Selection and characterization of an L-thiazolidine-4-carboxylic acid resistant callus culture of Vigna radiata (L.) Wilczek var. radiata

Callus cultures were established from seedling root tips of mungbean (Vigna radiata (L.) Wilczek var. radiata) cv. K 851. The growing calli were exposed to increasing concentrations of thioproline — an analog of proline, in the medium. A concentration of 3.0 mM thioproline completely inhibited the growth of the cells. However, after 25 days incubation 5 cell clones were obtained which could grow on this concentration of thioproline. Out of them one vigorously growing cell clone was further characterized. This selected clone contained higher endogenous levels of free proline (5 fold) and K⁺ (1.5 fold) and exhibited elevated tolerance, not only to thioproline but also to exogenously applied NaCl in the growth medium, as compared to the normal sensitive callus cells. Higher endogenous levels of free proline and K⁺ appear to impart dual resistance to thioproline and NaCl to the selected cell strain.     

Selection and characterization of mannitol-tolerant callus lines of Vigna radiata (L.) Wilczek

An osmotically (mannitol) tolerant callus line of Vigna radiata (L.) Wilczek has been isolated from callus cultures grown on modified PC-L2 medium supplemented with increasing concentrations of mannitol. The tolerance was stable and retained after growth in the absence of mannitol selection for 2 months. The growth of the tolerant line, in the presence of mannitol (540 mol m^-3) was comparable to that of a sensitive callus line growing in the absence of mannitol. This line not only grew well on media containing up to 720 mol m^-3 mannitol, but also required 450 mol m^-3 mannitol for its optimal growth. Osmotically tolerant callus also showed increased tolerance to NaCl (0–250 mol m^-3) stress as compared to sensitive callus. Accumulation of Na⁺ was lower, and the level of K⁺ was more stable in osmotically tolerant than in sensitive calli, when both were exposed to salt. The free proline content of both tolerant and sensitive calli increased on media supplemented with mannitol or NaCl. However, the proline content of sensitive callus was higher than in tolerant callus in the presence of same concentrations of mannitol or NaCl.Abbreviations NAA -naphthaleneacetic acid - 2,4-d 2,4-dichlorophenoxyacetic acid - BAP 6-benzylaminopurine     

Effect of Sudden Salt Stress on Ion Fluxes in Intact Wheat Suspension Cells

Although salinity is one of the major problems limiting agriculturalproduction around the world, the underlying mechanisms of highNaCl perception and tolerance are still poorly understood. Theeffects of different bathing solutions and fusicoccin (FC),a known activator of plasma membrane ATPase, on plasma membranepotential (E_m) and net fluxes of Na⁺, K⁺and H⁺were studied inwheat suspension cells (Triticum aestivum) in response to differentNaCl treatments. E_mof cells in Murashige and Skoog (MS) mediumwas less negative than in cells exposed to a medium containing10 mM KCl + 0.1 m M CaCl₂(KSM) and to a basic salt medium (BSM),containing 1 m M KCl and 0.1 m M CaCl₂. Multiphasic Na⁺accumulationin cells was observed, peaking at 13 min after addition of 120m M NaCl to MS medium. This time scale was in good agreementwith net Na⁺flux changes measured non-invasively by moving ion-selectivemicroelectrodes (the MIFE system). When 120 m M NaCl was addedto all media studied, a quick rise of Na⁺influx was reversedwithin the first 20 min. In both 120 and 20 m M NaCl treatmentsin MS medium, net Na⁺efflux was observed, indicating that activeNa⁺transporters function in the plant cell response to saltstress. Lower external K⁺concentrations (KSM and BSM) and FCpre-treatment caused shifts in Na⁺fluxes towards net influxat 120 m M NaCl stress. Copyright 2000 Annals of Botany Company Sodium, potassium, proton, membrane potential, fusicoccin, salt stress, wheat, Triticum aestivum     

Selection of callus cultures of sugarcane (Saccharum sp.) tolerant to NaCl and their response to salt stress

Stable callus cultures tolerant to NaCl (68 mM) were developed from salt-sensitive sugarcane cultivar CP65-357 by in vitro selection process. The accumulation of both inorganic (Na⁺, Cl⁻ and K⁺) and organic (proline and soluble sugars) solutes was determined in selected and non-selected calli after a NaCl shock in order to evaluate their implication in in vitro salt tolerance of the selected lines. Both salt-tolerant and non-selected calli showed similar relative fresh weight growth in the absence of NaCl. No growth reduction was observed in salt-tolerant calli while a significant reduction about 32% was observed in nonselected ones when both were cultivated on 68 mM NaCl. Accumulation of Na⁺ was similar in both salt-tolerant and non-selected calli in the presence of NaCl. Accumulation of Cl⁻ was lower in NaCl-tolerant than in non-selected calli while proline and soluble sugars were more accumulated in salt-tolerant than in non-selected calli when both were exposed to salt. K⁺ level decreased more severely in non-selected calli than in NaCl-tolerant ones after NaCl shock. The results indicated that K⁺ and Cl⁻ may play a key role in in vitro salt-tolerance in sugarcance cell lines obtained by in vitro selection and that organic solutes could contribute mainly to counteract the negative water potential of the outside medium.     

Salt Tolerance in Cell Suspension Cultures of the Halophyte Kosteletzkya virginica

Tolerance to NaCl was studied in cell suspension cultures ofKosteletzkya virginica (L.) Presl. (Malvaceae), a dicotyledonoushalophyte that grows in tidal marshes of the eastern UnitedStates. Growth of salinized cultures was significantly inhibitedat high (255 mol m^–3 NaCl), but not at lower externalsalinities. Adjustment of cell suspensions to Nacl was rapid,with the duration of the normal growth cycle unaffected by salinity.Maximum biomass was attained when cultures were exposed to NaClduring early log growth. Patterns of inorganic ion accumulationreflected the utilization of both Na⁺ and K⁺ as osmotica, withNa⁺ content substantially increasing when cells were grown atan external salinity sufficient to reduce growth. K⁺ uptakeselectivity was high and Na⁺/K⁺ ratios were low in salt-treatedcultures even though K⁺ content was somewhat lower comparedto unsalinized cultures. Free proline and microsomal lipid contentincreased in salt-treated cell cultures. Key words: Kosteletzkya virginica, halophyte, salt tolerance, cell suspension culture     

Effects of Na2SO4, K2SO4 and KCl on Growth and Ion Uptake of Callus Cultures of Vaccinium corymbosum L. cv. Blue Crop

Non-selected and Na₂SO-, K₂SO₄- or KCl-selected callus culturesof Vaccinium corymbosum L. cv. Blue Crop were grown on mediasupplemented with 0, 25 and 50 mM Na₂SO₄ (non-selected and Na₂SO(-selectedonly), 0, 25 and 50mMK₂SO₄ (non-selected and K₂SO₄-selectedonly) or 0, 50 and 100 mM KCl (non-selected and KCl-selectedonly). On all media, growth of selected callus (on a fresh-weightor dry-weight basis) was greater than that of non-selected callus,and selected callus grew optimally on the level and type ofsalt on which it was selected. Selected callus was friable andmaintained a higher f. wt:d. wt ratio. Tissue water potentialin selected callus was more negative than in non-selected callus. Flame photometry and chloridometry showed Na⁺, K⁺ and Cl^–accumulated in callus to concentrations equal to or greaterthan the initial concentration in the medium. Turbidometry showedthat tissue SO₄^2- concentration was lower than the concentrationin the medium. In most cases selected callus accumulated moreNa⁺, K^sup, SO₄^2– or Cl^– than non-selected callus.Vacuolar ion concentration was measured by electronprobe X-raymicroanalysis, and on most media selected callus had highervacuolar ion concentrations than non-selected callus. SO₄^2–and Cl^– were accumulated in the vacuoles at concentrationshigher than the external medium, but vacuolar Na⁺ concentrationdid not reach external concentration on Na₂SO₄ and on potassiumsalts was maintained between 12 and 17 mM. Vacuolar K⁺ concentration(approx. 142–191 mM on no salt) decreased on Na₂SO₄ andincreased on K₂SO₄ and KCl. There was no precise correlation between total or specific ionaccumulation (Na⁺, K⁺, SO₄^2– and Cl^– and fresh-weightyield. Results suggest that selection results in adaptationin response to decreased water potential of the medium. Vaccinium corymbosum, blueberry, electronprobe X-ray microanalysis, callus, in vitro selection, salt tolerance, KCl, K₂SO₄, Na₂SO₄     

Growth, proline accumulation and ion content in sodium chloride-stressed callus of date palm

Summary Growth and physiological responses of date palm. Phoenix dactylifera L. cv. Barhee, callus to salinity stress were examined. Callus induced from shoot tips of offshoots was cultured on Murashige and Skoog medium supplemented with NaCl at concentrations ranging from 0 to 225 mM, in consective increments of 25 mM. Data obtained after 6 wk of exposure to salt have shown a significant increase in callus proliferation in response to 25 mM NaCl the lowest level tested, beyond which callus weight decreased. At 125 mM NaCl and higher, callus growth was nearly completely inhibited. Physiological studies on callus exposed to salt stress have shown an increase in proline accumulation in response to increased salinity. Proline accumulation was correlated to callus growth inhibition. Furthermore, increasing the concentration of NaCl in the culture medium generally resulted in a steady increase in Na⁺ and reduction in K⁺ concentrations. However, at 25 mM NaCl, the only level at which callus growth was significantly enhanced, an increase in K⁺ content was noted, in comparison to the NaCl free control. In response to increasing external NaCl level, the Na⁺/K⁺ ratio increased The Na⁺/K⁺ ratio was positively correlated to proline accumulation and hence callus growth inhibition. This study provides, an understanding of the response of date palm callus to salinity, which is important for future studies aimed at developing strategies for selecting and characterizing somaclonal variants tolerant to salt stress.     

Characteristic Changes in Relaxation Times of Water Protons in Vigna radiata Seedlings Exposed to Temperature Stress

Water protons in hypocotyl tissues from etiolated seedlingsof Vigna radiata that were exposed to temperature stress showedcharacteristic relaxation behaviors for ¹H-NMR. Cold stresstreatment (0C) caused gradual prolongation of NMR relaxationtimes (T₁). After exposure of tissues to cold stress for 24h, T₁ returned to the initial value as a result of subsequentincubation at normal temperature (20C). By contrast, heat stresstreatment (40C) induced a time-dependent decrease in T₁, whichdid not return completely to the initial value upon subsequentincubation at 20C after exposure to heat stress for 4 h. Weexamined changes in various physical factors that influencethe response of T₁ to temperature stress, namely, water contentand the concentrations of protein, diamagnetic (K⁺, Na⁺, Ca²⁺and Mg²⁺) and paramagnetic (Mn²⁺ and Fe²⁺) ions in the tissues.From the relationships between T₁ and these factors in vitro,we could not interpret the responses of T₁ to the temperaturestress only in terms of a change in water content. A synergisticeffect of an Mn²⁺ -protein complex and pH might be essentialfor the mechanism of changes in T₁ that are due to cold stress.The influence of heat stress on structural water in tissuesis discussed in terms of water-protein interactions. (Received December 28, 1992; Accepted May 6, 1993)     

Effects of salt stress in relation to osmotic adjustment on sugarcane (<Emphasis Type="Italic">Saccharum officinarum</Emphasis> L.) callus cultures

In vitro responses of embryogenic sugarcane (Saccharum officinarum L.; cv. CoC-671) calli stressed with different levels of NaCl (0.0, 42.8, 85.6, 128.3, 171.1, 213.9 or 256.7 mM) were studied. The results showed that a significant decrease in callus growth and cell viability occurred with ≥85.6 mM NaCl. Higher amounts of free proline and glycine betaine were accumulated in NaCl-stressed calli. Although the leached and retained Na⁺ contents increased, the retained K⁺ content decreased with increasing levels of NaCl. Such a mechanism implies that sugarcane can be considered as a Na⁺-excluder. The accumulation of salt ions and osmolytes could play an important role in osmotic adjustment in sugarcane cells under salt 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     

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     

Characterization of ATPases Associated with Various Cellular Membranes Isolated from Etiolated Hypocotyls of Vigna radiata (L.) Wilczek

Cellular membrane fractions, including endoplasmic reticum (ER),Golgi-enriched membrane, plasma membrane and tonoplasts, wereisolated from Vigna radiata seedlings. Each of these membranefractions was associated with specific ATPases which were highlydependent on Mg²⁺. ATPases of ER, Golgi-enriched membrane andplasma membrane were sensitive to vanadate but the tonoplastATPase was not. ATPases were mostly dependent on Cl¹, but aslight stimulation by K⁺ was observed in the case of ATPasesof Golgi-enriched membrane and plasma membrane. KNO₃ inhibitedtonoplast ATPase but stimulated the other ATPases. ER ATPasecan be distinguished from other ATPases by the following characteristics:specific inhibition by KNO₂ and Triton X-100, stimulation bylow concentrations of diethylstilbestrol and 4,4'-diisothiocyanostilbene-2,2'-disulfonicacid, and high sensitivity to heat. The ATPases showed typicalMichaelis-Menten kinetics and had K_m values of 0.5 to 0.6 ITIMMg²⁺-ATP for ER, Golgienriched-membrane and tonoplast ATPases,and 2.27 msi Mg²⁺-ATP for plasma membrane ATPase. ATPases ofGolgi-enriched membranes and plasma membranes had similar properties,but they were still distinguishable by the differences in theirK_m values and their responses to Triton X-100. Based on theseresults, it is postulated that each cellular membrane is associatedwith a specific ATPase in cells of V. radiata. ¹Contribution No. 3171 from the Institute of Low TemperatureScience. (Received April 22, 1988; Accepted September 28, 1988)     

The effect of NaCl on proline accumulation in potato seedlings and calli

The effects of salt stress were studied on the accumulation and metabolism of proline and its correlation with Na⁺ and K⁺ content in shoots and callus tissue of four potato cultivars, viz., Agria, Kennebec (relatively salt tolerant), Diamant and Ajax (relatively salt sensitive). Na⁺ and proline contents increased in all cultivars under salt stress. However, K⁺ and protein contents decreased in response to NaCl treatments. The activities of enzymes involved in proline metabolism, Δ¹-pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (ProDH) increased and decreased, respectively, in response to elevated NaCl concentrations. The changes of P5CS and ProDH activities in more salt sensitive cultivars (Diamant, Ajax) were more than those in the tolerant ones. Then the stimulation of synthesis in combination with a partially increase of protein proteolysis, a decrease in proline utilization and inhibition of oxidation resulted in high proline contents in seedlings and calli under salt stress. In callus tissue, reduced growth and cell size may be partially responsible for high proline accumulation in response to high NaCl levels. However, although the basic proline contents in the seedlings of more salt tolerant cultivars were higher than the sensitive ones, a clear relationship was not generally observed between accumulation of proline and salt tolerance in potato.     

Development of callus and suspension cultures of potato resistant to NaCl and mannitol and their response to stress

Callus and suspension cultures adapted to various concentrations of NaCl or mannitol were developed from the cultivated potato Solanum tuberosum cv. Desire. Growth of the calli was less inhibited by mannitol than by iso-osmotic concentrations of NaCl. Reduction of growth by both NaCl and mannitol was considerably lower in osmotically adapted calli than in non-adapted ones. Salt-adapted suspension cultures that grew in the medium to which they had been originally adapted had a shorter lag in growth as well as a shorter time required to achieve the maximum growth, as compared with non-adapted cells. Suspension cultures adapted to NaCl concentrations higher than 150 mM were obtained only after preadaptation to osmotic stress. Adaptation of these cells was found to be stable. Accumulation of Na⁺ was lower and level of K⁺ was more stable in osmotically adapted than in non-adapted calli, when both were exposed to salt. Potassium level in NaCl-adapted calli exposed to saline medium was lower than that in non-adapted calli in standard medium. The maximum of Cl^– and Na⁺ accumulation was reached at higher external salt concentration in salt-adapted than in non-adapted suspension cultures. In both callus and suspension cultures, Cl^– accumulated more than Na⁺. Potassium level decreased more in non-adapted than in NaCl-adapted suspension cultures. The decrease of osmotic potential in osmotically adapted calli exposed to mannitol and in salt-adapted calli and suspension cultures exposed to salt was correlated to the increase of the external concentration. Such a correlation was not found in osmotically adapted calli exposed to salt. Non-electrolytes were found to be the main contributors to the decrease is osmotic potential in both callus and suspension cultures.     

Effects of Some Amino Acid Analogues on the Uptake and Transport of K+ and Ca2+ in Wheat and Mung Bean Seedlings: I. CORTICAL CELL FLUXES AND TRANSPORT TO THE STELE IN EXCISED ROOT SEGMENTS, AS AFFECTED BY p-FLUOROPHENYLALANINE

Effluxes of K⁺ and Ca²⁺ from root segments of both wheat, Triticunaestivum L. cv. Capelle and mung bean, Vigna radiata (L.) Wilczek,were measured in the presence or absence of 20 mol m^–3para-fluorophenylalanine (p-FPA). The results were used to estimatethe compartment contents and transmembrane K⁺ and Ca²⁺ fluxesin root cortex cells. Using the Ussing-Teorell flux equationas the criterion, it was concluded that entry of K⁺ from theoutside solution to the cytoplasm, and from the cytoplasm tothe vacuole were active in both wheat and mung bean. Also, inboth species, Ca²⁺ entered the cytoplasm passively across theplasmalemma and was actively pumped back to the external solution.However, interpretation of the direction of active transportacross the tonoplast depends upon an assumption about Ca²⁺ activityin the cytoplasm. The only qualitative effect of p-FPA was to alter the drivingforce for K⁺ influx, across the plasmalemma in wheat, from anactive to a passive one. Quantitative effects of the analoguewere seen for K⁺ fluxes in both wheat and mung bean and forCa²⁺ fluxes in wheat. The p-FPA reduced transport of K⁺ in bothspecies, while transport of Ca²⁺ was unaffected. The implicationsof these results for the ‘two pump hypothesis’ arediscussed. Key words: Triticum aestivum, Vigna radiata, Two pump hypothesis     

Establishment of stable NaCl-resistant rice plant lines from anther culture: distribution pattern of K+/Na+ in callus and plant cells

 Soil salinity markedly suppresses the growth of rice (Oryza sativa L.). We established rice anther culture to select for rice callus lines adapted to NaCl stress and regenerated plant progenies resistant to a NaCl stress of E.C. 16–18 mS. When exposed to NaCl, NaCl-adapted rice calli lost K⁺ and accumulated little Na⁺. Conversely, plant cells lost relatively little K⁺ and accumulated Na⁺. It is plausible that, NaCl-resistant mechanisms are different at callus and plant level. The stable NaCl-resistant lines produced have potential use in elucidating the molecular mechanisms behind NaCl resistance in rice and in rice breeding. Received: 27 February 1997 / Accepted: 4 April 1997     

Comparison between a Stable NaCl-Selected Nicotiana Cell Line and the Wild Type : K, Na, and Proline Pools as a Function of Salinity

An NaCl-resistant line has been developed from suspension-cultured tobacco cells (Nicotiana tabacum/gossii) by stepwise increases in the NaCl concentration in the medium. Resistance showed stability through at least 24 generations in the absence of added NaCl.

Above an external NaCl concentration of 35 millimolar, proline concentration in the selected cells rose steeply with external NaCl, particularly so above 100 millimolar NaCl. Proline accumulation in the wild type was far slighter. Selected cells which had been grown for 24 generations in the absence of added NaCl accumulated proline strongly on re-exposure to NaCl medium, indicating stability of this character. Proline accumulation was fully reversible with a half-time of about 6 hours. When selected cells were transferred sequentially to lower and lower NaCl concentrations, their proline content fell to the level corresponding to the new NaCl concentration. The NaCl-selected cells responded to water stress (i.e. added mannitol) by accumulating markedly more proline than did the wild type.

The addition of Ca²⁺ to the growing and rinsing media minimized Na⁺ and K⁺ binding in the Donnan free space of cell walls and thus allowed assessment of intracellular Na⁺ and K⁺. In both cell types, internal Na⁺ content rose steadily as a function of external NaCl concentration. In the course of 7 days in NaCl media, the wild type cells lost a considerable part of their K⁺ content, the extent of the loss increasing with rise in external NaCl concentration. The selected cells, by contrast, lost no K⁺ at external NaCl concentrations below 50 millimolar external NaCl, and at higher concentrations lost less than the wild type.

     

Abnormal Stomatal Behaviour and Ion Imbalance in Capsicum scabrous diminutive

An attempt was made to explain the abnormal behaviour of stomatain Capsicum scabrous diminutive, a wilty pepper mutant. Stomatalmovement in the pepper plant was found to be associated withchanges in the ion content of the guard cells. These changeswere smaller in the mutant than in the normal plants. In addition,total ion content was higher in the mutant under both controland NaCl treatments. Na⁺ substituted K⁺ in its function in stomatalmovement under high salinity. This phenomenon was more pronouncedin the mutant plants. Analysis of whole root systems and leavesof plants grown on solutions of high NaCl or KCl concentrationconfirmed that the regulation of K⁺ and Na⁺ uptake mechanismswas not functioning properly in the mutant. Evidence was presentedthat the difference in K⁺ staining between mutant and normalepidermal cells is an artefact resulting from the differencein leaf anatomy.     

等渗盐分、干旱胁迫下冬小麦叶片部分渗透调节物质的动态变化

分别以PEG-6000、NaCl模拟干旱胁迫及盐胁迫,采用水培方法研究了抗旱耐盐冬小麦沧-6001在干旱胁迫、盐胁迫条件下叶片可溶性糖、脯氨酸和可溶性蛋白质含量的动态变化以及Na⁺、K⁺在地上部和根系的分布。结果表明可溶性糖和可溶性蛋白变化趋势相似,其含量随干旱胁迫或盐胁迫时间延长而增加,但在胁迫处理后期下降,并且随胁迫强度增加,二者出现下降时间提前;脯氨酸在干旱胁迫条件下快速积累达到峰值后下降但在胁迫处理后期再次增加,在盐胁迫条件下,随胁迫强度的增加和胁迫时间的延长而增加;Na⁺在干旱胁迫下随胁迫程度增加而下降,盐胁迫条件下随胁迫程度的增加而增加,K⁺在干旱胁迫或盐胁迫下均随胁迫程度的增加而下降,且在根系中下降的速度大于地上部。     

In vitro selection of salinity tolerant variants from triploid bermudagrass (<Emphasis Type="Italic">Cynodon transvaalensis</Emphasis> × <Emphasis Type="Italic">C. dactylon</Emphasis>) and their physiological responses to salt and drought stress

A protocol was established for in vitro selection of salinity tolerant somaclonal variations from suspension cultured calli of triploid bermudagrass cv. TifEagle. To induce somaclonal variations the calli were subcultured for 18 months and were then subject to three-round selections for salt-tolerant calli by placing on solid medium containing 0.3 M NaCl for 10 days followed by a recovery for 2 weeks. The surviving calli were regenerated on regeneration medium containing 0.1 M NaCl. Three somaclonal variant lines (2, 71, and 77) were obtained and analyzed. The selected somaclonal lines showed higher relative growth and less injury than TifEagle under salt stress, indicating that they increased salt tolerance. In addition, they had higher relative water content and lower electrolyte leakage than TifEagle after withholding irrigation, indicating that they also increased drought tolerance. The three somaclonal variant lines had higher proline content than TifEagle under normal growth condition. The line 71 had a higher K⁺/Na⁺ ratio, whereas the lines 2 and 77 had higher CAT activity under control and salt stress conditions, indicating that different mechanisms for salt tolerance might exist in these three lines.