Grafting influence on the weight and quality of tomato fruit under salt stress

Two commercial tomato cultivars were used to determine whether grafting could prevent decrease of fruit weight and quality under salt stress conditions. The cultivars Buran F1 and Berberana F1 were grafted onto rootstock ‘Maxifort’ and grown under three levels of elevated soil salinity (EC 3.80 dS m^?1, 6.95 dS m^?1 and 9.12 dS m^?1). Fruit weight reduction of grafted plants was lower (about 20–30%) in comparison with non‐grafted ones. Salt stress at the second salinity level (EC 6.95 dS m^?1) induced the highest alteration of examined growth and quality parameters. The total increase of phenols, flavonoids, ascorbate and lycopene content in the fruits of both grafted and non‐grafted plants for both cultivars had a similar trend and intensity, though some inter‐cultivar variation was observed. The possibility of grafting tomato plants to improve salt tolerance without fruit quality loss is discussed.     

Improved Tolerance of <Emphasis Type="Italic">Acacia nilotica</Emphasis> to Salt Stress by Arbuscular Mycorrhiza, <Emphasis Type="Italic">Glomus fasciculatum</Emphasis> may be Partly Related to Elevated K/Na Ratios in Root and Shoot Tissues

A pot experiment was conducted to examine the effect of arbuscular mycorrhizal fungus, Glomus fasciculatum, and salinity on the growth of Acacia nilotica. Plants were grown in soil under different salinity levels (1.2, 4.0, 6.5, and 9.5 dS m⁻¹). In saline soil, mycorrhizal colonization was higher at 1.2, 4.0, and 6.5 dS m⁻¹ salinity levels in AM-inoculated plants, which decreased as salinity levels further increased (9.5 dS m⁻¹). Mycorrhizal plants maintained greater root and shoot biomass at all salinity levels compared to nonmycorrhizal plants. AM-inoculated plants had higher P, Zn, and Cu concentrations than uninoculated plants. In mycorrhizal plants, nutrient concentrations decreased with the increasing levels of salinity, but were higher than those of the nonmycorrhizal plants. Mycorrhizal plants had greater Na concentration at low salinity levels (1.2, 4.0 dS m⁻¹), which lowered as salinity levels increased (6.5, 9.5 dS m⁻¹), whereas Na concentration increased in control plants. Mycorrhizal plants accumulated a higher concentration of K at all salinity levels. Unlike Na, the uptake of K increased in shoot tissues of mycorrhizal plants with the increasing levels of salinity. Our results indicate that mycorrhizal fungus alleviates deleterious effects of saline soils on plant growth that could be primarily related to improved P nutrition. The improved K/Na ratios in root and shoot tissues of mycorrhizal plants may help in protecting disruption of K-mediated enzymatic processes under salt stress conditions.     

Effect of salinity on growth,water use and nutrient use in radish (Raphanus sativus L.)

Radish (Raphanus sativus L.) plants were grown at five soil salinity levels (1, 2, 4, 9 and 13 dS m^-1) to analyse the effects on growth, dry matter partitioning, leaf expansion and water and nutrient use. Salinity was varied by proportionally changing the concentration of all macro nutrients. When the electrical conductivity (EC) of the soil solution increased from 1 to 13 dS m^-1, the influx concentration of the nutrients absorbed by the plants (the ratio between the uptakes of nutrients and water) increased only from 1.6 to 3.5 dS m^-1. The total nutrient uptake showed an optimum at an EC of the soil solution of about 4 dS m^-1. The data suggest that at low salinity level (≤ 2 dS m^-1) the nutrient uptake was limited by availability while at high salinity (>4 dS m^-1) it was limited by the growth of the plant. Total water use by the plants decreased and water use efficiency increased at high salinity. Plant growth was optimal at 2–4 dS m^-1. At salinities higher than 4 dS m^-1 total plant dry weight decreased 2.8% per dS m^-1. About 80% of the growth reduction at high salinity could be attributed to reduction of leaf area expansion and hence to reduction of light interception. The remaining 20% of the salinity effect on growth was most likely explained by a decrease in stomatal conductance. The small leaf area at high salinity was related to a reduced specific leaf area and increased tuber/shoot weight ratio. The latter could be attributed to tuber formation starting at a smaller plant size at high salinity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Response of mesquite to nitrate and salinity in a simulated phreatic environment: Water use,dry matter and mineral nutrient accumulation

Mesquite plants (Prosopis glandulosa var. Torreyana) were grown in 2-m long columns 20 cm in diameter, and provided with a constant, stable ground water source 10 cm above the sealed base of the column. Ground water contained 0, 1 or 5 mM nitrate, or a mixed salt solution (1.4, 2.8, or 5.6 dS m^-1) with the ionic ratios of ground water found in a field stand of Prosopis at Harper's Well (2.8 dS m^-1). Water uptake in the highly salinized columns began to decrease relative to low salt columns when soil salinity probes 30 cm above the column base read approximately 28 dS m^-1, a potential threshold for mesquite salt tolerance. Prosopis growth increased with increasing nitrate, and decreased with increasing salinity. Water use efficiency was little affected by treatment, averaging approximately 2 g dry matter L^-1 water used. Most fine roots were recovered from a zone about 25 cm above the ground water surface where water content and aeration appeared to be optimal for root growth. Root-shoot ratio was little affected by nitrate, but increased slightly with increasing salinity. Plant tissue P concentrations tended to increase with increasing salinity and decrease with increasing N, approaching potentially deficient foliage concentrations at 5 mM nitrate. The whole-plant leaf samples increased in sodium concentration both with added salt and with added nitrate. Foliar manganese concentrations increased with increasing salt in the absence of nitrate. Concentrations of sodium in leaves were low (<10 g kg^-1), considering the high salt concentrations in the ground water. Prosopis appears to exclude sodium very effectively, especially from its younger leaves. Although Prosopis is highly salt tolerant, the degree to which it utilizes soil nitrate in place of biologically fixed N may lower its salinity tolerance and affect its nutrient relations in phreatic environments.     

Effect of salinity and inoculation on growth,nitrogen fixation and nutrient uptake ofVigna radiata (L.) Wilczek

This study reports the effect of salinity and inoculation on growth, ion uptake and nitrogen fixation byVigna radiata. A soil EC_e level of 7.5 dS m⁻¹ was quite detrimental causing about 60% decline in dry matter and grain yield of mungbean plants whereas a soil EC_e level of 10.0 dS m⁻¹ was almost toxic. In contrast most of the studied strains of Rhizobium were salt tolerant. Nevertheless, nodulation, nitrogen fixation and total nitrogen concentration in the plant was drastically affected at high salt concentration. A noticeable decline in acetylene reduction activity occurred when salinity level increased to 7.5 dS m⁻¹.     

Nitrogen mineralization rates in salinevs. salt-amended soils

Studies were conducted to compare N mineralization rates in salt-amended nonsaline soils to naturally-occurring saline soils. NaCl, CaCl₂, and Na₂SO₄ were added to nonsaline soils at rates that produced electrical conductivities of the saturation extracts (EC_e) of 5, 10, 15, and 20 dS m⁻¹. Saline soils with similar properties were leached to the same EC_c levels. N mineralization in the Chino soil was inhibited by salt addition, particularly with sodium and calcium chlorides. In the Domino soil there was some inhibition of N mineralization with the chloride salts, but enhancement with Na₂SO₄ was observed. Nitrification in both soils was more sensitive to salt addition than ammonification. N mineralization occurred more slowly in both leached saline soils compared to the salt-amended soils. Leached saline soils often accumulated greater amounts of inorganic N compared to their native saline counterparts, particularly with the 5 dS m⁻¹ Chino soil (native, 44 dS m⁻¹) and with the 5, 10, 15 and 20 dS m⁻¹ Domino soils (native, 32 dS m⁻¹). Kinetic parameters were estimated by the linear least squares (LLS) and the nonlinear least squares (NLLS) methods. Generally, the LLS transformation estimated greater values of potentially mineralizable N (N_o) and lower rate constants (k). With the NLLS equation, N_o values for the leached saline soils were usually lower, and k values usually higher than in the salt-amended soils. The nonsaline controls generally had the highest N_o and lowest k estimates. Average LLS rate constants for the salt-amended and leached saline soils were 0.055 and 0.083 for the Chino, and 0.104 and 0.137 week⁻¹, respectively, for the Domino soils. With the NLLS equation, average k values for the salt-amended and leached saline soils were 0.087 and 0.089 for the Chino, and 0.181 and 0.387 week⁻¹, respectively, for the Domino soils. These results suggest that N mineralization rates obtained in salt-amended nonsaline soils may not be representative of those in naturally-occurring saline soils.     

Nostoc, Microcoleus and Leptolyngbya inoculums are detrimental to the growth of wheat (Triticum aestivum L.) under salt stress

Background and aims

This study investigated the effect of cyanobacterial inoculants on salt tolerance in wheat.

Methods

Unicyanobacterial crusts of Nostoc, Leptolyngbya and Microcoleus were established in sand pots. Salt stress was targeted at 6 and 13 dS m^?1, corresponding to the wheat salt tolerance and 50 % yield reduction thresholds, respectively. Germinated wheat seeds were planted and grown for 14 (0 and 6 dS m^?1) and 21 (13 dS m^?1) days by which time seedlings had five emergent leaves. The effects of cyanobacterial inoculation and salinity on wheat growth were quantified using chlorophyll fluorescence, inductively coupled plasma-optical emission spectrometry and biomass measurements.

Results

Chlorophyll fluorescence was negatively affected by soil salinity and no change was observed in inoculated wheat. Effective photochemical efficiency correlated with a large range of plant nutrient concentrations primarily in plant roots. Inoculation negatively affected wheat biomass and nutrient concentrations at all salinities, though the effects were fewer as salinity increased.

Conclusions

The most likely explanation of these results is the sorption of nutrients to cyanobacterial extracellular polymeric substances, making them unavailable for plant uptake. These results suggest that cyanobacterial inoculation may not be appropriate for establishing wheat in saline soils but that cyanobacteria could be very useful for stabilising soils.     

Influence of salt stress on propagation,growth and nutrient uptake of typical aquatic plant species

Anthropogenic activities and natural causes contribute to an increase in the area and degree of degraded saline wetlands in arid/semi‐arid and coastal regions. The objective of this study was to determine the salt tolerance of the seven aquatic plant species Phragmites australis, Arundo donax, Canna indica, Scirpus validus, Alternanthera philoxeroides, Phyllostachys heteroclada and Potederia cordata during asexual reproduction and continuous growth. The species were exposed to five salinity treatments from 0.3 (control) to 20 dS m^?1 during a 30 day experiment. Data were collected on asexual reproduction and growth, chlorophyll content in leaves, Na⁺ and K⁺ concentrations, total nitrogen (TN) and total phosphorus (TP) concentrations in above‐ground biomass (AGB) and below‐ground biomass (BGB). The results showed that: 1) increase in salinity (especially at a salinity level of EC ≥15 dS m^?1) generally inhibited the capacity for asexual reproduction and reduced the chlorophyll content of leaves; 2) total dry biomass of plants was significantly negatively related to asexual reproduction; 3) species‐specific salt tolerance mechanisms were reflected by the Na⁺ and K⁺ concentrations and Na⁺/K⁺ ratios in different parts of the plants; and 4) the absorption of TN and TP were inhibited at high salinity (i.e. EC = 20 dS m^?1) in AGB and BGB of most tested plant species. However, salinity may enhance plant uptake of TN and TP under certain conditions (e.g. EC at 5, 10 and 15 dS m^?1). In general, as compared to the other species tested, giant reed A. donax and alligator weed A. philoxeroides showed relatively high asexual reproduction and growth capacity under high salt stress, and these species should thus be considered as candidates for restoration of degraded saline wetlands and/or for decontaminating saline wastewater.     

The K/Na and Ca/Na ratios and rapeseed yield,under soil salinity or sodicity

Rapeseed (Brassica napus) is a crop relatively tolerant to salt and sodium. Our objective was to study the interactions between Na, K and Ca and their relationship with its yield under the isolated effects of soil salinity or sodicity.Two experiments were carried out using pots filled with the Ah horizon of a Typic Natraquoll. There were three salinity levels (2.3 dS m^-1; 6.0 dS m^-1 and 10.0 dS m^-1) and three sodicity levels, expressed as sodium adsorption ratios (SAR: 12; 27 and 44). The soil was kept near field capacity.As soil salinity increased, the K/Na and Ca/Na ratios in the tissues decreased markedly but yields and aerial biomass production were not affected. As soil SAR value increased, the K/Na and Ca/Na ratios in plants and K-Na and Ca-Na selectivities decreased. Plants could not maintain their Ca concentration in soil with a high SAR. The grain yield and biomass production diminished significantly in the highest SAR treatment. Our results are consistent with those showing detrimental osmotic effects of salts in Brassica napus. Conversely, under sodicity, the K/Na and Ca/Na ratios in plant tissues decreased considerably, in accordance with grain and biomass production. These results show that the effects of sodicity are different from those of salinity.     

Effects of salinity and nitrogen on cotton growth in arid environment

The influences of different N fertilization rates and soil salinity levels on the growth and nitrogen uptake of cotton was evaluated with a pot experiment under greenhouse conditions. Results showed that cotton growth measured as plant height was significantly affected by the soil salinity and N-salinity interaction, but not by N alone. Cotton was more sensitive to salinity during the emergence and early growth stages than the later developmental stages. At low to moderate soil salinity, the growth inhibition could be alleviated by fertilizer application. Soil salinity was a dominated factor affecting cotton’s above-ground dry mass and root development. Dry mass of seed was reduced by 22%, 52%, and 84% respectively, when the soil salinity level increased from control level of 2.4 dS m^?1 to 7.7 dS m^?1, 12.5 dS m^?1 and to 17.1 dS m^?1, respectively. N uptake increased with N fertilization at adequate rates at both low and medium soil salinities but was not influenced by over N fertilization. At higher salinities, N uptake was independent of N rates and mainly influenced by soil salinity. The uptake of K decreased with soil salinity. The concentration of Na, Cl and Ca in plant tissues increased with soil salinity with highest concentrations in the cotton leaf.     

Comparison of Distichlis spicata and Suaeda aegyptiaca in response to water salinity: Candidate halophytic species for saline soils remediation

Distichlis spicata and Suaeda aegyptiaca are two potential halophytic plant species for bioremediation of salt degraded soils, and development of saline agriculture. The physiological responses of the species to different levels of salinity (EC 0, 12, 24, 36, and 48 dS/m) in a controlled environment experiment were studied. Both species showed a high level of tolerance to elevated concentrations of salt in the irrigation water. The shoot fresh and dry weights in S. aegyptiaca increased till 36 dS/m and were sustained under 48 dS/m while in D. spicata, both parameters decreased as salinity increased. Glycine betaine accumulation did not change in D. spicata with increasing salinity, whereas proline content revealed a marked increase of 7.13 fold in 48 dS/m salinity compared to the control, which showed its critical osmoprotection role in the plant. In S. aegyptiaca, both osmolytes content significantly increased at high salinity levels (36 and 48 dS/m) up to 3.22 and 2.0 folds, respectively. Overall, S. aegyptiaca had a better potential of Na⁺ phytoremediation, and tolerated higher salinity compared to D. spicata. In contrast, the vigorous root and rhizome growth in D. spicata made it a proper solution for protecting the soils against further erosion under saline conditions.     

Foliar and root absorption of Na+ and Cl− in maize and barley: Implications for salt tolerance screening and the use of saline sprinkler irrigation

Above-canopy sprinkler irrigation with saline water favours the absorption of salts by wetted leaves and this can cause a yield reduction additional to that which occurs in salt-affected soils. Outdoor pot experiments with both sprinkler and drip irrigation systems were conducted to determine foliar ion accumulation and performance of maize and barley plants exposed to four treatments: nonsaline control (C), salt applied only to the soil (S), salt applied only to the foliage (F) and salt applied to both the soil and to the foliage (F+S). The EC of the saline solution employed for maize in 1993 was 4.2 dS m^–1 (30 mM NaCl and 2.8 mM CaCl₂) and for barley in 1994, 9.6 dS m^–1 (47 mM NaCl and 23.5 mM CaCl₂). The soil surface of all pots was covered so that in the F treatment the soil was not salinized by the saline sprinkling and drip irrigation supplied nutrients in either fresh (treatments C and F) or saline water (treatments S and F+S).Saline sprinkling increased leaf sap Na⁺ concentrations much more than did soil salinity, especially in maize, even though the saline sprinkling was given only two or three times per week for 30 min, whereas the roots of plants grown in saline soil were continuously exposed to salinity. By contrast, leaf sap Cl^– concentrations were increased similarly by saline sprinkling and soil salinity in maize, and more by saline sprinkling than saline soil in barley. It is concluded that barley leaves, and to a greater extent maize leaves, lack the ability to selectively exclude Na⁺ when sprinkler irrigated with saline water. Moreover, maize leaves selectively absorbed Na⁺ over Cl^– whereas barley leaves showed no selectivity. When foliar and root absorption processes were operating together (F+S treatment) maize and barley leaves accumulated 11–14% less Na⁺ and Cl^– than the sum of individual absorption processes (treatment F plus treatment S) indicating a slight interaction between the absorption processes. Vegetative biomass at maturity and cumulative plant water use were significantly reduced by saline sprinkling. In maize, reductions in biomass and plant water use relative to the control were of similar magnitude for plants exposed only to saline sprinkling, or only to soil salinity; whereas in barley, saline sprinkling was more detrimental than was soil salinity. We suggest that crops that are salt tolerant because they possess root systems which efficiently restrict Na⁺ and Cl^– transport to the shoot, may not exhibit the same tolerance in sprinkler systems which wet the foliage with saline water. ei]T J Flowers     

Alleviation of salinity stress in chickpea byRhizobium inoculation or nitrate supply

Influence of inoculation with efficient rhizobia or nitrate fertilization in alleviating salinity (NaCl, CaCl₂ and Na₂SO₄) stress was investigated in sand culture experiments. Shoot dry mass declined beyond salinity level corresponding to electrical conductivity (EC) 5.6 dS m^?1 in control or in inoculated plants and after EC 7.4 dS m^?1 in nitrate fed ones. Root growth was more sensitive and decreased at EC 3.3 dS m^?1. Nitrate reductase activity in leaves reduced at EC 3.3 dS m^?1 but in inoculated and nitrate fed plants it reduced at EC 5.6 dS m^?1. Na⁺ accumulation increased at EC 5.6 and 7.4 dS m^?1 in roots and, shoots, respectively. In inoculated and nitrate fed plants Na⁺ content in roots increased at EC 7.4 dS m^?1. Content of Ca²⁺ increased slightly only in shoots and content of K⁺ was unaffected. Besides inoculation, application of small doses of nitrogen should prove beneficial for legume cultivation in saline soils.     

Seaweed Liquid Extract as an Alternative Biostimulant for the Amelioration of Salt-stress Effects in Calotropis procera (Aiton) W.T

Scientists consider saltwater one of the effective environmental stress that negatively affects the growth and establishment of trees and shrubs worldwide. Utilizing the potential of Bio-stimulant compounds present in the brown seaweed extract is an alternative strategy to improve crop tolerance to salinity. This study focused on the application of seaweed extract as a Bio-stimulant agent to counteract the salt stress on the growth and some physiochemical aspects of milkweed seedlings. In this experiment, the seedlings were treated with seaweed extract (SWE) of Sargassum angustifolium at four concentrations (non-SWE or control, 0.5, 1.0, and 1.5%) and then exposed to salt stress at four levels (0, 7.5, 15, and 30 dS m^?1 of diluted seawater) in a completely randomized design (four replications per treatment) over a time-span of 3 months. The results indicated that SWE-treated seedlings could tolerate salinity up to 15 dS m^?1 and also increase the survival rate by 69%. The growth parameters like height, specific leaf area, root length and volume, root and shoot dry weight were considerably enhanced by SWE (1%) from 7.5 to 30 dS m^?1. Moreover, gas exchanges and chlorophyll pigments were markedly increased using SWE (0.5%) under salt lower 15 dS m^?1 than control. Also, both SWE and salt stress significantly enhanced antioxidant enzymes over control, but SWE more increased the parameters. SWEs agent at different dosages significantly decreased electrolyte leakage at all salinity levels (except in 7.5 and 15 dS m^?1) compared to control. SWEs (1%) resulted in increasing K⁺ uptake but decreasing Na⁺ uptake and markedly enhancing K^+/Na⁺ ratio in stressed-milkweed versus free-salt stress. Totally, this research illustrates the potential of SWEs (at lower dosages) for elevating milkweed tolerance to moderate salinity stress and highlights the possibility of applying it as Bio-stimulant fertilizer.

     

Response of microbial activity and biomass in rhizosphere and bulk soils to increasing salinity

Background and aims

The impact of salinity on microbes has been studied extensively but little is known about the response of soil microbial activity and biomass to increasing salinity in rhizosphere compared to bulk (non-rhizosphere) soil.

Methods

Barley was grown for 5 weeks in non-saline loamy sand to which salt (NaCl) was added. The electrical conductivity in the saturated extract (ECe) was 1, 13 and 19 dS m^?1 for non-saline and two saline soils. Pots without plants were prepared in the same manner and placed next to those with plants. The water content in all pots was maintained at 75 % of water-holding capacity by weight. After 5 weeks the planted and unplanted pots were harvested to collect rhizosphere and bulk soil, respectively. The collected soil was then used for an incubation experiment. The EC levels in the pot experiment (EC1, EC13 and EC19, referred to as original) were either maintained or increased by adding NaCl to adjust the EC to 13, 19, 31 and 44 dS m^?1. CO₂ release was measured continuously for 20 days, microbial biomass C (MBC) was measured at the start and the end of the incubation experiment.

Results

In general, cumulative respiration and microbial biomass C concentration in rhizosphere and bulk soil decreased to a similar extent with increasing adjusted EC. However, compared to the treatments where the EC was maintained, the percentage decrease in cumulative respiration when the EC was increased to EC44 was smaller in rhizosphere than in bulk soil.

Conclusion

Overall, the reduction of cumulative respiration with increasing salinity did not differ between rhizophere and bulk soil. But microbes in rhizosphere soil were more tolerant to high EC than those in bulk soil which could be due to the greater substrate availability in the rhizosphere even after the soil was removed from the roots.     

Emergence and seedling growth of soybean cultivars and maturity groups under salinity

Soybean is an important agricultural crop and has, among its genotypes, a relatively wide variation in salt tolerance. As measured by vegetative growth and yield, however, the achievement or failure of a high emergence ratio and seedling establishment in saline soils can have significant economic implications in areas where soil salinity is a potential problem for soybean. This study was conducted to determine the effects of salinity, variety and maturation rate on soybean emergence and seedling growth. Included in the study were the variety ‘Manokin’; four near-isogenic sibling lines of the variety ‘Lee’ belonging to maturity groups IV, V, VI and VII; and the variety ‘Essex’ and two of its near-isogenic related lines representing maturity groups V, VI and VII, respectively. Field plots were salinized with sodium chloride and calcium chloride salts prior to planting. The soybeans were irrigated with furrow irrigation which redistributed the salts towards the tail ends of the field plots. Elevated soil salinity near the tail ends of the field significantly reduced soybean emergence rate, shoot height and root length. No significant reduction was found for emergence or seedling growth of variety ‘Manokin’ when the electrical conductivity of soil solution extract (ECe) was less than 3 dS m⁻¹. Soybean emergence and seedling growth was significantly reduced when soil ECe reached about 11 dS m⁻¹. Maturity groups V and VII of variety ‘Lee’ or V and VI of ‘Essex’ appeared to be more sensitive to salinity stress than other maturity groups. Salt tolerance of different genotypes and maturity groups should be considered, among other limiting factors, in minimizing salinity effects on soybean growth. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of salinity on mycorrhizal onion and tomato in soil with and without additional phosphate

Summary Vesicular-arbuscular mycorrhizal fungi (VAM) are known to increase plant growth in saline soils. Previous studies, however, have not distinguished whether this growth response is due to enhanced P uptake or a direct mechanism of increased plant salt tolerance by VAM. In a glasshouse experiment onions (Allium cepa L.) were grown in sterilized, low-P sandy loam soil amended with 0, 0.8, 1.6 mmol P kg^–1 soil with and without mycorrhizal inoculum. Pots were irrigated with saline waters having conductivities of 1.0, 2.8, 4.3, and 5.9 dS m^–1. Onion colonized withGlomus deserticola (Trappe, Bloss, and Menge) increased growth from 394% to 100% over non-inoculated control plants when soil P was low ( 0.2 mmol kg^–1 NaHCO₃-extractable P) at soil saturation extract salinities from 1.1 dS m^–1 to 8.8 dS m^–1. When 0.8 and 1.6 mM P was added no dry weight differences due to VAM were observed, however, K and P concentrations were higher in VAM plants in saline treatments.Glomus fasciculatum (Gerdeman and Trappe) andGlomus mosseae (Nicol. and Gerd.) isolates increased growth of VAM tomato 44% to 193% in non-sterilized, saline soil (10 dS m^–1 saturation extract) despite having little effect on growth in less saline conditions when soil P was low. Higher tomato water potentials, along with improved K nutrition by VAM in onion, indicate mechanisms other than increased P nutrition may be important for VAM plants growing under saline stress. These effects appear to be secondary to the effects of VAM on P uptake.     

Naturally Saline Boreal Communities as Models for Reclamation of Saline Oil Sand Tailings

Reclaimed landscapes after oil sands mining have saline soils; yet, they are required to have similar biodiversity and productivity as the predisturbance nonsaline landscape. Given that many species in the boreal forest are not tolerant of salinity, we studied the effects of soil salinity on plant communities in natural saline landscapes to understand potential plant responses during the reclamation process. Vegetation–soil relationships were measured along transects from flooded wetlands to upland forest vegetation in strongly saline, slightly saline, nonsaline, and reclaimed boreal landscapes. In strongly saline landscapes, surface soil salinity was high (>10 dS/m) in flooded, wet‐meadow, and dry‐meadow vegetation zones as compared to slightly saline (<5 dS/m) and nonsaline (<2 dS/m) landscapes. Plant communities in these vegetation zones were quite different from nonsaline boreal landscapes and were dominated by halophytes common to saline habitats of the Great Plains. In the shrub and forest vegetation zones, surface soil salinity was similar between saline and nonsaline landscapes, resulting in similar plant communities. In strongly saline landscapes, soils remained saline at depth through the shrub and forest vegetation zones (>10 dS/m), suggesting that forest vegetation can establish over saline soils as long as the salts are below the rooting zone. The reclaimed landscape was intermediate between slightly saline and nonsaline landscapes in terms of soil salinity but more similar to nonsaline habitats with respect to species composition. Results from this study suggest it may be unrealistic to expect that plant communities similar to those found on the predisturbance landscape can be established on all reclaimed landscapes after oil sands mining.     

Salinity-yield response functions of barley genotypes assessed with a triple line source sprinkler system

Evaluation of the salt tolerance of crop cultivars under field conditions is greatly complicated by the typical temporal and spatial variability of soil salinity. We obtained the grain yield – salinity response functions of 124 barley genotypes by growing them in ten salinity treatments imposed by a Triple Line Source Sprinkler (TLS) system during five consecutive years. Additional objectives were to ascertain the consistency and reproducibility over years of these functions, to quantify the deleterious effects of saline sprinkling irrigations, and to assess correlations between salinity tolerance and leaf sap salt concentration. The consistency and reproducibility of the response functions within and between years were adequate (only 8% of the response functions were discarded for statistical reasons). The Y _m (grain yield without salinity) and the EC₅₀ (the EC _e that reduces yield by 50%) estimates were not correlated (P > 0.05) suggesting that the most productive genotypes were not necessarily less salinity tolerant. Y _m was positively and significantly (P < 0.01) correlated with Y₆ and Y₁₂ (fitted grain yields at EC _e values of 6 dS m^-1, and 12 dS m^-1, respectively), indicating that it is a useful statistic in the selection of barley genotypes most productive under medium and high salinities. Foliar salt uptake due to saline sprinkling irrigations decreased the EC₅₀ by around 50% as compared with the salinity tolerance obtained with surface irrigation systems. No consistent relationships were found between either Y _m or EC₅₀ and the leaf sap osmotic potential, Cl, Ca, Na and K concentrations. They could not therefore be used in screening for salinity tolerance of barley. On the basis of the evidence from the present study, Y _m is the best statistic for predicting the most productive barley genotypes in salt-affected soils. This revised version was published online in June 2006 with corrections to the Cover Date.     

Impact of the microalga Dunaliella salina (Dunal) Teodoresco culture and its β-carotene extract on the development of salt-stressed squash (Cucurbita pepo L. cv. Mabrouka)

Salinity is a major threat to crop production and global food security. Algae and their extracts containing bioactive compounds can enhance the salt tolerance of plants, including the salt-sensitive plants. The current study evaluated the efficacy of Dunaliella salina (Dunal) Teodoresco culture and/or its β-carotene extract in improving the salt tolerance of squash (Cucurbita pepo L. cv. Mabrouka). Amendment of C. pepo with D. salina culture and/or its β-carotene extract was more effective in alleviating the impact of moderate salinity imposed by seawater dilution of 2.5 dS m⁻¹ than either low (0.55 dS m⁻¹) or high (3.5 dS m⁻¹) salinity, with a comparable effect to that of salicylic acid (SA). Plants that received a combination of D. salina culture and its β-carotene extract showed significantly higher growth (total biomass, fruit productivity) and physiological attributes (photosynthetic pigments, nitrogen (N), phosphorus (P), and potassium (K⁺) contents) than those receiving either amendment alone, reaching up to 80–90% of the SA-treated plants at moderate salinity (2.5 dS m⁻¹). The combination could enhance the antioxidant activity of moderately salt-stressed C. pepo via increasing carotenoids and phenolics contents, suggesting that this combination could enhance the adaptation of C. pepo to the moderate salinity. The present study recommends using the blooms of D. salina and its β-carotene that is naturally secreted in situ in natural or synthetic open systems in improving the salt tolerance of C. pepo instead of using the expensive synthetic hormones.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-022-01176-6.