Alleviation of cadmium toxicity by cerium in rice seedlings is related to improved photosynthesis,elevated antioxidant enzymes and decreased oxidative stress

Cadmium contamination is a critical constraint to plant production in agricultural soils in some regions. Cerium is one of the rare earth elements, it plays a positive role in plant growth with a appropriate content. The present study was conducted to examine the role of cerium nutrition in the amelioration of effects on cadmium toxicity in rice (Oryza sativa L.) seedlings by a hydroponic experiment. Measurements included growth condition, photosynthesis related parameters, chloroplast ultra-structure and antioxidant enzymes content. Our results showed that the growth of rice seedlings was markedly inhibited by cadmium (100 μM), and the inhibition was significantly alleviated by cerium (10 μM). Fresh weight, single seedling height and chlorophyll content of rice plants in cerium treated groups were increased by 24.4, 18.2 and 32.05 % compared to those of plants cultivated in only cadmium-present condition. Additionally, in cadmium treated plants, the addition of cerium significantly increased the value of the maximum quantum yield of primary photochemistry (F _v /F _m ), indicator of PSII ‘structure and functioning’ (SFI _ABS ) and the performance index on absorption basis (PI _ABS ), elevated the activity of whole chain electron transport activity, enhanced photophosphorylation and its coupling factor Ca²⁺-ATPase activities. The result showed that the chloroplasts and thylakoid membrane of the rice seedlings leaves grown in cerium treatment developed better than that in cerium-absent group under cadmium toxicity. Moreover, addition with 10 μM cerium mitigated cadmium stress by inducing leaf enzyme activities for antioxidation like superoxide dismutase, peroxidase and catalase, dramatically depressed superoxide (O ₂ ^·? ), hydrogen peroxide and malondialdehyde accumulation. Results indicated that alleviation of cadmium toxicity by cerium application is partly related to improved light-use-efficiency, increased antioxidant enzymes, decreased oxidative stress in rice seedlings.     

The Effect of Nutritional Factors and Plant Growth Regulators on Micropropagation and Production of Phenolic Acids and Saponins from Plantlets and Adventitious Root Cultures of Eryngium maritimum L.

Eryngium maritimum L. is a valuable medicinal species, but since it is protected plant, collection from natural populations is forbidden. Therefore, establishing an efficient system for micropropagation of this species is desirable. To determine the optimal nutritional factors needed for shoot multiplication, root development and secondary metabolites accumulation, different media and plant growth regulators were tested. The highest plant regeneration efficiency (over 96 %), with 4.4 shoots per explant was induced on Murashige and Skoog (MS) medium supplemented with 1.0 mg L^?1 benzyladenine (BA) and 0.1 mg L^?1 indole-3-acetic acid (IAA). The in vitro-regenerated shoots were rooted (83.3–100 %) and transferred to an experimental plot with 62 % efficiency. Flow cytometric analysis revealed no variation in nuclear DNA content in field- and in vitro-delivered plant material. Ultra high performance liquid chromatography (UHPLC) indicated that multiple shoots and roots from in vitro-regenerated plantlets and adventitious root cultures maintained the production of rosmarinic (RA) and chlorogenic (CGA) acids and triterpenoid saponins found in the rosette leaves and roots of E. maritimum intact plants. UHPLC revealed a 12-fold increase of RA and CGA and 3.2-fold higher accumulation of triterpenoid saponins in roots of in vitro-derived plantlets in comparison to roots from field-grown plants. Adventitious root cultures allowed continuous growth of excised root in liquid media with or without exogenous auxins. The roots grown in liquid medium supplemented with 0.1 mg L^?1 IAA showed higher (227-fold) phenolic acids accumulation than those without auxin. Obtained results confirmed that micropropagation is a useful strategy in the protection of endangered species and a renewable source of a high quality plant material for secondary metabolites production.     

Alfalfa plant-derived biostimulant stimulate short-term growth of salt stressed Zea mays L. plants

Background & Aims

The effects of an alfalfa plant (Medicago sativa L.) hydrolysate-based biostimulant (EM) containing triacontanol (TRIA) and indole-3-acetic acid (IAA) were tested in salt-stressed maize plants.

Methods

Plants were grown for 2 weeks in the absence of NaCl or in the presence (25, 75 and 150 mM). On the 12th day, plants were supplied for 48 h with 1.0 mg L^?1 EM or 11.2 μM TRIA.

Results

EM and TRIA stimulated the growth and nitrogen assimilation of control plants to a similar degree, while NaCl reduced plant growth, SPAD index and protein content. EM or TRIA increased plant biomass under salinity conditions. Furthermore, EM induced the activity of enzymes functioning in nitrogen metabolism. The activity of antioxidant enzymes and the synthesis of phenolics were induced by salinity, but decreased after EM treatment. The enhancement of phenylalanine ammonia-lyase (PAL) activity and gene expression by EM was consistent with the increase of flavonoids.

Conclusion

The present study proves that the EM increases plant biomass even when plants are grown under salinity conditions. This was likely because EM stimulated plant nitrogen metabolism and antioxidant systems. Therefore, EM may be proposed as bioactive product in agriculture to help plants overcome stress situations.     

Gibberellins and indole-3-acetic acid producing rhizospheric bacterium Leifsonia xyli SE134 mitigates the adverse effects of copper-mediated stress on tomato

Beneficial bacteria Supplemental data for this article can be accessed at https://doi.org/10.1080/17429145.2017.1370142.View all notesliving in the rhizosphere pose several implications on plant growth promotion and are highly desirable for sustainable agriculture. In the current study, we explored the ameliorative capacity of Leifsonia xyli SE134, a plant growth-promoting rhizobacteria (PGPR), against copper (Cu) stress on tomato grown under elevated Cu levels of 50 and 100?mM. Initially, L. xyli SE134 modulated innate gibberellins (GAs) and indole-3-acetic acid (IAA) metabolism in response to elevated Cu toxicity. The IAA contents increased, whereas that of bioactive GAs decreased in relation to Cu concentration gradient in the broth media. Furthermore, exposure to elevated Cu caused detrimental effects on the physiological attributes as revealed by attenuated shoot length, root length, stem diameter, shoot dry weight, root dry weight, and chlorophyll content in non-inoculated tomatoes as compared to L. xyli SE134 inoculated plants. The growth rescuing effect of L. xyli SE134 may be attributed to the modulation of endogenous amino acids contents in plants, such as glutamic acid, threonine, phenylalanine, glycine, proline, and arginine. Moreover, L. xyli SE134 inoculation stimulated total polyphenol and flavonoid content, reduced super oxide dismutase activity, strongly inhibited Cu, and increased phosphorus and iron content in plants grown under elevated Cu stress. In the absence of Cu toxicity, L. xyli SE134 significantly enhanced amino acid content, improved total flavonoids, and increased phosphorus content, thus resulting in higher plant growth.     

Growth characteristics of aquatic macrophytes cultured in nutrient-enriched water: I. Water hyacinth,water lettuce,and pennywort

Seasonal growth characteristics and biomass yield potential of 3 floating aquatic macrophytes cultured in nutrient nonlimiting conditions were evaluated in central Florida’s climatic conditions. Growth cycle (growth curve) of the plants was found to be complete when maximum plant density was reached and no additional increase in growth was recorded. Biomass yield per unit area and time was found to be maximum in the linear phase of the growth curve; plant density in this phase was defined as “operational plant density,” a density range in which a biomass production system is operated to obtain the highest possible yields. Biomass yields were found to be 106, 72, and41 t(drywt)ha^-1yr^-1, respectively, for water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and pennywort (Hydrocotyle umbellata). Operational plant density was found to be in the range of 500–2,000 g dry wt m^-2 for water hyacinth, 200–700 g dry wt m^-2 for water lettuce, and 250–650 g dry wt m^-2 for pennywort. Seasonality was observed in growth rates but not in operational plant density. Specific growth rate (% increase per day) was found to maximum at low plant densities and decreased as the plant density increased. Results show that water hyacinth and water lettuce can be successfully grown for a period of about 10 mo, while pennywort, a cool season plant, can be integrated into water hyacinth/water lettuce biomass production system to obtain high yields in the winter.     

Effect of calcium on water-stress-induced biochemical changes and yield of field-grown rice

Three different treatments by calcium (10²M), namely seed treatment, foliar spraying and their combination were applied on field-grown rice (Oryza sativa L. cv. Ratna) under both water stressed and non-stressed conditions in the course of plant development. The relative water content and leaf water potential decreased with increase in age of stressed and non-stressed plants. Pretreatment of seeds with Ca improved the water status of the plants most prominently at the vegetative stage but the effect gradually faded away with plant development. The foliar spraying by Ca was more effective in improving the water status of the plants at the reproductive stage. The combined Ca treatment significantly improved water status of the plants both at the vegetative and reproductive stages. The contents of chlorophyll and protein decreased and the activities of protease and RNase increased in the course of plant development in both non-stressed and even more in stressed plants. Ca treatments of seeds or plants or their combination inhibited the decline in chlorophyll and protein contents and the rising trends of protease and RNase activities, the combined treatment being most effective. During plant development free proline content increased significantly more in water stressed plants. In non-stressed plants there was a marked increase in the free proline content at the mature fruit stage. Ca treatment inhibited the rise of free proline in stressed plants. A significant reduction in yield components and yield of the crop in water stressed plants was increased by Ca treatment.     

Fungal mutualists enhance growth and phytochemical content in Echinacea purpurea

An emerging paradigm in sustainable biotechnique is the use of mutualists to enhance plant growth and secondary metabolism. Our objective was to determine impact of two groups of fungal mutualists on growth and phytochemistry of Echinacea purpurea. Growth, development, and phytochemical concentration were measured in greenhouse-grown 12-week-old plants colonized by arbuscular mycorrhizal fungi (AMF) (Rhizophagus intraradices and Gigaspora margarita) or the endophytic entomopathogen, Beauveria bassiana. In one experiment, all measured growth parameters were increased in mycorrhizal plants. Biomass of AMF-colonized plants was over 13-fold greater than non-mycorrhizal controls receiving the same levels of phosphorous, and over 4-fold greater than non-mycorrhizal controls given additional phosphorous. Endophytic colonization by B. bassiana had minor effects on growth. Colonization by AMF and B. bassiana alone or in combination altered concentrations of phytochemicals (pigments, polyphenolics, alkylamides, and terpenes). Mycorrhizal plants produced up to 4.6-fold higher concentration of polyphenolics. Specific alkylamides increased 1.7 fold in plants colonized only with B. bassiana and up to a 2.4-fold increase in plants colonized by both mutualists. Changes in other phytochemical classes were related to differences in plant size induced by AMF. Phytochemical content (concentration × biomass) was increased up to 30-fold in mycorrhizal plants. Phytochemical relationships to plant biomass were confirmed in a second experiment in which non-mycorrhizal plants were fertilized to produce biomass equivalent to that of mycorrhizal plants. Based on this study, mycorrhizal colonization of E. purpurea enhances phytochemical content; this has major implications for the natural product industries and growers of E. purpurea.     

Arbuscular mycorrhiza improve growth,nitrogen uptake,and nitrogen use efficiency in wheat grown under elevated CO<Subscript>2</Subscript>

Effects of the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis on plant growth, carbon (C) and nitrogen (N) accumulation, and partitioning was investigated in Triticum aestivum L. plants grown under elevated CO₂ in a pot experiment. Wheat plants inoculated or not inoculated with the AM fungus were grown in two glasshouse cells with different CO₂ concentrations (400 and 700 ppm) for 10 weeks. A ¹⁵N isotope labeling technique was used to trace plant N uptake. Results showed that elevated CO₂ increased AM fungal colonization. Under CO₂ elevation, AM plants had higher C concentration and higher plant biomass than the non-AM plants. CO₂ elevation did not affect C and N partitioning in plant organs, while AM symbiosis increased C and N allocation into the roots. In addition, plant C and N accumulation, ¹⁵N recovery rate, and N use efficiency (NUE) were significantly higher in AM plants than in non-AM controls under CO₂ enrichment. It is concluded that AM symbiosis favors C and N partitioning in roots, increases C accumulation and N uptake, and leads to greater NUE in wheat plants grown at elevated CO₂.     

Stable cesium uptake and accumulation capacities of five plant species as influenced by bacterial inoculation and cesium distribution in the soil

The effects of inoculation with Bacillus and Azospirillum strains on growth and cesium accumulation of five plant species, Komatsuna, Amaranth, sorghum, common millet and buckwheat, grown on cesium-spiked soil were assessed for potential use in cesium remediation. Pot experiments were performed using “artificially” Cs-contaminated soil. Three treatments were applied based on Cs location in the soil. For a soil height of 15 cm in the pots, Cs was added as follows: in the top five cm to imitate no ploughing condition; in the bottom five cm simulating inverted ploughing; and uniformly distributed Cs reproducing normal plowing. Generally, inoculation of Cs-exposed plants significantly enhanced growth and tolerance to this element. Transfer factor (ratio of Cs concentration in the plant tissues to that in surrounding soil) was strongly influenced by Cs distribution, with higher values in the top-Cs treatment. Within this treatment, inoculation of Komatsuna with Bacillus and Azospirillum strains resulted in the greatest transfer factors of 6.55 and 6.68, respectively. Cesium content in the shoots was high in the Azospirillum-inoculated Komatsuna, Amaranth, and buckwheat, i.e., 1,830, 1,220, and 1,030 µg per pot, respectively (five plants were grown in each pot). Therefore, inoculation of Komatsuna and Amaranth with the strains tested here could be effective in enhancing Cs accumulation. The decrease of Cs transfer under uniform- and bottom-Cs treatments would suggest that countermeasures aiming at decreasing the transfer of Cs could rely on ploughing practices.     

Photosynthetic adaptation of pea plants grown at different light intensities: State 1 - State 2 transitions and associated chlorophyll fluorescence changes

A study of pea plants grown at different light intensities has been made. Using a leaf oxygen electrode, it was shown that plants grown under low light intensities had lower saturated rates of photosynthesis than high-light-grown plants however, at low light intensities the photosynthetic rates were similar for both types of plants. State 1- State 2 transitions have been monitored with attached leaves using a modulated fluorescence technique. It is shown that peas grown under low light intensities (20 W m^-2) had a faster State 1 to State 2 transition when compared with medium-(50 W m^-2) and high-(70 W m^-2) light-grown plants. Measurement of fast-fluorescence-induction curves in the absence of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) have shown that low-light plants are, when in State 1, more effective at using Photosystem-two (PSII) light to reduce their plastoquinone pool than high-light plants. Transition from State 1 to State 2 for all plants led to a decrease in the reduction level of the plastoquinone pool inidcating that the transition had increased electron flow through Photosystem one (PSI) relative to PSII. Analyses of fast fluorescence induction in the presence of DCMU indicate that low-light-grown plants have a higher PSII-α/PSII-β ratio than high-light-grown plants. Such a difference is in line with the increase in the PSII/PSI ratio of low-light plants and is reflected in their high chlorophyll b/chlorophyll a ratio and their larger appressed to non-appressed thylakoid-membrane areas. It is suggested that these two latter factors give rise to the faster State 1 - State 2 transitions in low-light plants.     

Combined Effects of Lead and Acid Rain on Photosynthesis in Soybean Seedlings

To explore how lead (Pb) and acid rain simultaneously affect plants, the combined effects of Pb and acid rain on the chlorophyll content, chlorophyll fluorescence reaction, Hill reaction rate, and Mg²⁺-ATPase activity in soybean seedlings were investigated. The results indicated that, when soybean seedlings were treated with Pb or acid rain alone, the chlorophyll content, Hill reaction rate, Mg²⁺-ATPase activity, and maximal photochemical efficiency (F _v/F _m) were decreased, while the initial fluorescence (F ₀) and maximum quantum yield (Y) were increased, compared with those of the control. The combined treatment with Pb and acid rain decreased the chlorophyll content, Hill reaction rate, Mg²⁺-ATPase activity, F _v/F _m, and Y and increased F ₀ in soybean seedlings. Under the combined treatment with Pb and acid rain, the two factors showed additive effects on the chlorophyll content in soybean seedlings and exhibited antagonistic effects on the Hill reaction rate. Under the combined treatment with high-concentration Pb and acid rain, the two factors exhibited synergistic effects on the Mg²⁺-ATPase activity, F ₀, F _v/F _m, as well as Y. In summary, the inhibition of the photosynthetic process is an important physiological basis for the simultaneous actions of Pb and acid rain in soybean seedlings.     

Adventitious shoot regeneration from in vitro leaf explants of <Emphasis Type="Italic">Fraxinus nigra</Emphasis>

In order to establish an attractive method for the production of valuable medicinal alkaloids (galanthamine and lycorine), the plants of Leucojum aestivum and L. aestivum ‘Gravety Giant’ grown in bioreactor RITA® were subjected to various concentrations of methyl jasmonate (MeJA), salicylic acid (SA), 1-aminocyclopropane-1-carboxylic acid (ACC) and 2-chloroethylphosphonic acid (ethephon) at different times of culture. The application of MeJA showed a negative effect on L. aestivum and L. aestivum ‘Gravety Giant’ plant growth. We observed that the incubation of plants during 168 h with 100 µM of MeJA resulted above two times lower F.W. (fresh weight) increments compared with control. While SA showed an inhibitory effect only on the growth of L. aestivum cultures. ACC and ethephon had a positive effect on both types of culture. Treatment with 50 µM of MeJA during 168 h stimulated galanthamine and lycorine biosynthesis in L. aestivum and L. aestivum ‘Gravety Giant’ cultures. In addition, the accumulation of galanthamine was increased when 10 µM of ACC were added to both types of culture. 10 µM of ACC stimulated also lycorine biosynthesis by L. aestivum ‘Gravety Giant’. The addition of 10 µM of ethephon had a positive effect only on lycorine production in plants of L. aestivum. SA promoted galanthamine and lycorine biosynthesis in tested plants. Indeed the highest galanthamine (0.8 mg/g dry weight: D.W.) and lycorine (1.53 mg/g D.W.) concentrations were observed in L. aestivum ‘Gravety Giant’ plants treated with 5 µM of SA during 10 h.     

Overexpression of NAC gene from Lepidium latifolium L. enhances biomass,shortens life cycle and induces cold stress tolerance in tobacco: potential for engineering fourth generation biofuel crops

We report elevated biomass and altered growth characteristics of tobacco plants up on transformation with a NAC (NAM, ATAF1/2,CUC2) gene (GenBank Accession FJ754254) isolated from Lepidium latifolium L. (LlaNAC). Transgenic plants showed significant differences in fresh weight, midrib length of longest leaf, leaf area, height of the plant, root and shoot weights, etc. during vegetative phase. On 100th day after sowing (DAS), plants of transgenic lines were 2–3 times taller than the wild type plants, though no significant difference was recorded in moisture contents of any of the plant tissues. Over-expression of NAC gene up to 2,000 fold was recorded in leaves of transgenic plants on 100th DAS. Interestingly, transgenic plants showed significantly shortened (P(t) = 0.02–0.04) life cycle, as they showed a completely altered growth behaviour. Transgenic plants entered reproductive phase earlier by 60 days, with lines NC2 and NC7b entering first, followed by line NC10. However, the time period spent in the reproductive phase by the plant was nearly twice in case of transgenic lines NC2, NC7b and NC10, as compared to the wild type plants. Despite that, these lines completed their life cycle in 45–60 days lesser than the time taken by wild-type tobacco plants. No difference was recorded in fruit and seed yield of transgenic or wild type plants. To the best of our knowledge, this is the first report on over-expression of NAC gene causing altered growth and biomass patterns. We expect this study to become an important reference towards future engineering of plants for fuel and fodder purposes.     

Salicylic acid promotes plant growth and salt-related gene expression in <Emphasis Type="Italic">Dianthus superbus</Emphasis> L. (Caryophyllaceae) grown under different salt stress conditions

Salt stress is a critical factor that affects the growth and development of plants. Salicylic acid (SA) is an important signal molecule that mitigates the negative effects of salt stress on plants. To elucidate salt tolerance in large pink Dianthus superbus L. (Caryophyllaceae) and the regulatory mechanism of exogenous SA on D. superbus under different salt stresses, we conducted a pot experiment to evaluate leaf biomass, leaf anatomy, soluble protein and sugar content, and the relative expression of salt-induced genes in D. superbus under 0.3, 0.6, and 0.9% NaCl conditions with and without 0.5 mM SA. The result showed that exposure of D. superbus to salt stress lead to a decrease in leaf growth, soluble protein and sugar content, and mesophyll thickness, together with an increase in the expression of MYB and P5CS genes. Foliar application of SA effectively increased leaf biomass, soluble protein and sugar content, and upregulated the expression of MYB and P5CS in the D. superbus, which facilitated in the acclimation of D. superbus to moderate salt stress. However, when the plants were grown under severe salt stress (0.9% NaCl), no significant difference in plant physiological responses and relevant gene expression between plants with and without SA was observed. The findings of this study suggest that exogenous SA can effectively counteract the adverse effects of moderate salt stress on D. superbus growth and development.     

Effects of plant extracts on the rates of parasitization ofAnagasta kuehniella [Lep.: Pyralidae] eggs byTrichogramma pretiosum [Hym.: Trichogrammatidae] under greenhouse conditions

In the greenhouse, rates of parasitization ofAnagasta kuehniella (Zeller) eggs byTrichogramma pretiosum (Riley) were significantly increased when treated with water extracts of the weed,Amaranthus retroflexus L.: 1) Parasitization rates appeared to be dose dependent with greatest percentage parasitization obtained fromVicia faba L. plants sprayed with 2.5 ml of the extract, 2) Parasitization rates increased with an exposure time of 24 h, and 3) Plants sprayed withA. retroflexus in mosaic patterns interspersed with 2 additional plant extracts (Chenopodium album L. andPortulaca oleracea L.) did not show a total increase of parasitization over control plants treated with water.     

Copper oxide nanoparticle toxicity in mung bean (Vigna radiata L.) seedlings: physiological and molecular level responses of in vitro grown plants

In this study, the toxic effect of copper oxide nanoparticles (CuONPs) at the physiological and molecular level was investigated in mung bean (Vigna radiata L.) plants. The seedlings were grown in half strength Murashige and Skoog medium supplemented with different concentrations of CuONPs (0, 20, 50, 100, 200 and 500 mg l^?1) for 21 days under controlled growth conditions. Exposure to 200 and 500 mg l^?1 of CuONPs significantly reduced shoot length and biomass. Significant reduction in root length and biomass was observed upon exposure to all concentrations of CuONPs. Retardation of primary and lateral root growth was observed upon exposure to different concentrations of CuONPs. At 100, 200 and 500 mg l^?1 of CuONPs exposure, the total chlorophyll contents reduced significantly. Exposure to different concentrations of CuONPs has not resulted in any significant change in carotenoid contents. The proline content significantly increased upon exposure to 100, 200 and 500 mg l^?1 of CuONPs. Significant increase in hydrogen peroxide content and lipid peroxidation was observed in roots upon exposure to 20, 50, 100, 200 and 500 mg l^?1 of CuONPs. Histochemical staining with nitroblue tetrazolium and treatment with 3′-(p-hydroxyphenyl) fluorescein indicated a concentration-dependent increase in reactive oxygen species generation in roots. Exposure to CuONPs has resulted in excess lignification of roots cells as revealed by phloroglucionol-HCl staining. Gene expression analysis using real-time polymerase chain reaction showed modulations in the expression of CuZn superoxide dismutase, catalase and ascorbate peroxidase genes in roots of CuONPs exposed plants.     

Trace metal uptake by garden herbs and vegetables

In many regions of Iran, crops are irrigated with municipal and industrial wastewater that contain a variety of metals. The purpose of this study was to simulate the level of metals that may be presented to plants over a growing season in a controlled laboratory setting. Cadmium, lead, arsenic, chromium, mercury, nickel, copper, zinc, and selenium were applied to plants at the high rate of 200 g metal/ha/wk. The following plants were examined for metal accumulation and effects on yield: garden cress (Lipidium sativum), leek (Allium porrum L.), basil (Ocimum basilicum L.), mint (Mentha arvensis L.), onion (Allium capa L.), radish (Raphanus sativus L.), and tarragon (Artemisia draculus L.). All plants showed significant uptake of all metals when compared to control (p=0.05), and growth was significantly reduced (p=0.05). Cadmium and chromium levels of 85±7.4 and 47.6±8.9 μg/g); selenium levels were highest in tarragon (16.5±5.8 μg/g). Zinc levels were similar (p=0.05) in all species tested, as were mercury and lead. The remaining metals (nickel and copper) showed significant differences in uptake, depending on plant species.