An inland and a coastal population of the Mediterranean xero-halophyte species Atriplex halimus L. differ in their ability to accumulate proline and glycinebetaine in response to salinity and water stress

Soil salinity and drought compromise water uptake and lead toosmotic adjustment in xero-halophyte plant species. These importantenvironmental constraints may also have specific effects onplant physiology. Stress-induced accumulation of osmocompatiblesolutes was analysed in two Tunisian populations of the Mediteraneanshrub Atriplex halimus L.—plants originating from a salt-affectedcoastal site (Monastir) or from a non-saline semi-arid area(Sbikha)—were exposed to nutrient solution containingeither low (40 mM) or high (160 mM) doses of NaCl or 15% polyethyleneglycol. The low NaCl dose stimulated plant growth in both populations.Plants from Monastir were more resistant to high salinity andexhibited a greater ability to produce glycinebetaine in responseto salt stress. Conversely, plants from Sbikha were more resistantto water stress and displayed a higher rate of proline accumulation.Proline accumulated as early as 24 h after stress impositionand such accumulation was reversible. By contrast, glycinebetaineconcentration culminated after 10 d of stress and did not decreaseafter the stress relief. The highest salt resistance of Monastirplants was not due to a lower rate of Na⁺ absorption; plantsfrom this population exhibited a higher stomatal conductanceand a prodigal water-use strategy leading to lower water-useefficiency than plants from Sbikha. Exogenous application ofproline (1 mM) improved the level of drought resistance in Monastirplants through a decrease in oxidative stress quantified bythe malondialdehyde concentration, while the exogenous applicationof glycinebetaine improved the salinity resistance of Sbikhaplants through a positive effect on photosystem II efficiency. Key words: Atriplex halimus, glycinebetaine, halophyte, NaCl, osmotic adjustment, proline, salinity, water stress     

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 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     

Free Proline and Prolamin Protein in the Grain of Three Barley Varieties Subjected to a Gradient of Water Supply

Three barley varieties (Atem, Arabic Abiad and Beecher) weregrown on a line source sprinkler to establish a gradient ofwater supply from rain-fed (218 mm) to fully irrigated (330mm). Developing ‘seeds’ were analysed for free grainproline at three stages up to maturity. At the milk stage allthree varieties showed a strong inverse correlation (r>0–95)between free proline and irrigation treatment. A pronouncedinter-varietal difference was evident with the relatively drought-intolerantAtem having 213 nmol seed^–1 free proline when rain-fedas compared with Arabic Abiad or Beecher which had about 120nmol seed^–1 free proline at this stage. By maturity thiscorrelation was lost in all varieties, with most of the freeproline being incorporated into protein. Prolamin protein production was not impaired by drought in anyof the varieties, when measured on a per seed basis. There wassome indication that it may even rise in concentration in severelydrought-stressed plants. The results are discussed in relation to the decline in finalgrain yield with increased water deficit. Each of the threevarieties tested showed different yield responses along theirrigation gradient. These may reflect the physiological tolerancesto drought of each variety. At the milk stage the measurementof free ‘grain’ proline as a diagnostic for droughtstress tolerance may be of some value. Key words: Drought stress, seed physiology, proline     

Ecotypic Variation in the Osmotic Responses of Enteromorpha intestinalis (L.) Link.

Young, A. J., Collins, J. C. and Russell, G. 1987. Ecotypicvariation in the osmotic responses of Enteromorpha intestinalis(L.) Link.—J. exp. Bot. 38: 1309–1324. The physiological basis for salt tolerance has been studiedin the euryhaline marine alga Enteromorpha intestinalis. Adaptationto dilute and concentrated seawaters has been investigated inthree separate populations of this alga: marine, rock pool andestuarine. Internal K⁺, Na⁺ and Cl^– levels have been determined usingtracer efflux analyses. K⁺ has been shown to be the major osmoticsolute within this alga. Cellular levels of Cl^– and, inparticular, Na⁺ are low although levels in the cell wall arehigh. Levels of these ions varied considerably between the separateplants; K⁺ levels within marine plants of E. intestinalis aretwo to four times those found in the other populations. Thetertiary sulphonium compound ß-dimethylsulphonio-propionateis maintained at relatively high levels, although it remainsfairly insensitive to change in the external salinity. Changes in the tissue water content and cell volume are large,particularly within the estuarine plants. The thin cell wallsof these plants allow large changes in volume in the diluteconditions experienced in an estuary, while low turgor preventscell rupture. Thicker cell walls and small cells of the marineand rock pool plants assist in tolerating high and low externalosmotic potential—the estuarine plants respond poorlyto concentrated seawater. Key words: Enteromorpha, osmoregulation, ecotypes     

Occurrence of Inducible Crassulacean Acid Metabolism in Leaves of Talimum triangulare (Portulacaceae)

In this paper we report for the first time the occurrence ofan inducible weak CAM in leaves of Talinwn triangulare (Jacq.)Willd. This plant is a terrestrial perennial deciduous herbwith woody stems and succulent leaves which grows under fullexposure and in the shade in northern Venezuela. Plants grownin a greenhouse (‘sun’ plants) and a growth cabinet(‘shade’ plants) with daily irrigation showed CO₂uptake only during the daytime (maximum rate, 4?0 µmolm^–2 s^–1) and a small acid accumulation during thenight (6?0 µmol H⁺g^–1 FW). Twenty-four hours aftercessation of irrigation, no CO₂ exchange was observed duringpart of the night. Dark fixation reached a maximum (1?0 µmolCO₂ m^–2 s^–1, 100 µmol H⁺ g^–1 FW) onday 9 of drought. By day 30 almost no gas exchange was observed,while acid accumulation was still 10 µmol H⁺ g^–1FW. Rewatering reverted the pattern of CO₂ exchange to thatof a C₃ plant within 24 h. Daytime and night-time phosphoenolpyruvatecarboxylase activity increased up to 100% (shade) and 62% (sun)of control values after 10 and 15 d of drought, respectively.Light compensation point and saturating irradiance were similarin well-watered sun and shade plants, values being characteristicof sun plants. CAM seems to be important for the tolerance ofplants of this species to moderately prolonged (up to 2 months)periods of drought in conditions of full exposure as well asshade, and also for regaining high photosynthetic rates shortlyafter irrigation. Key words: Talinum triwigulare, inducible CAM, PEP-C activity, recycling     

Salt Tolerance in the Triticeae: Growth and Solute Accumulation in Leaves of Thinopyrum bessarabicum

Gorham, J., McDonnell, E., Budrewicz, E. and Wyn Jones, R. G.1985. Salt tolerance in the Triticeae: growth and solute accumulationin leaves of Thinopyrum bessarabicum.—J. exp. Bot. 36:1021–1031. The diploid wheatgrass Thinopyrum bessarabicum was found towithstand prolonged exposure to 350 mol m^–3 NaCl in hydroponicculture. During the gradual addition of salt to the externalmedium, osmotic adjustment was rapidly achieved by the accumulationof Na and Cl. Following osmotic adjustment constant leaf Naand Cl concentrations were maintained, and K was retained ata high level. Thinopyrum bessarabicum may be described as anosmoconformer, adjusting its internal osmotic pressure to 400–500mOsmol kg^–1 above that of the external medium in hydroponicculture. Both slower shoot initiation and reduced leaf lengthcontributed to the reduced growth rates at higher salinities.Leaf width was not affected. Increasing salinity resulted inincreases in leaf concentrations of phosphate, glycinebetaine,sucrose and proline, and in decreases in the concentrationsof nitrate, sulphate, magnesium, calcium, total amino acidsand organic acids. Thinopyrum bessarabicum exhibits salt tolerancecharacters which may be useful in wheat breeding. Key words: Salt stress, solute accumulation, osmotic adjustment, Thinopyrum     

Overexpression of wheat Na+/H+ antiporter TNHX1 and H+-pyrophosphatase TVP1 improve salt- and drought-stress tolerance in Arabidopsis thaliana plants

Transgenic Arabidopsis plants overexpressing the wheat vacuolarNa⁺/H⁺ antiporter TNHX1 and H⁺-PPase TVP1 are much more resistantto high concentrations of NaCl and to water deprivation thanthe wild-type strains. These transgenic plants grow well inthe presence of 200 mM NaCl and also under a water-deprivationregime, while wild-type plants exhibit chlorosis and growthinhibition. Leaf area decreased much more in wild-type thanin transgenic plants subjected to salt or drought stress. Theleaf water potential was less negative for wild-type than fortransgenic plants. This could be due to an enhanced osmoticadjustment in the transgenic plants. Moreover, these transgenicplants accumulate more Na⁺ and K⁺ in their leaf tissue thanthe wild-type plants. The toxic effect of Na⁺ accumulation inthe cytosol is reduced by its sequestration into the vacuole.The rate of water loss under drought or salt stress was higherin wild-type than transgenic plants. Increased vacuolar soluteaccumulation and water retention could confer the phenotypeof salt and drought tolerance of the transgenic plants. Overexpressionof the isolated genes from wheat in Arabidopsis thaliana plantsis worthwhile to elucidate the contribution of these proteinsto the tolerance mechanism to salt and drought. Adopting a similarstrategy could be one way of developing transgenic staple cropswith improved tolerance to these important abiotic stresses. Key words: H⁺-pyrophosphatase, Na⁺/H⁺ antiporter, salt and drought tolerance, sodium sequestration, transgenic Arabidopsis plants     

Properties of Phosphoenolpyruvate Carboxylase and Carbohydrate Accumulation in the C3-CAM Intermediate Sedum telephium L. Grown Under Different Light and Watering Regimes

A comparison of the activity and properties of the enzyme phosphoenolpyruvatecarboxylase (PEPC) was made for plants of Sedum telephium L.grown under low (70 µmol m^–2 s^–1) or high(500µmol m^–2 s^–1) PPFD and subjected to varyingdegrees of water stress. Under well-watered conditions onlyplants grown under high PPFD accumulated titratable acidityovernight and the extractable activity of PEPC was almost 2-foldhigher in these plants than in plants grown under low PPFD.Increasing drought stress resulted in a substantial increasein the activity of PEPC extracted both during the light anddark periods and a decrease in the sensitivity to inhibitionby malic acid. The magnitude of these changes was determinedby the severity and duration of drought and by light intensity.A comparison of the kinetic properties of PEPC from severelydroughted plants revealed that plants droughted under high PPFDhad a lower K_m for PEP than plants under low PPFD. Additionof 2·0 mol m^–3 malate resulted in an increase inthe K_m for PEP, with plants draughted under low PPFD havinga significantly higher K_m in the presence of malic acid comparedto those under high _PPFD. Response to the activator glc-6-P,which lowered the K_m for PEP, also varied between plants grownunder the two light regimes. Under well-watered conditions PEPCextracted from plants under high PPFD was more sensitive toactivation by glc-6-P than those under low PPFD. After the severedrought treatment, however, the K_m for PEP in the presence ofglc-6-P was similar for enzyme extracted from plants grown underboth light regimes. Soluble sugars and starch were depletedovernight and were both possible sources of substrate for PEPC.With increasing drought, however, the depletion of starch relativeto soluble sugars increased under both light regimes. The propertiesof PEPC and the characteristics of carbohydrate accumulation/depletionare discussed in relation to the regulation of CAM in S. telephiumgrown under different light and watering regimes. Key words: PEP carboxylase, CAM, carbohydrates, Sedum telephium     

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     

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     

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     

Influence of Proline and Glycinebetaine on Salt Tolerance of Cultured Barley Embryos

Lone, M. I., Kueh, J. S. H., Wyn Jones, R. G. and Bright, S.W. J. 1987. Influence of proline and glycinebetaine on salttolerance of cultured barley embryos.—J. exp. Bot. 38:479–490. The addition of exogenous proline and glycinebetaine to culturedbarley (Hordeum vulgare L. cv. Maris Mink) embryos increasedshoot elongation under saline conditions. Inhibition of shootelongation by NaCl was relieved by proline when plantlets weregrown in deep crystallizing dishes but not in Petri dishes whereshoots come into direct contact with the medium. The effectof proline could be related to a decrease in shoot Cl^–and Na⁺ accumulation which was only observed in plantlets grownin crystallizing dishes. Proline but not betaine uptake intocultured plantlets was stimulated by NaCl while each organicsolute inhibited the endogenous synthesis of the other soluteunder salt stress. Comparison of the effects of exogenously supplied proline withenhanced endogenous proline accumulation in the mutant lineR5201 suggested that the increased proline accumulation in themutant is an order of magnitude too low to have a significantphysiological effect. The implications of the effect of prolineon ion transport, discrimination and accumulation are discussed. Key words: Salt tolerance, proline, ion transport, barley embryo culture     

Effect of Salt Stress on Viability, Germination and Endogenous Levels of Some Metabolites and Ions in Maize (Zea mays L.) Pollen

Maize plants, subjected to 0, 80, 120 and 160 meq l^–1salinity using NaCl, showed adverse effects on viability, germinationand tube growth of pollen, besides enhancing the bursting ofpollen. The endogenous levels of various metabolites in pollenwere also affected. Pollen grains from salinized plants hadmore soluble carbohydrates, free amino acids, especially proline,phenols and DNA and less starch, protein and RNA compared tothe non-saline controls. Salinity also resulted in the accumulationof ions such as Na⁺, K⁺ and Cl^– while it caused a reductionin the boron content of pollen. These metabolic disturbancespossibly lead to decreased viability, germination and tube growthof pollen thereby resulting into a reduction in reproductivecapacity of the plants under salt stress. Zea mays L., maize, pollen, viability, germination, salt stress     

In Vitro Embryo Culture and Induction of Multiple Shoots in Lychee (Litchi chinensis Sonn.)

Immature embryos of different sizes and ages from commercialvarieties of lychee (Litchi chinensis Sonn.) were cultured ina range of different media. Embryos as small as 3 mm could becultured using in vitro techniques and subsequently grown intoplants. MS solid medium with 2% sucrose supplemented with 150ml l^–1 coconut water was most effective in stimulatingthe germination of immature lychee embryos. Embryos of lycheewere treated to induce adventitious buds from embryonic shootsas a means of achieving multiplication. The different varietiesexhibited differences in response, with Bengal embryonic shootsproducing 15 adventitious buds after pretreatment with 100 mgl^–1 BAP for 3 h. Root formation was achieved in 65% ofadventitious shoots using MS medium supplemented with 0.5 mgl^–1 NAA and activated charcoal. These plants were successfullydeflasked and grown on in the glasshouse. This technique providesof means of producing some multiple shoots from lychee embryosand has value for multiplication in a breeding program wherea method of micropropagation is unavailable. Litchi chinensis Sonn., lychee, embryo culture, multiple shoots, in vitro     

Kinetics of Maize Leaf Elongation: II. RESPONSES OF A NA-EXCLUDING CULTIVAR AND A NA-INCLUDING CULTIVAR TO VARYING NA/CA SALINITIES

Salinity causes physiological and morphological changes in plantsand calcium can mitigate many of these effects. In this study,the effects of salinity (75 mol m^–3 NaCl) with or withoutsupplemental Ca (10 mol m^–3) on the kinetics of maize(Zea mays L.) leaf elongation were examined using Linear VariableDifferential Transformers (LVDTs). Short-term growth responsesof two cultivars (Dekalb hybrid XL75 and Pioneer hybrid 3906)differing in salt tolerance were compared. Salinity caused animmediate reduction in the leaf elongation rate (LER). Within2 h, elongation rates had increased and reached new steady rates.Significant differences between salinity treatments with highand low Ca could be detected within the first 2 h after impositionof salinity for Dekalb hybrid XL75, but not for Pioneer hybrid3906. After 24 h, distinct differences for both cultivars weredetected. Dekalb hybrid XL75, a Na-includer, was more salt-sensitiveand responsive to supplemental Ca (10 mol m^–3) than Pioneerhybrid 3906, a Na-excluder. Turgor was not reduced 24 h aftersalinization because there was complete osmotic adjustment inthe elongation zone of the leaves. Analysis of the growth parameterslimiting LER indicated that the yield threshold (Y) was increasedfor salt-stressed plants. In addition, both the cell wall extensibilityand hydraulic conductance were reduced 24 h after salinization.Supplemental Ca increased LER of salt-stressed plants by increasinghydraulic conductance. The differences in LER of the two cultivarsunder saline conditions was attributed to differences in theincrease of Y caused by salinity. Key words: Calcium, growth, salinity, sodium, Zea mays L.     

Ionic and Water Relations Responses of Two Populations of a Non-Halophyte to Salinity

Bowman, W. D. 1988. Ionic and water relations responses of twopopulations of a non-halophyte to salinity.–J. exp. Bot39: 97–105 Salinity-induced changes in the ionic and water relations inplants from two naturally-occurring populations of the C₄ non-halophyteAndropogon glomeratus were measured to detect differences inthe capacity to adjust osmotic potentials and in ion contentpotentially responsible for the osmotic adjustment Pressure-volumecurves and leaf ion content were measured in plants from twopopulations, salt marsh and inland, after long-term exposureto three salinity levels. Osmotic adjustment and decreases inthe bulk tissue elasticity occurred to a similar extent in bothpopulations with increasing salinity. Cl^– concentrationsincreased with increasing salinity in both populations, whereasleaf Na⁺ concentrations increased only in the inland population,but were higher at all salinities in the marsh population. K⁺concentrations changed little with increasing salinity. Prolineconcentrations increased only at the highest salinity level,and did not difler significantly between populations. Theseresults suggest a role for Na⁺ uptake and regulation in osmoticadjustment in the marsh population, contrasting with studiesof salt tolerance in other nonhalophytic grasses     

Response of Melanthera biflora to Salinity and Water Stress

Melanthera biflora (Asteraceae) is a moderately salt-tolerantplant from the Indo-Pacific region. In laboratory studies itsgrowth was inhibited by salt above 50 mol m^–3, but itwas able to survive salinities approaching that of seawater,namely 400 mol m^–3. Shoot potassium concentrations weremaintained over a range of salinities up to 400 mol m^–3,while sodium and chloride accumulation followed closely theincrease in external osmotic pressure. In contrast, the increasein osmotic pressure of the leaf sap of Melanthera biflora, subjectedto water stress, was due mainly to a decrease in the ratio offresh weight/dry weight. 3-dimethylsulphoniopropionate (3-DMSP)and glycinebetaine were identified by fast atom bombardmentmass and ¹H -NMR spectroscopy, with 3-DMSP being the main oniumcompound and glycinebetaine absent in some accessions. Onium(quaternary ammonium and/or tertiary sulphonium) compounds andproline increased during salt and water stress due mainly toa decrease in the fresh weight/dry weight ratio of tissue, althoughpart of the increase in salt-stressed tissue was due to an increasein the accumulation of the onium compound. This salt-inducedincrease in 3-DMSP was inhibited in conditions of low sulphursupply and there was no compensatory increase in proline. Key words: Melanthera biflora, Asteraceae, salinity, glycinebetaine, 3-dimethylsulphonioproprionate     

Exogenous trehalose affects morphogenesis in vitro of jojoba

Trehalose is a stress protecting and reserve carbohydrate in a variety of organisms. The effect of trehalose on micropropagation of jojoba [Simmondsia chinensis (Link) Schneider] was investigated using a modified Murashige–Skoog as the basal medium (BM). Proliferation rate was significantly higher in explants grown on BM + 1 mM trehalose compared to that in the phytohormone control medium. In multiplication stage, shoot proliferation rate of 4.8 was achieved in BM with 4.44 μM BA and 1 mM trehalose. The rooting induction with 14.7 μM IBA had a significant effect on root regeneration; the highest rooting percentage (46.6%) was obtained with 7 days of induction. The incorporation of trehalose to the IBA-rhizogenesis media decreased basal callus but with trehalose alone, root development was scant. In vitro plants showed anatomical features typical for the acclimatization stage.