Proline and Polyamine Involvement in Chilling Tolerance of Maize Suspension Cultures

We have assessed the effect of various medium supplements inpromoting the ability of maize (Zea mays L.) inbred FR27rhmsuspension cultures to grow following a period of 4 °C chillingstress. Following a 4 week exposure to 4 °C in culture mediumwithout proline, no cell growth occurred upon subsequent incubationat 28°C for 2 weeks. This inhibition was reversed when 3to 48 mol m^–3 proline or 0.1 mol m^–3 putrescineor 0.01 mol m^–3 spermidine were present in the mediumduring the chilling stress. On the other hand, suspensions weremade more sensitive to 4°C by blocking polyamine biosynthesiswith 1.0 mol m^–3 methylglyoxal bis (guanylhydrazone) (MGBG)or a combination of 1.0 mol m^–3 difluoromethylornithine(DFMO) and 1.0 mol m^–3 difluoromethylarginine (DFMA).The addition of 10 mol m^–3 putrescine to the suspensioncontaining DFMO and DFMA prevented the increased chilling sensitivity.Electrolyte leakage studies conducted to assess membrane integrityafter 4 weeks at 4°C and a 2 week regrowth period showedthat cells treated with no polyamines (control), 0.01 mol m^–3spermidine, 1.0 mol m^–3 putrescine, or 1.0 mol m^–3MGBG lost 43, 32, 14, and 100% of the total electrolyte pool,respectively. These results suggest that proline and polyaminesare beneficial for inducing chilling tolerance in FR27rhm suspension. Key words: Proline, polyamine, chilling stress     

Effect of Salt Stress on Callus Cultures of Oryza sativa L.

Kavi Kishor, P.B 1988. Effect of salt stress on callus culturesof Oryza sativa L.—. exp. Bot 39 235–240 Callus cultures of rice adapted to grow under increasing NaClstress were found to accumulate considerable amounts of freeproline, compared with unadapted cells. Salt-adapted cells grownfor 10 passages (25 d each) on NaCl-free medium accumulatedproline on re-exposure to salt as did cells which were growncontinuously on NaCl. On replacing NaCl (100 mol m^–3)with 100 mol m^–3 of KC1, fresh and dry weights as wellas free proline content of salt-adapted callus declined comparedto that attained on 100 mol m^–3 NaCl medium. However,equimolar concentrations of NaCl and KC1 (when added together)produced an increase in growth and free proline accumulationin salt adapted callus. Omission of Ca²⁺ from the growth mediuminhibited the growth of salt-adapted cells in the presence ofNaCl, while it had little effect on the growth of non-adaptedcells in the presence of NaCl. ABA increased the fresh and dryweights of the non-adapted callus only in the presence of 200mol m^–3 of NaCl but not in the absence of NaCl. ABA failedto evoke the same response in salt adapted cells in the presenceof the salt. Tissues exhibited good growth under inhibitorylevels of NaCl (500 mol m^–3) only when glycine betaine,choline and proline were added to the medium but showed no growthin the presence of sarcosine, glycine and dimethylglycine. Key words: Oryza saliva, callus cultures, NaCl stress     

Effect of NaCl Salinity on Somatic Embryo Development in Sapindus trifoliatus L.

The effect of NaCl salinity on growth and development of somaticembryos of Sapindus trifoliatus L. was examined. Incorporationof 25 and 50 mol m^–3 NaCl into the medium greatly increasedthe growth and development of somatic embryos and both theseconcentrations favoured the production of secondary embryoids.However, supplementation of 100 mol m^–3 NaCl to the mediumdid not have any significant effect on the growth and developmentof somatic embryos. On the other hand, the culturing of proembryostructures in medium containing 200 mol m^–3 NaCl resultedin complete death within 7 d of salt exposure. Analysis of somatic embryos revealed that, upon salinization,they accumulated Na⁺ and Cl^– in significant amounts butthe content of Na⁺ was much less compared to that of Cl^–.Addition of NaCl (up to 50 mol m^–3) in the medium resultedin a considerable increase in the K⁺ content of somatic embryos.The content of proline in somatic embryos, however, increasedsubstantially in response to salinization. The amount of freesterols, steryl glycosides, steryl esters, and phospholipidsalso rose to higher values in salt-affected somatic embryos.The results suggest that somatic embryos of S. trifoliatus cantolerate concentrations of NaCl up to 100 mol m^–3 withoutaffecting growth and that they have sufficient cellular mechanismsto tolerate salinity at relatively high levels. Key words: Salinity, somatic embryo, sterols, phospholipids     

The Partitioning of Nitrate Assimilation Between Root and Shoot of a Range of Temperate Cereals and Pasture Grasses

Nitrate reductase activity (NRA, in vivo assay) and nitrate(NO^-₃) content of root and shoot and NO^-₃ and reduced nitrogencontent of xylem sap were measured in five temperate cerealssupplied with a range of NO^-₃ concentrations (0·1–20mol m^–3) and three temperate pasture grasses suppliedwith 0·5 or 5 0 mol m^–3 NO^-₃ For one cereal (Hordeumvulgare L ), in vitro NRA was also determined The effect ofexternal NO^-₃ concentration on the partitioning of NO^-₃ assimilationbetween root and shoot was assessed All measurements indicatedthat the root was the major site of NO3 assimilation in Avenasatwa L, Hordeum vulgare L, Secale cereale L, Tnticum aestivumL and x Triticosecale Wittm supplied with 0·1 to 1·0mol m^–3 NO^-₃ and that for all cereals, shoot assimilationincreased in importance as applied NO^-₃ concentration increasedfrom 1.0 to 20 mol m^–3 At 5.0–20 mol m^–3 NO3,the data indicated that the shoot played an important if notmajor role in NO^-₃ assimilation in all cereals studied Measurementson Lolium multiflorum Lam and L perenne L indicated that theroot was the main site of NO^-₃ assimilation at 0.5 mol m^–3NO^-₃ but shoot assimilation was predominant at 5.0 mol m^–3NO^-₃ Both NRA distribution data and xylem sap analysis indicatedthat shoot assimilation was predominant in Dactylis glomerataL supplied with 0.5 or 5.0 mol m^–3 NO^-₃ Avena sativa L., oats, Hordeum vulgare L., barley, Secale cereale L., rye, x Triticosecale Wittm., triticale, Triticum aestivum L., wheat, Dactylis glomerata L., cocksfoot, Lolium multiflorum Lam., Italian ryegrass, Lolium perenne L., perennial ryegrass, nitrate, nitrate assimilation, nitrate reductase activity, xylem sap     

Spatial and Temporal Aspects of Growth in the Primary Root of Cotton Seedlings: Effects of NaCl and CaCl2

Seedlings of cotton (Gossypium hirsutum L. cv. Acala SJ-2) weregrown in modified Hoagland nutrient solution with various combinationsof NaCl and CaCl₂. Marking experiments and numerical analysiswere conducted to characterize the spatial and temporal patternsof cotton root growth at varied Na/Ca ratios. At 1 mol m^–3Ca, 150 mol m^–3 NaCl reduced overall root elongation rateto 60% of the control, while increasing Ca to 10 mol m^–3at the same NaCl concentration restored the elongation rateto 80% of the control. Analysis of the spatial distributionof elongation revealed that the presence of 150 mol m^–3NaCl in the medium shortened the growth zone by about 2 mm fromthe approximate 10 mm in the control and also reduced the relativeelemental elongation rate (i.e. the longitudinal strain rate,defined as the derivatives of displacement velocity of a cellularparticle with respect to position on root axis). Supply of 10mol m^–3 Ca at the high salt condition restored partiallythe relative elemental elongation rate, but not the length ofthe growth zone. Compared to the control, the growth trajectoriesshowed that at 1 mol m^–3 CaCl2 it took more time for acellular particle to move through the growth zone at 150 molm^–3 NaCl, while at 10 mol m^–3 CaCl it took lesstime and there was no difference between the NaCl treatments Key words: Gossypium hirsutum, salinity stress, root growth kinematics     

Salt Tolerance in the Succulent, Coastal Halophyte, Sarcocornia natalensis

The effects of 0, 50, 100, 200, 300, 400 and 500 mol m^–3NaCl on growth and ion accumulation in the succulent, coastalhalophyte Sarcocornia natalensis (Bunge ex Ung.-Sternb.) A.J. Scott were investigated. Increase in salinity from 0 to 300 mol m^–3 NaCl stimulatedproduction of fresh, dry, and organic dry mass, increased succulenceand shifted resource allocation from roots to shoots. Growthwas optimal at 300 mol m^–3 and decreased with furtherincrease in salinity. Water contributed to a large proportion of the increase in freshmass. Inorganic ions, especially Na⁺ and Cl– contributedsubstantially to the dry mass. At 300 mol m^–3 NaCl inorganicions contributed to 37% of total dry mass and NaCl concentrationin the shoots was 482 mol m^–3. Expressed sap osmotic potentialsdecreased from –2.10 to –3.95 MPa as salinity increasedfrom 0 to 300 mol m^–3 NaCl. Massive accumulation of inorganicions, especially Na⁺ and Cl^–, accounted for 86% of theosmotic adjustment at 300 mol m^–3 NaCl. Salinity treatments decreased the concentrations of K+ in shoots.Plant Na+ :K+ ratios increased steadily with salinity and reacheda maximum of 16.6 at 400 mol m3 NaCl. It is suggested that the exceptional salt tolerance of S. natalensisis achieved by massive inorganic ion accumulation which providessufficient solutes for osmoregulation, increased water fluxand turgor-induced growth. Key words: Sarcocornia natalensis, salt tolerance, halophyte     

Effects of Sodium Chloride Stress on Callus Cultures of Cicer arietinum L. cv. BG-203: Growth and Ion Accumulation

Growth and ion accumulation were measured in callus culturesof Cicer arietinum L. cv. BG-203, grown on media supplementedwith 0–200 mol m^–3 NaCl. Fresh and dry weights decreasedat concentrations ranging from 100–200 mol m^–3,the reduction being greater during the third and fourth weeksof culture. Slight stimulation of growth was observed at 25and 50 mol m^–3 NaCl. There was also a decrease in tissuewater content (fresh weight: dry weight) at 100–200 molm^–3 NaCl. The concentration of Na⁺ and Cl^– in thetissue increased with increasing salinity of the medium. Mostof the accumulation of these ions occurred by the first weekwhile significant growth inhibition became apparent by onlythe third week of culture. Tissue K⁺ and Mg²⁺ decreased withincreasing salinization, the decrease being greater in K⁺ levels.Levels of Ca²⁺, however, were maintained throughout the experimentalrange. Key words: Cicer arietinum, NaCl stress, Callus cultures, Ion accumulation     

Interactive effects of salinity, nitrogen and sulphur on the organic solutes in Spartina alterniflora leaf blades

Glycinebetaine, proline, asparagine, sucrose, glucose, and dimethylsulphoniopropionate(DMSP) were the major organic solutes in Spartina alternifloraleaf blades. To investigate the physiological role(s) of thesesolutes, the effects of salinity, nitrogen, and sulphur treatmentson leaf blade solute levels were examined. Glycinebetaine wasthe major organic solute accumulated in leaf blades grown at500 mol m^–3 NaCl, although asparagine and proline alsoaccumulated when the supply of nitrogen was sufficient. Thesesolutes may play a role in osmotic adjustment. In contrast,DMSP levels either did not change or were reduced in responseto the 500 mol m^–3 NaCl treatment. Furthermore, elevatednitrogen supply decreased leaf blade DMSP levels, which wasopposite to the response of glycinebetaine, proline, and asparagine.A 1000-fold increase in external sulphate concentration hadno effect on the leaf blade levels of DMSP, glycinebetaine,proline, or asparagine. These findings suggest that the majorphysiological role of DMSP in S. alterniflora leaf blades isnot for osmotic adjustment, even under conditions of nitrogendeficit and excess sulphur. Instead, DMSP which was presentat 45—130 µmol g^–1 dry weight, may play arole as a constitutive organic osmoticum. Key words: Spartina alterniflora, dimethylsulphoniopropionate, glycinebetaine, nitrogen, salinity     

Possible reasons for relative salt stress tolerance in nodules of white lupin cv. Multolupa

The effects of different NaCl concentrations on the growth andnitrogen fixation activity of white lupin (Lupinus albus [L.])was studied over a 6 d period. Plant growth parameters, photosynthesisand shoot respiration were unaffected by NaCl concentrationsup to 150 mol m^–3. However, nitrogenase activity decreasedwith increased NaCl concentration up to 100 mol m_–3, whilstthe O₂ diffusion resistance increased with 100 mol m^–3NaCl, but showed no further change when 150 mol m^–3 NaClwas applied for 6 d. Increases in NaCl concentration decreasednodular starch content while increasing sucrose content, suggestingan osmotic regulation. These changes were associated with a77% decrease in sucrose synthase activity. The effect on theO₂ diffusion resistance was paralleled by changes in glycoproteincontent of the nodules, as determined by immunogold localizationand ELISA. X-ray microanalysis studies of nodules showed that,following a 6 d exposure to 150 mol m^–3 NaCl, Na⁺ ionswere largely excluded from the infected zone, whilst only lowlevels of Cl^- ions penetrated into this region. Na⁺ entry intoroots and leaves was also at a low level. Leghaemoglobin contentdecreased with saline stress, as did superoxide dismutase; whichdecreased by 36% following exposure to 100 mol m^–3 saltfor 6 d. These results are discussed in relation to the relativesalt tolerance of the Multolupa/ISLU-16 symbiosis. Key words: Salt stress, nodules, nitrogen fixation, oxygen diffusion, carbohydrates, Lupinus albus     

Effect of Salinity on Growth, Nodulation and Nitrogen Yield of Chickpea (Cicer arietinum L.)

Chickpea cultivar ILC 482 was inoculated with salt-tolerantRhizobium strain Ch191 in solution culture with different saltconcentrations added either immediately with inoculation or5 d later. The inhibitory effect of salinity on nodulation ofchickpea occurred at 40 dS m^–1 (34.2 mol m^–3 NaCl)and nodulation was completely inhibited at 7 dS m^–1 (61.6mol m^–3 NaCl); the plants died at 8 dS m^–1 (71.8mol m^–3 NaCl). Chickpea cultivar ILC 482 inoculated with Rhizobium strain Ch191^spcstrwas grown in two pot experiments and irrigated with saline water.Salinity (NaCl equivalent to 1–4 dS m^–1) significantlydecreased shoot and root dry weight, total nodule number perplant, nodule weight and average nodule weight. The resultsindicate that Rhizobium strain Ch191 forms an infective andeffective symbiosis with chickpea under saline and non-salineconditions; this legume was more salt-sensitive compared tothe rhizobia, the roots were more sensitive than the shoots,and N₂ fixation was more sensitive to salinity than plant growth. Key words: Cicer arietinum, nodulation, N₂ fixation, Rhizobium, salinity     

Induction of Increased Salt Tolerance in Sorghum bicolor by NaCl Pretreatment

Following 20 d of exposure to 75 or 150 mol m^–3 NaCl Sorghumbicolor (L.) Moench plants become capable of growing in mediumcontaining 300 mol m^–3 NaCl. Control plants, which havenot been pretreated, or plants pretreated for less than 20 ddie within 2 weeks when exposed to 300 mol m^–3 NaCl. Weconsider this induction of a capacity to survive in and toleratea high NaCl concentration as an adaptation to salinity. We suggestthat adaptation to salinity is more than osmotic adjustmentand that it takes longer to develop than osmotic adjustment.Concomitantly with the appearance of the ability to grow inhigh salinity, adaptation also comprises the development ofa capacity to regulate internal Na⁺ and Cl^– concentrations,even when external salinity is high. Shoot mean relative growthrates are similar for both control plants and for adapted plantsgrowing in 300 mol m^–3 NaCl, although their shoot Na⁺and Cl^– concentrations are quite different. Based on thesedata, we propose that adaptation of Sorghum to high salinityresults from a modulation of genome expression occurring duringextended exposure to non-lethal NaCl concentrations. Key words: Sorghum bicolor (L.) Moench, NaCl, salt tolerance, adaptation to salinity     

Salt Tolerance in the Halophyte Suaeda maritima L.Dum.: Abscisic Acid Concentrations in Response to Constant and Altered Salinity

Endogenous abscisic acid contents were measured by gas-liquidchromatography in shoots of Suaeda maritima growing both inthe steady state over a range of salinities and over a time-coursefollowing an increase in the culture solution salinity of betweenapproximately 100 and 400 mol m^–3 NaCl. In steady-stateplants, the ABA content was maximal in the absence of salt at41 ng g^–1 fr. wt., declining to a minimum at 200 mol m^–3NaCl of 24 ng g^–1 fr. wt. Increase of culture solutionsalinity resulted in a marked increase in shoot ABA which wasmaximal after 6 h or 24 h in plants previously growing at 200mol m^–3 NaCl and in the absence of salt, respectively.Additionally, culture solution water potentials were loweredby 1.0 MPa (equivalent to raising the salt concentration byaround 200 mol m^–3); this resulted in a similar increasein endogenous ABA content to that brought about by an iso-osmoticsalt increase. Results are discussed in relation to the possiblerole of ABA in halophyte salt tolerance mechanisms. Key words: Suaeda, halophyte, abscisic acid, salt tolerance     

Determination of Volume of Dunaliella Cells by Lithium Dilution Measurements and Derivation of Internal Solute Concentrations

A method has been developed to measure the cell volume of theunicellular green alga Dunaliella parva 19/9 using Li⁺ measurementsonly. Concentrations of internal solutes can also be calculatedif they are assayed in the same samples as Li⁺. We found thatD. parva cells grown in 0.4 kmol m^–3 NaCl have an averageaqueous cell volume of 65.1 ?2.9 µm³, a K⁺ concentrationof 126?6 mol m^–3, a Na⁺ concentration of 11?11 mol m^–3and a glycerol concentration of 615?27 mol m–3 (n= 12).Algae grown in 1.5 kmol m^–3 NaCl have an average aqueouscell volume of 131 ?7.5 µm³, a K⁺ concentration of 109?4mol m^–3, a Na⁺ concentration of 10?39 mol m^–3 anda glycerol concentration of 1 425?59 mol m^–3 (n = 12).These results indicate that D. parva cells adapted to high salinitieshave larger cell volumes than those adapted to lower salinities.However, there is no evidence for a significant difference ininternal Na⁺ concentration, despite the almost 4-fold differencein the concentration of external NaCl. The intracellular glycerolconcentration alone accounts for 65% and 54%, respectively,of the osmotic balance in low and high salt grown cells. Key words: Dunaliella, cell volume, intracellular solutes     

X-Ray Microanalysis and Ultrastructural Studies of Cell Compartments of Dunaliella parva

Hajibagheri, M. A., Gilmour, D. J., Collins, J. C. and Flowers,T. J. 1986. X-ray microanalysis and ultrastructural studiesof cell compartments of Dunaliella parva. -J. exp. Bot. 37:1725–1732. Ultrastructural studies of the unicellular green alga Dunaliellaparva showed the presence of cytoplasmic vacuoles. X-ray microanalysiswas performed on sections of cells which had been freeze substitutedin acetone. It was found that the concentrations of both Naand Cl were much higher in the vacuoles than in the cytoplasm.When cells were grown in 0·4 kmol m^–3 NaCl theNa and Cl concentrations in the vacuoles were 349 and 283 molm ^–3 respectively, whilst cytoplasmic Na and Cl concentrationswere 37 and 26 mol m^–3. Corresponding values for cellsgrown in 1·5 kmol m^–3 NaCl were 392 mol m^–3Na and 325 mol m^–3 Cl in the vacuoles and 36 mol m^–3Na and 30 mol m^–3 Cl in the cytoplasm. Immediately afterexposure to an increase in external salinity Na and Q concentrationsincreased in both vacuoles and cytoplasm. The results are discussedwith reference to compartmental models for the ionic relationsof Dunaiiella. Key words: X-ray microanalysis, ultrastructural studies, Dunaliella parva     

Interaction Between Mineral Nutrients, Cytokinin and Gibberellic Acid During Growth of Sorghum at High NaCI Salinity

Sorghum bicolor (L.) Moench, cv. 610, adapted to high salinitywas able to grow at 300 mol m^–3 NaCl only when half-strengthHoagland's solution was enriched with mineral nutrients. Theoptimal growth rate was observed in full strength Hoagland'ssolution; at higher or lower concentrations growth rates werelower. In contrast, growth rate of plants exposed to 150 molm^–3 NaCl was not affected by similar modification of theHoagland solution concentration. At high salinity, additionof cytokinin (CK) or gibberellic acid (GA), or a mixture ofboth, can induce the same effect on growth as the increasedmineral nutrient concentration. Phytohormones and increasedmineral concentration have similar effects, possibly becausean imbalance in phytohormones, rather than a mineral deficiency,limits growth at 300 mol m^–3 NaCl in the presence of half-strengthHoagland solution. The change in mineral concentration in thenutrient medium, in addition to its nutritional effect, alsoapparently acts as a signal involved in hormonal balance whichallows growth at high salinity. Exposure of Sorghum to 300 molm^–3 NaCl causes a decrease in the range of nutrient concentrationswhich can sustain growth. Adjustment of the nutrient concentrationmay induce the synthesis of endogenous CK and GA concentrationsrequired for growth. In contrast, addition of CK or GA at similarconcentrations during the adaptation (pretreatment) period inhibitsgrowth and prevents the adaptation process. The response tothe exogenous phytohormone treatments depends on the time elapsedfrom the beginning of salinization. Key words: Adaptation to salinity, cytokinin, gibberellic acid, mineral nutrition, growth, Sorghum, NaCl     

Nitrate Inhibition of Chloride Influx in Barley: Implications for a Proposed Chloride Homeostat

Net accumulation of Cl^– by intact barley plants was virtuallyeliminated in roots and reduced by 40% in shoots when externalmedia (0.5 mol m^–3 CaSO₄ plus 0–5 mol m^–3KCI) were supplemented with 0.25 mol m^– Ca(NO₃)₂. Plasmalemma³⁶Cl^– influx (_oc) was shown to be insensitive to externalNO₃^- in plants which had previously been grown in solutionslacking ^–3, but _oc became sensitive to NO₃^-after a lagperiod of 3–6 h. Kinetic analyses revealed that the inhibitionof 36C1^– influx by external NO₃^- was complex. At 0.25mol m^–3 NO₃^- the V_max for Cl^– influx was reducedby greater than 50%, with insignificant effects upon K_m. At0.5 mol m^–3 NO₃^- there was no further effect upon V_maxbut K_m for influx increased from 38±5 mmol m^–3to 116±26 mmol m^–3. By contrast, Cl^– effluxwas found to be insensitive to external NO₃^-. A model for theregulation of Cl^– influx is proposed which involves bothnegative feedback effects from vacuolar NO₃^- +Cl^–) concentrationand (external) NO₃^- inhibition of Cl^– influx at the plasmalemma.These combined effects serve to discriminate against Cl^–accumulation, favouring NO₃^- accumulation, when the latter ionis available. Such observations are inconsistent with recentproposals for the existence of bona fide homeostats for chlorideaccumulation in higher plants. Key words: Nitrate inhibition, Chloride influx, Barley     

Ion Transport in Suaeda maritima: Its Relation to Growth and Implications for the Pathway of Radial Transport of Ions across the Root

The ion relations of the halophytc Suaeda maritima are described.When plants grew in 340 mol m^–3 sodium chloride (—1•76MPa) leaf solute potentials decreased, and were sustained around—2•5 MPa Inorganic ion concentration (mostly of sodiumchloride) accounted for this. Comparable shoot ion concentrationsof potassium, nitrate and sulphate occurred when plants grewon different salinity types characterized by these ions. Netsodium transport and shoot sodium concentration increased dramaticallywith increases in external sodium chloride concentration upto 85 mol m^–3; thereafter, further increases in externalsodium chloride concentration had relatively little effect uponeither shoot sodium concentration or upon net transport of sodiumto the shoot. The net transport of sodium plus potassium onlydoubled when the external concentration of sodium plus potassiumincreased from 24 to 687 mol m^–3 Shoot ion concentrationswere remarkably constant with time, external concentration andsalinity type. The membrane flux rates and symplasmic ion concentrations neededto sustain the observed net transport of sodium (of some 10mmol g^–1 dry wt. of roots d^–1) are calculated fromanatomical and stereological data for the root system of thisspecies. The minimum net sodium chloride flux to load the symplasmwould be 260 nmol m^–2s^–1 if the whole cortical andepidermal plasmalemmal surface area were used uniformly, butthe flux rate required would be 3000 nmol m^–2s^–1if uptake took place only at the root surface. A flux rate ofat least 1000 nmol m^–2s^–1 is needed between symplasmand xylem. The symplasmic concentration of NaCl would be atleast 80 mol m^–3. It is argued (1), that both symplasmicand xylem loading are likely to be passive processes mediatedby ion channels rather than active carriers, (2), that net iontransport at 340 mol m^–3 sodium chloride is close to themaximum which is physiologically sustainable and (3), that growthof this halophyte is limited by NaCl supply from the root. Key words: Suaeda maritima, halophyte, salinity, roots, radial ion transport     

Salt Tolerance in the Triticeae: Leymus sabulosus

Elymus dahuhcus, Leymus giganteus, L. angustus, L. sabulosusand, to a lesser extent, L. triticoides, were found to tolerate200 mol m^–3 NaCl in solution culture. Elymus dahuricusdiffered from the Leymus species in its ion-uptake characteristics,showing a greater uptake of Cl and Na and a greater loss ofK from the shoots. In a more detailed experiment on Leymus sabulosusit was found that transpiration rates altered rapidly in responseto changes in external salinity whereas the accumulation ofNa and Cl in the leaves exhibited a lag of several days. Insalt stressed L. sabulosus Cl partially replaced the high levelsof nitrate found in the leaves of control plants. Glycinebetainelevels increased in the leaves from 8.0 mol m^–3 plantsap in the controls to 28 mol m^–3 plant sap at 250 molm^–3 NaCl. Key words: Salt stress, Transpiration, Solute accumulation, Leymus     

Isolation and Characterization of Sodium Chloride-Resistant Callus Culture of Vigna radiata (L.) Wilczek var. radiata

Callus cultures were initiated from seedling root segments ofmungbean (Vigna radiata (L.) Wilczek var. radiata) cv. K 851on modified PC-L2 basal medium. Growing cells were exposed toincreasing concentrations of NaCl in the medium. A concentrationof 300 mol m^–3 NaCl proved completely inhibitory to growthof the calli. On incubation for 25 d, cells which could toleratethis concentration of NaCl grew to form cell clones. Selectedclones were characterized with regard to their growth behaviour,K⁺, Na⁺ and free proline content when grown under stress aswell as on normal media and were compared with the normal sensitivecallus. The selected callus was capable of growing on mediumcontaining NaCl at the inhibitory concentration. The K⁺ contentof the selected callus was lower in the case of the NaCl mediumthan for the normal medium. However, the selected clones maintainedhigher K⁺ and Na⁺ levels, with increased salinization comparedwith the wild-type cells. Salt-selected cells accumulated higherlevels of free proline under NaCl stress compared to wild-typecells. Under normal conditions, however, the amounts of freeproline in selected and non-selected calli were comparable. Key words: Vigna radiata, callus culture, NaCl stress