Studying the roles of calcium and magnesium in cell death in the serpentine native plant Alyssum inflatum NYÁRÁDY through cell suspension culture technique.

Calcium is an essential element for plants' survival and ability to deal with environmental stresses. However, it can cause cell death due to cellular disequilibrium. Serpentine plants are sensitive to high concentrations of Ca2+, which induces lethal symptoms, especially under environmental stress. In this study, the direct effects of Ca2+ on cell death were investigated in cell cultures of Alyssum inflatum, a serpentine plant native to Western Iran, and results were compared to a non-serpentinitic congeneric species A. saxatile. The results were also compared to the effects of Mg2+ treatments in both species, as another determinative factor in serpentinite soil is high Mg2+ content. Plasma membrane permeability, reactive oxygen species (ROS), and malondialdehyde (MDA) production were measured as physiological cell injury indices. In A. inflatum higher levels of ROS and MDA were observed in Ca2+-treated cells (5 mM or more), while in A. saxatile they were measured in Mg2+-treated cells (5 mM or more). In serpentine species, results indicated that cell death by Ca2+ was more intensive than the cell death by Mg2+, which were observed with less intensity in non-serpentine plants. Microscopic studies showed that cell death occurred via apoptosis-like programmed cell death (AL-PCD). Therefore, Ca2+ sensitivity and AL-PCD as mechanistic reasons for their non-serpentine intolerance would be a crucial consideration in cellular researches concerning serpentine plants, which could be employed in green technologies such as phytoremediation.

Effects of antimony on enzymatic and non-enzymatic antioxidants in a metallicolous and a non-metallicolous population of Salvia spinosa L.

The present study aimed at elucidating the role of antioxidants and stress metabolites in antimony (Sb) tolerance in a metallicolous (M), Sb[V]-hypertolerant population, and a non-metallicolous (NM) population of Salvia spinosa, particularly with regard to the question of whether they could be involved in constitutive Sb tolerance or, specifically, in Sb[V] hypertolerance in the M population. Plants were exposed in hydroponics to 0, 8, 24, 74, 221 µM Sb (Ш or V). Superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) activities, and the concentrations of phenolics, flavonoids, and proline in leaves were measured after 20 d. As potential stress/tolerance markers, the concentrations of chlorophyll a and b, anthocyanins, and those of total soluble and reducing sugars were also measured. Chlorophyll a concentration reflected the difference, both in Sb[III] and Sb[V] tolerance, between N and NM, and the higher toxicity of Sb[III], compared to Sb[V]. APX and proline accumulation were more induced in M than in NM, and more by Sb[V] than by Sb[III], which is theoretically compatible with a role in Sb[V] hypertolerance. CAT was more induced in M than in NM, but more by Sb[III] than Sb[V], suggesting that is not functional in Sb[V] hypertolerance. The other enzymes and compounds did not exhibit significant Sb redox status*population interactions, suggesting that they don't play a role in, specifically, Sb[V] hypertolerance in M, but at most in the constitutive Sb[III] or Sb[V] tolerance of the species.

Cadmium accumulation and its effects on physiological and biochemical characters of summer savory (Satureja hortensis L.).

The objective of this study was to determine the effects of cadmium (Cd) toxicity on accumulation, growth, physiological responses, and biochemical characters in summer savory (Satureja hortensis L.). Plants were subjected to different levels of Cd concentrations including 0 (control), 2.5, 5, and 15 mg L-1 in the growing medium. Cd exposure led to a significant increase in root and shoot Cd content. Calculation of bioaccumulation factor, translocation factor, and transfer coefficient revealed that Cd mostly accumulated in roots of S. hortensis and root to shoot transport was effectively restricted. Cd toxicity negatively affected plant growth and significantly reduced chlorophyll content. Contrarily, proline, soluble and reducing carbohydrates, anthocyanin content, and the activity of antioxidant enzymes significantly increased as a result of Cd exposure. Cd application led to a significant increase in essential oil content of S. hortensis. GC-MS analysis revealed that percentage main constitute of S. hortensi, carvacrol, which determines the quality of oil increased under the highest Cd treatment. Based on our findings, S. hortensis can be considered an invaluable alternative crop for mildly Cd-contaminated soils. Besides, due to the high potential of Cd accumulation in the root, S. hortensis may offer a feasible tool for phytostabilization purposes.

Improving the growth of Ni-hyperaccumulating plants in serpentine quarry tailings.

Phytomining techniques based on metal-hyperaccumulating plants can be implemented in serpentine quarry wastes for Ni recovery. However, strategies must be developed to overcome the unfavourable plant growth conditions that these substrates present and to optimize Ni yields. In this study, the Ni hyperaccumulators Alyssum serpyllifolium, Alyssum inflatum, and Alyssum bracteatum were evaluated for their Ni phytoextraction efficiency from quarry tailings. Effects of two organic amendments, composted municipal sewage sludge and cow manure, on plant growth and physiological status and Ni removal were determined. Organic amendments were incorporated at two addition rates (5% and 20% w/w). The best-performing hyperaccumulators were A. inflatum and A. serpyllifolium. Organic amendments improved plant biomass production, photosynthetic efficiency and nutrition, but reduced shoot Ni concentrations. However, the stimulation in biomass resulted in significantly enhanced Ni yields. The most promising results were found using low addition rates and after manure incorporation.

Lead, zinc, and cadmium uptake, accumulation, and phytoremediation by plants growing around Tang-e Douzan lead-zinc mine, Iran.

In the current study, soils of Tang-e Douzan mine, located in Isfahan, Iran, were collected and analyzed for soluble, exchangeable, and total amounts of Pb, Zn, Cd, Ca, and Mg. The maximum Pb, Zn, Cd, Ca, and Mg concentrations in soils were 2500, 1100, 59, 43,800, and 1320 mg/kg for total metals, 86, 83, 6.3, 4650, and 48 mg/kg for their exchangeable fractions, and 59, 3.7, 0.53, 430, and 6.4 mg/kg for their soluble fractions, respectively. All specimens collected, including 69 plant species, were analyzed for Pb, Zn, and Cd. Moreover, their phytoremediation potential was investigated by calculating bioconcentration factors (BCF), translocation factors (TF), and extraction factors (EF) for each heavy metal. Analysis of the leaves for heavy metals showed no metal hyperaccumulation. The highest shoot concentrations of Pb (298 mg/kg) and Zn (740 mg/kg) were found in Roemeria hybrida subsp. dodecandra and Cd (43 mg/kg) in Chenopodium foliosum. Plants having BCFs and TFs > 1 are capable of phytoextraction. Among the analyzed species, four had both TFs and BCFs > 1 for Zn, 13 for Cd, and none for Pb. R. hybrida, Bromus squarrosus, Descurainia sophia, and Poa bulbosa seem to be the best choices for phytoextraction of Zn. Aegilops columnaris, Allium ampeloprasum subsp. iranicum, B. squarrosus, and Cousinia piptocephala are the best choices for phytoextraction of Cd. Plants with BCF > 1 and TF < 1, including Cerastium dichotomum and Muscari neglectum for Pb, Ceratocephala falcata, M. neglectum, Ornithogalum orthophyllum, and Ranunculus arvensis for Zn and C. falcata, M. neglectum, O. orthophyllum, and R. hybrida subsp. dodecandra for Cd, are proposed to be the most efficient species for metal phytostabilization.

A comparative study of antimony accumulation in plants growing in two mining areas in Iran, Moghanlo, and Patyar.

Antimony occurs locally at high concentrations in some mineralized soils. Very little is known about behavior of antimony in plants. In this study, we analyzed the soil and vegetation of two mining areas in Iran, Patyar, and Moghanlo. Total Sb concentrations in soil were 358-3482 mg/kg in Moghanlo and 284-886 mg/kg in Patyar. Corresponding Sb concentrations in plant shoots were 0.8-287 and 1.3-49 mg/kg, respectively. In both areas, foliar Sb concentrations increased with acid-extractable soil Sb, although the slope was about 2-fold steeper for Patyar than for Moghanlo. Regressing the foliar concentrations on water-soluble Sb yielded identical slopes for both areas, suggesting that the soluble fraction of Sb rather than total Sb is the direct determinant of foliar Sb accumulation. Both in Patyar and Moghanlo, only a minor part of the total variance of shoot Sb was explained by soluble Sb. The major part was explained by plant species, demonstrating that plant taxonomic identity is the most important determinant of foliar Sb accumulation capacity in both areas. The translocation factor (TF) was highly variable too, with species as the only significant variance component. Only four species were able to accumulate more than 100 mg/kg Sb in their leaves. Among these species, Achillea wilhelmsii and Matthiola farinosa were by far the best Sb accumulators, with, on average, 141 and 132 mg/kg Sb in their leaves. Of these two, only Matthiola farinosa consistently maintained TF values far above unity across the whole range of soluble Sb in Moghanlo.

The effect of EDDS and citrate on the uptake of lead in hydroponically grown Matthiola flavida.

Root and shoot lead concentrations and the impact of chelating agents on these were investigated in two populations of the novel metallophyte Matthiola flavida. Plants were exposed in hydroponics to Pb(NO3)2, supplied alone, or in combination with citric acid, or EDDS. When supplied at concentrations expected to bind about 95% of the Pb in a solution containing 1-µM Pb (1000 µM citrate or 3.1 µM EDDS, respectively), the root and shoot Pb concentrations were dramatically lowered, in comparison with a 1-µM free ionic Pb control exposure. A 1-mM EDDS+1-µM Pb treatment decreased the plants' Pb concentrations further, even to undetectable levels in one population. At 100 µM Pb in a 1-mM EDDS-amended solution the Pb concentration increased strongly in shoots, but barely in roots, in comparison with the 1-µM Pb+1-mM EDDS treatment, without causing toxicity symptoms. Further increments of the Pb concentration in the 1-mM EDDS-amended solution, i.e. to 800 and 990 µM, caused Pb hyperaccumulation, both in roots and in shoots, associated with a complete arrest of root growth and foliar necrosis. M. flavida seemed to be devoid of constitutive mechanisms for uptake of Pb-citrate or Pb-EDDS complexes. Hyperaccumulation of Pb-EDDS occurred only at high exposure levels. Pb-EDDS was toxic, but is much less so than free Pb. Free EDDS did not seem to be toxic at the concentrations tested.

An arsenic-accumulating, hypertolerant brassica, Isatis capadocica.

Isatis capadocica, a brassica collected from Iranian arsenic-contaminated mine spoils and control populations, was examined to determine arsenate tolerance, metabolism and accumulation. I. cappadocica exhibited arsenate hypertolerance in both mine and nonmine populations, actively growing at concentrations of > 1 mm arsenate in hydroponic solution. I. cappadocica had an ability to accumulate high concentrations of arsenic in its shoots, in excess of 100 mg kg(-1) DW, with a shoot : root transfer ratio of > 1. The ability to accumulate arsenic was exhibited in both hydroponics and contaminated soils. Tolerance in this species was not achieved through suppression of high-affinity phosphate/arsenate root transport, in contrast to other monocotyledons and dicotyledons. A high percentage (> 50%) of arsenic in the tissues was phytochelatin complexed; however, it is argued that this is a constitutive, rather than an adaptive, mechanism of tolerance.