Suaeda Maritima Research Articles

Directional and non‐directional vegetation changes in a temperate salt marsh in relation to biotic and abiotic factors

The effects of reduction and cessation of sheep grazing on salt-marsh vegetation were studied on a formerly intensively grazed salt marsh in northern Germany. Plant species cover was recorded in 45 permanent plots from 1992 to 2000. In 1995, physical and chemical soil parameters were analysed. Results of Redundancy Analysis (RDA) indicated that salinity and the depth of anoxic conditions below the surface were the most important soil factors related to the spatial vegetation pattern. Furthermore, plant species distribu- tion was influenced by present and past grazing intensity, by soil grain size and nitrogen content. Vegetation changes over 9 yr were analysed by non-linear regression. The cover of Aster tripolium, Atriplex portulacoides, and, to a lesser extent, Artemisia maritima and Elymus athericus increased due to reduced grazing pressure, whereas the cover of Salicornia europaea decreased. After a strong increase in the first years Aster decreased 2 to 6 yr after abandonment. In the mid salt-marsh zone Puccinellia maritima was replaced by Festuca rubra. The cover of Puccinellia, Festuca, Suaeda maritima, Glaux maritima and Salicornia fluctuated strongly, probably due to differences in weather conditions and inunda- tion frequency. Species richness per 4 m 2 generally increased while vegetation evenness decreased during the study period. Only in the high salt marsh abandoned for 9 yr did the number of species decrease slightly. Thus far, cessation of grazing did not lead to large-scale dominance of single plant species.

Influence of UV-B Supplemental Radiation on Growth and Pigment Content in Suaeda Maritima L.

In a field experiment with a mangrove species Suaeda maritima L. grown under ambient and supplementary UV-B radiation corresponding to 20 % ozone depletion, changes in growth and contents of photosynthetic and UV-absorbing pigments were determined. Supplemental UV-B irradiation for 9 d significantly reduced the growth and concentration of photosynthetic pigments. However, anthocyanin and flavonoid contents were significantly increased in UV-treated plants and which could be reduce the UV-B penetration and damage to the underlying tissues.

Influence des facteurs biotiques et abiotiques sur la morphologie et la reproduction de Suaeda maritima sur un marais salé

The aim of this study was to estimate the influence of biotic and abiotic factors on Suaeda maritima reproduction on a salt marsh. Individuals of Suaeda maritima were submitted in natural conditions to four series of densities (100, 1 000, 4 000 and 8 000 plants/m 2). When density increases, individuals tend to be less or non-branched, while individual biomass decreases. Consequently, individual seed production decreases as density increases. Despite morphological modifications, Suaeda maritima present density-dependent mortality. For a unit area, total biomass and seed production are higher at intermediate density (1 000 plants/m 2). Environmental factors could interfere with self-thinning. They seem to limit the effect of competition on mortality and to have an influence on individual and total seed production. This experiment stressed the importance of a biotic factor such as intra-specific competition, which occurs at the same time as abiotic factors, in Suaeda maritima dynamics in the field.

Factors affecting the population dynamics of Suaeda maritima at initial stages of development

This study describes life history and population dynamics of the annual halophyte Suaeda maritima, at initial stages of seedling development, in salt-marshes of the Mont-Saint-Michel Bay. Effects of salinity on seed germination and seedling development were studied both in the laboratory and in the field. Salinity was measured as sediment electrical conductivity. Experiments in the laboratory showed that Suaeda maritima was relatively tolerant to salinity during the germination stage. In the field, germination occurred when soil salinity was minimal. Almost all seeds germinated in the field; this may explain the absence of a persistent seed bank. Salinity did not seem to affect the growth of seedlings either. Mortality in the field was attributed to physical factors such as anoxia during temporary immersion, burial by sediment and tidal uprooting. The intensity of these effects varied according to the location of Suaeda maritima seedlings: in hollows, along the edge of tidal creeks, in gaps among dense vegetation cover, or in pattern with Puccinellia maritima. Perennial vegetation did not restrict Suaeda maritima germination. In contrast, perennials such as Puccinellia maritima and Halimione portulacoides limited the development of Suaeda maritima seedlings since only a small number of this annual emerged beneath their canopies. The fate of seedlings depended to a great extent on the permeability of the perennial canopy to light. Thus, disturbance resulting in bare patches inside the perennial vegetation seemed essential for the development of this annual species. Suaeda maritima can grow in the presence of Puccinellia maritima so long as the latter present as an open matrix. Suaeda maritima may also benefit from protection against desiccation and tidal action where this occurs.

Mosquito Larvicidal Activity of Mangrove Plant Extracts and Synergistic Activity of Rhizophora apiculata with Pyrethrum against Culex quinquefasciatus

Plant samples were collected from 15 mangrove species, Acanthus ilicifolius, Aegiceras corniculatum, Avicennia marina. A. officinalis, Bruguiera cylindrica, Ceriops decandra, Excoecaria agallocha, Rhizophora apiculata, R. Lamarckii, R. mucronata, Salicornia brachiata, Sesuvium portulacastrum, Sonneratia apetala, Suaeda maritima, S. monoica and Xylocarpus granatum. The 22 samples were extracted in acetone and petroleum ether separately, and the extracts were tested for their activity against the larvae of mosquito, Culex quinquefasciatus. Petroleum ether extract of R. apiculata was found most effective with LC 50 of 25.7 mg/l. The extract was studied further with pyrethrum for its synergistic larvicidal activity. The extract exhibited synergism and the synergistic factor was 0.81 at 5 mg/l.

Nutrient limitation and plant species composition in temperate salt marshes.

Addition of inorganic nitrogen, phosphorus and potassium in a factorial design in two ungrazed Wadden-Sea salt marshes at low and high elevations showed that nitrogen was the limiting nutrient. No effects of nutrient addition were detected in the 1st year, probably due to a considerable rainfall deficit during the growing season. In the 2nd year, which was more humid, only nitrogen addition caused significant effects in both the low salt marsh dominated by Puccinellia maritima and the high marsh dominated by Festuca rubra. No two-way or three-way interactions with phosphorus or potassium were found. In the low marsh, nitrogen addition had a negative effect on the biomass of Puccinellia, but a positive effect on the biomass of Suaeda maritima and on the total above-ground biomass. Puccinellia was replaced by Suaeda after nitrogen addition, due to shading. In the high salt marsh, no significant effects of fertilizer application on total above-ground biomass were found, due to the weak response of the dominant species Festuca rubra, which accounted for 95% of total biomass. The biomass of Spergularia maritima increased, however, as a response to nitrogen addition.The shoot length of Festuca was positively affected by nitrogen fertilization. It is suggested that stands of Festuca reached maximal biomass at the study site without fertilization and that its growth was probably limited by self-shading.

Impact of different sheep grazing intensities on salt marsh vegetation in northern Germany

Abstract. Mainland salt marshes in Schleswig‐Holstein (northern Germany) have been grazed intensively by sheep for several decades. In 1988 experimental sites were established in the lower and middle salt marsh of Sönke‐Nissen‐Koog and subjected to different grazing intensities. From 1989 to 1993 the impact of sheep grazing on the composition and structure of the salt marsh vegetation was studied through the yearly analysis of permanent plots, vegetation mapping and measurements of the vegetation height.The intensively grazed site (10 sheep/ha) is covered by a short monotonous Puccinellia maritima sward with Salicornia europaea and Suaeda maritima. Halimione portulacoides and Aster tripolium, especially flowering plants, are rare.On the sites with 1.5 and 3 sheep/ha Puccinellia maritima remained dominant. The population density of Salicornia europaea decreases after reduction of the grazing intensity, whereas Suaeda maritima finds optimal growing conditions. Stands of Halimione portulacoides and flowering Aster tripolium plants are rare near the sea dike but their cover and size increases further away from the dike. In the plot with 1.5 sheep/ha the height of the vegetation increases along the gradient from the dike towards the tidal flats, due to local differences in actual grazing intensity.When grazing is stopped, Puccinellia maritima is successively replaced by Festuca rubra, Halimione portulacoides and Aster tripolium. High variability of vegetation height indicates structural diversity. Patches of higher and lower vegetation correspond with the distribution pattern of different plant species.In terms of nature conservation cessation of grazing is recommended.

In vitrosalt tolerance of cell wall enzymes from halophytes and glycophytes

The halophyte Suaeda maritima grows optimally in high concentrations (40-60% seawater) of salt. In these conditions the concentration of salt in the apoplast of the leaves is at least 500 mM, a concentration which severely inhibits the activity of cytoplasmic enzymes of both glycophytes and halophytes. The in vitro salt tolerance of a number of cell wall enzymes was assayed in the presence of a range of concentrations of NaCI. There was no significant inhibition of the activity of galactosidase, glucosidase, peroxidase or xyloglucan endo-transglycosylase extracted from Suaeda maritima by in vitro concentrations of NaCI up to at least 1 M. In vitro salt tolerance of cell wall enzymes was not restricted to the halophyte, similar enzymes from the non-halophilic relative Kochia tricophylla, and from the glycophytes Vigna radiata and Cicer arietinum, were inhibited little, or not at all, by the same concentrations of salt. Pectin esterase was somewhat less tolerant, but activity at 500 mM NaCI was still greater than at 0 mM NaCI in both Suaeda and Vigna. It is concluded that these enzymes of the cell wall compartment are much more salt-tolerant than cytoplasmic enzymes of higher plants. The results are discussed in relation to conditions thought to pertain in the apoplast.

Edaphic characteristics of salt meadow vegetation in the eastern regions of Spain

Mediterranean halophytic rush vegetation was studied in the coastal marshes found in the Valencian region (Spain). Species achieving a frequency > 10% in vegetation relevés have been considered : Aeluropus littoralis , Artemisia caerulescens subsp. gallica , Arthrocnemum macrostachyum , Aster tripolium subsp. tripolium , Carex extensa , Centaurium spicatum, Inula crithmoides, Juncus acutus , Juncus maritimus , Juncus subulatus , Linum maritimum, Phragmites australis , Plantago crassifolia, Samolus valerandi , Schoenus nigricans, Scirpus maritimus var. compactus, Sonchus maritimus subsp. maritimus and Suaeda maritima. Four sociological groups were established by means of Principal Components Analysis (PCA) and their relationship to edaphic factors (water level, pH, total calcium carbonate, lime (active calcium carbonate), sulphates, organic matter, conductivity over saturation extract of the soil, salinity, Ca++, Mg++, Na+, Cl", S.A.R., total nitrogen and texture) were carried out using statistical analysis. Soil texture, total nitrogen and active calcium carbonate have a significant correlation on the distribution of this species. High lime content allows some glycophytes to support high concentrations of salt. Nomenclature follows Tutin, T.G. et al. (1964-1980).

Germination and early establishment of lower salt‐marsh species in grazed and mown salt marsh

Abstract. Lower salt‐marsh species occur more in the grazed than in the mown sites of a salt marsh in Schiermonnikoog in the Netherlands. This was demonstrated by a sowing experiment which determined which characteristic of the stand structure, height of the canopy or percentage of bare soil, is responsible for this difference. The total number of seedlings which emerged was negatively related to the height of the canopy and positively to the percentage of bare soil. The survival of seedlings of Suaeda maritima and Plantago maritima could be explained by the height of the canopy and for the latter species also by the percentage of bare soil. The survival of Aster tripolium and Plantago maritima was higher in grazed than in mown sites. Since the amount of bare soil was higher than seemed necessary for germination and survival, it was concluded that the taller canopy was responsible for the absence of lower salt‐marsh species in the mown sites.

Sodium Chloride Compartmentation in Leaf Vacuoles of the Halophyte Suaedamaritima(L.) Dum. and its Relation to Tonoplast Permeability

Single channel properties, whole vacuole currents and proton pumping capacity were investigated in the intact vacuoles and membrane patches of leaf tonoplast from the halophyte Suaeda maritima. ATP-dependent proton pumping capacity was similar to non-halophytes whether the plants were or were not grown with added sodium chloride (200 mM). The most abundant ion channel was inward rectifying and had a single channel conductance of 58 pS in symmetrical KCl solutions (100 mM) to 170 pS using physiological conditions (50/150 mM KCl/NaCl cytoplasmic side, 50/450 mM KCl/NaCl vacuolar side). The channel showed all the characteristics of the SV type channel described in many other species. In the open state these channels caused tonoplast conductances in excess of 0.5 nS m2– but conductances were much lower using physiological ion concentrations and membrane potentials. In spite of the poor selectivity and the potentially large tonoplast conductance it is calculated that compartmentation of NaCl in leaf vacuoles can be sustained by about 30% of ATP-dependent proton pumping capacity. The results do not indicate any special adaptation of the tonoplast ion channels in the halophyte.

Molecular Markers for Ion Compartmentation in Cells of Higher Plants

The tonoplast plays a crucial role in ion compartmentation, which is a central feature of the salt tolerance of halophytes, but we do not know the properties of the membrane that confer this ability. A method was, therefore, developed for the isolation of vacuoles from Suaeda maritima (L.) Dum. of sufficiently high purity to enable biochemical characterization of their lipid and protein composition. Tonoplast fractions produced by density gradient centrifugation, as well as vacuoles isolated by a variety of methods (including DEAE dextran lysis, digitonin lysis, and mechanical shear forces) were unacceptably contaminated. A highly pure vacuole preparation was obtained when protoplasts were lysed by a mild hypotonic shock in alkaline buffer, in the presence of the compatible cytosolute glycine-betaine, followed by shear force during ultracentrifugation; cytoplasmic contamination was prevented by the addition of the zwitterionic detergent 3-([3-cholamidopropyl]dimethylammonio)-l-propanesulphonate (CHAPS). Light microscopy of this preparation revealed no intact protoplasts and no contamination by chlorophyll could be detected. Electron microscopy showed the vacuoles to be single-membrane-bound structures, and was the only criterion upon which vacuoles could be separated reliably from vacuoplasts, in which the plasmalemma is collapsed on to the tonoplast. Analysis by SDS-PAGE showed that a total of 15 polypeptides were enriched in the tonoplast and 27 in the soluble fraction from vacuole preparations, with a pattern similar to that reported for glycophytic species. The pure tonoplast exhibited both vanadate-insensitive ATPase and pyrophosphatase activities, but the properties of these enzymes were broadly similar to those of glycophytes. Analysis of membrane fatty acids showed that the degree of saturation of the putative tonoplast preparation increased as the assessment of the purity of the preparation (made by microscopy) increased. The ATPase could be substantially purified by ion-exchange FPLC. The results are discussed in relation to the degree of purity needed in membrane preparations in order to be suitable for biochemical analysis.

Molecular Markers for Ion Compartmentation in Cells of Higher Plants

Vacuoles of high purity were isolated from the leaves of the halophyte Suaeda maritima (L.) Dum. The relative compositions of phospholipids, phytosterols, and fatty acids in the tonoplast membrane were determined and membrane fluidity was assessed by electron spin resonance. The characteristics of the tonoplast were consistent with minimizing passive permeability to NaCI. The phospholipid: protein ratio (1.1: 1.0) was higher than that recorded in other membrane preparations, including vacuoles from beetroot storage material, commensurate with the low density (1.05 g cm−3) of the S. maritima tonoplast. The tonoplast fatty acids were highly saturated and dominated by n-hexadecanoic acid and n-octadecanoic acid. Phytosterols identified by gas chromatography were cholesterol, campesterol, stigmasterol, and β-sitosterol. Cholesterol was a trace percentage in protoplasts, but comprised 30% of the tonoplast sterols. Semi-quantitative analysis by chromatography on silica gel revealed an enrichment in the tonoplast of glycolipid which was not accounted for as chloroplast contamination. The fluidity of the tonoplast, determined by electron spin resonance, was lower than the protoplasts, consistent with the high degree of saturation of the fatty acid chains. The relevance of the lipid composition of the tonoplast to its central role in ion compartmentation within the halophyte cell is discussed.

Quantitative ion localization within Suaeda maritime, cortical cells using the combined techniques of freeze-substitution and X-ray microanalysis

The present paper describes ion distribution within mature root cortical cells of the halophyte Suaeda maritima, grown at a NaCl concentration of 200 mol/m3, by X-ray microanalysis of freeze-substituted thin sections using established methods (Harvey et al., 1981; Hajibagheri et al., 1983), but with a resolution enhanced by a new generation of analytical microscope. In addition, we have tried to assess whether there are characteristic differences between the cytoplasmic concentration of K+ in mature and meristemic cells.

Morphological Determinants of Self-Thinning in Plant Monocultures and a Proposal concerning the Role of Self-Thinning in Plant Evolution

Understanding density-dependent dynamics in plant populations has been limited by the lack of a clear mechanism responsible for self-thinning in plant monocultures. Although many plant populations exhibit predictable thinning dynamics based on the self-thinning rule, experimental support for possible mechanisms generating the self-thinning rule is lacking. Here, I review the formulation of the self-thinning rule based on plant geometry, and describe an experimental test of the geometrical hypothesis of self-thinning. Geometric theory predicts that plants of disparate morphologies should thin along lines with slopes different from -3/2. I examined the thinning dynamics of three species in the family Chenopodiaceae, Salicornia europaea, Suaeda maritima, and Atriplex triangularis, whose morphologies range from leafless, sparsely-branched and short (Salicornia) to bushy (Atriplex). As predicted by the geometric theory of self-thinning, Salicornia did not self-thin, Atriplex thinned along a line with slope -1.82, and Suaeda thinned along a line of intermediate slope, -2.50. These results strongly support a geometric basis for self-thinning. Morphologically, Salicornia is similar to the earliest vascular land plants, and by analogy I propose that self-thinning was not a selective force in early land plant evolution. Competition for light among plants would result in selection for increased height and canopy spread, and the widespread occurrence of the self-thinning rule in contemporary natural plant populations is hypothesized to be a result of these morphological changes.

Effect of Salinity Stress on Ribonucleolytic Activities in Glycophytic and Halophytic Plant Species

Summary The ribonuclease activities (RNase, EC 2.7.7.17) of the halophyte, Suaeda maritima (L.) DUM var. macrocarpa MOQ, and the glycophytes, Phaseolus vulgaris (L.) and Vicia faba (L.), were studied in relation to the salinity (NaCl) of the nutrient medium. A reduction of growth was observed for the three species subjected to «salt stresso (i.e. hypersalinity for glycophytes or absence of salt for the halophyte). Both short-term (salt shock) and long-term treatments with NaCl induced a marked increase in RNase activity, and a close relationship was established between «salt stress» and a high RNase activity. The stimulation of RNase activity was independent of the species (halophyte or glycophyte), the analyzed organ (root or leaf) and the nature of the salt treatment (saline shock or steady state culture). Ribonuclease activities of S. maritima leaves and V. faba roots were studied in detail by ion-exchange chromatography. Under the influence of salt treatment it appears that both anionic and cationic RNase activities were increased. It has been demonstrated for the first time that an anionic RNase is stimulated to a greater extent than any other ribonucleolytic enzyme in both the halophyte and the glycophyte. The RNases, particularly the anionic enzymes, can thus be considered as good markers for conditions of saline contraint.

X-ray microanalysis of ion distribution within root cortical cells of the halophyte Suaeda maritima (L.) Dum.

The ion content of compartments within cortical cells of mature roots of the halophyte Suaeda maritima grown at 200 mol·m(-3) NaCl has been studied by X-ray microanalysis of freeze-substituted thin sections. Sodium and Cl were found in the vacuoles at about four-times the concentration in the cytoplasm or cell walls, whereas K was more concentrated in the cell walls and cytoplasm than in vacuoles. The vacuolar Na concentration was 12- to 13-times higher than that of K. The Na concentration of cell walls of cortical cells was about 95 mol·m(-3) of analysed volume. The cytoplasmic K concentration within the mature cortical cells was estimated to be 55 mol·m(-3) of analysed volume.

Cytological studies of some mangroove flora of Tamilnadu.

16 taxa coming under 10 families occurring in the Mangroove forests of Tamilnadu, have been studied cytologically, of which first record of chromosome number has been made in lanceolate leaf type of Sesuvium portulacastrum, Rhizophora candelaria, Ceriops roxburghiana, Bruguiera conjugata, Avicennia marina, Suaeda maritima, S. monoica, Arthrocnemum fruticosum, Aegiceros corniculatus and Ilysanthes tenuifolia.n=18 may be the common primary basic number of the vegetation and from this the basic numbers 8, 9, 11, 12 and 15 should have arisen by decrease of chromosome numbers and the basic numbers n=19, 20, 22 should have originated by increase of chromosome numbers.Smaller size of chromosomes and mostly chromosomes with submedian and subterminal constrictions are the other advanced cytological characters of the mangroove vegetations studied.

Salt Tolerance in the HalophyteSuaeda maritimaL.Dum.: Abscisic Acid Concentrations in Response to Constant and Altered Salinity

Endogenous abscisic acid contents were measured by gas-liquid chromatography in shoots of Suaeda maritima growing both in the steady state over a range of salinities and over a time-course following an increase in the culture solution salinity of between approximately 100 and 400 mol m−3 NaCl. In steady-state plants, the ABA content was maximal in the absence of salt at 41 ng g−1 fr. wt., declining to a minimum at 200 mol m−3 NaCl of 24 ng g−1 fr. wt. Increase of culture solution salinity resulted in a marked increase in shoot ABA which was maximal after 6 h or 24 h in plants previously growing at 200 mol m−3 NaCl and in the absence of salt, respectively. Additionally, culture solution water potentials were lowered by 1.0 MPa (equivalent to raising the salt concentration by around 200 mol m−3); this resulted in a similar increase in endogenous ABA content to that brought about by an iso-osmotic salt increase. Results are discussed in relation to the possible role of ABA in halophyte salt tolerance mechanisms.

SALT TOLERANCE IN THE HALOPHYTE SUAEDA MARITIMA (L.) DUM.: THE EFFECT OF SALINITY ON THE CONCENTRATION OF SODIUM IN THE XYLEM.

Rates of ion transport and transpiration were measured during the day and night in whole seedlings of Suaeda maritima growing over a range of salinities, in order to calculate concentrations of sodium and potassium in the xylem during these periods. Mean sodium concentration in the xylem was maximal at 56 mol m-3 Na with an external salinity of 200 mol m-3 NaCl. The sodium concentration in the xylem was greater in the dark than in the light at all external salinities investigated. Comparison of the external sodium with that in the xylem indicated that sodium was more strongly excluded from the transpiration stream as salinity increased. The mean concentration of potassium in the xylem declined as external NaCl concentration increased, although selectivity for potassium increased at higher salinities. Results are discussed in relation to osmotic adjustment in S. maritima.