Concentrations In Plant Tissues Research Articles

Endophytic bacterium CIMAP-A7 mediated amelioration of atrazine induced phyto-toxicity in Andrographis paniculata

The presence of atrazine, a triazine herbicide, and its residues in agriculture soil poses a serious threat to human health and environment through accumulation in edible plant parts. Hence, the present study focused on atrazine induced stress amelioration of Andrographis paniculata, an important medicinal plant, by a plant growth promoting and atrazine degrading endophytic bacterium CIMAP-A7 inoculation. Atrazine has a non-significant effect at a lower dose while at a higher dose (lower: 25 and higher: 50 mg kg−1) 22 and 36% decrease in secondary metabolite content and plant dry weight of A. paniculata was recorded, respectively. Endophyte CIMAP-A7 inoculation significantly reduced atrazine soil content, by 78 and 51% at lower and a higher doses respectively, than their respective control treatments. Inoculation of CIMAP-A7 exhibited better plant growth in terms of increased total chlorophyll, carotenoid, protein, and metabolite content with reduced atrazine content under both atrazine contaminated and un-contaminated treatments. Atrazine induced oxidative stress in A. paniculata was also ameliorated by CIMAP-A7 by reducing stress enzymes, proline, and malondialdehyde accumulation under contaminated soil conditions than un-inoculated treatments. Furthermore, the presence of atrazine metabolites deisopropylatrazine (DIA) and desethylatrazine (DEA) strongly suggests a role of CIMAP-A7 in mineralization however, the absence of these metabolites in uninoculated soil and all plant samples were recorded. These findings advocate that the amelioration of atrazine induced stress with no/least pesticide content in plant tissues by plant-endophyte co-interactions would be efficient in the remediation of atrazine contaminated soils and ensure safe crop produce.

Effects of Garden Amendments on Soil Available Lead and Plant Uptake in a Contaminated Calcareous Soil

Gardeners use organic and inorganic substances to enhance plant growth, which can inadvertently impact soil solubility and plant uptake of unknown contaminants. Consequently, human exposure can increase through gardening and consumption of produce grown in potentially contaminated soils. A greenhouse experiment was established to examine the effects of biochar, compost, and common inorganic fertilizer on soil lead (Pb) availability for radish (Raphanus sativus, L.) and lettuce (Lactuca sativa, L.) grown in a calcareous soil containing excessively high lead (Pb), along with Pb accumulation in radish tissue. Results indicate that soil amended with biochar and planted to radish saw an 18% reduction in available Pb and an 11% decrease in plant tissue content when compared to the control. Compost showed an 8% reduction in available Pb, but a 19% increase in tissue content. In contrast, soil with inorganic fertilizer planted to radish increased in both soil Pb availability by 11% and Pb tissue content by 40%. Adding water-soluble inorganic fertilizers to contaminated calcareous soils without added organic matter enhances soil Pb availability and often asymptomatic plant Pb bioaccumulation. In conclusion, gardeners are encouraged to test their soils for contamination and apply biochar in combination with compost, as this combination is recommended to improve soil health and aid in overcoming initial N deficiencies induced by biochar.

Elevated zinc concentrations did not induce thiols in spinach (Spinacia oleracea) and parsley (Petroselinum crispum)

AbstractBackgroundPlants evolved various mechanisms to cope with metal stress. Cadmium (Cd) exposure specifically induces the synthesis of thiol‐rich substances such as phytochelatins. Due to the chemical similarity of Cd and zinc (Zn), similar detoxification mechanisms for both metals are under discussion.AimWe conducted a nutrient solution experiment to investigate thiol accumulation of parsley (Petroselinum crispum) and spinach (Spinacia oleracea) cultivars at different metal toxicity levels in vivo.MethodsThree metal treatments were applied: 1 µM Zn (control), 10 µM Zn, and 1 µM Zn + 1 µM Cd. After 10 days, thiol accumulation in parsley and spinach cultivars, which differ in their Zn tissue tolerance, was measured.ResultsSpinach and parsley cultivars differed in metal uptake, translocation, and resistance. In spinach, Cd application induced more severe toxicity symptoms and biomass reduction than Zn. Cadmium toxicity was more pronounced in spinach than in parsley due to higher Cd translocation of spinach cultivars. Despite comparable Zn tissue concentrations, parsley did not show any Zn toxicity symptoms. Due to lower Cd tissue concentrations, only a slight browning of parsley roots was found after Cd treatment. Whereas Cd application induced thiol synthesis in both plant species, Zn excess did not.ConclusionAs elevated Zn concentrations in plant tissues did not induce thiol synthesis, a contribution of phytochelatins to Zn homeostasis and detoxification was excluded.

Foliar Application of Zn Agrichemicals Affects the Bioavailability of Arsenic, Cadmium and Micronutrients to Rice (Oryza sativa L.) in Flooded Paddy Soil

Zinc (Zn) is a key micronutrient affecting bio-functions of crops. Impacts of foliar application of three forms of Zn-containing agrichemicals on the physiology of rice seedlings and their uptake of heavy metal(loid)s and micronutrients from fully flooded paddy soils were investigated in a greenhouse study. Rice seedlings 45 days after germination were randomly exposed to an equivalent amount of 100 mg L−1 of zinc oxide nanoparticles (ZnONPs), zinc oxide bulk particles (ZnOBPs), and zinc salts (Zn2+) through foliar exposure. At termination, rice seedlings were divided into roots and shoots and the concerned metal contents in plant tissues were determined with an inductively coupled plasma mass spectrometry (ICP-MS). Our results demonstrated that all Zn agrichemicals displayed a similar effect on plant growth, but ZnONPs led to the greatest root exudate excretion and greatest inhibition in arsenic (As) uptake. Foliar application of ZnONPs resulted in 28% less As in rice shoots while Zn2+ only caused a 15% decrease in As accumulation in the same tissues. ZnOBPs had minimal impact on As concentration in rice shoots. ZnONPs also promoted iron (Fe) and copper (Cu) uptake in rice shoots, both of which are essential micronutrients for humans. The results suggest that foliar application of ZnONPs resulted in more favorable outcomes for plant growth and food safety than other two types of Zn. Overall, our results showed that application of nanoagrichemicals have important food safety and nutrition implications in addition to their agronomical roles and ZnONPs could be potentially used to alleviate As uptake and fortify Zn and other essential micronutrients in rice grains.

Effect of Biochar Treated Sewage Sludge on the Yield and Uptake of Copper and Zinc in Chinese Cabbage (Brassica rapa)

One of the potential uses of treated sewage sludge is its application as a soil conditioner in agricultural fields. A factorial experiment was conducted to compare the main effects of biochar and sewage sludge and the interaction effect between biochar and sewage sludge on the plant uptake of copper and zinc and vegetable yield. The experiment was done in a green house and Chinese cabbage was used as the test crop. The experiment consisted of two factors namely, biochar and sewage sludge, each of which was applied to the soil at four levels. The copper and zinc concentration were determined in the laboratory based on Atomic Absorption Spectroscopy. A two-way analysis of variance test was performed, and the Tukey’s HSD test was used to separate statistically significant treatment means at 5% level of significance. Results showed a significant interaction effect between biochar and sewage sludge (p = 0.012) on the level of copper concentration in plant tissue. It was observed that sewage sludge had a significant effect on zinc concentration (p < 0.001) in the plant tissue while biochar did not show any significant effect. Further, results showed significant increase in dry matter yield of Chinese cabbage with increasing levels of biochar applied (p < 0.001). This study demonstrates that biochar-treated sewage sludge has potential for use as a soil conditioner in vegetable production. However, it is recommended that care should be taken to avoid overuse by utilizing evaluated and treated sludge for soil amendment.

Soil eutrophication in seabird colonies affects cell wall composition: Implications for the conservation of rare plant species

Seabird colonies exert a strong influence on coastal ecosystems, increasing soil nitrogen bioavailability and modifying plant communities. Previous studies have evidenced that increased N in soils leads to changes in plant cell wall composition; however, this effect has not been assessed in seabird colonies. The main objective of this study was to determine the influence of seabird colonies on nitrogen, cellulose and lignin content in cell walls. For this purpose, analyses were performed on droppings, soils and three native plant species (Armeria pubigera, Armeria pungens and Corema album) growing in yellow-legged gull colonies. The results showed that N excreted by yellow-legged gull is assimilated by plants, increases N content in plant tissues and reduces cellulose and lignin synthesis, therefore potentially altering plant resistance against phytoparasites.

Assessment of the Streptomyces-plant system to mitigate the impact of Cr(VI) and lindane in experimental soils.

Phytoremediation techniques have been proposed as ecological methods to clean up contaminated sites. This study is aimed to evaluate the effect of the Streptomyces sp. Waksman & Henrici and Zea mays L. plant system on the dissipation of Cr(VI) and/or lindane from a co-contaminated soil, being 2mgkg-1 of lindane and 150mgkg-1 of chromium used. Lindane dissipation was improved in the presence of plant-microorganism association; however, Cr(VI) removal was higher when plants or the microorganism were separately. In co-contaminated systems, chromium content in plant tissues was lower than metal content in plants grown only with Cr(VI), suggesting that lindane could interfere with metal accumulation in the plant. The high malondialdehyde (MDA) concentration detected in non-inoculated plants grown with chromium could be consequence of high metal concentration in plant tissues. Interestingly, plants inoculated with Streptomyces sp. Z38 growing with Cr(VI) showed decrease in MDA concentration, indicating that the bacterium could activate defense mechanisms in the plant. Also, inoculated plants showed the highest value of superoxide dismutase activity. Lettuce plants used as bioindicators grew better in biologically treated soils compared with lettuce grown on non-treated soil. The results presented in this work provide the basis that will allow the optimization of future trials on a larger scale.

Soil and leaf potassium, calcium and magnesium in oil palm (Elaeis guineensis Jacq.) plantations grown on three different soils of India: Status, stoichiometry and relations

The knowledge pertaining to phyto-availability of potassium (K), calcium (Ca) and magnesium (Mg) in soils and K, Ca and Mg concentrations in plant tissues and their relations in different productions systems of the world is limited. Understanding soil and leaf K, Ca and Mg concentrations and their stoichiometry in oil palm (Elaeis guineensis Jacq.), a globally demanding crop for vegetable oil production, is important for efficient K, Ca and Mg management. We, therefore, collected soil and leaf samples from oil palm plantations (OPP) established on three different soil series of India, and analysed to assess soil properties (pH, electrical conductivity, soil organic carbon) and concentrations of exchangeable K (Ex. K), Ca (Ex. Ca) and Mg (Ex. Mg) in soil and leaf K, Ca and Mg concentrations and their stoichiometry, and to visualize their relations. Soil properties, concentrations of Ex. K, Ex. Ca and Ex. Mg and their ratios in OPP of different soil series varied widely and differed significantly. The mean concentrations of Ex. K, Ex. Ca and Ex. Mg in OPP of Jangareddigudem and Madukkur series followed the order: Ex. Ca > Ex. Mg > Ex. K. However, soils of OPP of Karmali series had higher mean concentration of Ex. Ca followed by Ex. K followed by Ex. Mg. Leaf K, Ca and Mg concentration and their ratios in oil palm plantations of all the three-soil series varied widely and differed significantly. The mean concentrations of leaf K, Ca and Mg followed the order: Ca > K > Mg. There were positive and significant correlations of Ex. K with Ex. Ca in soils of Jangareddigudem and Madukkur series. Leaf Ca concentration was negatively and significantly correlated with leaf K concentration and Ex. K and Ex. Mg in soils of Jangareddigudem series. There were no correlations of leaf K, Ca and Mg concentration with Ex. K, Ex. Ca and Ex. Mg in soils of Madukkur and Karmali soil series. This study highlighted the need for maintaining equilibrium concentrations of Ex. K, Ex. Ca and Ex. Mg in soils for ensuring proper K, Ca and Mg nutrition of oil palm.

Tomato growth, yield, and quality response to mixed chemical–organic fertilizers and grafting treatments in a high tunnel environment

Tomato (Solanum lycopersicum L.) is a major vegetable crop world-wide and grown in high tunnels in many regions. This study investigates the use of two fertilizer sources, chemical and integrated (composted poultry manure plus urea) fertilizers, and grafting on growth, nitrate-N content, yield, and fruit quality of tomato grown in high tunnels in northwestern Washington. Grafting treatments consisted of ‘Panzer’ tomato grafted on one of three tomato rootstocks ‘Estamino’, Maxifort’, ‘DRO138TX’, or non-grafted (control). Application of chemical fertilizer increased number of leaves per plant, plant height, and cumulative fresh biomass of pruned suckers relative to tomato plants grown with the integrated fertilizer treatment. Grafted tomato plants had greater plant growth than non-grafted plants throughout the growing season. There was no significant difference between fertilizer treatments on nitrate-N concentration in plant tissue or fresh petiole sap; however, grafted plants contained higher levels of nitrate-N than non-grafted plants. Total and marketable fruit weight and number did not differ due to fertilizer source, but total and marketable fruit weight was higher for grafted plants than for non-grafted plants in 2016. There was no significant effect due to fertilizer source on fruit firmness, water content, pH, titratable acidity, and β-carotene; however, total soluble solids (TSS) and lycopene content were higher for fruit grown with integrated fertilizer in 2016. Grafting enhanced water content of tomato fruit in 2015, and TSS (°Brix) in 2016.

Hazard of Contamination with Heavy Metals in Thymus serpyllum L. Herbs from Rural Areas

The aim of the research has been to assay the contents of Zn, Cu, Mn, Fe, and Pb in soil and in the organs of wild Thymus serpyllum L. acquired from three natural habitats from the Kuyavia-Pomerania Province (Poland) not exposed to contamination with metals. As compared with the contents of the geochemical background of the soils in the region and the value of enrichment factor (EF), there was noted a considerable content of Pb in the soil from two locations. The Pb content in plant tissues in one of the three locations was higher than the admissible content specified by the World Health Organization WHO (above 10 mg kg−1 d.w.). As for the Zn content, only the plants from the locations with the relatively youngest phytocenosis met the conditions for herbs to be used for phytotherapy. The Zn content in the dry weight of the plants collected from the other two locations exceeded 50 mg kg−1. The risk of an elevated content of Zn and Pb in the plants makes it necessary to monitor the soil environment and to limit the collection of the plants from natural habitats, as well as to encourage the collection from controlled habitats.

Physiological and biochemical changes in tree seedlings growing in urban forest soil contaminated with copper in São Paulo, Brazil

Soil pollution by heavy metals is a worldwide environmental concern. Owing to their proximity to sources of anthropogenic emission, urban forest fragments are highly affected by the excessive input of heavy metals into the soil. Thus, this study aimed to assess the physiological and biochemical responses of two native Brazilian Atlantic Forest tree species, Schinus terebinthifolia Raddi (pioneer species) and Eugenia uniflora L. (non-pioneer species), when cultivated in soils contaminated with Cu. Plants were cultivated in soils of an urban forest fragment contaminated with 0 (control), 60, 120, 180 or 240 mg Cu kg−1 soil. Growth variables, Cu content in plant tissues, translocation index, bioaccumulation factor, pigment contents, leaf gas exchange and chlorophyll fluorescence were all measured to assess physiological alterations resulting from Cu stress, while enzymatic (superoxide dismutase) and nonenzymatic (ascorbic acid and glutathione) antioxidants were quantified to assess the biochemical responses of the species. Both species presented high uptake and accumulation of Cu in roots with low translocation rates to shoots; however, S. terebinthifolia showed higher Cu restriction in roots than E. uniflora. S. terebinthifolia and E. uniflora showed distinct responses in growth and leaf gas exchange. Neither enzymatic contents nor oxidative reduction showed any difference between the species. The restriction of Cu in roots appears to be the principal protective mechanism against Cu phytotoxicity, preventing negative effects on the physiological and biochemical status of the species. S. terebinthifolia shows potential as a Cu phytostabilizer.

Effects of exogenous spermidine on poplar resistance to leaf and root herbivory as affected by soil cadmium stress

Elemental defense hypothesis (EDH) proposed that metal accumulation in plants could increase plant resistance to herbivores. However, the over-accumulation of metals in low-accumulators such as woody plants will cause adverse effects on plant health. Thus, the application of EDH on low-accumulators in metal contaminated areas is strongly limited. Since the supplement of exogenous spermidine (Spd) was reported to alleviate metal-induced toxicity in plants while stimulating metal accumulation in plant tissues, we hypothesized that such application will further improve plant resistance to herbivores. In this study, we employed a woody plant species, Populus yunnanensis, to test this hypothesis. We first tested a Spd concentration series applied on plants subjected to soil cadmium (Cd) stress and found that the 1 mM Spd strongly promoted plant growth while stimulated Cd accumulation in plant leaves and roots. We further conducted herbivore bioassays to test the growth performance and feeding preference of two leaf herbivore species and a root herbivore species that fed on plants from different treatments. The results showed that the inhibition effect of Cd stressed-plants on herbivore growth was significantly magnified by the addition of Spd. The growth weight of all the three tested herbivores were negatively correlated with increased Cd concentrations in plant tissues. In addition, the feeding preferences of the two leaf herbivore species were strongly repelled by leaf discs from Cd-treated plants with Spd supplement. The results suggested that the application of exogenous Spd at a certain dose could enhance elemental defense of plants against herbivory.

Crop irrigation (soybean, bean, and corn) with enrofloxacin-contaminated water leads to yield reductions and antibiotic accumulation

The increasing use of antibiotics in animal production has become an emergent environmental problem. The large percentages of applied antibiotic doses eliminated in animal excrement often end up contaminating water resources, which are then used for irrigation – compromising agricultural production and/or food security. Here, we evaluated the effects of crop irrigation with water artificially contaminated by enrofloxacin (10 μg l−1) and its accumulation in soybean, bean, and corn tissues. Grain production was evaluated on the basis of grain dry weight plant−1, while enrofloxacin and ciprofloxacin (its breakdown metabolite) concentrations in plant tissues were evaluated by HPLC after harvesting. Diminished production was observed only in soybean plants irrigated with antibiotic-contaminated water. Enrofloxacin [1.68 ng g fresh weight (FW)−1 to 26.17 µg g FW−1] and ciprofloxacin (8.23 ng g FW−1 to 51.05 ng g FW−1), were found in all of the plant tissues (roots, leaves, and seeds) of the three species. Regardless of the species, the highest enrofloxacin concentrations were observed in their roots, followed by the leaves and seeds, while ciprofloxacin concentrations varied among the different plant tissues of the different species. The presence of enrofloxacin in the water used for irrigating soybeans can result in productivity losses and, as that antibiotic was encountered in plant tissues (leaves and seeds) of all of the three species analyzed that are consumed in the diets of both humans and animals, it can interfere with food security.

Assessment of potential winter hardiness in winter bread wheat cultivars and genotypes by analyzing autofluorescence in seedling tissues

Background.Winter crops are the most productive component of agricultural biocenoses. In Russia, winter wheat suffers the greatest losses in winter, so a search for traits marking high or low winter hardiness in autumn-sown genotypes, including improved cultivars, is needed to assess their potential for overwintering. One of such markers of high winter hardiness is an increased lignin content in plant tissues. The terminal enzyme in the phenylpropanoid pathway of metabolism, wherein lignin components are formed, is cinnamyl-alcohol dehydrogenase (CAD, EC 1.1.1.195). In plants, the CAD enzyme is one of the links in the aromatic metabolism, which generates, in addition to lignin, a number of aromatic compounds, such as lignans, aromatic glycosides, etc. Many of these compounds, like lignin, contain chromophore groups and are capable of autofluorescence.Correlations of the genotypes that incorporate CAD1-F with overwintering are studied in this work.Materials and methods.The winter bread wheat cultivars ‘Zitnica’ (Yugoslavia) and ‘Novosibirskaya 9’ (ICG SB RAS, Russia), contrasting in winter hardiness and CAD isozyme spectra, their hybrids, and 28 improved winter cultivars developed in Krasnodar were selected for the study. Fluorescence analysis of 28 winter wheat cultivars was also performed. Correlation coefficients between fluorescence and frost tolerance were calculated using the results of the analysis of 7 most contrasting cultivars.Conclusions. The tested winter bread wheat genotypes demonstrated the interplay between CAD1-F and successful overwintering: a correlation was found in the genotypes carrying the 00 CAD1-F allele with higher percentage of overwintered plants. This dependence was not observed in every season. The analysis of seedling sections for fluorescence can also be used for preliminary assessment of winter tolerance in winter bread wheat under laboratory conditions.

Utilization of biochar and Trichoderma harzianum to promote growth of shallot and remediate lead-contaminated soil

This study aimed to determine the effect of biochar and Trichoderma harzianum toward lead removal in soil, lead absorption, lead content in plant tissue also growth and yield of shallot cultivated on lead-contaminated soil. The experimental design used was a completely factorial randomized block design consisting of 2 factors. The first factor was corn cobs biochar which was applied 1 week after basic fertilizer treatment and consisted of 4 levels, namely B0: without biochar, B1: 2.5 t ha-1, B2: 5 t ha-1, and B3: 10 t ha-1. The second factor was the dosage of liquid of Trichoderma harzianum, namely TR0: without T.harzianum, TR1: 10 mL L-1, and TR2: 20 mL L-1, which was applied three times at 14, 28 and 42 days after planting. Data were analyzed using the F test and continued with DMRT (Duncan Multiple Range Test) at P= 0.05 level. The results showed that the application of 5 t biochar ha-1 was able to remove lead and decreased lead uptake in plants. Application of T. harzianum could remove and decrease absorption in plant tissue biochar was not able to increase the growth of shallot while T. harzianum increased the number of leaves and the number of tubers.

In Vivo Imaging of Plant Oxygen Levels.

Oxygen is essential for multicellular aerobic life due to its central role in energy metabolism. The availability of oxygen can drop below the level to sustain oxidative phosphorylation when plants are flooded, posing a severe threat to survival. However, under non-stressful conditions, the internal oxygen concentration of most plant tissue is not in equilibrium with the environment, which is attributed to cellular respiration and diffusion constrains imposed by O2 barriers and bulky tissue. This is exemplified by the observations of steep oxygen gradients in roots, fruits, tubers, anthers and meristems. To adapt to a varying availability of oxygen, plants sense O2 via the conditional proteolysis of transcriptional regulators. This mechanism acts to switch oxidative metabolism to anaerobic fermentation, but it was also shown to play a role in plant development and pathogen defense. To investigate how dynamic and spatial distribution of O2 impacts on these processes, accurate mapping of its concentration in plants is essential. Physical oxygen sensors have been employed for decades to profile internal oxygen concentrations in plants, while genetically encoded oxygen biosensors have only recently started to see use. Driven by the critical role of hypoxia in human pathology and development, several novel oxygen-sensing devices have also been characterized in cell lines and animal model organisms. This review aims to provide an overview of available oxygen biosensors and to discuss their potential application to image oxygen levels in plants.

Combined action of gamma radiation and exposure to copper ions on Lemna minor L

Purpose Under natural conditions, the reaction of living organisms to the action of acute gamma radiation depends on other stressors, including heavy metals. The aim of this work was to study changes in morphometric parameters, the content of photoassimilation pigments and the level of oxidative stress in irradiated duckweed at various copper concentrations in the culture medium. Materials and methods As a model organism, we used Lemna minor L. Duckweed was exposed to acute γ-radiation at doses of 18, 42, 63 Gy. After irradiation, the plants were transferred into a medium containing 3, 5, 6.3 μmol/L Cu. On the 4th day of exposure, the levels of chlorophyll, carotenoids, malondialdehyde (MDA) were measured; after 7 days, the specific growth rate, the level of damage, the change in the frond area, copper concentration in plant tissues were determined. Results The action of γ-radiation (18, 42, 63 Gy) and copper ions (3, 5, 6.3 μmol/L) reduced the growth rate, increased the membrane lipid peroxidation, reduced the area of the fronds more significantly than under the separate action of the factors. The factors acted antagonistically on the specific growth rate. The content of copper in the tissues of irradiated plants (42, 63 Gy) increased. Conclusion Irradiation of duckweed with acute doses of gamma radiation reduced the resistance of plants to excess copper in the environment.

Effects of zinc oxide nanoparticles on antioxidants, chlorophyll contents, and proline in Persicaria hydropiper L. and its potential for Pb phytoremediation.

Applications of nanoparticles and plants for efficient restoration of heavy metal-polluted water and soil are an emerging approach and need to be explored. Hydroponic study was performed to find the role of zinc oxide nanoparticles (ZnO NPs) in plant growth, antioxidative response, and lead (Pb) accumulation in Persicaria hydropiper. Seedlings were grown in Pb-polluted media amended with 5, 10, 15, and 20 mg L-1 ZnO NPs. Inductively coupled plasma spectroscopy (ICP) was used for Pb analysis in plant tissues. Pb significantly inhibited seedling growth, and ZnO NPs alleviated Pb-induced stress by promoting plant growth, and improved chlorophyll and carotenoid contents. Oxidative stress ameliorated in ZnO NPs exposed seedlings through enhanced production of free proline, phenolics, flavonoids, and activation of antioxidative enzymes. Pb accumulation boosted in ZnO NP treatments, and highly significant increase in Pb accumulation in roots (255.60±4.80 mg kg-1), stem (124.07±2.84 mg kg-1), and leaves (92.00±3.22 mg kg-1) was observed in T3 (15 mg L-1 ZnO NPs) for P. hydropiper. Contrarily, ZnO NPs at 20 mg L-1 dose suppressed plant growth, Pb accumulation, secondary metabolites, and antioxidative enzyme activities. Moreover, positive correlation was found in Pb accumulation with free proline and secondary metabolite contents in plant tissues. These results suggest that ZnO NPs at optimum concentration may augment efficacy of plants to remove heavy metal from polluted water through nanophytoremediation.

Induction of Systemic Resistance in Tomato (Solanum lycopersicom L.) Against Damping-off Disease by Using a Mixture of Mycorrhizae

Khrieba, M.I., M.F. Azmeh, W. Chouman, I. Ghazal, and A.K. Ali. 2021. Induction of Systemic Resistance in Tomato (Solanum lycopersicom L.) Against Damping-off Disease by Using a Mixture of Mycorrhizae. Arab Journal of Plant Protection, 39(1): 61-68. The effect of vesicular-arbuscular mycorrhiza (VAM) in improving the activity of the enzyme peroxidase and its role in controlling tomato damping-off caused by Pythium ultimum was studied in a pot experiment during the 2013 growing season. Five treatments were compared with a non-treated control (C): in treatment 1, soil was infested only with Pythium (Py), in treatment 2, soil was infested with mycorrhiza only (My), in treatment 3 soil was infested with Pythium and mycorrhiza at sowing (My+Py), in treatment 4, soil was infested with Pythium and two weeks after sowing with Mycorrhiza (Py-My) and in treatment 5, soil was infested with mycorrhiza and two weeks after sowing with Pythium (My-Py). The results showed that peroxidase concentration in plant tissues 14 days after seed germination in the My treatment (361.91 μmole/mg) significantly exceeded the other treatments. In the treatment where mycorrhiza was added before the pathogen 67 Arab J. Pl. Prot. Vol. 39, No. 1 (2021) peroxidase activity reached 183.73 μmole/mg, which was 41% significantly higher than the My+Py treatment in which the pathogen and mycorrhizal inoculant were added together at sowing (108.27 μmole/mg). The peroxidase concentration increased significantly 28 days after seed germination in the My treatment (687.52 μmole/mg) as compared with the Py treatment (10.52 μmole/mg). Results also showed that in the treatment My-Py, where the mycorrhyzal inoculum was added before the pathogen, peroxidase activity (458.27 μmole/mg) was significantly higher than in the treatment Py+My, when the pathogen was added simultaneously with the vesicular-arbuscular mycorrhizal inoculum (98.67 μmole/mg). Furthermore, results showed that 35 days after seed germination, the enzyme concentration was significantly higher in the My-Py treatment (763.39 μmole/mg) as compared with My+Py treatment (143.5 μmole/mg). Keywords: Vesicular-arbuscular mycorrhiza, VAM, Pythium ultimum, peroxidase, tomato, Syrian coast, induced resistance.

Response of mangrove plant species to a saline gradient: Implications for ecological restoration

Mangroves are salt tolerant plants that occur in tropical and sub-tropical sheltered coasts. Saltwater intrusions into terrestrial landscapes often occur due to either anthropogenic reasons or natural calamities such as tsunamis. We investigated the potential of using mangrove species for rehabilitation of high saline environments by revealing the capacities of species to remove salt from sediment. We established the salt retention capacity of common mangrove species in Sri Lanka i.e., Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal, and Avicennia marina through ex-situ and in-situ measurements of NaCl content in plant tissue and soil samples, by titrating with 0.01 N AgNO3. The results revealed A. marina to be the most efficient in retaining salt within plant tissues while C. tagal is superior to R. mucronata but inferior to A. marina in performing this function. These findings were further confirmed by measuring salt uptake rates of hydroponically grown seedlings of the same species. Although R. mucronata is the most popular species used for restoration, A. marina appears the most suitable mangrove species not only for coastal mangrove restoration but also for rehabilitating salinity affected landscapes.