Anatomical adaptations to salinity in cogon grass [Imperata cylindrica (L.) Raeuschel] from the Salt Range, Pakistan

To examine anatomical adaptations in a potential forage grass, Imperata cylindrica (L.) Raeuschel, a population was collected from the natural salt-affected soils of the Salt Range, Pakistan. Using a hydroponic system, the degree of salt tolerance in terms of structural modifications in the Salt Range ecotype was compared with that in an ecotype collected from a normal non-saline habitat of the Faisalabad region. The Salt Range ecotype was superior to the Faisalabad ecotype in biomass production under saline conditions. High salt tolerance of the Salt Range ecotype was associated with increased succulence in root and leaf (mainly midrib), formation of aerenchyma in leaf sheath, increased vascular bundle area, metaxylem area and phloem area, highly developed bulliform cells on leaves and increased sclerification in root and leaf. Furthermore, both stomatal density and stomatal area were considerably reduced under high salinities in the Salt Range ecotype.     

Anatomical and physiological characteristics relating to ionic relations in some salt tolerant grasses from the Salt Range,Pakistan

Populations of three salt tolerant forage grasses (Cynodon dactylon, Imperata cylindrica, and Sporobolus arabicus) were collected from the salt-affected soils of the Salt Range and normal non-saline soils of the Faisalabad region to assess their mechanism of adaptation to saline stress by determining ion relations and some specific anatomical modifications. The population of S. arabicus from the Salt Range showed increased growth (root and shoot length, and root and shoot dry weights) under saline conditions. Salt tolerance in this species was related to structural modifications such as increased area of root, stem, leaf blade, and leaf sheath for toxic ion accumulation, increased vesicular hair density in leaves and aerenchyma formation in leaf sheath for ion exclusion. Uptake of toxic ions was high in the Salt Range population of C. dactylon and salt tolerance was related to ion exclusion through specific leaf structural modifications such as vesicular hairs. Salt tolerance in the Salt Range population of I. cylindrica was mainly associated with restricted uptake of toxic Na⁺ and Cl⁻ at root level, and accumulation of toxic ions via increased succulence in leaf blades and leaf sheaths in addition to some excretion of toxic ions through leaf sheath aerenchyma.     

Physiological and biochemical adaptations of Cynodon dactylon (L.) Pers. from the Salt Range (Pakistan) to salinity stress

Naturally adapted salt tolerant populations provide a valuable material for exploring the adaptive components of salt tolerance. Under this aspect, two populations of Cynodon dactylon (L.) Pers. were subjected to salt stress in hydroponics. One was collected from a heavily salt-affected soil in the vicinity of a natural salt lake, Uchhali Lake, in the Salt Range of the Punjab province of Pakistan, and the other from a normal non-saline habitat from the Faisalabad region. The NaCl treatments in Hoagland's nutrient solution were: Control (no salt), 50, 100, 150 and 200 mM of NaCl. After 8 weeks of growth in hydroponics produced biomass, ion relations, and photosynthetic capacity were measured in the differently adapted ecotypes. In the ecotype of C. dactylon from the Salt Range, shoot dry weight was only slightly affected by varying levels of salt. However, in contrast, its root weight was markedly increased. On the other hand, the ecotype from Faisalabad (non-saline habitat) showed a marked decrease in shoot and root dry weights under saline regimes. The ecotype from the Salt Range accumulated relatively less amount of Na⁺ in the shoot than did that from Faisalabad, particularly at higher salt levels. Shoot or root K⁺ and Ca²⁺ contents varied inconsistently in both ecotypes under salt stress. All the photosynthetic parameters, leaf water potential and osmotic potential, and chlorophyll content in both ecotypes were adversely affected by salt stress, but all these physiological attributes except turgor potential and soluble sugars were less affected at high salinities in the salt tolerant ecotype from Salt Range. This ecotype accumulated significantly higher organic osmotica (total free amino acids, proline, total soluble proteins, and total soluble sugars) under saline conditions than its intolerant counterpart. Overall, the salt tolerant ecotype of C. dactylon from the Salt Range showed high salt tolerance due to its restricted uptake of Na⁺ accompanied by an increased uptake of K⁺ and Ca²⁺ in the roots as well as shoot due to its higher photosynthetic capacity and accumulation of organic osmotica such as free amino acids and proline under saline conditions.     

Morpho-anatomical and physiological attributes for salt tolerance in sewan grass (Lasiurus scindicus Henr.) from Cholistan Desert,Pakistan

Three differently adapted populations of sewan grass (Lasiurus scindicus Henr.) were evaluated for structural and functional adaptations to high salinity. The habitats were Derawar Fort (DF, least saline, ECe 15.21), Bailahwala Dahar (BD, moderately saline, ECe 27.56 dS m^?1) and Ladam Sir (LS, highly saline, ECe 39.18 dS m^?1) from within the Cholistan Desert. The adaptive components of salt tolerance in sewan grass were assessed by determining various morpho–anatomical and physiological attributes. The degree of salt tolerance of all three ecotypes of L. scindicus from the saline habitats was compared in a controlled hydroponic system to evaluate the adaptive components that are expected to be genetically fixed during a long evolutionary process. Salinity tolerance in the most tolerant LS population relied on increased root length and total leaf area, restricted uptake of toxic Cl^?, increased uptake of Ca²⁺, high excretion of Na⁺, accumulation of organic osmolytes, high water use efficiency, increased root, thicker leaf and cortical region, intensive sclerification, large metaxylem vessels, and dense pubescence on abaxial leaf surface. The BD population (from moderately saline soil) relied on high Ca²⁺ uptake, Na⁺ excretion, epidermal thickness, large cortical cells, thick endodermis and large vascular tissue. The DF population (from less saline soil) showed a significant decrease in all morphological characteristics; however, it accumulated organic osmolytes for its survival under high salinities. Structural modifications in all three populations were crucial for checking undue water loss under physiological stress that is caused by high amounts of soluble salts in the soil.     

Growth attributes,biochemical modulations,antioxidant enzymatic metabolism and yield in Brassica napus varieties for salinity tolerance

Improvement in salinity tolerance of plants is of immense significance as salt stress particularly threatens the productivity of agricultural crops. This study was designed to assess the tolerance level of six Brassica napus varieties (Super, Sandal, Faisal, CON-111, AC Excel and Punjab) under different levels of salinity (0, 50, 100, 150 & 200 mM) with three replications under CRD. Salt induced osmotic stress curtailed the plant growth attributes, photosynthetic pigments and disturbed ionic homeostasis (K⁺, Na⁺, Ca^2+, Cl^-) but least disturbance as compared to control was found in Super and Sandal cultivars. Punjab canola and AC Excel canola cultivars were least tolerant to salinity because these displayed greater decline in all growth and biochemical attributes. Plants subjected to NaCl induced stress exhibited considerable decline in all attributes under study with proline as exception. Antioxidants (CAT, SOD & POD) showed an obvious change in Canola plants under stress, but greatest decline was displayed at 200 mM NaCl level in all six cultivars. Over all these attributes presented a comparatively stable trend in super and sandal cultivars. This shows presence of physiological resilience and metabolic capacity in these two cultivars to tackle salinity. Similarly, all yield attributes displayed adverse behavior under 150 mM & 200 mM salinity stress. Our results demonstrated that Super and Sandal cultivars of Brassica napus exhibit good performance in salinity tolerance and can be good option for cultivation in salt affected areas.     

Zinc improves salt tolerance by increasing reactive oxygen species scavenging and reducing Na+ accumulation in wheat seedlings

Salt decreases the uptake of Zn and other minerals and causes nutritional disorders in plants. Zn is an essential micronutrient for all organisms and it is reasonable to hypothesize that Zn status is essential for maintaining salt tolerance in plants. In this study, the physiological and molecular mechanisms of Zn-based alleviation of salt stress in wheat seedlings were investigated. Our results indicate that sufficient Zn nutrition maintained antioxidative enzyme activities and decreased a reactive oxygen species over-accumulation in wheat seedlings. Our data also reveal that sufficient Zn nutrition improved the expression of Na⁺/H⁺ antiporter genes, TaSOS1 and TaNHX1, thereby decreasing the Na⁺ accumulation and subsequently improving salt tolerance in wheat seedlings.     

Salinity tolerance of Aegilops cylindrica genotypes collected from hyper-saline shores of Uremia Salt Lake using physiological traits and SSR markers

Uremia Salt Lake, in North West Iran, has a hyper-saline water. A rare highly salinity-tolerant grass species, Aegilops cylindrica grows along its shores. Salinity tolerance of 44 genotypes of Ae. cylindrica, mainly collected from the Lake, was evaluated under control and 400 mM NaCl conditions using the physiological traits of plant height, dry weight, proline content, Na⁺ and K⁺ concentrations as well as K⁺/Na⁺ ratio. To evaluate the association between microsatellite (EST-SSR and SSR) markers and salinity tolerance, 35 primer pairs were used. Results showed a significant variation in the 44 genotypes studied in terms of their traits except for proline content. Ten most salinity-tolerant genotypes were identified based on their ability to survive, to produce the highest dry weight, and to sustain the least leaf Na⁺ concentration under salinity stress. The very high negative correlation found between Na⁺ concentration and salinity tolerance revealed the importance of individual or a combination of Na⁺ exclusion and excretion mechanisms contributing to the hyper-salinity tolerance of these genotypes. Clustering analysis based on marker data divided the 44 studied genotypes into two groups that were consistent with their saline and non-saline geographical areas. Results of molecular markers showed that four microsatellite markers (Xgwm312, Xwmc170, Xgwm291 and Xgwm410) generated a distinguished banding pattern in ten most salinity-tolerant genotypes. These results supported previous reports on their linkage with Na⁺ exclusion genes (HKT1;5 and HKT1;4) in wheat, which provided further evidence of usefulness of both genes and the linked markers to the salinity tolerance of the halophytic grass family species.     

22Na influx is significantly lower in salt tolerant groundnut (Arachis hypogaea) varieties

Distinct varieties differing in salt tolerance were initially identified from two separate green house experiments using two systems; solution as well as soil culture. The first screening involved a diverse group of 27 cultivars. Several physiological traits; Chlorophyll Stability Index (CSI), Salt Tolerance Index (STI) and ion content were determined to screen the cultivars for differences in salt tolerance using solution culture in the first experiment. A set of six varieties (three tolerant and three susceptible) were selected from this experiment and then subjected again to salt stress adopting a natural soil system in the second experiment which involved a screening approach essentially similar to that of the first experiment. In the third experiment using two distinct cultivars differing in salt tolerance selected from experiment II, ²²Na influx rate was determined in the root and shoot at the end of a 24 h salt imposition in Hoagland’s nutrient system containing 180 KBq of ²²Na. The results suggested that there were distinct differences in ²²Na influx rate into root and concurrently in the shoot. The salt tolerant Spanish improved and one of the moderately tolerant Trombay variety TAG 24, showed good regulation of ²²Na influx resulting in low ²²Na concentration. The salt susceptible variety JSP39 had nearly 7–8 fold higher root ²²Na content as compared to the tolerant and moderately tolerant cultivars. The results have highlighted the importance of Na exclusion as an important determinant of salt tolerance in groundnut.     

Mapping and confirmation of loci for salt tolerance in a novel soybean germplasm,Fiskeby III

Key message

The confirmation of a major locus associated with salt tolerance and mapping of a new locus, which could be beneficial for improving salt tolerance in soybean.

Abstract

Breeding soybean for tolerance to high salt conditions is important in some regions of the USA and world. Soybean cultivar Fiskeby III (PI 438471) in maturity group 000 has been reported to be highly tolerant to multiple abiotic stress conditions, including salinity. In this study, a mapping population of 132 F₂ families derived from a cross of cultivar Williams 82 (PI 518671, moderately salt sensitive) and Fiskeby III (salt tolerant) was analyzed to map salt tolerance genes. The evaluation for salt tolerance was performed by analyzing leaf scorch score (LSS), chlorophyll content ratio (CCR), leaf sodium content (LSC), and leaf chloride content (LCC) after treatment with 120 mM NaCl under greenhouse conditions. Genotypic data for the F₂ population were obtained using the SoySNP6K Illumina Infinium BeadChip assay. A major allele from Fiskeby III was significantly associated with LSS, CCR, LSC, and LCC on chromosome (Chr.) 03 with LOD scores of 19.1, 11.0, 7.7 and 25.6, respectively. In addition, a second locus associated with salt tolerance for LSC was detected and mapped on Chr. 13 with an LOD score of 4.6 and an R ² of 0.115. Three gene-based polymorphic molecular markers (Salt-20, Salt14056 and Salt11655) on Chr.03 showed a strong predictive association with phenotypic salt tolerance in the present mapping population. These molecular markers will be useful for marker-assisted selection to improve salt tolerance in soybean.

     

Acclimation of hydrogen peroxide enhances salt tolerance by activating defense-related proteins in Panax ginseng C.A. Meyer

The effect of exogenously applied hydrogen peroxide on salt stress tolerance was investigated in Panax ginseng. Pretreatment of ginseng seedlings with 100 μM H₂O₂ increased the physiological salt tolerance of the ginseng plant and was used as the optimum concentration to induce salt tolerance capacity. Treatment with exogenous H₂O₂ for 2 days significantly enhanced salt stress tolerance in ginseng seedlings by increasing the activities of ascorbate peroxidase, catalase and guaiacol peroxidase and by decreasing the concentrations of malondialdehyde (MDA) and endogenous H₂O₂ as well as the production rate of superoxide radical (O₂ ^?). There was a positive physiological effect on the growth and development of salt-stressed seedlings by exogenous H₂O₂ as measured by ginseng dry weight and both chlorophyll and carotenoid contents. Exogenous H₂O₂ induced changes in MDA, O₂ ^?, antioxidant enzymes and antioxidant compounds, which are responsible for increases in salt stress tolerance. Salt treatment caused drastic declines in ginseng growth and antioxidants levels; whereas, acclimation treatment with H₂O₂ allowed the ginseng seedlings to recover from salt stress by up-regulation of defense-related proteins such as antioxidant enzymes and antioxidant compounds.     

Overexpression of a poplar two-pore K+ channel enhances salinity tolerance in tobacco cells

Populus euphratica is a plant model intensively studied for elucidating physiological and molecular mechanisms of salt tolerance in woody species. Several studies have shown that vacuolar potassium (K⁺) ion channels of the two-pore K⁺ (TPK) family play an important role in maintaining K⁺ homeostasis. Here, we cloned a putative TPK channel gene from P. euphratica, termed PeTPK. Sequence analysis of PeTPK1 identified the universal K-channel-specific pore signature, TXGYGD. Over-expression of PeTPK1 in tobacco BY-2 cells improved salt tolerance, but did not enhance tolerance to hyperosmotic stress caused by mannitol (200?C600?mM). After 3?weeks of NaCl stress (100 and 150?mM), PeTPK1-transgenic cells had higher fresh and dry weights than wild-type cells. Salt treatment caused significantly higher Na⁺ accumulation and K⁺ loss in wild-type cells compared to transgenic cells. During short-term salt stress (100?mM NaCl, 24-h), PeTPK1-transgenic cells showed higher cell viability and reduced membrane permeabilization compared to wild-type cells. Scanning ion-selective electrode data revealed that salt-shock elicited a significantly higher transient K⁺ efflux from PeTPK1-transgenic callus cells and protoplasts compared to that observed in wild-type cells and protoplasts. We concluded that salt tolerance in P. euphratica is most likely mediated through PeTPK1. We propose that, under salt stress, PeTPK1 functions as an outward-rectifying, K⁺ efflux channel in the vacuole that transfers K⁺ to the cytosol to maintain K⁺ homeostasis.     

The modulation of various physiochemical changes in <Emphasis Type="Italic">Bruguiera cylindrica</Emphasis> (L.) Blume affected by high concentrations of NaCl

Bruguiera cylindrica is a major mangrove species in the tropical mangrove ecosystems and it grows in a wide range of salinities without any special features for the excretion of excess salt. Therefore, the adaptation of this mangrove to salinity could be at the physiological and biochemical level. The 3-month-old healthy plantlets of B. cylindrica, raised from propagules were treated with 0 mM, 400 mM, 500 mM and 600 mM NaCl for 20 days under hydroponic culture conditions provided with full strength Hoagland medium. The modulation of various physiochemical changes in B. cylindrica, such as chlorophyll a fluorescence, total chlorophyll content, dry weight, fresh weight and water content, Na⁺ accumulation, oxidation and antioxidation (enzymatic and non-enzymatic) features were studied. Total chlorophyll content showed very minute decrease at 500 mM and 600 mM NaCl treatment for 20 days and the water content percentage was decreased both in leaf and root tissues with increasing concentration. A significant increase of Na⁺ content of plants from 84.505 mM/plant dry weight in the absence of NaCl to 543.38 mM/plant dry weight in plants treated with 600 mM NaCl was recorded. The malondialdehyde and the metabolites content associated with stress tolerance (amino acid, total phenols and proline) showed an increasing pattern with increasing NaCl concentration as compared to the control in both leaf and root tissues but the increase recorded in plantlets subjected to 500 mM was much less, indicating the tolerance potential of this species towards 500 mM NaCl. The significant decrease of sugar content was found only in 600 mM NaCl on 20 days of treatment, showing that the process of sugar synthesis was negatively affected but the same process remains less affected at 500 mM NaCl. A slight reduction in ascorbate and glutathione content and very less increase in carotenoid content were observed at 500 mM and 600 mM NaCl stress. Antioxidant enzymes (APX, GPX, SOD and CAT) showed an enhanced activity in all the treatments and the increased activity was more significant in 600 mM treated plants. The result establishes that B. cylindrica tolerates high NaCl concentration, to the extent of 500 mM NaCl without any major inhibition on photosynthesis and metabolite accumulation. Understanding the modulation of various physiological and biochemical changes of B. cylindrica at high levels of NaCl will help us to know the physiochemical basis of tolerance strategy of this species towards high NaCl.     

Physiological homeostasis for ecological success of Typha (Typha domingensis Pers.) populations in saline soils

The natural capacity of plants to endure salt stress is largely regulated by multifaceted structural and physio-biochemical modulations. Salt toxicity endurance mechanism of six ecotypes of Typha domingensis Pers. was evaluated by analyzing photosynthesis, ionic homeostasis, and stomatal physiology under different levels of salinity (0, 100, 200 and 300 mM NaCl). Typha populations were collected across different areas of Punjab, an eastern province in Pakistan. All studied attributes among ecotypes presented differential changes as compared to control. Different salt treatments not only affected gas exchange attributes but also shown significant modifications in stomatal anatomical changes. As compared to control, net photosynthetic rate, transpiration rate, total chlorophyll contents and carotenoids were increased by 111%, 64%, 103% and 171% respectively, in Sahianwala ecotype among all other ecotypes. Similarly, maximum water use efficiency (WUE), sub stomatal CO₂ concentration, sodium (Na⁺) and chloride (Cl⁻) contents were observed in Sahianwala (191%, 93%, 168%, 158%) and Knotti (162%, 75%, 146%, 182%) respectively, as compared to the others ecotypes. Adaxial and abaxial stomatal areas remained stable in Sahianwala and Knotti. The highest abaxial stomatal density was observed in Gatwala ecotype (42 mm²) and maximum adaxial stomatal density was recorded in Sahianwala ecotype (43 mm²) at 300 mM NaCl salinity. The current study showed that Typha ecotypes responded varyingly to salinity in terms of photosynthesis attributes to avoid damages due to salinity. Overall, differential photosynthetic activity, WUE, and changes in stomatal attributes of Sahianwala and Knotti ecotypes contributed more prominently in tolerating salinity stress. Therefore, Typha domingensis is a potential species to be used to rehabilitate salt affected lands for agriculture and aquatic habitat.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-00963-x.     

Indigenous salt-tolerant rhizobacterium <Emphasis Type="Italic">Pantoea dispersa</Emphasis> (PSB3) reduces sodium uptake and mitigates the effects of salt stress on growth and yield of chickpea

Salt stress has multiple damaging effects on plants including physiological damage, reduced growth, and productivity. Plant growth-promoting rhizobacteria (PGPR) are one of the valuable options to mitigate the negative effects of this stress. In the present study, native bacteria from chickpea’s rhizosphere were isolated, and checked for their salt tolerance and plant growth-promoting attributes (phosphate (P) solubilization, siderophores, indole-3-acetic acid (IAA) production, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase production). One isolate, subsequently identified as Pantoea dispersa, showed appreciable production of IAA (218.3 µg/ml) and siderophores (60.33% SU), P-solubilization (3.64 µg/ml) and ACC deaminase activity (207.45 nmol/mg/h) in the presence of 150 mM NaCl, under laboratory conditions. Salt stress in uninoculated chickpea (GPF2 cultivar) plants induced high accumulation of Na⁺ ions (3.86 mg g^?1 dw) in the leaves, along with significant reduction in K⁺ uptake, membrane integrity, chlorophyll concentration, and leaf water content, thus resulting in impaired growth of the plant and yield (pods and seeds) in a salt concentration-dependent manner. The damage due to salt stress was restored significantly in plants inoculated with P. dispersa. A significant improvement in biomass (32–34%), pods number (31–34.5%), seeds number (32–35.7%), pods weight (30–32.6%), and seeds weight (27–35%) per plant occurred in salt stress-affected plants, which was associated with significant reduction in Na⁺ uptake, reduced membrane damage, significantly improved leaf water content, chlorophyll content, and K⁺ uptake. This study suggests for the first time that native P. dispersa strain PSB3 can be used to alleviate the negative effects of salt stress on chickpea plants and holds the potential to be used as a biofertilizer.     

Co-expression of the Arabidopsis SOS genes enhances salt tolerance in transgenic tall fescue (Festuca arundinacea Schreb.)

Crop productivity is greatly affected by soil salinity; therefore, improvement in salinity tolerance of crops is a major goal in salt-tolerant breeding. The Salt Overly Sensitive (SOS) signal-transduction pathway plays a key role in ion homeostasis and salt tolerance in plants. Here, we report that overexpression of Arabidopsis thaliana SOS1+SOS2+SOS3 genes enhanced salt tolerance in tall fescue. The transgenic plants displayed superior growth and accumulated less Na⁺ and more K⁺ in roots after 350 mM NaCl treatment. Moreover, Na⁺ enflux, K⁺ influx, and Ca²⁺ influx were higher in the transgenic plants than in the wild-type plants. The activities of the enzyme superoxide dismutase, peroxidase, catalase, and proline content in the transgenic plants were significantly increased; however, the malondialdehyde content decreased in transgenic plants compared to the controls. These results suggested that co-expression of A. thaliana SOS1+SOS2+SOS3 genes enhanced the salt tolerance in transgenic tall fescue.     

Foliar application of the triterpene derivative 24-methylen-elemo-lanosta-8,24-dien-3-one alleviates salt toxicity in grapevine

This work focused on the effect triterpene derivative 24-methylen-elemo-lanosta-8,24-dien-3-one (F3) on the induction of salt stress tolerance of the Moroccan grapevine cv. “Doukkali”. Hardwood cuttings of the grapevine from a homogeneous plant material collected in the field were grown in hydroponic medium under different salt concentrations and treated with 50 or 100 µg ml^?1 of F3. Salt stress affected several physiological and biochemical parameters including relative water content, chlorophyll a and b content, peroxidase, and polyphenol oxidase activities, which decreased along with time. Meanwhile, proline, proteins, soluble sugars, H₂O₂, and carotenoid content, as well as phenolic compound content increased, suggesting an evidence of tolerance of this local variety to salinity. An exogenous supply of the triterpenic product increased all these parameters under normal conditions. In addition, F3 at low dose was found to be successful in lowering Na⁺ content and alleviating the inhibitory effects of salt stress on relative water content as well as on chlorophyll a and b.     

Hybridization of wheat and Aegilops cylindrica: development,karyomorphology, DNA barcoding and salt tolerance of the amphidiploids

The development of salt‐tolerant genotypes is key to a better utilization of salinized irrigated lands. Given the relatively low genetic diversity within the cultivated wheats for salt tolerance, exploring the Aegilops cylindrica's genetic diversity for salt tolerance is thus crucial to breed wheat for saline environments. In the current study, wheat genotypes were hybridized with Ae. cylindrica (a hyper salt-tolerant genotype), and amphidiploid plants were produced using embryo rescue and chromosome doubling techniques. Crossability and cytological examinations of amphidiploids and BC₁ were performed before sequencing the ITS4/5 and trnE/trnF DNAs to explore the phylogenetic relationships of the amphidiploids and their parents. Finally, amphidiploids were assessed for salt tolerance. Only two common wheat cultivars (‘Chinese Spring’ and ‘Roshan’) were crossable with Ae. cylindrica. The resultant intergeneric hybrids possessed 70 chromosomes, and morphologically either were similar to the male parent in ‘Chinese Spring’ × Ae. cylindrica or tended to be intermediate between parents in ‘Roshan’ × Ae. cylindrica. The phylogenetic tree divided the genotypes into two groups, in which Clade I contained Ae. cylindrica and three amphidiploids, and Clade II consisted of female parents and one amphidiploid. Amphidiploids exhibited significantly higher tolerance to salt stress compared to the female parents (wheat cultivars) in terms of a higher dry matter, lower accumulation of Na, higher K, and higher K/Na ratio in their root and leaf tissues. Taken together, the amphiploid plants might contain valuable salt tolerance factors.

     

Growth responses of Stylosanthes humilis (Fabaceae) populations to saline stress

The growth responses to salinity of seedlings of six populations of Stylosanthes humilis from three ecogeographic regions of Northeast Brazil, characterized by wet or semi-arid climate, were analyzed following 28 days in solution cultures at concentrations of 0, 40, 80 and 120 mM NaCl. Root and shoot mass, shoot length and characters of foliar damage (number of leaves with chlorosis and necrosis) of the populations were more affected by increasing NaCl than numbers of leaves and branches and root length. Although S. humilis has been considered a salt sensitive legume, significant differences in salt tolerance between populations were found. The estimated concentrations which reduced shoot dry mass by 50 and 25% varied between populations from 84 to 108 and from 49 to 83 mM NaCl, respectively. Salt tolerance in S. humilis during the initial growth stage was lower than the reported one for germination. With one exception, populations from semi-arid climate with saline soils showed higher salt tolerance than those from non saline soils. The results suggest that salt tolerance in these populations is mainly associated with the occurrence of salinity in the soil of their provenance.     

Salt tolerance in the halophyte Salicornia dolichostachya Moss: Growth,morphology and physiology

Salinization of agricultural land is an increasing problem. Because of their high tolerance to salinity, Salicornia spp. could become models to study salt tolerance; they also represent promising saline crops. The salinity-growth response curve for Salicornia dolichostachya Moss was evaluated at 12 salt concentrations in a hydroponic study in a greenhouse and at 5 different seawater dilutions in an outside setting. Salt concentrations ranged between 0 mM and 500 mM NaCl (≈seawater salinity). Plants were grown for six weeks and morphological and physiological adaptations in different tissues were evaluated.S. dolichostachya had its growth optimum at 300 mM NaCl in the root medium, independent of the basis on which growth was expressed. The relative growth rate (RGR) in the greenhouse experiment was comparable with RGR-values in the outdoor growth experiment. Leaf succulence and stem diameter had the highest values at the growth optimum (300 mM NaCl). Carbon isotope discrimination (δ¹³C) decreased upon salinity. S. dolichostachya maintained a lower leaf sap osmotic potential relative to the external solution over the entire salinity range, this was mainly accomplished by accumulation of Na⁺ and Cl⁻. Glycine betaine concentrations did not significantly differ between the treatments. Na⁺:K⁺-ratio and K⁺-selectivity in the shoots increased with increasing salinity, both showed variation between expanding and expanded shoot tissue. We conclude that S. dolichostachya was highly salt tolerant and showed salt requirement for optimal growth. Future growth experiments should be done under standardized conditions and more work at the tissue and cellular level needs to be done to identify the underlying mechanisms of salt tolerance.