Halophyte Suaeda Maritima Research Articles

Salt Tolerance in the HalophyteSuaeda maritimaL. Dum.: Intracellular Compartmentation of Ions

The time-course of exchange of sodium and potassium ions from root and leaf material of the halophyte Suaeda maritima has been followed and the data analysed according to the phenomenology of efflux, or compartmental, analysis. Sodium ions were exchanged much more slowly (c. 4 times) from the vacuoles of leaf cells of plants grown in sodium chloride than were potassium ions from the vacuoles of leaf cells of plants grown either in similar concentrations of potassium chloride or in low concentrations of potassium. In plants grown in sodium chloride, sodium ions were exchanged 9 times more slowly from the vacuoles of leaf cells than from the vacuoles of root cells. The concentration of sodium ions in the cytoplasm of leaf cells of plants growing in 340 mol m-3 sodium chloride was estimated to be 165 mol rrr3 when the average concentration in the leaf tissue was about 600 mol m~3. As measured by movement from mature to developing leaves in intact plants; there was less in vivo retranslocation of 22Na and 36C1 in plants growing in sodium chloride than there was of 86Rb in plants growing either in potassium chloride or in non-saline conditions. The results are discussed in terms of the concept and energetics of compartmentation of ions in the cells of halophytes.

Rubidium Transport in Membrane Vesicles from the Halophyte Suaeda maritima

The uptake and efflux of Rb+ by membrane vesicles isolated from shoots of the halophyte Suaeda maritima have been investigated. Uptake came to an apparent equilibrium after 1 h and the initial rate of uptake was considerably slower than that reported for bacterial membrane vesicles Additions of ATP reduced both Rb+ uptake and the half-time for loss in efflux experiments, although this effect was not specific for ATP and probably was not associated with energy transfer The permeability coefficient for Rb+ was calculated to be between 0 1 and 0 3 × 10−2 cm s−1. The value of membrane vesicles in ion transport studies in plants is discussed.

Effect of NaCl on the activities of glutamate synthase from a halophyte Suaeda maritima and from a glycophyte Phaseolus vulgaris

The action of NaCl on the activity of root and leaf glutamate synthase is compared in a halophyte, Suaeda maritima var. macrocarpa and in a glycophyte Phaseolus vulgaris. The addition of salt in the nutrient medium lowers the activity of glutamate synthase from Phaseolus without affecting that of Suaeda. This result, attributed to the fact that glutamate synthase is stimulated while glutamate dehydrogenase is partly inhibited in the halophyte grown in presence of high NaCl concentrations, suggests that the GS-GOGAT pathway is the primary route for ammonia assimilation. This pathway is especially active in the leaves. In vitro, NaCl (25–300mM) reduces the activity of glutamate synthase in Phaseolus as well as in Suaeda. Comparison with results obtained in situ suggests that there are differences in intracellular compartmentalization between the two types of plant.

Determination of the sodium, potassium and chloride ion concentrations in the chloroplasts of the halophyteSuaeda maritima by non-aqueous cell fractionation

Leaf material from the halophyteSuaeda maritima L. Dum. grown under both saline and non-saline conditions was fractionated under non-aqueous conditions in order to determine the ion content of various subcellular compartments. Fractions containing cell walls, nuclei and chloroplasts were successfully prepared and contents of DNA, chlorophyll, protein and Na+, K+, and Cl− determined. The cell wall fraction was not apparently heavily contaminated by the other fractions and had a low ion content although the nuclear fraction was contaminated by other organelles. The ion contents of chloroplasts were determined and the results discussed in relation to earlier microscopical data.

Caractérisation de la glutamate déshydrogénase chez un halophyte obligatoire: le Suaeda maritima var. macrocarpa

AbstractCharacterization of the glutamate dehydrogenase from an obligate halophyte: Suaeda maritima var. macrocarpaThe glutamate dehydrogenase (GDH), E.C. 1.4.1.3, of the obligate halophyte Suaeda maritima (L.) Dum. var. macrocarpa Moq. has been studied. NaCl increase in the culturing solution (0 to 23 g NaCl/litre) lowers the specific activity but does not affect the kinetic characteristics of the enzyme collected after purification on G‐25 Sephadex gel. In optimal conditions, GDH is activated by the addition of 25 mM NaCl in the incubation medium and inhibited with concentrations over 100 mM. The inhibitory activity of the salt induces both a modification of the affinity of the enzyme for substrate (competitive inhibition for ketoglutarate) and a modification of the catalytic potency (non‐competitive inhibition with NADH and ammonium ion). It is suggested that NaCl has a depressing influence on GDH synthesis. There is a fundamental difference between its short time action (in vitro) versus its continuous effect in the culturing solution.

Salt Tolerance in the Halophyte, Suaeda maritima (L.) Dum.: The Influence of the Salinity of the Culture Solution on the Content of Various Organic Compounds

Plants of the halophyte Suaeda maritima were grown in tap water or in a culture solution in the presence or absence of sodium chloride and the levels of sugars, amino acids, organic acids and quaternary ammonium compounds determined in relation to the balance between cytoplasmic and vacuolar water potentials. The sugar content (some 7 μmol. g f. wt−1) was unaffected by the salinity of the growth medium as was the overall content of amino acids (about 4 μmol. g f. wt−1). The organic acid content was maximal in plants kept in tap water alone where the dominant acid was malic. Plants grown in culture solution contained the same acids, although addition of sodium chloride to the medium brought about the apparent loss of glycolic acid and the appearance of oxalic acid. Only a single quaternary ammonium compound, glycinebetaine, was apparently present in the tissues: the content of betaine doubled (to 35 μrmol. g f. wt−) when sodium chloride was added to the culture solution. The content of these various compounds is discussed in relation to the relative values of the cytoplasmic and vacuolar components of the overall tissue water potential.

Salt tolerance in the halophyte Suaeda maritima. Further properties of the enzyme malate dehydrogenase

Malate dehydrogenase activity in supernatant fractions prepared from the halophyte Suaeda maritima was modified by added NACl with an optimal concentration for activation of about 50 mM. At this ionic strength of 0.05 the chlorides of sodium, potassium, ammonium, rubidium, calcium and magnesium all produced a similar degree of stimulation, while the nitrates of potassium and sodium were somewhat less effective. A similar result was obtained whether the plants were grown in the presence or absence of NACl. Furthermore, malate dehydrogenase activity in preparations from the glycophyte Pisum sativum behaved in a similar manner. The enzyme activity from both Suaeda and Pisum was separable into two fractions (I and II) by gel filtration on Sephadex G200. The MW of fraction II from Suaeda was estimated to be 165000 and that from Pisum approximately 282000: fraction I from both species eluted at the void volume of Sephadex G200. Storage of lyophilised supernatant resulted in the loss of enzyme activity from fraction I and a decrease in the overall stimulation by NaCl. Treatment of the lyophilised enzyme with NACl at a concentration of 100 mM also resulted in the loss of enzyme activity from fraction I.

Properties of Membranes from the HalophyteSuaeda maritima

The fine structure and certain cytochemical properties of the shoots from the halophyte Suaeda maritima have been examined. No major fine structural differences were observed between plants grown in the presence or absence of salt. Considerable evidence of vesiculation was observed, particularly in cells of the stelar tissue from the stems. The specificity of the phosphotungstic acid-chromic acid stain for plasma membranes was examined and some doubt raised as to its widespread applicability as a plasma membrane marker in plant cells. The suitability of other membrane markers such as ruthenium red and ATPase activity were investigated.

Salt tolerance inSuaeda maritima(L.) Dum

Mitochondria were isolated from green leaves and stems of the glycophyte Pisum sativum and the halophyte Suaeda maritima. The preparations oxidized malate, succinate, and 2-oxoglutarate as well as externally added NADH. Acceptor control ratios were about 2.8 for mitochondria from Pisum and 1.8 for mitochondria from Suaeda oxidizing malate+pyruvate in 125 mM sodium chloride. The mitochondrial fraction was contaminated with chloroplast fragments which resulted in relatively low rates of oxygen uptake when these were expressed on a protein basis. The addition of sodium chloride at concentrations greater than 200 mM considerably reduced the rates of oxygen uptake by both species in the presence and absence of phosphate acceptor (ADP). Acceptor control ratios were reduced and there was a marked decline in the ADP/O ratio. Sucrose at equivalent molar concentrations had a much less drastic effect on the mitochondria. There was no significant difference in the effects of these two solutes on mitochondria from the two species and the similarity of response is discussed in relation to the cytoplasmic ion content of the halophyte.

The effect of salt on protein synthesis in the halophyte Suaeda maritima

An amino acid-incorporating microsomal fraction has been isolated from the leaves of the halophyte Suaeda maritima and the characteristics of the incorporation described. There were no differences in the properties of the microsomes isolated from plants grown in saline and non-saline conditions. The incorporation was severely inhibited by high concentrations of sodium or potassium ions. The results are discussed in relation to the mechanism of salt tolerance in halophytes and the localization of salt in the cells.