Ethylenediamine‐N,N′‐disuccinic acid mitigates salt‐stress damages in strawberry by interfering with effects on the plant ionome

This study evaluated the hypothesis that the organic chelant ethylenediamine‐N,N′‐disuccinic acid (EDDS) mitigates plant damage under salinity, and that this is accomplished by EDDS‐induced effects on cation uptake. Damaging effects of salinity on plants often involve inhibited uptake of nutritional cations, such as K and Ca, and excessive accumulation of Na. Therefore, mechanisms that improve uptake of K and Ca, or reduce Na uptake, have a potential for ameliorating salinity damages. Organic chelants increase heavy‐metal cation availability at the site of uptake and increase their uptake by the roots or in planta transport. Although organic chelants are routinely used in agriculture to enhance uptake of heavy‐metal cations into plants, and for soil bioremediation, their effect on uptake of cation‐macronutrients is not known, and neither is their impact on plant function under salinity. In this study, we evaluated the response of strawberry plants to EDDS application (0, 1, 3 and 5 mmol kg soil^?1), under six levels of NaCl (0, 3, 6, 9, 12 and 15 mmol L^?1). EDDS application under salinity improved vegetative development, as well as reproductive growth and chlorophyll content, with statistically significant interaction between chelant dosage and level of salinity. The mitigation of salinity damage by EDDS occurred at high salinity treatments (from 9 mM NaCl). Application rates of 1–3 mmol EDDS kg^?1 were optimal for mitigating salinity effects on reproductive development, but in accordance with the extent of chelant‐induced accumulation of the macronutrients K, Ca and P in the leaves, higher application rates (3–5 mmol EDDS kg^?1) were required for optimal improvement of vegetative development. These results suggest that EDDS improves plant function under mild salinities by interfering with salinity effects on the plant ionome.     

Brassica juncea tested on urban soils moderately contaminated by lead: Origin of contamination and effect of chelates

Urban garden soils are a potential repository of heavy metal pollution, resulting from either anthropogenic or geogenic origin. The efficiency of phytoextraction was compared on two garden soils with the same texture and topsoil Pb concentration (170 mg kg^?1) but not the same origin: one geogenic, the other anthropogenic. Two varieties of Brassica juncea were tested with citric acid (25 mmol kg^?1) or ethylenediaminetetraacetic acid (EDTA, 2.5 mmol kg^?1). Geogenic Pb was shown to be two times less available than anthropogenic Pb, as a result of which the phytoextraction efficiency was reduced by 59%. Pb mobility in the soil was solely enhanced with EDTA, which increased the Pb concentration in shoots of B. juncea by between 14 and 26 times in comparison with the control. The highest Pb concentration in shoots still remained low, however (i.e., 45 mg kg^?1 dry weight). Regardless of the chelates introduced, B. juncea 426308 accumulated roughly twice as much lead as B. juncea 211000, but only for the anthropogenic contaminated soil. Under these conditions, the amount of Pb accumulated by B. juncea (even when assisted by EDTA) was not high enough to envision achieving soil clean-up within a reasonable time frame.     

Multiple stress and growth of barley: Effect of salinity and temperature shock

The effect of preconditioning to NaCl salinity (0 to 135 mmol L^-1) on the subsequent response of barley (Hordeum vulgare L.) to two days of low (5°C) temperature shock (LTS) was investigated. Both salinity and LTS reduced the final growth of barley tops and roots. The effect of LTS on growth of tops and roots depended on the level of salinity stress imposed. At salinity level of 45 mmol L^-1, for example, exposing the plants to LTS reduced top growth by an additional 34%; at 135 mmol L^-1 salinity, however, LTS reduced the top growth by only 2%. Salinity increased the concentration of Na, Cl, total P, PO₄, and Zn, reduced the concentration of K, Ca, total N, NO₃, and SO₄, but did not affect the concentration of total S in the barley tops. LTS increased the concentration of Ca and Zn in the tops; the concentrations of other elements (cations and anions) were not changed by the temperature treatment. In the tops of the control plants, NO₃, PO₄, and SO₄ accounted for 15%, 72% and 93% of the total N, P, and S, respectively. In the plants grown at 135 mmol L^-1 NaCl, however, the above values were 8%, 84%, and 70%, respectively, which indicates that salinity had altered the incorporation of N, P, and S into organic compounds. We suggest that salinity and low temperature affect growth and nutrient uptake and incorporation into organic matter by different mechanisms. Although barley subjected to low salinity becomes more sensitive to subsequent low temperature stress, preconditioning of barley to higher salinity stress seems to reduce the plant's sensitivity to subsequent low temperature.     

Seed germination,plant growth and physiological responses of Salsola ikonnikovii to short-term NaCl stress

Salsola ikonnikovii (Chenopodiaceae), a drought-tolerant plant species that is distributed in sand or light-saline soil in Xinjiang, China, produces seeds (fruits) with attached winged perianths. To study the role of the wing in seed germination under salt stress and to further investigate the growth and physiological responses of the plants to salt stress, the germination behaviour of S. ikonnikovii was determined after winged and non-winged seeds were treated with 0–1000 mmol · L^?1 NaCl. Several parameters of two-month old plants that had been treated with NaCl for three weeks were measured. The results revealed that the winged perianths limited germination but protected the seeds from salt damage. The growth of the plants was stimulated by lower concentrations of salt (≤100 mmol · L^?1 NaCl), while increasing salt concentrations inhibited growth. The level of reactive oxygen species and malondialdehyde increased significantly at high concentrations of salt. Correspondingly, concentrations of the osmolytes proline, betaine, and soluble sugars, and the activities of antioxidative enzymes (catalase, peroxidase and superoxide dismutase) increased, but the levels of non-enzymatic antioxidants (carotenoids, glutathione) were significantly reduced at high salt concentrations. These results imply that osmotic adjustment and the antioxidative system may work synergistically to ensure that a plant grows normally under high salt concentrations.     

Physiological response of Nannochloropsis sp. to saline stress in laboratory batch cultures

In the present paper, we investigated the physiological response of the marine microalga Nannochloropsis sp. to salt stress (13, 27, 54, and 81 g L^?1 NaCl). Increasing the sodium chloride concentration caused up to a 70 % decrease in the chlorophyll a concentration, cell growth, and net photosynthesis rate. The chlorophyll a fluorescence measurements indicated a strong reduction in the effective quantum yield of photosystem II (?60 %) and an increase in nonphotochemical quenching when the cells were exposed to NaCl concentrations greater than 27 g L^?1 (control). In contrast, the specific lipid content increased up to 80 % when the sodium chloride concentration was increased from 27 to 54–81 g L^?1. These results are relevant for the outdoor cultivation of this microalga using open photobioreactors, in which microalgae are subjected to strong changes in salinity concentration caused by water evaporation.     

The Possible Roles of Priming with ZnO Nanoparticles in Mitigation of Salinity Stress in Lupine (Lupinus termis) Plants

To our knowledge, little attention has been paid to evaluating ZnO nanoparticles (ZNPs) roles in plants grown under salinity stress. In this study, seeds of lupine (Lupinus termis) plants were grown in plastic pots and exposed to 0 (control) and 150 (S) mM NaCl with or without priming with different concentrations of ZnO [20 mg L^?1 (ZNPs1), 40 mg L^?1 (ZNPs2), and 60 mg L^?1 (ZNPs3)] for 20 days. Salinized plants showed a reduction in plant growth parameters (root length, shoot length, fresh weight, and dry weight) and in the contents of photosynthetic pigments (chlorophyll a and b, and carotenoids) and Zn, as well as in the activity of catalase (CAT) against control plants. On the other side, salinity stress boosted the contents of organic solutes (soluble sugar, soluble protein, total free amino acids, and proline), total phenols, malondialdehyde (MDA), ascorbic acid and Na, as well as the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in stressed plants over control plants. However, seed-priming with ZNPs mostly stimulated growth of stressed plants, which was accompanied by reinforcement in the levels of photosynthetic pigments, organic solutes, total phenols, ascorbic acid and Zn, as well as in the activities of SOD, CAT, POD, and APX enzymes over stressed plants alone. On the contrary, priming with ZNPs caused a decrement in the contents of MDA and Na in stressed plants relative to salinized plants alone. It is worthy to mention that, this improvement in salt tolerance of plants primed with ZNPs was more obvious in plants primed with ZNPs3 and grown both in unstressed and stressed regimes. Thus, our findings suggest that seed-priming with ZNPs, especially 60 mg L^?1 ZnO is an effective strategy that can be used to enhance salt tolerance of lupine plants.

     

Effect of zinc nutrition on salinity-induced oxidative damages in wheat genotypes differing in zinc deficiency tolerance

Zinc deficiency and salinity are well-documented soil problems and often occur simultaneously in cultivated soils. Usually, plants respond to environmental stress factors by activating their antioxidative defense mechanisms. The antioxidative response of wheat genotypes to salinity in relation to Zn nutrition is not well understood. So, we investigated the effect of Zn nutrition on the growth, membrane permeability and sulfhydryl group (–SH groups) content of root cells and antioxidative defense mechanisms of wheat plants exposed to salt stress. In a hydroponic experiment, three bread wheat genotypes (Triticum aestivum L. cvs. Rushan, Kavir, and Cross) with different Zn-deficiency tolerance were exposed to adequate (1 μM Zn) and deficient (no Zn) Zn supply and three salinity levels (0, 60, and 120 mM NaCl). The results obtained showed that adequate Zn nutrition counteracted the detrimental effect of 60 mM NaCl level on the growth of all three wheat genotypes while it had no effect on the root and shoot growth of ‘Rushan’ and ‘Kavir’ at the 120 mM NaCl treatment. At the 0 and 60 mM NaCl treatments, Zn application decreased root membrane permeability while increased –SH group content and root activity of catalase (CAT) and superoxide dismutase (SOD) in ‘Rushan’ and ‘Kavir’. In contrast, Zn had no effect on the root membrane permeability and –SH group content of ‘Rushan’ and ‘Kavir’ exposed to the 120 mM NaCl treatment. At all salinity levels, ‘Cross’ plants supplied with Zn had lower root membrane permeability and higher –SH group content compared to those grown under Zn-deficient conditions. At the 0 and 60 salinity levels, Zn-deficient roots of Kavir and Rushan genotype leaked significantly higher amounts of Fe and K than the Zn-sufficient roots. In contrast, at the 120 mM treatment, Zn application had no effect or slightly increased Fe and K concentration in the root ion leakage of these wheat genotypes. For ‘Cross’, at all salinity levels, Zn-deficient roots leaked significantly higher amounts of Fe and K compared with the Zn-sufficient roots. The differential tolerance to salt stress among wheat genotypes examined in this study was related to their tolerance to Zn-deficiency, –SH group content, and root activity of CAT and SOD. Greater tolerance to salinity of Zn-deficiency tolerant genotype ‘Cross’ is probably associated with its greater antioxidative defense capacity.     

PLANT GROWTH REGULATORS ENHANCE GOLD UPTAKE IN BRASSICA JUNCEA

The use of plant growth regulators is well established and they are used in many fields of plant science for enhancing growth. Brassica juncea plants were treated with 2.5, 5.0 and 7.5 μM auxin indole-3-butyric acid (IBA), which promotes rooting. The IBA-treated plants were also sprayed with 100 μM gibberellic acid (GA₃) and kinetin (Kin) to increase leaf-foliage. Gold (I) chloride (AuCl) was added to the growth medium of plants to achieve required gold concentration. The solubilizing agent ammonium thiocyanate (1 g kg^?1) (commonly used in mining industries to solubilize gold) was added to the nutrient solution after six weeks of growth and, two weeks later, plants were harvested. Plant growth regulators improved shoot and root dry biomass of B. juncea plants. Inductively Coupled Plasma Optical Emission Spectrometry analysis showed the highest Au uptake for plants treated with 5.0 μM IBA. The average recovery of Au with this treatment was significantly greater than the control treatment by 45.8 mg kg^?1 (155.7%). The other IBA concentrations (2.5 and 7.5 μM) also showed a significant increase in Au uptake compared to the control plants by 14.7 mg kg^?1 (50%) and 42.5 mg kg^?1 (144.5%) respectively. A similar trend of Au accumulation was recorded in the roots of B. juncea plants. This study conducted in solution culture suggests that plant growth regulators can play a significant role in improving phytoextraction of Au.     

Phytoremediation of Cd,Ni, Pb and Zn by Salvinia minima

Most metals disperse easily in environments and can be bioconcentrated in tissues of many organisms causing risks to the health and stability of aquatic ecosystems even at low concentrations. The use of plants to phytoremediation has been evaluated to mitigate the environmental contamination by metals since they have large capacity to adsorb or accumulate these elements. In this study we evaluate Salvinia minima growth and its ability to accumulate metals. The plants were cultivated for about 60 days in different concentrations of Cd, Ni, Pb and Zn (tested alone) in controlled environmental conditions and availability of nutrients. The results indicated that S. minima was able to grow in low concentrations of selected metals (0.03 mg L^?1 Cd, 0.40 mg L^?1 Ni, 1.00 mg L^?1 Pb and 1.00 mg L^?1 Zn) and still able to adsorb or accumulate metals in their tissues when cultivated in higher concentrations of selected metals without necessarily grow. The maximum values of removal metal rates (mg m² day^?1) for each metal (Cd = 0.0045, Ni = 0.0595, Pb = 0.1423 e Zn = 0.4046) are listed. We concluded that S. minima may be used as an additional tool for metals removal from effluent.     

Leaf cell membrane stability‐based mechanisms of zinc nutrition in mitigating salinity stress in rice

• Excess salt affects about 955 million ha of arable land worldwide, and 49% of agricultural land is Zn‐deficient. Soil salinity and zinc deficiency can intensify plant abiotic stress. The mechanisms by which Zn can mitigate salinity effects on plant functions are not well understood.
• We conducted an experiment to determine how Zn and salinity effects on rice plant retention of Zn, K⁺ and the salt ion Na⁺ affect chlorophyll formation, leaf cell membrane stability and grain yield. We examined the mechanisms of Zn nutrition in mitigating salinity stress by examining plant physiology and nutrition. We used native Zn‐deficient soils (control), four salinity (EC ) and Zn treatments – Zn 10 mg·kg^?1 (Zn₁₀), EC 5 dS ·m^?1 (EC ₅), Zn₁₀+EC ₅ and Zn₁₅+EC ₅, a coarse rice (KS ‐282) and a fine rice (Basmati‐515) in the study.
• Our results showed that Zn alone (Zn₁₀) significantly increased rice tolerance to salinity stress by promoting Zn/K⁺ retention, inhibiting plant Na⁺ uptake and enhancing leaf cell membrane stability and chlorophyll formation in both rice cultivars in native alkaline, Zn‐deficient soils (P  <  0.05). Further, under the salinity treatment (EC ₅), Zn inputs (10–15 mg·kg^?1) could also significantly promote rice plant Zn/K⁺ retention and reduce plant Na⁺ uptake, and thus increased leaf cell membrane stability and grain yield. Coarse rice was more salinity‐tolerant than fine rice, having significantly higher Zn/K⁺ nutrient retention.
• The mechanistic basis of Zn nutrition in mitigating salinity impacts was through promoting plant Zn/K⁺ uptake and inhibiting plant Na⁺ uptake, which could result in increased plant physiological vigour, leaf cell membrane stability and rice productivity.

     

Feasibility of Typha Latifolia for High Salinity Effluent Treatment in Constructed Wetlands for Integration in Resource Management Systems

High salinity wastewaters have limited treatment options due to the occurrence of salt inhibition in conventional biological treatments. Using recirculating marine aquaculture effluents as a case study, this work explored the use of Constructed Wetlands as a treatment option for nutrient and salt loads reduction. Three different substrates were tested for nutrient adsorption, of which expanded clay performed better. This substrate adsorbed 0.31 mg kg^?1 of NH₄ ⁺?N and 5.60 mg kg^?1 of PO₄ ^3??P and 6.9 mg kg^?1 dissolved salts after 7 days of contact. Microcosms with Typha latifolia planted in expanded clay and irrigated with aquaculture wastewater (salinity 2.4%, 7 days hydraulic retention time, for 4 weeks), were able to remove 94% NH₄ ⁺?N (inlet 0.25 ± 0.13 mg L^?1), 78% NO₂ ^??N (inlet 0.78 ± 0.62 mg L^?1), 46% NO₃ ^??N (inlet 18.83 ± 8.93 mg L^?1) whereas PO₄ ^3??P was not detected (inlet 1.41 ± 0.21 mg L^?1). Maximum salinity reductions of 52% were observed. Despite some growth inhibition, plants remained viable, with 94% survival rate. Daily treatment dynamics studies revealed rapid PO₄ ^3??P adsorption, unbalancing the N:P ratio and possibly affecting plant development. An integrated treatment approach, coupled with biomass valorization, is suggested to provide optimal resource management possibilities.     

SALT‐INDUCED ALTERATIONS IN LIPID COMPOSITION OF DIATOM NITZSCHIA LAEVIS (BACILLARIOPHYCEAE) UNDER HETEROTROPHIC CULTURE CONDITION1

The diatom Nitzschia laevis Hust. is a potential producer of eicosapentaenoic acid (EPA). To elucidate its cellular response to salt stress, the effects of salinity on EPA production, lipid composition, and fatty acid distribution in the lipid pool were investigated. The highest contents of total fatty acids, EPA, and polar lipids were all obtained at NaCl of 20 g · L^?1, under which 71.3% of total EPA existed in polar lipid fractions. In N. laevis, high salt concentration might induce the decrease in neutral lipids (NLs), whereas the production of polar lipids, including phospholipids (PLs) and glycolipids (GLs), was enhanced. The degree of fatty acid unsaturation of both neutral and polar lipid fractions increased sharply when NaCl concentration increased from 10 to 20 g · L^?1 but decreased at NaCl concentration of 30 g · L^?1. The amount of total free sterols was increased with the increase in salt concentration. All these changes in lipid and fatty acids suggested a decrease in membrane permeability and fluidity under high salt concentration, which could help the alga acclimate to the salinity stress.     

Characterizing the growth of <Emphasis Type="Italic">Sarcoptes scabiei</Emphasis> infrapopulations

The plant stress hypothesis posits that a herbivore’s reproductive success increases when it feeds on stressed plants, while the plant vigor hypothesis predicts that a herbivore preferentially feeds on more vigorous plants. We examined these opposing hypotheses by growing spider mites (Tetranychus urticae) on the leaves of stressed and healthy (vigorous) cucumber plants. Host plants were grown under controlled conditions at low, moderate, and high concentrations of NaCl (to induce salinity stress), at low, moderate, and high fertilizer concentrations (to support growth), and without these additions (control). The effects of these treatments were evaluated by measuring fresh and dry plant biomass, carotenoid and chlorophyll content, antioxidant enzyme activity, and concentrations of PO₄^3?, K⁺, and Na⁺ in plant tissues. The addition of low concentrations of fertilizer increased dry mass, protein, and carotenoid content relative to controls, suggesting a beneficial effect on plants. The highest NaCl treatment (2560 mg L^?1) resulted in increased Na⁺ and protein content relative to control plants, as well as reduced PO₄^3?, K⁺, and chlorophyll levels and reduced catalase and ascorbate peroxidase enzyme activity levels. Analysis of life table data of T. urticae mites raised on leaves from the aforementioned plant groups showed the intrinsic rate of increase (r) for mites was 0.167 day^?1 in control specimens, 0.125 day^?1 for mites reared on plants treated with a moderate concentration of fertilizer (10 mL L^?1), and was highest (0.241 day^?1) on plants grown under moderate salinity conditions (1920 mg L^?1 NaCl). Reproductive success of T. urticae did not differ on plants watered with a moderate concentration of NaCl or a high concentration of fertilizer. The moderately-stressed plants formed a favorable environment for the development and reproduction of spider mites, supporting the plant stress hypothesis.     

Responses of ectomycorrhizal American elm (Ulmus americana) seedlings to salinity and soil compaction

American elm (Ulmus americana) seedlings were either non-inoculated or inoculated with Hebeloma crustuliniforme, Laccaria bicolor and a mixture of the two fungi to study the effects of ectomycorrhizal associations on seedling responses to soil compaction and salinity. The seedlings were grown in the greenhouse in pots containing non-compacted (0.4 g cm^?3 bulk density) and compacted (0.6 g cm^?3 bulk density) soil and subjected to 60 mM NaCl or 0 mM NaCl (control) treatments for 3 weeks. All three fungal inocula had similar effects on the responses of elm seedlings to soil compaction and salt treatment. In non-compacted soil, ectomycorrhizal fungi reduced plant dry weights, root hydraulic conductance, but did not affect leaf hydraulic conductance and net photosynthesis. When treated with 60 mM NaCl, ectomycorrhizal seedlings had several-fold lower leaf concentrations of Na⁺ compared with the non-inoculated plants. Soil compaction reduced Na⁺ leaf concentrations in non-ectomycorrhizal plants and decreased dry weights, gas exchange and root hydraulic conductance. However, in ectomycorrhizal plants, soil compaction had little effect on the leaf Na⁺ concentrations and on other measured growth and physiological parameters. Our results demonstrated that ECM associations could be highly beneficial to plants growing in sites with compacted soil such as urban areas.     

Study on salt tolerance with YHem1 transgenic canola (Brassica napus)

5‐Aminolevulinic acid (5‐ALA) has been suggested for improving plant salt tolerance via exogenous application. In this study, we used a transgenic canola (Brassica napus), which contained a constituted gene YHem1 and biosynthesized more 5‐ALA, to study salt stress responses. In a long‐term pot experiment, the transgenic plants produced higher yield under 200 mmol L^?1 NaCl treatment than the wild type (WT). In a short‐term experiment, the YHem1 transformation accelerated endogenous 5‐ALA metabolism, leading to more chlorophyll accumulation, higher diurnal photosynthetic rates and upregulated expression of the gene encoding Rubisco small subunit. Furthermore, the activities of antioxidant enzymes, including superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase, were significantly higher in the transgenic plants than the WT, while the levels of O₂·^? and malondialdehyde were lower than the latter. Additionally, the Na⁺ content was higher in the transgenic leaves than that in the WT under salinity, but K⁺ and Cl^? were significantly lower. The levels of N, P, Cu, and S in the transgenic plants were also significantly lower than those in the WT, but the Fe content was significantly improved. As the leaf Fe content was decreased by salinity, it was suggested that the stronger salt tolerance of the transgenic plants was related to the higher Fe acquisition. Lastly, YHem1 transformation improved the leaf proline content, but salinity decreased rather than increased it. The content of free amino acids and soluble sugars was similarly decreased as salinity increased, but it was higher in the transgenic plants than that in the WT.     

Isolation of phytase-producing bacteria from Himalayan soils and their effect on growth and phosphorus uptake of Indian mustard (Brassica juncea)

Phytase-producing bacteria (PPB) is being investigated as plant growth promoting rhizobacteria (PGPR) to improve the phosphorus (P) nutrition and growth of plants grown in soil with high phytate content. Phytate is dominant organic P forms in many soils and must be hydrolyzed to be available for plants. Indian mustard (Brassica juncea) is a plant with economic importance in agriculture and phytoremediation, therefore biotechnological tools to improve growth and environmental stress tolerance are needed. In this study, we isolated and characterized PPB from Himalayan soils and evaluated their effect on growth and P uptake by B. juncea under greenhouse conditions. Sixty five PPB were isolated and based on phytate hydrolysis, three efficient PPB were chosen and identified as Acromobacter sp. PB-01, Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13. Selected PPB showed ability to grow at wide range of pH, temperature and salt concentrations as well as to harbour diverse PGPR activities, such as: solubilization of insoluble Ca-phosphate (193–642 μg ml^?1), production of phytohormone indole acetic acid (5–39 μg ml^?1) and siderophore. Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13 showed 50 and 70 % inhibition of phytopathogen Rhizoctonia solani, respectively. Greenhouse potting assay also showed that the bacterization of B. juncea seeds with Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13 significantly increased the biomass and P content in 30 days old seedlings. This study reveals the potential of PPB as PGPR to improve the growth of B. juncea.     

Annuario della Società Botanica Italiana 1932

A sandy culture experiment was conducted to investigate the effects of exogenous CaCl₂ on the indole alkaloid accumulation in Catharanthus roseus under salt stress. One-month seedlings of C. roseus were treated with the different concentrations of NaCl (0, 50, and 100 mmol l^? 1) and 7.5 mmol l^? 1 CaCl₂. The plant samples were analyzed after 7 days of the treatments. The NaCl-stressed plants showed decrease of fresh and dry weight and increase of malondialdehyde (MDA) content compared to control. Tryptophan decarboxylase (TDC) activity increased significantly under 50 mmol l^? 1 NaCl without CaCl₂ addition, 50 mmol l^? 1 NaCl with 7.5 mmol l^? 1 CaCl₂, and CaCl₂ treatment without NaCl addition. There was a significant increase in peroxidase activity under NaCl stress compared to control. The vindoline, catharanthine, vincristine, and vinblastine contents increased under salt stress (especially with 50 mmol l^? 1 NaCl treatment with or without CaCl₂). Addition of CaCl₂ to NaCl-stressed plants increased biomass, TDC activity, vindoline, and catharanthine contents and lowered MDA and vincirstine contents compared to the plants without CaCl₂. The plants treated with CaCl₂ alone showed higher TDC activity, vindoline, catharanthine, and vinblastine content when compared to control. The results showed that exogenous CaCl₂ could promote the indole alkaloid metabolism under salt stress.     

Ethylene reverses photosynthetic inhibition by nickel and zinc in mustard through changes in PS II activity,photosynthetic nitrogen use efficiency,and antioxidant metabolism

We investigated the influence of exogenously sourced ethylene (200 μL L^?1 ethephon) in the protection of photosynthesis against 200 mg kg^?1 soil each of nickel (Ni)- and zinc (Zn)-accrued stress in mustard (Brassica juncea L.). Plants grown with Ni or Zn but without ethephon exhibited increased activity of 1-aminocyclopropane carboxylic acid synthase, and ethylene with increased oxidative stress measured as H₂O₂ content and lipid peroxidation compared with control plants. The oxidative stress in Ni-grown plants was higher than Zn-grown plants. Under metal stress, ethylene protected photosynthetic potential by efficient PS II activity and through increased activity of ribulose-1,5-bisphosphate carboxylase and photosynthetic nitrogen use efficiency (P-NUE). Application of 200 μL L^?1 ethephon to Ni- or Zn-grown plants significantly alleviated toxicity and reduced the oxidative stress to a greater extent together with the improved net photosynthesis due to induced activity of ascorbate peroxidase and glutathione (GSH) reductase, resulting in increased production of reduced GSH. Ethylene formation resulting from ethephon application alleviated Ni and Zn stress by reducing oxidative stress caused by stress ethylene production and maintained increased GSH pool. The involvement of ethylene in reversal of photosynthetic inhibition by Ni and Zn stress was related to the changes in PS II activity, P-NUE, and antioxidant capacity was confirmed using ethylene action inhibitor, norbornadiene.     

Effects of sodium chloride on the fatty acids composition in Boekelovia hooglandii (Ochromonadales, Chrysophyceae)

Composition of fatty acids in Boekelovia hooglandii Nicolai et Baas Becking (Chrysophyceae) was investigated as a function of salinity. It was confirmed by gas chromatography that the composition of fatty acids in cells cultured in a 50 mmol L^?1 NaCl medium consisted of C14:0, C15:0, C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C18:4, C20:0, C20:4, C20:5, C22:5 and C22:6, in which C14:0, C16:0, C16:1, C18:4, C20:0, C20:5, C22:5 and C22:6 were main constituents. When the cells were cultured in a medium with different concentrations of NaCl ranging from 50 to 800 mmol L^?1, the mole percentage of fatty acids such as C14:0, C16:0 and C16:1 decreased with increases in the salinity, while the mole percentage of highly polyunsaturated fatty acids such as C18:4, C20:5, C22:5 and C22:6 increased. When the cells were transferred from a 200 mmol L^?1 NaCl medium to a 600 mmol L^?1 NaCl medium, a decrease in mole percentage of C14:0, C16:0 and C16:1, and an increase in C18:4, C20:5, C22:5 and C22:6 were observed within 4 h. However, no change in the compositions of fatty acids was observed within 4 h when the cells were transferred from a 600 mmol L^?1 NaCl medium to a 200 mmol L^?1 NaCl one. The increase in the content of highly polyunsaturated fatty acids was considered to reflect the rapid response to upshock and to be the characteristic of salt tolerance in B. hooglandii.     

Effects of citric acid and the siderophore desferrioxamine B (DFO-B) on the mobility of germanium and rare earth elements in soil and uptake in Phalaris arundinacea

Effects of citric acid and desferrioxamine B (DFO-B) on the availability of Ge and selected rare earth elements (REEs) (La, Nd, Gd, Er) to Phalaris arundinacea were investigated. A soil dissolution experiment was conducted to elucidate the effect of citric acid and DFO-B at different concentrations (1 and 10 mmol L^?1 citric acid) on the release of Ge and REEs from soil. In a greenhouse, plants of P. arundinacea were cultivated on soil and on sand cultures to investigate the effects of citric acid and DFO-B on the uptake of Ge and REEs by the plants. Addition of 10 mmol L^?1 citric acid significantly enhanced desorption of Ge and REEs from soil and uptake into soil-grown plants. Applying DFO-B enhanced the dissolution and the uptake of REEs, while no effect on Ge was observed. In sand cultures, the presence of citric acid and DFO-B significantly decreased the uptake of Ge and REEs, indicating a discrimination of the formed complexes during uptake. This study clearly indicates that citric acid and the microbial siderophore DFO-B may enhance phytoextraction of Ge and REEs due to the formation of soluble complexes that increase the migration of elements in the rhizosphere.