Increasing NaCl and CaCl<Subscript>2</Subscript> concentrations in the growth medium of quince leaves: I. Effects on somatic embryo and root regeneration

Summary The effects of increasing concentrations of NaCl and CaCl₂ on quince (Cydonia oblonga Mill. BA 29 clone) somatic embryogenesis and adventitious root regeneration were investigated. Leaves collected from in vitro-grown shoots were used as explants and induced for 2d in liquid Murashige and Skoog medium containing 11.3 μM 2,4-dichlorophenoxyacetic acid. Explants were then cultured on semisolid Murashige and Skoog medium enriched with 4.7 μM kinetin and 0.5 μM naphthaleneacetic acid under red light for 25 d and under white light for another 25 d. Two experiments were performed: in the first, NaCl was used at 0,25, 50, 100, and 200 mM in factorial combination with CaCl₂ at 3, 9, and 27 mM; in the second, NaCl was applied at 0, 5, 10, 20, 40, and 80 mM in combination with CaCl₂ at 0.3, 1.0, and 3.0 mM. Quince leaves revealed the capacity to regenerate somatic embryos and/or adventitious roots. Quantitative and qualitative regeneration from leaves was affected by NaCl treatments: increasing NaCl concentrations, in combination with CaCl₂ at 1 mM, led to an increase in the proportion of leaves producing somatic embryos only, and to a decrease of both leaves regenerating roots only and leaves simultaneously producing somatic embryos and adventitious roots. This suggests a beneficial effect of salt stress on the embryogenic process. The regeneration response decreased with increasing salt concentrations and was almost totally inhibited above 50 mM NaCl and 9 mM CaCl₂. The presence of CaCl₂ in the culture medium apparently mitigated the effects of salt stress, but only when NaCl was applied at 40 mM. NaCl at 5 mM, in the presence of 0.3 or 1 mM CaCl₂, was favorable both to somatic embryo and root production. No value of the ratio Na⁺/Ca²⁺ was found to be optimal for the regeneration processes.     

Effect of NaCl and CaCl<Subscript>2</Subscript> on the antioxidant mechanism of leaves and stems of the rootstock CAB-6P (<Emphasis Type="Italic">Prunus cerasus</Emphasis> L.) under in vitro conditions

The effect of salinity on the non-enzymic and enzymic antioxidant activity, shoot proliferation and nutrient accumulation was studied in in vitro cultures of the rootstock CAB-6P (Prunus cerasus L.). Three concentrations (0, 30 and 60 mM) of NaCl or CaCl₂ were added to a modified MS medium. Between the two salt treatments used, only the explants treated with CaCl₂ presented significant decrease in growth parameters. The concentrations of Na⁺ and Cl⁻ in the explants treated with NaCl were increased, as NaCl in the culture medium increased. Furthermore, in the explants treated with CaCl₂ the concentrations of Ca²⁺ and Cl⁻ were increased while that of K⁺ decreased, as CaCl₂ concentration increased. The activity of peroxidase in leaves as well as the number of its anionic isoforms was increased under 30 mM CaCl₂ as well as 60 mM NaCl or CaCl₂. On the contrary, increasing salinity, from 0 to 60 mM CaCl₂, resulted in a reduction of the catalase activity in leaves followed by disappearance of the only one catalase isoform that was detected in leaves (60 mM CaCl₂). In the stems of the explants treated with NaCl the peroxidase activity was reduced. In the stems and leaves of the explants grown in saline substrate the non-enzymic antioxidant activity was significantly increased. The results suggest that the stems and leaves of CAB-6P explants presented variable antioxidant responses that were depended on the salt form used. The contribution of enzymic and non-enzymic protection mechanisms to the adaptation of CAB-6P explants under salinity stress is discussed.     

Comparison of the effects of NaCl and KCl at the roots on seedling growth,cell death and the size,frequency and secretion rate of salt glands in leaves of <Emphasis Type="Italic">Limonium sinense</Emphasis>

Twenty days’ exposure to 50 or 100 mM NaCl in the rooting medium substantially increased fresh and dry weights of seedling shoots of the recretohalophyte Limonium sinense while 200 or 300 mM were increasingly inhibitory. KCl treatment was only slightly stimulating (50 mM) or strongly inhibitory (100–300 mM). Lesser effects on leaf area were also seen. Diameter of foliar salt glands was significantly larger than that of controls in 100 and 200 mM NaCl with the effect being reversed at higher concentrations. Gland enlargement was also observed in the presence of 100 mM KCl, while larger concentrations reduced gland size. Generally, gland diameter was larger in the presence of NaCl than in KCl. NaCl and KCl also increased gland number per leaf and secretion rate per gland. At 100 and 200 mM NaCl or KCl, Na⁺ secretion per leaf from NaCl-treated plants exceeded K⁺ secretion rate from KCl-treated plants while at 200 mM, Na⁺ secretion per gland was significantly higher for Na⁺ than for K⁺. Evidence of cell death in leaves of salt-treated plants using Evans blue staining indicates that release of cell contents through loss of membrane integrity contributed to the secretion values. We conclude that the greater tolerance of L. sinenseto to NaCl compared to KCl is linked to the more effective secretion of Na⁺ than of K⁺ and, in turn, to a greater stimulation of salt gland formation and activity and larger gland diameter.     

Effect of sodium chloride-induced stress on growth, proline, glycine betaine accumulation, antioxidative defence and bacoside A content in in vitro regenerated shoots of Bacopa monnieri (L.) Pennell

Growth, osmotic adjustment, antioxidant enzyme defense and the principle medicinal component bacoside A were studied in the in vitro raised shoot cultures of Bacopa monnieri, a known medicinal plant, under different concentrations of NaCl [0.0 (control), 50, 100, 150 or 200 mM]. A sharp increase in Na⁺ content was observed at 50 mM NaCl level and it was about 6.4-fold higher when compared with control. While Na⁺ content increased in the shoots with increasing levels of NaCl in the medium, both K⁺ and Ca²⁺ concentrations decreased. Significant reduction was observed in shoot number per culture; shoot length, fresh weight (FW), dry weight (DW) and tissue water content (TWC) when shoots were exposed to increasing NaCl concentrations (50–200 mM) as compared with the control. Decrease in TWC was not significant at higher NaCl level (150 and 200 mM). At 200 mM NaCl, growth of shoots was adversely affected and microshoots died under prolonged stress. Minimum damage to the membrane as assessed by malondialdehyde (MDA) content was noticed in the controls in contrast to sharp increase of it in NaCl-stressed shoots. Higher amounts of free proline, glycinebetaine and total soluble sugars (TSS) accumulated in NaCl-stressed shoots indicating that it is a glycinebetaine accumulator. About 2.11-fold higher H₂O₂ content was observed at 50 mM NaCl as compared with control and it reached up to 7.1-folds more at 200 mM NaCl. Antioxidant enzyme activities (superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) also increased with a rise in NaCl level. Increase in bacoside A, a triterpene saponin content was observed only up to 100 mM NaCl level. Higher salt concentrations inhibited the accumulation of bacoside A. It appears from the data that accumulation of osmolytes, ions and elevated activities of antioxidant enzymes play an important role in osmotic adjustment in shoot cultures of Bacopa under salt stress.     

Response of the pear rootstock to boron and salinity in vitro

The effects of boron and NaCl induced salinity on growth and mineral composition of the pear (Pyrus communis L.) rootstock OH × F 333 shoots cultured in vitro were investigated. Shoots were grown in vitro for seven weeks on a Murashige and Skoog medium containing two B concentrations (0.1 and 2 mM) combined with five NaCl concentrations (0, 10, 20, 40, and 80 mM). The longest shoots were produced at 0.1 mM B and 80 mM NaCl, but highest number of shoots were produced at 0.1 mM B and 0–20 mM NaCl. Inclusion of 20 and 40 mM NaCl in the culture medium significantly increased fresh mass of cultures compared to 0 mM NaCl for all B concentrations tested. The concentrations of P, K, Ca, Mg, Na, Fe, Mn and Zn of plants were affected by B and NaCl concentration of the medium.     

Effect of potassium chloride and calcium chloride induced stress on in vitro cultures of Bacopa monnieri (L.) Pennell and accumulation of medicinally important bacoside A

Growth, osmotic adjustment, antioxidant enzyme defense and principle medicinal component bacoside A was studied in in vitro raised shoots of Bacopa monnieri under different concentrations of KCl and CaCl₂ (0, 50, 100, 150 or 200 mM). Significant reduction was observed in shoot number per culture; shoot length, fresh weight, dry weight and tissue water content (TWC) when shoots were exposed to increasing KCl and CaCl₂ concentrations (50–200 mM) as compared to control. Minimum damage to the membrane as assessed by malondialdehyde (MDA) content was noticed in control in contrast to sharp increase in KCl and CaCl₂ stressed shoots. Higher amounts of free proline, glycine betaine and total soluble sugars (TSS) accumulated in KCl and CaCl₂ exposed shoots compared to the controls. Among different concentrations of KCl and CaCl₂, increasing concentration of CaCl₂ showed more increase in osmolyte accumulation. Na⁺ content decreased with increasing concentrations of KCl and CaCl₂. Accumulation of K⁺ increased significantly in KCl (50–100 mM) stressed shoots as compared to control, while it decreased in CaCl₂ treated shoots indicating that it prevents the uptake of K⁺ ions. Ca²⁺ accumulation significantly increased with increasing concentrations of CaCl₂ up to 150 mM but decreased at higher concentrations. Shoots treated with KCl and CaCl₂ (0–100 mM) showed higher antioxidant enzyme (SOD, CAT, APX and GPX) activities but KCl suppressed the activities at higher concentrations. Accumulation of bacoside A was enhanced with an increase in KCl and CaCl₂ concentration up to 100 mM. It appears from the data that accumulation of osmolytes, and elevated activities of antioxidant enzymes play an important role in osmotic adjustment in shoot cultures of Bacopa and the two salts tested have a positive effect on bacoside accumulation.     

Exopolysaccharide production in <Emphasis Type="Italic">Anabaena</Emphasis> sp. PCC 7120 under different CaCl<Subscript>2</Subscript> regimes

Influence of various levels of CaCl₂ (0, 1, 10 and 100 mM) on exopolysaccharide production has been investigated in the cyanobacterium Anabaena 7120. At the concentration of 1 mM CaCl₂, growth was found to be stimulatory while 100 mM was sub lethal for the cyanobacterial cells. Estimation of EPS content revealed that EPS production depends on the concentration of calcium ions in the immediate environment with maximum being at10 mM CaCl₂. A possible involvement of alr2882 gene in the process of EPS production was also revealed through qRT-PCR. Further, FTIR-spectra marked the presence of aliphatic alkyl-group, primary amine-group, and polysaccharides along with shift in major absorption peaks suggesting that calcium levels in the external environment regulate the composition of EPS produced by Anabaena 7120. Thus, both quantity and composition of EPS is affected under different calcium chloride concentrations presenting possibilities of EPS with novel unexplored features that may offer biotechnological applications.     

Salinity stress response of non-transformed and AtCKX transgenic centaury (Centaurium erythraea Rafn.) shoots and roots grown in vitro

Common centaury (Centaurium erythraea Rafn.) is a plant species that can inhabit saline soils. It is known as a plant with high spontaneous regeneration potential in vitro. In the present work we evaluated shoots and roots salinity tolerance of non-transformed and three AtCKX transgenic centaury lines to graded NaCl concentrations (0, 50, 100, 150, 200 mM) in vitro. Overexpression of AtCKX genes in transgenic centaury plants resulted in an altered cytokinins (CKs) profile leading to a decline of bioactive CK levels and, at the same time, increased contents of storage CK forms, inactive CK forms and/or CK nucleotides. Significant increment of fresh shoot weight was obtained in shoots of non-transformed and AtCKX1 transgenic line only on medium supplemented with 50 mM NaCl. However two analysed AtCKX2 transgenic lines reduced shoot growth at all NaCl concentrations. In general, centaury roots showed higher tolerance to salinity than shoots. Non-transformed and AtCKX1 transgenic lines tolerated up to 100 mM NaCl without change in frequency of regeneration and number of regenerated plants. Roots of two analysed AtCKX2 transgenic lines showed different regeneration potential under salt stress. Regeneration of transgenic AtCKX2-26 shoots even at 200 mM NaCl was recorded. Salinity stress response of centaury shoots and roots was also evaluated at biochemical level. Free proline, malondialdehyde and hydrogen peroxide content as well as antioxidative enzymes activities were investigated in shoots and roots after 1, 2, 4 and 8 weeks. In general, adition of NaCl in culture medium elevated all biochemical parameters in centaury shoots and in roots. Considering that all analysed AtCKX transgenic centaury lines showed altered salt tolerance to graded NaCl concentrations in vitro it can be assumed that CKs might be involved in plant defence to salt stress conditions.     

The effects of NaCl on growth,water relations,osmolytes and ion content in <Emphasis Type="Italic">Kochia prostrata</Emphasis>

The effects of NaCl (0, 50, 100, 150 and 200 mM) on growth, water relations, glycinebetaine, free proline, ion contents, stomata number and size of Kochia prostrata (L.) Schard were determined. Shoot and root fresh and dry matter, root and shoot length, relative growth rate, net assimilation rate, relative water content, water use efficiency, soluble sugars and glycinebetaine contents were not changed at low NaCl concentrations, but they were significantly decreased at 200 mM NaCl. The K⁺, Mg²⁺ and Ca²⁺ contents, water potential, chlorophyll a+b and carotenoides contents, and stomata number and size were reduced already at low concentrations of NaCl. In contrast, the Na⁺, Cl^– and proline contents increased several times with increasing NaCl concentration. Kochia prostrata is a salt tolerant species, the optimal growth of this plant occurred up to 150 mM NaCl. The mechanisms of salt tolerance in the plant may be balance among ion accumulation and production of glycinebetaine, proline, soluble sugars for maintenance of pressure potential.     

Effects of salt-tolerant rootstock grafting on ultrastructure,photosynthetic capacity,and H<Subscript>2</Subscript>O<Subscript>2</Subscript>-scavenging system in chloroplasts of cucumber seedlings under NaCl stress

Plant growth, photosynthetic parameters, chloroplast ultrastructure, and the ascorbate-glutathione cycle system in chloroplasts of self-grafted and rootstock-grafted cucumber leaves were investigated. Grafted plants were grown hydroponically and were exposed to 0, 50, and 100 mM NaCl concentrations for 10 days. Under NaCl stress, the hydrogen peroxide (H₂O₂) content in cucumber chloroplasts increased, the chloroplast ultrastructure was damaged, and the gas stomatal conductance, intercellular CO₂ concentration, as well as shoot dry weight, plant height, stem diameter, leaf area, and leaf relative water content were inhibited, whereas these changes were less severe in rootstock-grafted plants. The activities of ascorbate peroxidase (APX; EC 1.11.1.11), glutathione reductase (GR; EC 1.6.4.2), and dehydroascorbate reductase (DHAR EC 1.8.5.1) were higher in the chloroplasts of rootstock-grafted plants compared with those of self-grafted plants under 50 and 100 mM NaCl. Similar trends were shown in leaf net CO₂ assimilation rate and transpiration rate, as well as reduced glutathione content under 100 mM NaCl. Results suggest that rootstock grafting enhances the H₂O₂-scavenging capacity of the ascorbate–glutathione cycle in cucumber chloroplasts under NaCl stress, thereby protecting the chloroplast structure and improving the photosynthetic performance of cucumber leaves. As a result, cucumber growth is promoted.     

Effects of optimal and supra-optimal salinity stress on antioxidative defence,osmolytes and in vitro growth responses in <Emphasis Type="Italic">Sesuvium portulacastrum</Emphasis> L.

The effect of optimal and supra-optimal concentrations (0, 200, 400 or 600 mM) of NaCl on the growth, osmotic adjustment and antioxidant enzyme defence was studied in the in vitro cultures of Sesuvium portulacastrum. A significant increase in growth, tissue water content (TWC) and fresh to dry weight ratio (FW/DW) was observed in the shoots exposed to 200 mM salt. Minimum damage to the membrane in terms of low relative electrolytic leakage (REL) and malondialdehyde (MDA) content and better osmotic adjustment at 200 mM salt stress was coupled with the higher accumulation of sodium ions and total soluble sugars as against low proline and glycine betaine contents. A fine tuning of antioxidant enzyme activities (superoxide dismutase, catalase and ascorbate peroxidase) was also found to be responsible for the optimum growth of shoots. In contrast, sub-optimal (0 mM) and supra-optimal concentrations (400–600 mM) of NaCl significantly affected the growth, water status and increased the REL as well as MDA content of the shoots due to the accumulation of toxic concentrations of saline ions. The highest accumulation of proline and glycine betaine in addition to antioxidant enzyme activities exhibited higher osmotic adjustment and survival of the shoots under sub- or supra-optimal concentrations of NaCl as a penalty to reduced growth.     

Enhanced salt stress tolerance in transgenic potato plants (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) expressing a bacterial <Emphasis Type="Italic">mtl</Emphasis>D gene

Bacterial mannitol 1-phosphate dehydrogenase (mtlD) gene was introduced into potato (Solanum tuberosum L.) by Agrobacterium tumefaciens-mediated transformation. Transgenic plants were selected on a medium containing 100 mg l⁻¹ kanamycin and confirmed by polymerase chain reaction (PCR), Southern blotting, and RT-PCR analyses. All of the selected transformants accumulated mannitol, a sugar alcohol that is not found in wildtype potato. Experiments designed for testing salt tolerance revealed that there was enhanced NaCl tolerance of the transgenic lines both in vitro and in hydroponic culture. Compared to 0 mM NaCl, the shoot fresh weight of wildtype plants was reduced by 76.5% at 100 mM NaCl under hydroponic conditions. However, under the same condition, the shoot fresh weight of transgenic plants was reduced only by 17.3%, compared to 0 mM NaCl treatment. The improved tolerance of this transgenic line may be attributed to the induction and progressive accumulation of mannitol in the roots and shoots of the plants. In contrast to in vitro experiments, the mannitol content in the transgenic roots and shoots increased at 50 mM NaCl and decreased slightly at 75 and 100 mM NaCl, respectively. Overall, the amount of accumulated mannitol in the transgenic lines was too small to act as an osmolyte; thus, it might act as an osmoprotectant. However, the results demonstrated that mannitol had more contribution to osmotic adjustment in the roots (but not in shoots). Finally, we concluded that mtlD expression in transgenic potato plants can significantly increase the mannitol accumulation that contributes to the enhanced tolerance to NaCl stress. Furthermore, although this enhanced tolerance resulted mainly from an osmoprotectant action, an osmoregulatory effect could not be ruled out.     

Salt stress effects on growth,pigments, proteins and lipid peroxidation in <Emphasis Type="Italic">Salicornia persica</Emphasis> and <Emphasis Type="Italic">S. europaea</Emphasis>

The effects of NaCl stress on growth, water status, contents of protein, proline, malondialdehyde (MDA), various sugars and photosynthetic pigments were investigated in seedlings of Salicornia persica and S. europaea grown in vitro. Seeds were germinated under NaCl (0, 100, 200, 300, 400, 500 and 600 mM) on Murashige and Skoog medium for 45 d. The shoot growth of both species increased under low NaCl concentration (100 mM) and then decreased with increasing NaCl concentrations. In contrast to S. persica, root length in S. europaea reduced steadily with an increase in salinity. Proline content in S. persica was higher than in S. europaea at most NaCl concentrations. Proline, reducing saccharide, oligosaccharide and soluble saccharide contents increased under salinity in both species. In contrast, contents of proteins and polysaccharides reduced in both species under salt stress. MDA content remained close to control at moderate NaCl concentrations (100 and 200 mM) and increased at higher salinities. MDA content in S. europaea was significantly higher than S. persica at higher salinities. Salt treatments decreased K⁺ and P contents in seedlings of both species. Significant reduction in contents of chlorophylls and carotenoids due to NaCl stress was also observed in seedlings of both species. Some differences appeared between S. persica and S. europaea concerning proteins profile. On the basis of the data obtained, S. persica is more salt-tolerant than S. europaea.     

Effect of salt stress on physiological and antioxidative responses in two species of <Emphasis Type="Italic">Salicornia</Emphasis> (<Emphasis Type="Italic">S. persica</Emphasis> and <Emphasis Type="Italic">S. europaea</Emphasis>)

The effects of salt stress on growth parameters, free proline content, ion accumulation, lipid peroxidation, and several antioxidative enzymes activities were investigated in S. persica and S. europaea. The seedlings were grown for 2 months in half-strength Hoagland solution and treated with different concentrations of NaCl (0, 85, 170, 340, and 510 mM) for 21 days. The fresh and dry weights of both species increased significantly at 85 and 170 mM NaCl and decreased at higher concentrations. Salinity increased proline content in both the species as compared to that of control. Sodium (Na⁺) content in roots and shoots increased, whereas K⁺ and P_i content in both organs decreased. At all NaCl concentrations, the total amounts of Na⁺ and K⁺ were higher in shoots than in roots. Malondialdehyde (MDA) content declined at moderate NaCl concentrations (85 and 170 mM) and increased at higher levels. With increased salinity, superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (GPX) activities also increased gradually in both species. In addition, it seems that GPX, CAT, and SOD activities play an essential protective role in the scavenging reactive oxygen species (ROS) in both species. Native polyacrylamide gel electrophoresis (PAGE) indicated different isoform profiles between S. persica and S. europaea concerning antioxidant enzymes. These results showed that S. persica exhibits a better protection mechanism against oxidative damage and it is more salt-tolerant than S. europaea possibly by maintaining and/or increasing growth parameters, ion accumulation, and antioxidant enzyme activities.     

The peroxidase activity of cytochrome <Emphasis Type="Italic">b</Emphasis><Subscript>6</Subscript><Emphasis Type="Italic">f</Emphasis> complex from spinach chloroplasts

The cytochrome b ₆ f (Cyt b ₆ f) complex, which functions as a plastoquinol-plastocyanin oxidoreductase and mediates the linear electron flow between photosystem II (PSII) and photosystem I (PSI) and the cyclic electron flow around PSI, was isolated from spinach (Spinacia oleracea L.) chloroplasts using n-octyl-β-D-glucopyranoside (β-OG). The preparation was also able to catalyze the peroxidase-like reaction in the presence of hydrogen peroxide (H₂O₂) and guaiacol. The optimal conditions for peroxidase activity of the preparation included: pH 3.6, ionic strength 0.1, and temperature 35°C. The apparent Michaelis constant (K _m) values for H₂O₂ and guaiacol were 50 mM and 2 mM, respectively. The bimolecular rate constant (k _obs) was about 26 M⁻¹ s⁻¹ and the turnover number (K _cat) was about 60 min⁻¹ (20 mM guaiacol, 100 mM sodium phosphate, pH 3.6, 25°C, [H₂O₂]<100mM). These parameters were similar to those of several other heme-containing proteins, such as myoglobin and Cyt c.     

Growth and mineral content of coriander (<Emphasis Type="Italic">Coriandrum sativum</Emphasis> L.) plants under mild salinity with different salts

Soil salinity is a complex issue in which various anions and cations contribute to have a general adverse effect on plant growth. In the present study, effects of salinity from various salts including sodium chloride (NaCl), potassium chloride?+?sodium chloride?+?calcium chloride (KCl?+?NaCl?+?CaCl₂), potassium sulfate?+?magnesium nitrate (K₂SO₄?+?Mg(NO₃)₂) at two electric conductivities (EC) of 2 and 4 dS m^?1 of irrigation water, and a distilled water control were evaluated on coriander plants (Coriandrum sativum L.). At EC?=?2, all salts increased plant yield (shoot fresh weight) than control. Most growth traits including plant height, shoot fresh and dry weight, leaf SPAD value and vitamin C, leaf K, Mg and P concentrations were increased by K₂SO₄?+?MgNO₃, and remained unchanged by KCl?+?NaCl?+?CaCl₂ treatment (except reduced plant height). Leaf’s zinc concentration reduced by either treatment. Even sodium chloride at EC?=?2 showed some beneficial effects on leaf chlorophyll index, root fresh weight, leaf’s calcium and phosphorus concentration; however, most traits remained unchanged than control. Treatment of plants with NaCl or KCl?+?NaCl?+?CaCl₂ at either EC increased the number of flowered shoots and leaf proline content than control. Most growth and quality traits including leaf minerals and vitamin C content were reduced by NaCl at EC?=?4; however, shoot fresh and dry weights remained unchanged than control. Plant root fresh weight increased by NaCl at EC?=?2 and decreased at EC?=?4 than control. At EC?=?4, shoot dry weight was increased and leaf Ca, P, Zn and Mn were decreased by KCl?+?NaCl?+?CaCl₂, whereas shoot dry weight, leaf SPAD value and vitamin C content, leaf Mg and P were increased and leaf Zn was decreased by K₂SO₄?+?MgNO₃ than control. The results indicate that in contrast to sodium chloride, the salinity effects of other salts can not be detrimental on coriander plant growth.     

Effect of NaCl on biomass, protein and proline contents, and antioxidant enzymes in seedlings and calli of two Trigonella species

The effects of NaCl on growth, contents of proteins and proline, and activities of catalase, peroxidase and polyphenol oxidase were investigated in seedlings and calli of Trigonella foenum-graecum L. and T. aphanoneura Rech. f. Seeds and hypocotyl explants were cultured on Murashige and Skoog medium supplemented with 0, 50, 100, 150 and 200 mM NaCl. Seed germination and the fresh and dry mass of the seedlings decreased significantly under salinity. In both species significant increases in protein content of seedlings over that of control were observed at 150 and 200 mM NaCl. Protein content in calli decreased at 200 mM NaCl over that of control. Protein content was higher in seedlings than in calli at all NaCl concentrations. Conversely, proline content was lower in seedlings than in calli at all the tested NaCl concentrations. NaCl caused changes in the activities of peroxidase, catalase and polyphenol oxidase in seedlings and calli.     

Effects of the timing of calcium application on the alleviation of salt stress in the maize, tall fescue, and reed canarygrass seedlings

Calcium chloride (0.3 or 10 mM) was applied to the growth medium before, together with, or after sodium chloride application, and the effect of the timing of Ca application on the alleviation of salt stress was investigated. Seedlings of maize, tall fescue, and reed canarygrass were grown in medium with 0 and 200 mM NaCl for 5 d. Regardless of the plant species the maximum alleviation of NaCl stress was achieved when CaCl₂ and NaCl coexisted in the growth medium. The effects of Ca application were connected with the decrease in the Na content in the plant roots and shoots and increased ATPase activity in the roots.     

Salinity attenuates nickel-accumulating capacity of <Emphasis Type="Italic">Atropa belladonna</Emphasis> L. plants

Comparative analysis of growth and composition of Atropa belladonna L. plants was performed after separate and combined additions of NaCl and NiCl₂ to the nutrient medium. Plants were grown in water culture on modified Johnson solution for 8 weeks until the formation of the fifth leaf pair. Thereafter, NiCl₂ was introduced at final concentrations of 100 and 150 μM into the medium either separately or in combination with 100 mM NaCl. After completing the 7-day treatment with Ni ions, the plants' weight and the content of water and photosynthetic pigments were determined. The content of Ni, free polyamines (putrescine, spermidine, spermine), and atropine was determined in plant roots and leaves, whereas the content of Fe, proline, and malondialdehyde (MDA) was examined in leaves only. The distribution of Ni in various tissues was inspected using the dimethylglyoxime method. The presence of NiCl₂ in growth media diminished the increments in fresh weight of shoots and roots; lowered the content of water, pigments, and iron in leaves; and initiated chlorosis. The leaves of Ni-treated plants accumulated larger amounts of atropine, putrescine, proline, and MDA with respect to the control levels of these compounds. In contrast to the action of Ni alone, the combined application of NaCl and NiCl₂ was followed by the increased content of water and pigments in leaves. The presence of NaCl in the medium restricted the entry of Ni into roots and diminished the levels of MDA and proline in leaves. After growing the plants in the presence of 100 and 150 μM NiCl₂, nickel was located in the root outer cortex and the rhizoderm. In plants treated with 150 μM NiCl₂, nickel was also observed in tissues of the central cylinder, mostly in the pericycle, phloem, and xylem. In plants grown in the presence of 150 μM NiCl₂ and 100 mM NaCl, the decreased accumulation of nickel was noted in the tissues of the central cylinder in the root hair zone. Thus, the combined action of Ni and moderate salinity reduced nickel accumulation in roots and aboveground organs of A. belladonna plants. The reduced Ni content in plants mitigated the toxic effect of Ni present in the medium. This was manifested in stabilization of leaf water status, an increase in the content of photosynthetic pigments, and alleviation of oxidative stress, which was assessed from the content of low-molecular organic compounds exhibiting stress-protective and antioxidant action (proline, MDA, free polyamines, and atropine).     

Regeneration of plantlets of guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.) from somatic embryos developed under salt-stress condition

The present study demonstrates the regeneration of plantlets of guava (Psidium guajava L.) from somatic embryos developed under salt-stress conditions. With increasing concentrations of NaCl in induction medium (MS + 4.52 μM 2,4-d + 5% sucrose) from 0 to 200 mM, the number of somatic embryos per responsive explant decreased. Somatic embryos induced on 0–100 mM NaCl containing medium developed into torpedo stages, whereas, the development of somatic embryos that differentiated on 150 and 200 mM NaCl-supplemented medium was arrested prior to torpedo stage and did not undergo maturation phase. Somatic embryos that developed on NaCl-containing medium, showed better germination in the presence of NaCl as compared with those developed on medium without NaCl. The effect of increasing salt-stress was also investigated on plant growth, chlorophyll and carotenoids, Na⁺ and K⁺, and proline and glycine betaine accumulation in in vitro grown plantlets. The level of Na⁺ in leaves increased with increasing concentrations of NaCl in the medium. Accumulation of free proline and glycine betaine in leaves significantly increased with increasing salinity. The results suggest that accumulation of proline and glycine betaine may be important for osmotic adjustment in guava under salinity stress.