Ulteriori indagini sul rapporto tra nichel e acidi malico e malonico in Alyssum

Abstract

Further contribution on the relationship between nickel and malic and malonic acids in Alyssum.—Further research has been carried out on extracts of leaves and seeds of A. bertolonii Desv., grown on serpentine and normal garden soil, in order to investigate the nature of the nickel compounds present in this plant. On the purified extracts, obtained with water and formic acid, malic and malonic acids have been determined through gas-chromatography of the trimethyl-sililderivatives; Ni, Ca, Mg and K have been analysed by atomic absorption spectrophotometry.

Both malic and malonic acids are present in the leaves of the plants collected on serpentine and therefore rich in nickel, whilst they are present only in small amounts in the plants grown in garden soil. Seeds contain mainly high levels of malic acid. Remarkable amounts of malic acid, related to a high nickel content, have been observed also in the leaves of another nickel accumulator in the genus Alyssum, i.e. A. serpyllifolium Desf. ssp. lusitanicum Dudley et P. Silva, endemic of Portugal serpentines.     

Nickel speciation in the xylem sap of the hyperaccumulator Alyssum serpyllifolium ssp. lusitanicum growing on serpentine soils of northeast Portugal

Nickel speciation was studied in the xylem sap of Alyssum serpyllifolium ssp. lusitanicum, a Ni-hyperaccumulator endemic to the serpentine soils of northeast Portugal. The xylem sap was collected from plants growing in its native habitat and characterized in terms of carboxylic and amino acids content. The speciation of nickel was studied in model and real solutions of xylem sap by voltammetric titrations using Square Wave Voltammetry (SWV). The results showed that Ni transport in the xylem sap occurs mainly as a free hydrated cation (about 70%) and complexed with carboxylic acids, mainly citric acid (18%). Altogether, oxalic acid, malic acid, malonic acid and aspartic acid complexed less than 13% of total Ni. A negligible amount bounded to the amino acids, like glutamic acid and glutamine (<1%). Histidine did not play a role in Ni translocation in the xylem sap of A. serpyllifolium under field conditions. Amino acids are one of the main forms of N transport in the xylem sap, and under field conditions, N is usually a limited nutrient. We hypothesize that the translocation of Ni in the xylem sap as a free ion or chelated with carboxylic acids is ‘cheaper’ in terms of N resources.     

Rhizosphere Microbial Densities and Trace Metal Tolerance of the Nickel Hyperaccumulator Alyssum Serpyllifolium Subsp. Lusitanicum

In this study we determine culturable microbial densities (total heterotrophs, ammonifiers, amylolytics and cellulolytics) and bacterial resistance to Co, Cr, and Ni in bulk and rhizosphere soils of three populations of the Ni-hyperaccumulator Alyssum serpyllifolium subsp. lusitanicum and the excluder Dactylis glomerata from ultramafic sites (two populations in Northeast (NE) Portugal (Samil (S), Morais (M)) and one population in Northwest (NW) Spain (Melide (L)). The relationship between bioavailable metal concentrations (H₂O-soluble) and microbial densities were analysed. Significant differences in microbial densities and metal-resistance were observed between the two species and their three populations. The hyperaccumulator showed higher microbial densities (except cellulolytics) and a greater rhizosphere effect, but this was only observed in S and M populations. These populations of A. serpyllifolium also showed selective enrichment of Ni-tolerant bacteria at the rhizosphere where Ni solubility was enhanced (densities of Ni-resistant bacteria were positively correlated with H₂O-soluble Ni). These rhizobacteria could solubilise Ni in the soil and potentially improve phytoextraction strategies.     

Some observations on the ecology,metal uptake and nickel tolerance of Alyssum serpyllifolium subspecies from the Iberian peninsula

Experiments were carried out on the tolerance to, and uptake of, nickel by three iberian subspecies of Alyssum serpylliforium Desf. Two of these subspecies, the serpentine-endemic ssp. lusitanicum from Bragança, Portugal and ssp. malacitanum from Málaga, Spain, are hyperaccumulators (> 1000 g/g in dried material) of nickel. Their possible ancestor, ssp. serpyllifolium (from Granada, Spain) was a non-accumulator of this element. Seeds of the two serpentine-endemics germinated extensively in nickel concentrations up to 12 000 g/g (1.2%) whereas ssp. serpyllifolium only germinated in nickel concentrations below 60 g/ml. Tolerance tests involving measurement of new root lengths of excised seedlings placed in varying nickel concentrations, again showed much greater tolerance of the two serpentinophytes. In both series of experiments, the order of tolerance was: ssp. lusitanicum > ssp. malacitanum > ssp. serpyllifolium. In pot trials involving seedlings of ssp. malacitanum grown in mixtures containing varying amounts of calcium, magnesium, and nickel, the most important finding was that plants will tolerate higher nickel contents in the soil when excess calcium is added. This is achieved by lowering the uptake of nickel. There appeared to be some concomitant reduction in calcium uptake in the presence of nickel, and some increase in uptake of magnesium. The resultant lower calcium/magnesium ratio in the plant, though not symptomatic of a favourable condition for colonization of serpentine soils, probably results from a mechanism which renders nickel innocuous to the plant at the expense of calcium uptake. It is suggested that the physiological characters of ssp. lusitanicum and ssp malacitanum are sufficiently different to support arguments for promoting the latter to full specific rank as has now been done for ssp. lusitanicum.     

Pattern analysis suggests that phosphoenolpyruvate carboxylase in maturing soybean seeds promotes the accumulation of protein

ABSTRACT

The protein and oil contents in soybean seeds are major factors in seed quality. Seed proteins and oils are synthesized from sucrose and nitrogenous compounds transported into maturing seeds. In this study, we compared changes in the activity of phosphoenolpyruvate carboxylase (PEPC) and the accumulation profiles of protein and oil in maturing seeds of two soybean cultivars, which exhibit different protein and oil contents in seeds, to determine the interrelationships of them. A principal component analysis indicated a concordance of seed PEPC activity with the protein content, but did not with the oil content. PEPC activity per seed was highest in the late maturation stage, when the physiological status of the vegetative organs drastically changed. The high-protein cultivar had higher PEPC activity compared to the low-protein cultivar. These results highlight the biological role of PEPC in the synthesis of protein, therefore it was implied that PEPC could be a biomarker in soybean breeding.

Abbreviations: ANOVA: analysis of variance; DS: developmental stage; DW: dry weight; FW: fresh weight; NIR: near infrared; PEP(C): phosphoenolpyruvate (carboxylase); PC(A): principal component (analysis); S.E.: standard error; WC: water content.     

Sub-cellular localization of Ni in the hyperaccumulator, Hybanthus floribundus (Lindley) F. Muell

The cellular and subcellular distribution of Ni within leaves of Hybanthus floribundus (Lindley) F. Muell, a hyperaccumulator of Ni, was investigated at relatively high spatial resolution using energy‐dispersive X‐ray microanalysis (EDAX). Elemental distribution maps showed that Ni was predominantly localized in the vacuoles of epidermal cells in the leaves. Quantification of Ni revealed concentrations up to 275 mmol kg^?1 (embedded tissue) in some epidermal vacuoles. The accumulation of Ni in these cells was associated with a decrease in the concentration of Na and K. There was no indication that Ni was associated with P, S or Cl in the vacuoles. Ni was also concentrated on the outside of cell walls throughout the leaves, indicating that apoplastic compartmentation is also involved in Ni tolerance and accumulation in this plant.     

Evaluation of the phytoremediation potential of Arundo donax L. for nickel-contaminated soil

This study investigates the accumulation and distribution of nickel in Arundo donax L. parts to assess the potential use of this plant in phytoremediation of Ni-contaminated soils. The effect of ethylene diamine tetra-acetic acid (EDTA) and nutrient solution containing NPK on the plant was proped. A 35-day pot experiment was performed in the laboratory and the pots were irrigated with Ni-contaminated solution combined or not with EDTA and NPK. The growth of plants was evaluated at the end of the experiment. The accumulation of Ni was analyzed by atomic absorption spectroscopy (AAS). The obtained results indicate that the plant was able to survive with high Ni content. The growth and the concentrations of Ni in the plant tissues were less affected. In the absence of the amendments, Ni was accumulated in the stems and leaves. However, the addition of NPK significantly reduced Ni concentration in the stems and leaves. The application of EDTA enhanced Ni uptake in roots. The translocation factor (TF) was greater than 1, which categorizes A. donax L. as a great candidate for Ni phytoextraction. A. donax L. is suitable for phytoremediation of Ni. This investigation contributes to the studies on the potential of phytoremediation technologies in Algeria.     

Nickel in Plants: II. Distribution and Chemical Form in Soybean Plants

The gross tissue distribution, intracellular fate, and chemical behavior of Ni²⁺ in soybean plants (Glycine max cv. Williams) were investigated. Following root absorption, Ni was highly mobile in the plant, with leaves being the major sink in the shoots for Ni during vegetative growth. A senescence >70% of the Ni present in the shoot was remobilized to seeds. Fractionation of root and leaf tissues showed >90% of the Ni to be associated with the soluble fraction of tissues; ultrafiltration of the solubles showed >77% of the Ni to be associated with the 10,000 to 500 molecular weight components of both roots and leaves. Chemical characterization of the soluble components (10,000 to 500 and >500 molecular weight) by thin layer chromatography and electrophoresis resolved a number of Ni-containing organic complexes. Major Ni-containing components formed in the root are transported in the xylem stream, and undergo partial modification on deposition in leaves. Nickel accumulated in seeds is primarily associated with the cotyledons. Chemical fractionation of cotyledon components showed 80% of the Ni to be associated with the soluble whey fraction, while 70% of this fraction was composed of Ni-containing components with molecular weight <10,000.     

Diversity and biogeography of Ni‐hyperaccumulators of Alyssum section Odontarrhena (Brassicaceae) in the central western Mediterranean: evidence from karyology,morphology and DNA sequence data

The diversity of Alyssum section Odontarrhena in the central–western Mediterranean region was investigated to elucidate relationships and biogeography of Ni‐hyperaccumulators in the group. Karyological, morphometric and molecular phylogenetic analyses were performed on accessions of Ni‐hyperaccumulators from serpentine outcrops and non‐hyperaccumulators from calcareous–dolomitic soils in the region. Alpine and Apennine populations of A. argenteum, Sardinian A. tavolarae and some Tuscan A. bertolonii had a tetraploid chromosome complement and larger silicles, seeds and seed wings than diploid accessions. DNA sequences from the plastid rpoC1 locus corroborated the monophyly of section Odontarrhena but species relationships were poorly resolved. Bayesian analysis of combined ITS‐rpoC1 sequences retrieved three main lineages including hyperaccumulators and non‐hyperaccumulators of contrasting geographical origin. One lineage was mainly continental and included alpine and northern Apennine populations of A. argenteum, the Balkan complex of A. murale and the Iberian group of A. serpyllifolium, sister to Corsican A. robertianum as suggested by their similar diploid karyotype. In this clade no divergence was found between typical A. serpyllifolium and related Ni‐hyperaccumulator races from the Iberian peninsula, supporting their conspecific status. A second lineage was prevalently Mediterranean and included the sister species A. bertolonii and A. tavolarae, and other endemics from Sicily, the southern Balkans and Turkey from dolomite and serpentine habitats. The present data suggest new model systems consisting of hyperaccumulators and non‐hyperaccumulators of proven phylogenetic affinity for further research on the molecular mechanisms of Ni‐hyperaccumulation and serpentine tolerance at the diploid and tetraploid level. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 269–289.     

Phenology of Dryopteris affinis ssp. affinis and Polystichum aculeatum: modeling relationships to the climatic variables in a Mediterranean area

The phenology of leaves and stages from immature sori to spore release were studied in natural populations of two perennial herbaceous ferns, Dryopteris affinis ssp. affinis and Polystichum aculeatum, for 2 years in Italy. The Generalized Additive Model for Location, Scale and Shape (GAMLSS) was used to predict a particular phenological event from the climatic variables. Both fern species are evergreen with leaf lifespan of 13–14 months in D. affinis ssp. affinis and 15–24 months in P. aculeatum. Their leaf production is seasonal with most flushed in spring. In D. affinis ssp. affinis the decaying of old leaves is sudden whereas in P. aculeatum it is gradual, and in both types the decaying is accelerated just as the new leaves emerge. Temperature is the best predictor for the development of sori and spore release. The end of spore release and leaf emergence are positively affected by temperature and negatively affected by rainfall and snow cover for P. aculeatum. An almost similar response to climatic factors of emergent and senescent leaves and their phenology supportsthe hypothesis that old leaves serve as nutrient storage organs for new leaf growth. Comparison the phenological patterns between the 2 years indicated that the time lapses between each phenological event were the same within seasons for D. affinis ssp. affinis but show some differences for P. aculeatum. We also hypothesize that endogenous factors may play an important role in the phenology of P. aculeatum.     

Two ecologically distinct subspecies ofHypochaeris radicata L.

Summary Two subspecies ofHypochaeris radicata were compared with respect to differences in drought tolerance. The soil water content of the sites ofH. radicata ssp. ericetorum Van Soest was always lower than that ofH. radicata L. ssp.radicata throughout a great part of the growing season. Two water culture experiments were conducted at different light intensities. Water stress was induced by addition of NaCl to the culture solution. Both subspecies accumulated free proline andmyo-inositol during water stress. The results are compared with those of field observations. In all experiments with stress application ssp.radicata showed heavier wilting symptoms than ssp.ericetorum, concomittantly with a lower osmotic potential of the cell sap, a higher percentage of dry-weight and irreversible desiccation of older leaves in some experiments after stress application. The observed effects are attributed to the higher transpiration rate maintained by ssp.radicata during stress. Free proline accumulation depended on the severity of the internal stress rather than on the applied level of external stress. At low light intensity the stress resulted in a significantly higher proline accumulation in ssp.ericetorum than in ssp.radicata whereas at high light intensity this was the reverse. No differences inmyo-inositol accumulation were observed in the water culture experiments. Since ssp.ericetorum occurs in a nitrogen poor environment, the effect of nitrogen deprivation on accumulation of free proline andmyo-inositol was investigated. Both subspecies tended to accumulate less proline under such conditions especially ssp.radicata. Accumulation ofmyo-inositol was not favoured by nitrogen deprivation in the water culture experiments. Neither of the subspecies accumulated proline during the sampling period in the field presumably as a result of the wet summer. Leaves of whole plants collected in the field and subsequently subjected to water deprivation showed a high capacity to accumulate free proline. The level ofmyo-inositol in the field was higher in ssp.ericetorum than in either ssp.radicata or control plants in the water culture experiments. When the cytoplasmic volume is estimated as 10% of the total cell volume, free proline andmyo-inositol account for 44–69% of the osmotic potential. It is concluded that ssp.ericetorum is better adapted to the drier environment by its higher capacity to accumulate proline and reduce transpiration during stress. Grassland species research group, publication no41.     

Effects of plant aqueous extract of Cymbopogon citratus (D.C.) Stapf. on sorghum seed germination and it efficacy in controlling Phoma sorghina (Sacc.) Boerema Dorenbosh and Van Kesteren transmission from naturally infected seed to sorghum plant organs and grains in field

The effect of aqueous extract of Cymbopogon citratus on sorghum seed germination and its efficacy against Phoma sorghina transmission to sorghum vegetative organs and seed were studied in field conditions in 2008–2010. During these years, we also examined the effect of panicle protection on the reduction of P. sorghina infection. The aqueous extract of C. citratus lowers sorghum seed germination compared to untreated seeds, seeds treated with water and those treated with fungicide calthio C. P. sorghina is transmitted to the whole vegetative organs and seed of all the treatments. However, the aqueous extract of C. citratus significantly reduces the transmission of P. sorghina compared to untreated seeds, to seeds treated with water and those treated with fungicide. The protection of sorghum panicles before flowering limits the infection by P. sorghina compared to the panicles not protected.     

Influence of root temperature on uptake and accumulation of Ni and Co in potato

The impact of root temperature on Ni and Co concentration and accumulation has been studied in organs (roots, tubers, stems and leaves) of Solanum tuberosum L. var. Spunta plants. The response of foliar- and root-urease activity was also determined under the same conditions. Four different polyethylene plastic covers were employed (T1: transparent; T2: white; T3: coextruded black+white; T4: black), using uncovered plants as control (T0). The different treatments had a significant effect on mean root zone temperatures (T0 = 16 °C, T1 = 20 °C, T2 = 23 °C, T3 = 27 °C and T4 = 30 °C) and induced a significantly different response in the Ni and Co distribution in potato organs, since T3 (27 °C) gave higher concentrations of Ni in roots, leaves and tubers. The T1 (20 °C) registered the greatest Co concentration in leaves and roots, while T3 gave higher Co concentrations in tubers. The tubers proved to be the organs with the highest biomass and also the highest Co and Ni accumulation. With respect to the response of the urease activity as Ni-bioindicator, the root urease activity was higher in T1, whereas the leaf urease activity was higher in T3 and T4, coinciding with higher concentrations of leaf Ni. It is necessary to ascertain the relevance and control of the thermal regime of the soil to optimize the phytoextraction (phytoremediation) of elements.     

Two new species of Alstroemeria L. (Alstroemeriaceae) from Brazil

Alstroemeria hygrophila andA. orchidioides are both described as new from the state of Goiás (including Distrito Federal) in Brazil.Alstroemeria hygrophila is a cerrado bog-dwelling species that grows semi-epiphytically on the culms of a sedge. The vegetative stems of this species characteristically zig-zag between the pseudonodes. Like other wetlandAlstroemeria in Brazil (e.g.,A. apertiflora, A. isabellana, andA. sellowiana),A. hygrophila has wiry stems bearing narrow, lanceolate, nonresupinate leaves, and does not form root tubers.Alstroemeria orchidioides is a hysteranthus forest understory species with large vegetative leaves aggregated at the apex of the stems. The leaves on flowering stems are reduced to scarious bract-like scales. Its flowers are a pale, nearly white, greenish yellow, a color not reported in any other Brazilian species. Both species have 2n=16 chromosomes.     

Systematics and conservation genetics of Dactylorhiza majalis ssp. elatior (Orchidaceae) on Gotland

A tall allotetraploid member of the Dactylorhiza incarnata/maculata complex with unspotted leaves and large pinkish flowers from the island of Gotland in the Baltic was examined for molecular variation patterns at five nuclear microsatellite loci, nuclear ITS and in plastid haplotypes. The allotetraploid was well separated from allopatric allotetraploids of similar appearance, including the western European D. majalis ssp. integrata (syn. D. praetermissa) and forms of D. majalis ssp. lapponica from mainland Sweden. It also differed from other allotetraploids distributed in the Baltic Sea region, including D. majalis ssp. baltica and D. majalis ssp. lapponica. It is here recognized as D. majalis ssp. elatior (Fr.) Hedrén & H. A. Pedersen. Dactylorhiza osiliensis Pikner, described from Saaremaa (Estonia) is regarded as a synonym. The distribution covers Gotland, Saaremaa and possibly Hiiumaa. Dactylorhiza majalis ssp. elatior may have one or several recent origins within its present distribution area, and it contains no other molecular markers than those found in the parental D. incarnata var. incarnata and D. maculata ssp. fuchsii in the same area. It appears to have weak barriers towards secondary hybridization with its parental lineages. The situation is reminiscent to that of other young allotetraploids in the D. majalis s.l. complex, suggesting that introgression may be an underestimated process explaining the accumulation of genetic diversity in evolving allopolyploid plants.     

Steviol Glycoside Content in Different Organs of Stevia rebaudiana and Its Dynamics during Ontogeny

The contents of three major steviol glycosides (SGs) (stevioside and rebaudiosides A and C) in vegetative and generative organs during ontogeny of Stevia rebaudiana Bertoni were analysed with HPLC. Plant organs contained different amounts of the SGs, which declined in the following order: leaves, flowers, stems, seeds, roots. The highest content of the SGs was found in upper young actively growing shoot sections, whereas lower senescent shoot sections exhibited the lowest amount of such compounds. During ontogeny a gradual increase in the SG content was observed in both mature stevia leaves and stems, and this process lasted up to the budding phase and the onset of flowering. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nickel localization in tissues of different hyperaccumulator species of Euphorbiaceae from ultramafic areas of Cuba

Pantropical species of the genera Phyllanthus and Euphorbia and the Cuban endemic genus Leucocroton from the Euphorbiaceae family, were selected for nickel localization microanalysis. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Microanalysis (SEM-EDX) was used for qualitative detection of nickel in the selected Ni-hyperaccumulator species: Euphorbia helenae, Leucocroton linearifolius, L. flavicans Phyllanthus orbicularis, P. discolor and P. xpallidus, all collected from Cuban ultramafic soils. The leaves and stems from the Euphorbiaceae species analyzed were the organs with higher nickel accumulation. Elemental mapping of leaves and stem tissues from these species have been compared. The highest Ni concentrations were found in the laticifer tubes of stems and the epidermis tissues of leaves in all the analyzed species, suggesting a general pattern of the Euphorbiaceae family for nickel accumulation. The high nickel concentrations and its rather homogeneous distribution found in leaves of these Ni-hyperaccumulating plants suggest a possible role in protection mechanisms against environmental stress, such as UV irradiation.     

Two ecologically distinct subspecies ofHypochaeris radicatal L.

Summary The present paper is part of a series of papers comparing two ecologically distinct subspecies ofHypochaeris radicata L.Hypochaeris radicata ssp.radicata grows in more fertile soils thanH. radicata ssp.ericetorum.The dry-weight yield of plants grown from seeds was measured after a 25 days culture period on varying levels of nitrate. Roots and shoots were analyzed for total organic nitrogen and free nitrate. Dry-weight yield showed an almost identical response over the whole range of nitrate concentrations used. The chemical analysis did not reveal differences between the subspecies that could explain the distribution in the field. In a second experiment the growth rate of the two subspecies was measured under optimal nitrate supply during a two month period. Both subspecies exhibited initially the same relative growth rate but one month after sowing the growth rate of both subspecies declined, with a sharper decline in ssp.ericetorum resulting in an 82 per cent difference in dry-weight between both subspecies two months after sowing. Some pronounced formative differences became evident. Shoot to root ratio of ssp.ericetorum showed little response to increasing nitrate concentrations whereas ssp.radicata was clearly responsive in this respect.The contribution of the tap root in total plant dry-weight was relatively higher in ssp.Ericetorum. The decline in growth rate and the formative differences can explain the absence of ssp.ericetorum from nutrient rich soils. when grown on ammonium ssp.radicata had a slightly but not significantly higher yield than ssp.ericetorum. The difference was even greater at low pH. It is concluded that both subspecies are adapted to ammonium nutrition at pH 4.5 as well as at pH 6 and that the absence of ssp.radicata from acidic soils cannot be explained by the low pH. The possibility that both subspecies have different abilities to reduce their growth when nitrate resources become limiting, and yet remain capable for further growth and reproduction is discussed.Grassland species research group, publ. no.16.