as good a host as the susceptible sorghum (‘Serena’) for shootfly oviposition. About 50–66% of shootfly eggs were laid on maize sprayed with sorghum seedling extract, either planted around sorghum or in strips alternating with strips of sorghum, compared with 6–17% laid on untreated maize. Because shootfly larvae cannot survive on maize, diverting oviposition onto maize would result in a reduction of the pest population. Our studies demonstrated the potential for using an oviposition stimulant for diverting shootfly eggs onto nonhost plants as a strategy for the management of the pest.

Pyruvate Decarboxylase from Zea mays L.

Pyruvate decarboxylase (PDC) was purified from mature, dry maize kernels and from roots of anaerobically treated maize seedlings and partially characterized. PDC was purified to a specific activity of 96 units per milligram protein from kernels and to 41 units per milligram protein from root. The subunit molecular masses were estimated to be 61,000 and 60,000 for kernel PDC and 59,000 and 58,000 for root PDC. The pH optimum for each enzyme was 5.8. Since the pH optimum is nearly one pH unit below the value reported for the cytoplasm of anaerobically metabolizing maize roots (pH 6.7 +/- 0.2), we investigated the effects of pH 5.8 and 6.6 on the cooperative kinetics observed for PDC from each source. The maximum Hill coefficients (n(H)) were much greater at each pH for the kernel PDC (pH 5.8, n(H) = 2.5 and pH 6.6, n(H) = 3.2) than for the root PDC (pH 5.8, n(H) = 1.4 and pH 6.6, n(H) = 1.8). The cooperative kinetics observed with respect to pyruvate were asymmetric. Potassium inhibited maize PDC and was competitive with pyruvate (root PDC K(i) = 16 millimolar and kernel PDC K(i) = 10 millimolar).