Arbuscular mycorrhizal fungi enhance root cadmium and copper accumulation in the roots of the salt marsh plant Aster tripolium L.

It is known that vegetation plays an important role in the retention of heavy metals in salt marshes by taking up and accumulating the metals. In this study, we investigated whether arbuscular mycorrhizal fungi (AMF) increase Cd and Cu uptake and accumulation in the root system of the salt marsh species Aster tripolium L., and whether indigenous AMF isolated from polluted salt marshes have higher capacity to resist and alleviate metal stress in A. tripolium than isolates of the same species originated from non-polluted sites. Plants inoculated with Glomus geosporum, either isolated from a polluted salt marsh site (PL isolate) or from a non-polluted site (NP isolate), and non-mycorrhizal (NM) plants were compared in a pot experiment at four different Cd and Cu concentrations. Cd had no effect in root colonization, whereas high concentrations of Cu decreased colonization level in plants inoculated with the NP isolate. AM colonization did not increase plant dry weight or P concentration but influenced root Cd and Cu concentrations. Inoculation with PL and NP isolates enhanced root Cd and Cu concentrations, especially at highest metal addition levels, as compared to NM plants, without increasing shoot Cd and Cu concentrations. There was no evidence of intraspecific variation in the effects between AMF isolated from polluted and non-polluted sites, since there were no differences between plants inoculated with PL or NP isolate in any of the tested plant variables. The results of this study showed that AMF enhance metal accumulation in the root system of A. tripolium, suggesting a contribution of AMF to the sink of metals within vegetation in the salt marshes.     

The performance of the leaf mining microlepidopteran Bucculatrix maritima (Stt.) on the salt marsh halophyte,Aster tripolium (L.), exposed to different salinity conditions

Summary The performance of phytophagous insects is influenced by the nutritional quality of the food plant, which may vary with environmental conditions. Hardly any information exists on food-plant mediated effects of variable soil salinity on the performance of phytophagous insects. Conspicuous differences in salinity levels, however, are found in soils of intertidal wetlands such as salt marshes and mangroves. The growth of larvae of Bucculatrix maritima, a leaf miner of the salt marsh halophyte Aster tripolium, was studied on the host plant along the salinity gradient of the Westerschelde estuary (S.W. Netherlands). In addition, its performance on A. tripolium grown on low or high salinity culture medium was investigated experimentally. Although salinity conditions significantly influenced the chemistry of the host plants, insect performance seemed almost unaffected, although near the mouth of the estuary high environmental salinities may have caused some inhibition of larval growth. The results contrast with our previous studies on the stem-borer Agapanthia villosoviridescens, which showed that growth and development was conspicuously influenced by the changing characteristics of Aster tripolium along the estuarine salinity gradient. The location-dependent qualities of halophytes in an estuary thus appear to have species-specific effects on insect performance. We hypothesize that this phenomenon contributes to the existence of non-identical distribution patterns of phytophagous insects associated with the same halophyte in an estuary.     

The parallel expression of metal tolerance in pollen and sporophytes of Silene dioica (L.) Clairv., S. alba (mill.) krause and Mimulus guttatus DC

Summary The purpose of this paper was to determine if heavy metal tolerance was expressed in pollen and if its expression was correlated with the tolerance of the pollen source. Clones of Silene dioica, tolerant to zinc, closely related but nontolerant S. alba and clones of Mimulus guttatus tolerant and sensitive to copper were grown in the greenhouse in either standard potting soil or nutrient culture. Pollen was collected shortly after dehiscence, hydrated, and tested over a broad range of metal concentrations. The tolerance of the pollen source was determined by comparing root growth in solutions with and without heavy metals. In both Silene species and M. guttatus, the tolerance of the parental clone was expressed in its pollen. Pollen from tolerant individuals was able to germinate and grow at concentrations of metals which markedly inhibited pollen from nontolerants.     

How do Mycorrhizas Affect C and N Relationships in Flooded Aster tripolium Plants?

The mycorrhizal associations established between plants and fungi have multiple effects on plant growth, directly affecting stress tolerance. This work aimed to explore arbuscular mycorrhizal (AM) effects on carbon and nitrogen relationships of Aster tripolium L. and consequently on its flooding tolerance. Mycorrhizal and non-mycorrhizal juvenile plants were submitted to non-flooding and tidal flooding conditions for 56 d. Tidal flooding reduced biomass, but the presence of mycorrhiza had an ameliorating effect. The AM symbioses seem to have, like flooding, a stressful effect on A. tripolium at an early stage of plant development. However, once the plant was established, an improvement of growth performance of plants with mycorrhiza under flooding conditions was observed. The better tolerance of AM plants to flooding was mediated through an improvement of the osmotic adjustment of the plant tissues (higher concentrations of soluble sugars and proline) and through the increment of nitrogen acquisition in tidal-flooded plants.     

Evolution de I'amidon et des sucres solubles chez des feuilles isoléaes d' Aster tripolium et de Cochlearia tniglica. Action du NaCI Par

Starch and soluble sugars in leaves of Aster tripolium L. and Cochlearia angliea L. Effect of NaCI. - The limbs or foliar disks of Aster tripolium L. and Cochlearia anglica L. synthelize starch when exposed to light at 25°C, and in the presence of glucose or saceharose together with 0.25 to 0.61 % of NaCI.     

Aspects of population dynamics in Halimione portulacoides communities

Summary Studies on sample plots inHalimione portulacoides communities show that environmental disturbances, either natural or induced by man, start a sequence of partly overlapping density maxima inSuaeda maritima, Aster tripolium andPuccinellia maritima successively, before the originalHalimione community totally recovers. When succession time before recovering is long enough, there are tendencies in redundancy of this sequence stressing the unilinear character of the succession. Minor environmental impacts induce a longer time-lag period of theSuaeda density maximum, suggesting threshold values of these impacts for the species to maintain minimal population densities or to become locally extinct. This sequence of interim species starting after an environmental disturbance, suggests also a gradient character in various biological attributes, for instance in life-time, propagation, nutrient and genetic plasticity strategies. The mechanism described can therefore be interpreted as a complex of mostly well-adapted and well-integrated inherent species strategies capable of absorbing environmental shocks. It is suggested that in the salt-marsh ccosystem the pattern of spatial variation in densities and that of temporal variation in fluctuations of the three species populations under natural conditions reflect corresponding patterns of environmental disturbances in the vegetation taking into account a timelag associated with the magnitude of the impact concerned.Contribution to the Symposium on Plant species and plant communities held at Nijmegen, 11–12 November 1976, on the occasion of the 60th birthday of Professor Victor Westhoff.Nomenclature follows Heukels-van Ooststroom. Flora van Nederland, 18e druk, 1975. Wolters-Noodhoff, Groningen.The authors are greatly indebted to Dr K.F. Vaas (Yerseke) for reviewing the English text.Communication Nr. 160.     

Salt tolerance in Aster tripolium L. I. The effect of salinity on growth

Abstract A study of the growth of the maritime halophyte Aster tripolium L. has been carried out over a range of salinity treatments. The regression approach to growth analysis using frequent small harvests has been used to allow ‘continuous’ measurement of growth over a period of 36 d. Salinity was applied with the major ions present in ratios typical of those found in seawater. Growth was inhibited in terms of both dry weight production and leaf expansion at salinity levels equivalent to 0.625 strength sea water (full culture solution 300) and above, with the greatest effect being seen in terms of leaf area. Aster tripolium did not show increased succulence at high salinity, leaf fresh weight to dry weight ratio in fact declined, whilst leaf fresh weight per unit area remained constant. It should be noted that the plants exhibit low growth rates due to the low light intensity used.     

Localization of a 170 kDa myosin heavy chain in plant cells

Summary A polyclonal antibody directed against a 170 kDa myosin heavy chain from lily pollen tubes was employed to (a) assess the cellular distribution of the polypeptide using immunofluorescence methods, and (b) ascertain if similar polypeptides are present in pollen tubes and somatic cells of other species. Fluorescence is associated with particles of various size as well as an amorphous component, and is concentrated in the apical cytoplasm of lily and tobacco pollen tubes. Apical fluorescence is more extensive in lily than in tobacco, which may be related to different streaming patterns and apical zonation seen at the ultrastructural level. In suspension cells of tobacco andArabidopsis, fluorescence is concentrated around the nuclei. Dual localizations indicate that anti-myosin fluorescence may be associated with the presence of actin. Little or no staining was seen in controls consisting of either pre-immune serum or mono-specific IgG that had been preadsorbed with the 170 kDa polypeptide. Immunoblots show that a 170 kDa immunoreactive polypeptide is present in pollen tubes of tobacco andTradescantia virginiana in addition to lily, and in suspension culture cells of tobacco andArabidopsis and extracts of wholeArabidopsis seedlings. Our results show that a conserved 170 kDa myosin heavy chain is present in a variety of monocot and dicot cells. They are also consistent with the presence of multiple myosins in plants in general and pollen tubes in particular.Abbreviations BSA bovine serum albumin - IgG immunoglobulin G - Mf microfilament - Mt microtubule - PBS phosphate-buffered saline - PME 50 mM Pipes, 5mM EGTA - 2mM MgSO₄, pH6.9.     

Competition alters plant species response to nickel and zinc

Phytoextraction can be a cost-efficient method for the remediation of contaminated soils. Using species mixtures instead of monocultures might improve this procedure. In a species mixture, an effect of heavy metals on the species' performance can be modified by the presence of a co-occuring species. We hypothesised that (a) a co-occuring species can change the effect of heavy metals on a target species, and (b) heavy metal application may modifiy the competitive behaviour between the plants. We investigated these mechanisms in a greenhouse experiment using three species to serve as a model system (Carex flava, Centaurea angustifolia and Salix caprea). The species were established in pots of monocultures and mixtures, which were exposed to increasing concentrations of Ni and Zn, ranging from 0 to 2,500 mg/kg. Increased heavy metal application reduced the species' relative growth rate (RGR); the RGR reduction being generally correlated with Ni and Zn concentrations in plant tissue. S. caprea was an exception in that it showed considerable Zn uptake but only moderate growth reduction. In two out of six cases, competitors significantly modified the influence of heavy metals on a target species. The interaction can be explained by an increased uptake of Zn by one species (in this case S. caprea) that reduced the negative heavy metal effect on a target species (C. flava). In two further cases, increasing heavy metal application also altered competitive effects between the species. The mechanisms demonstrated in this experiment could be of relevance for the phytoextraction of heavy metals. The total uptake of metals might be maximised in specific mixtures, making phytoextraction more efficient.     

Aerobiology of Fagaceae pollen in Trieste (NE Italy)

The aerobiological behaviour of Fagaceae in Trieste and the correlations with the meteorological parameters were examined. Airborne pollen grains of Castanea, Fagus and Quercus were collected from 1990 to 2003 using a Hirst type spore trap. The main pollen season (MPS) takes place in April and May for Quercus and Fagus, in June and July for Castanea. The highest values occur in year 1993 for Quercus, in 1998 for Castanea and in 1992 for Fagus. The Fagaceae content of the air is mainly due to Quercus and Castanea pollen, Fagus usually having a scarce pollen shedding in Trieste. The highest counts of Fagaceae pollen grains are found from late April to mid May and are mainly due to the pollen shedding of oaks. The cumulative counts vary over the years, with a mean value of 2.719 pollen grains, a lowest total of 1.341 in 2002 and a highest total of 4.704 in 1993. No positive nor negative long-term trends in pollen shedding are found. No cyclic variations were observed. Spearman’s correlation was used to establish the relationship between the daily pollen counts and the daily meteorological data. Daily pollen concentrations present sometimes positive correlation with temperature, negative with rainfall and wind speed, and no correlation with humidity. Fagus and Quercus start dates result positively correlated between themselves. Significant correlations are found between the start of MPS and the mean and maximum temperature in March for Fagus and Quercus, and May for Castanea.     

Heavy-metal uptake and distribution in Silene vulgaris and Minuartia verna growing on mining-dump material containing lead and zinc

Plant and soil samples from a mining area in Carinthia (Austria) were investigated for their heavy metal content. In the soil surrounding roots of plants (Minuartia verna and Silene vulgaris) growing on the mining dumps, high concentrations of lead and zinc are to be expected. The two species (Minuartia and Silene) show very different heavy metal concentrations in their above- and belowground organs. From these observations it can be concluded that the divergent distribution of heavy metals within the plants is an important mechanism of tolerance to heavy metals.     

Salt resistance and the environment of the cell wall of some halophytes

It was shown for Cochlearia anglica roots in comparison with Phaseolus vulgaris, roots that: (a) the cell walls of the halophyte are heavy; (b) they have a high Ca²⁺ content; (c) they may be a convenient means of transfer for Na⁺.In Aster tripolium as well as in Atriplex littoralis NaCl alters the composition of the various pectic fractions and maintains a low pectinemethylesterase activity and a great cellulase activity. This effect may be responsible for the great plasticity of the cell walls which allows an increased cell growth and leads to the formation of succulent organs, therefore to the dilution of salt within the cells.     

Response of ectomycorrhizalPinus banksiana andPicea glauca to heavy metals in soil

Pinus banksiana andPicea glauca inoculated or not with the ectomycorrhizal fungusSuillus luteus were grown in a sandy loam soil containing a range of Cd, Cu, Ni, Pb and Zn concentrations. Ectomycorrhizal colonization rates were significantly reduced on Pinus and Picea seedlings by the heavy metals, particularly Cd and Ni. Needle tissue metal concentrations were lower in ectomycorrhizal seedlings at low soil metal concentrations. However, at higher soil concentrations, heavy metal concentrations of needle tissue were similar in ectomycorrhizal and nonmycorrhizal plants. The growth of nonmycorrhizal seedlings exposed to heavy metals was reduced compared to those inoculated withSuillus luteus. Apparently ectomycorrhizal colonization can protect Pinus and Picea seedlings from heavy metal toxicity at low or intermediate soil concentrations of Cd, Cu, Ni, Pb and Zn.     

Peculiarities of muscles and skeleton structure in <Emphasis Type="Italic">Campiglossa plantaginis</Emphasis> (Haliday, 1833) ovipositor (Diptera,Terthritidae) in association with larval mode of life

Sclerites and muscles of the ovipositor in the tephritid fly Campiglossa plantaginis (Haliday, 1833), with phytophagous larvae developing in inflorescences of Aster tripolium L. and other Asteraceae, were examined. Structural adaptations of the ovipositor, providing oviposition into different substrates, are discussed in relation to different trophic specialization of larvae.     

Element distribution in mycorrhizal and nonmycorrhizal roots of the halophyte Aster tripolium determined by proton induced X-ray emission

Summary. The salt aster (Aster tripolium L.) colonized by the arbuscular mycorrhizal fungus Glomus intraradices Sy167 and noncolonized control plants were grown in a greenhouse for nine months with regular fertilization by Hoagland nutrient solution supplemented with 2% NaCl. Mycorrhizal roots showed a high degree of mycorrhizal colonization of 60–70% and formed approximately 25% more dry weight and much less aerenchyma than the nonmycorrhizal controls. Cryosectioning essentially preserved the root cell structures and apparently did not cause significant ion movements within the roots during cuttings. The experimental conditions, however, did not allow to discriminate between fungal and plant structures within the roots. Quantification of proton-induced X-ray emission (PIXE) data revealed that in control roots, Na⁺ was mainly concentrated in the outer epidermal and exodermal cells, whereas the Cl^– concentration was about the same in all cells of the roots. Cross sections of roots colonized by the mycorrhizal fungus did not show this Na1 gradient in the concentration from outside to inside but contained a much higher percentage of NaCl among the elements determined than the controls. PIXE images are also presented for the four other elements K, P, S, and Ca. Both in colonized and control roots, the concentration of potassium was high, probably for maintaining homoeostasis under salt stress. This is seemingly the first attempt to localize both Na⁺ and Cl^– in a plant tissue by a biophysical method and also demonstrates the usefulness of PIXE analysis for such kind of investigation.     

Sediment toxicity and heavy metals in the Kattegat and Skaggerak

Superficial (0 to 2 cm) sediments were sampled from 62 sites in Kattegat and Skagerrak during autumn 1989 and spring 1990, tested for toxicity to Daphnia magna and Nitocra spinipes (Crustacea) and analyzed for heavy metals (Cd, Cr, Cu, Hg, N, Pb, Zn), nutrients (N and P) and organic carbon. Whole sediment toxicity to Nitocra spinipes, expressed as 96-h LC50, ranged from 1.8 to > > 32 percent sediment (wet wt), which is equivalent to 0.63 to 53 percent dry wt. Sediment total metal concentrations (mg kg^-1 dry wt) ranged from 0.01 to 0.32 for Cd, 8 to 57 for Cr, 3 to 40 for Cu, 0.03 to 0.86 for Hg, 3 to 43 for Ni, 6 to 37 for Pb and 21 to 156 for Zn. Analyzed concentrations of heavy metals were tested for correlation with whole sediment toxicity normalized to dry wt, and significant correlations (Spearman p<0.05) were found for Cd, Cr, Cu, Hg, and Ni. However, the analyzed concentrations of these metals were below the spiked sediment toxicity of these heavy metals to N. spinipes, except for Cr and Zn for which analyzed maximum concentrations approached the 96-h spiked sediment LC50s. There was no improvement in correlation between the sum of heavy metal concentrations normalized to their spiked toxic concentrations (Toxic Unit approach) and the whole sediment toxicity. Calculated heavy-metal-derived toxicity based on toxic units and whole sediment toxicity ranged from 0.1 to 24 (mean value 2.3 and SD 4.2). Theoretically, a value of 1.0 would explain whole sediment toxicity from measured metal concentrations using this approach. Thus, in spite of the fact that the total concentrations of the heavy metals were sufficient to cause toxicity based on an additive model for most of these sediments, the observed toxicity of the sediments from Kattegat and Skagerrak could not exclusively be explained by the concentrations of heavy metals, except for Cr and Zn at their maximum concentrations. Therefore, other pollutants than these heavy metals must also be considered as possible sediment toxicants.     

A new species of Pemphigus Hartig (Hornoptera: Aphidoidea) from Western Europe

A new aphid species, Pemphigus trehernei, found on the roots of Aster tripolium L. in Western Europe is described. The gall, fundatrix and alate fundatrigenia were produced artificially on Populus nigra L. var. italica Duroi. The life cycle and host range of the species were investigated.     

Stomatal responses to sodium ions in Aster tripolium: a new hypothesis to explain salinity regulation in above-ground tissues

A study has been made of the ionic relations of stomata of Aster tripolium L., a maritime halophyte which colonizes coastal saltmarshes. The results obtained allow us to add this species to the growing list for which an involvement of K⁺ transport in stomatal movements has been demonstrated. However, an additional and ecologically important characteristic was found: there was a suppression of stomatal opening by increasing NaCl concentrations. A new hypothesis is offered of the mechanism for controlling salt and water relations in A. tripolium, a species which does not possess glands or other means of excreting salt. It is suggested that when the capacity of the tissues to accumulate salt in cell vacuoles is exceeded, the concentration of Na⁺ ions in the apoplast around the guard cells begins to rise. This causes partial stomatal closure, reduces transpiration and increases water-use-efficiency. Therefore, the flow of salt into the leaves is reduced but growth (and the manufacture of the new photosynthates required to support it) can continue. Aster tripolium can be added to the small list of known species which readily yield isolated epidermis suitable for detailed stomatal studies. Throughout this study, we have compared its stomatal physiology with C. communis, which has been thoroughly investigated in the past.     

Biological and Behavioral Effects of Heavy Metals in Drosophila melanogaster Adults and Larvae

Heavy metals are essential components of biological systems but are extremely toxic at high doses. As a result, we hypothesized that perception of heavy metals through gustation may exist in Drosophila melanogaster. In this study, we investigated the behavioral effects of iron, copper, zinc, and cadmium on D. melanogaster gustation, oviposition, and pupation-site selection. In addition, we examined the biological effects of heavy metals on the fruit fly survival and reproductive success. Our results illustrate that D. melanogaster responds behaviorally to the presence of high concentrations of heavy metals in food. All metals acted as repellents to the fruit flies at high doses, with the egg-laying and feeding of the female flies significantly decreasing. Furthermore, supplementation of heavy metals in the culture medium reduced survival to the adult stage and shortened the life span of adult flies. From these observations, we speculate that D. melanogaster avoidance behavior towards high concentrations of heavy metals may have a positive effect on their survival and reproductive success in nature, particularly in the presence of metal-contaminated food sources.     

The pollination biology of two species of Helicteres (Malvaceae) with different mechanisms of pollen deposition

Species of Helicteres are pollinated mainly by hummingbirds and bats. Most species pollinated by hummingbirds have a mechanism of depositing pollen on the top of the pollinator's head such as is shown in this work for Helicteres sacarolha. H. brevispira has an unusual mechanism of depositing pollen grains under the tail or on the abdomen of the hummingbirds. The top of the birds’ head may be considered an efficient place to transport pollen grains, because it is plain, easily accessible for deposition and donation of pollen and not easily accessible for grooming, while the tail is movable and inclined. Thus, H. brevispira pollinators may carry or transfer fewer amounts of pollen grains than H. sacarolha pollinators from one flower to another. If a large amount of pollen grains is lost, a higher quantity of flower or pollen has to be produced to guarantee reproductive success. Plants of H. brevispira set higher number of flowers and pollen grains per flower than H. sacarolha and have also higher rates of fruit and flower abortion. Thus, pollination efficiency of H. brevispira may be reached by high pollen and flower production. Flower change mechanism presented in this species may be also involved with the optimization of pollinator feeding and pollination efficiency.