Salt-tolerant Plant Species Research Articles

Characterization of macrophytes for Na+ removal in synthetic Na-salt solution batch under greenhouse conditions

Sodium salt contamination in the fresh water due to industrial effluents, underground rock salts and inland aquaculture is a major concern needs to be remediated, and subsequently recycled as sustainable bioeconomic strategy. Treatment of saline wastewater requires efficient, cost-effective, rapid, and green technologies, so as to mitigate the negative impacts of salinity on agricultural land. Green technology of phytodesalination is proposed to reduce salinity in the wastewater using salt tolerant plant species. present study was designed with an aim to investigate the sodium (Na+) removal capacity of salt tolerant and high biomass producing macrophytes on synthetic saline wastewater. Sesuvium portulacastrum (sea purslane), Pluchea indica (Indian camphorweed), Typha angustifolia (narrow leaf cattail) and Heliconia psittacorum (heliconia) were collected, cultivated in the greenhouse, subsequently treated with 0 (control) and 217 mM NaCl (salt stress) for 4 weeks. Overall growth performance, physiological change and Na+ removal rate in root and leaf tissues of the candidate plant species were measured. Plants were able to maintain their growth and physiological abilities except for shoot height in T. angustifolia (reduced by 13.7%) and chlorophyll content in S. portulacastrum (reduced by 64%). Major accumulation of Na+ was recorded in the shoots of S. portulacastrum and P. indica (halophytic plant species) and the roots of T. angustifolia and H. psittacorum (glycophytic plant species). Since T. angustifolia and H. psittacorum have high plant biomass, they showed higher Na+ removal efficiency at 4.4% and 5.7%, respectively; whereas due to lower plant biomass, S. portulacastrum and P. indica resulted in the removal of only 0.6 and 0.8% Na+ from the batch, respectively. Based on the information from this investigation, the selected candidate plant species can further be studied in the constructed wetland together with the controlled environments including optimized flowrate, vertical or horizontal flow system, plant densities and Na-removal rate in relation to swamp habitat. Novelty statement: T. angustifolia and H. psittacorum have high plant biomass, they showed higher Na+ removal efficiency at 4.4% and 5.7%, respectively; whereas due to lower plant biomass, S. portulacastrum and P. indica resulted in removal of only 0.6 and 0.8% Na+ from the batch. Based on the information from this investigation, the selected candidate plant species can further be studied in the constructed wetland together with the controlled environments including optimized flowrate, vertical or horizontal flow system, plant densities and Na-removal rate in relation to swamp habitat.

Taxonomic implications of leaf epidermis in halophytes of Amaranthaceae from Salt Range of Punjab, Pakistan

The leaf epidermal anatomy of 15 salt-tolerant plant species belonging to the Amaranthaceae from the Salt Range of Punjab-Pakistan was studied using light microscopy (LM). The main purpose of this investigation was to compare the leaf micro-morphologies of the studied taxa, which can provide diagnostic characters useful for correct identification of halophytic taxa. Various quantitative and qualitative foliar epidermal features of adaxial and abaxial surfaces, including epidermal cell shape, anticlinal wall pattern, lobes per cell, anomocytic, anisocytic, and paracytic types of stomata and trichome diversity, were studied. Eight types of trichomes reported for the halophytes studied i.e. stellate, glandular, conical, capitate, non-capitate, non-glandular, cylindrical, and falcate. The shapes of epidermal cells found are pentagonal, polygonal, irregular, wavy, and tetragonal. This is the first report on leaf epidermal micromorphology of halophytes of family Amaranthaceae of Salt Range of Punjab. The findings revealed that leaf epidermal features showed adequate variations among genera distinguishing the halophytic taxa of family Amaranthaceae.

Effect of Casuarina Plantations Inoculated with Arbuscular Mycorrhizal Fungi and Frankia on the Diversity of Herbaceous Vegetation in Saline Environments in Senegal

Land salinization is a major constraint for the practice of agriculture in the world. Considering the extent of this phenomenon, the rehabilitation of ecosystems degraded by salinization has become a priority to guarantee food security in semi-arid environments. The mechanical and chemical approaches for rehabilitating salt-affected soils being expensive, an alternative approach is to develop and utilize biological systems utilizing salt-tolerant plant species. Casuarina species are naturally halotolerant, but this tolerance has been shown to be improved when they are inoculated with arbuscular mycorrhizal fungi (AMF) and/or nitrogen-fixing bacteria (Frankia). Furthermore, Casuarina plantations have been proposed to promote the development of plant diversity. Thus, the aim of the current study was to evaluate the impact of a plantation comprising the species Casuarina inoculated with AMF and Frankia on the diversity of the sub-canopy and adjacent vegetation. Work was conducted on a plantation comprising Casurina equisetifolia and C. glauca variously inoculated with Frankia and Rhizophagus fasciculatus prior to field planting. The experimental area of 2500 m2 was divided into randomized blocks and vegetation sampling was conducted below and outside of the Casuarina canopy in 32 m2 plots. A total of 48 samples were taken annually over 3 years, with 24 taken from below the Casuarina canopy and 24 from outside the canopy. The results obtained show that co-inoculation with Frankia and Rhizophagus fasciculatus improves the height and survival rate of both species. After 4–5 years, there was greater species diversity and plant biomass in the sub-canopy environment compared with that of the adjacent environments. Our results suggest that inoculation of beneficial microbes can improve growth of Casuarina species and that planting of such species can improve the diversity of herbaceous vegetation in saline environments.

Multicore Study of Upper Holocene Mire Development in West-Frisia, Northern Netherlands: Ecological and Archaeological Aspects

We studied twelve late Holocene organic deposits in West-Frisia, The Netherlands. Pollen, spores, non-pollen palynomorphs, mosses, other botanical macrofossils and insect remains were recorded for reconstructions of changing environmental conditions. Eastern West-Frisia was a cultivated landscape during the Bronze Age, but it became a freshwater wetland in the Late Bronze Age. In most of our sites, radiocarbon dates show that time transgressive inundation of soils preceded the climate shift at 850 cal BC for several centuries. We suggest that solar forcing of climate change may have delivered the final push to the inundation and depopulation of West-Frisia, which had already commenced several centuries before, due to sealevel rise. We did not find evidence for significant Bronze Age tree growth in West-Frisia before the inundations. Vegetation successions in the new wetlands developed from shallow mineral-rich freshwater to rich-fen vegetation. Subsequently poor fen vegetation with birch and pine developed, and the natural succession led to ombrotrophic raised bog vegetation. Complete successions from shallow, mineral-rich lakes to raised bog lasted between 1000 and 1500 calendar years. We hypothesize that medieval drainage and reclamation became possible only when the mires of West-Frisia had reached the raised bog stage. Reclamation of raised bogs by medieval farmers (drainage, eutrophication, peat digging) caused compaction, oxidation and loss of the upper part of the peat deposit. Seeds of salt-tolerant and salt-demanding plant species indicate that the medieval sites were inundated during storm surges with brackish or salt water, which triggered the farmers to build artificial mounds and, later, dikes. Under mounds and dikes, peat deposits remained protected against further decay. With our data we deliver a long-term perspective on contemporary ecosystem dynamics of freshwater wetlands, relevant for nature conservation and future climate change.

Landscape structure of coastal cliffs of the Black Sea coast of the Caucasus

This work is devoted to the analysis of the landscape structure of the coastal cliffs of the Black Sea coast of the Caucasus. The paper analyzes the features of vegetation growth and the landscape structure of the cliffs of the Tuaphat massif, proposes and substantiates the classification of landscapes of coastal cliffs, reveals the features of coastal landscapes. In the landscape structure of the coastal cliffs of the Tuaphat massif, natural boundaries can be distinguished by: the nature of the apparent occurrence of geological layers; substates by the steepness of the slope; striae, which are characterized by more abundant growth of vegetation along cracks in the geological layer; facies usually coincide geographically with nanoand microforms of the relief and are usually represented by one type of vegetation (for example, a pillow rock form). The distribution of vegetation by striae on fine crushed stone of siltstone or mudstone, the absence of halophytes, but the predominance of salt-tolerant plant species with a wide ecological amplitude (petrophytes, cosmopolitans and ruderal) are typical.

Comparative Water Relations of Two Contrasting Date Palm Genotypes under Salinity

Salinity is a global agricultural problem, resulting in a significant reduction in the plantation areas and the crop yields, especially in arid and semiarid regions. The date palm is relatively salt-tolerant plant species, although the nature of salt tolerance is poorly understood. In this study, the salt stress responses of a salt-tolerant “Umsila” was compared with salt-susceptible “Zabad” date palm cultivars. Various physiological parameters, plant-water relations, and anatomical characteristics were analyzed. The results revealed that although salinity has negatively affected both cultivars, Umsila exhibited more stable photosynthesis than Zabad as reflected by the quantum yield (Qy) and the stomatal conductance (GS). Similarly, Umsila showed a more dynamic root system and efficient water relations than Zabad as demonstrated by the leaf water potential (LWP) and relative water content (RWC) during salinity. Umsila also accumulated greater abundances of soluble sugars, potassium (K+), calcium (Ca+2), proline, glycine betaine, and lignin and formed extra layers of Casparian strips in the root tissues when the seedlings were grown under saline conditions. Together, the results obtained from this study have offered some insights into the salt tolerance mechanisms in the date palm.

Transcriptome profiling and environmental linkage to salinity across Salicornia europaea vegetation

BackgroundSalicornia europaea, a succulent obligatory halophyte is the most salt-tolerant plant species in the world. It survives salt concentrations of more than 1 M. Therefore, it is a suitable model plant to identify genes involved in salt tolerance mechanisms that can be used for the improvement of crops. The changes in a plant’s gene expression in response to abiotic stresses may depend on factors like soil conditions at the site, seasonality, etc. To date, experiments were performed to study the gene expression of S. europaea only under controlled conditions. Conversely, the present study investigates the transcriptome and physicochemical parameters of S. europaea shoots and roots from two different types of saline ecosystems growing under natural conditions.ResultsThe level of soil salinity was higher at the naturally saline site than at the anthropogenic saline site. The parameters such as ECe, Na+, Cl−, Ca+, SO42− and HCO3− of the soils and plant organs significantly varied according to sites and seasons. We found that Na+ mainly accumulated in shoots, whereas K+ and Ca2+ levels were higher in roots throughout the growing period. Moreover, changes in S. europaea gene expression were more prominent in seasons, than sites and plant organs. The 30 differentially expressed genes included enzymes for synthesis of S-adenosyl methionine, CP47 of light-harvesting complex II, photosystem I proteins, Hsp70 gene, ATP-dependent Clp proteases, ribulose bisphosphate carboxylase/oxygenase (Rubisco), phenylalanine ammonia-lyase (PAL), cytochrome c oxidase (COX) and ATP synthase.ConclusionThe comparisons made based on two seasons, plant organs and two different sites suggest the importance of seasonal variations in gene expression of S. europaea. We identify the genes that may play an important role in acclimation to season-dependent changes of salinity. The genes were involved in processes such as osmotic adjustment, energy metabolism and photosynthesis.

Saline soil reclamation by agroforestry species under Kalaât Landelous conditions and irrigation with treated wastewater in Tunisia.

Irrigation with treated waste water (TWW) in combination with plantation of agroforest species was tested in the Kalaât Landelous region for the reclamation of salt affected soils. Five species (Atriplex nummularia, Eucalyptus gomphocephala, Acacia cyanophylla, Casuarina glauca, Pinus halepensis) were cultivated in saline soils that are affected by shallow, saline groundwater and were irrigated with TWW during the summer season. The results after 4 years of experimentation show a distinct decrease in soil pH and salinity accompanied by a decrease in Cl and Na concentrations. Irrigation decreased the heavy metal concentrations in the topsoil but an increase in deeper layers indicate to leaching due to TWW irrigation. The investigated plant species were differently affected in growth performance by salinity and TWW irrigation. Atriplex nummularia appeared to be the most resistant species and Pinus halepensis the most sensitive one to hydro-pedological conditions of the Kalaât Landelous plot. In conclusion, salt-tolerant plant species seem to be good candidates for the reclamation of salt-affected, waterlogged sites in combination with TWW irrigation, as the adaptations of such species seem to operate under different abiotic stress conditions.

Contrasting water sources and water-use efficiency in coexisting desert plants in two saline-sodic soils in northwest China.

Soil degradation resulting from various types of salinity is a major environmental problem, especially in arid and semiarid regions. Exploring the water-related physiological traits of halophytes is useful for understanding the mechanisms of salt tolerance. This knowledge could be used to rehabilitate degraded arid lands. To investigate whether different types of salinity influence the water sources and water-use efficiency of desert plants (Karelinia caspia, Tamarix hohenackeri, Nitraria sibirica, Phragmites australis, Alhagi sparsifolia, Suaeda microphylla, Kalidium foliatum) in natural environments, we measured leaf gas exchange, leaf carbon and xylem oxygen isotope composition and soil oxygen isotope composition at neutral saline-sodic site (NSS) and alkaline saline-sodic site (ASS) in northwest China. The studied plants had different xylem water oxygen isotope compositions (δ18 O) and foliar carbon isotope compositions (δ13 C), indicating that desert plants coexist through differentiation in water use patterns. Compared to that at the NSS site, the stem water in K.caspia, A.sparsifolia and S.microphylla was depleted in 18 O at the ASS site, which indicates that plants can switch to obtain water from deeper soil layers when suffering environmental stress from both salinity and alkalinisation. Alhagi sparsifolia had higher δ13 C at the ASS site than at the NSS site, while K.caspia and S.microphylla had lower δ13 C, which may have resulted from interspecific differences in plant alkali and salt tolerance ability. Our results suggest that under severe salinity and alkalinity, plants may exploit deeper soil water to avoid ion toxicity resulting from high concentrations of soluble salts in the superficial soil layer. In managed lands, it is vital to select and cultivate different salt-tolerant or alkali-tolerant plant species in light of local conditions.

Boron tolerance and accumulation potential of four salt-tolerant plant species

Boron (B) is an essential element for plants, but excess B is phytotoxic. Since excess B often occurs along with high salinity in the environment, the purposes of the experiments are to screen plants that tolerate both excess B and high salinity for the remediation of B-contaminated saline water or soils. Here we tested the capacities of B tolerance and accumulation of four salt-tolerant plant species, Tripolium pannonicum, Suaeda glauca, Iris wilsonii, and Puccinelliatenuiflora using hydroponic culture systems, and compared their potential for application in phytoremediation. The maximum B supply concentrations for the survival of T. pannonicum, S. glauca, I. wilsonii, and P. tenuiflora are 40, 250, 700, and 300 mg/L, respectively. The maximum B concentrations in the shoot tissue of these plants are 0.45, 2.48, 15.21, and 8.03 mg/g DW, and in the root are 0.23, 0.70, 6.69, and 2.63 mg/g DW, respectively. Our results suggest that S. glauca, I. wilsonii, and P. tenuiflora are capable of tolerating and accumulating high levels of B, and I. wilsonii is a most promising candidate for the remediation of B-contaminated sites. This study will provide evidence in support of our future pilot studies (e.g., constructed wetlands) on the phytoremediation of B-contaminated water and soil.

The Effects of Saline Stress on the Growth of Two Shrub Species in the Qaidam Basin of Northwestern China

Soil salinization is a serious issue in the Qaidam Basin and significantly limits economic development. To explore the salt tolerance of two shrubs in this area, we determined several parameters, including the Soil and Plant Analyzer Development (SPAD), net photosynthetic rate (Pn), transpiration rate (Tr), intercellular carbon dioxide (Ci, μmol mol−1), stomatal conductance (Gs, umol m−2s−1), and water use efficiency (WUE) under different salt concentrations (0, 100, 200, 300, and 400 mmol·L−1). In addition, the shrubs of Elaeagnus angustifolia and Lycium barbarum of salt tolerance were evaluated. The photosynthetic parameters of E. angustifolia were more sensitive to salinity than those of L. barbarum, and SPAD, Pn, Tr, and WUE of E. angustifolia decreased significantly with increasing salt concentrations (p < 0.05), while in L. barbarum, SPAD, Pn, and Tr decreased significantly with increasing salt concentrations (p < 0.05), but the WUE of L. barbarum showed no significantly variation under the salt concentration gradient. The results of correlation matrix of photosynthetic index also indicated that the minimum salt tolerance of E. angustifolia and L. barbarum were 108.4 and 246.3 mmol·L−1, respectively. Our results provide a scientific basis for the selection of salt-tolerant plant species in of northwest China.

Palyno-morphological investigations of halophytic taxa of Amaranthaceae through SEM from Salt range of Northern Punjab, Pakistan.

The pollen morphology of 11 salt tolerant plant species of family Amaranthaceae from the salt range of Northern Punjab, Pakistan has been studied. The palyno-morphological characters were examined using light and scanning electron microscope. The examined all salt tolerant species have a slight difference in size but have similarity in shape, pore ornamentation, and polarity. The observed morphological characters of pollen grains were pollen symmetry, size, shape, pore ornamentation, pore size, number of pores, exine thickness, polar and equatorial diameter and, P/E ratio. Apolar type of pollens has been observed in all species. Shape of pollens was spheroidal. Exine sculpturing of pollen grains was scabrate (six spp), microechinate (four spp), and microechinate-scabrate (one spp). Different pori numbers were observed in different species. The pantoporate aperturate and sunken pore ornamentation have been reported in all species. A pollen taxonomic key was developed using examined morphological characters for the accurate identification of halophytic taxa. The high fertility and low sterility of pollens confirmed that the selected halophytes are well-established in the salt region. The findings highlight the taxonomic significance of pollen morphology in correct identification and differentiation of salt tolerant plant species.

The responses of two native plant species to soil petroleum contamination in the Yellow River Delta, China.

Petroleum contamination is a significant environmental problem in the Yellow River Delta. The responses of two native salt-tolerant plant species, alfalfa (Medicago sativa) and bristle grass (Setaria uiridis Beauv), to soil petroleum contamination were investigated at five levels between 0 and 2.0% (w/w). Results showed that the total, aboveground and underground plant biomasses of both species were significantly reduced by petroleum contamination (p<0.05), with the inhibition enhanced with increased petroleum levels. However, the emergence rate of bristle grass was promoted by petroleum contamination. Following 100days of exposure, the number of soil petroleum degraders increased greatly, with a trend of initial increase followed by a decrease at 1.5% contamination or higher. Compared to bulk soils, bacteria-degrading alkanes, total hydrocarbons and PAHs in alfalfa rhizosphere soils increased by 1.33-4.18-, 0.85-3.01- and 4.12-12.75-fold, respectively, with an increase of 2.80-10.00-, 4.42-14.44- and 7.30-26.00-fold in bristle grass rhizosphere soils, respectively. The greatest number of petroleum degraders in bristle grass rhizosphere soils resulted in the highest petroleum degradation rate. Bristle grass may be the optimal species for petroleum remediation in the studied area.

CaMKK1 from Chenopodium album positively regulates salt and drought tolerance in transgenic tobacco

Plants encounter various abiotic stresses during the whole life cycle. The mitogen-activated protein kinase kinase (MAPKK) acts as the convergent point of MAPK cascade in stress signaling pathway, which has not widely been studied so far. In the present study, we isolated a group A MAPKK gene (named as CaMKK1) from Chenopodium album, a salt-tolerant plant species in Chenopodiaceae. Quantitative RT-PCR analysis indicates that CaMKK1 was significantly up-regulated and displayed a fast and transient activation, which was similar with MAPK expression pattern in C. album under salt and drought stress. Ectopic expression of CaMKK1 in Escherichia coli BL21 (DE3) strains showed that overexpression of CaMKK1 could increase the salt and drought tolerance to bacterium. Overexpression of CaMKK1 in transgenic tobacco exhibited attenuated salt and PEG sensitivity by means of improving germination percentage and seedling growth. Furthermore, transgenic tobacco lines significantly accumulated organic osmoprotectants, and increased antioxidant enzyme activities which effectively relieved the accumulated reactive oxygen species under stress; the water loss rate was reduced and net photosynthetic rate was significantly increased in transgenic lines compared to non-transgenic plant. The more worth mentioning is that the transcripts of downstream transcription factors (NtDREB2, NtDREB3, NtDREB4) were quickly and dramatically accumulated (from 15 to 224 folds) in transgenic lines under stress. In conclusion, our results indicate that CaMKK1 is a positive regulator in response to salt and drought stress in plants, which should provide new data for further analyzing the function of plant MAPK pathway.

Genome-wide expression profiling in leaves and roots of date palm (Phoenix dactylifera L.) exposed to salinity

BackgroundDate palm, as one of the most important fruit crops in North African and West Asian countries including Oman, is facing serious growth problems due to salinity, arising from persistent use of saline water for irrigation. Although date palm is a relatively salt-tolerant plant species, its adaptive mechanisms to salt stress are largely unknown.ResultsIn order to get an insight into molecular mechanisms of salt tolerance, RNA was profiled in leaves and roots of date palm seedlings subjected to NaCl for 10 days. Under salt stress, photosynthetic parameters were differentially affected; all gas exchange parameters were decreased but the quantum yield of PSII was unaffected while non-photochemical quenching was increased. Analyses of gene expression profiles revealed 2630 and 4687 genes were differentially expressed in leaves and roots, respectively, under salt stress. Of these, 194 genes were identified as commonly responding in both the tissue sources. Gene ontology (GO) analysis in leaves revealed enrichment of transcripts involved in metabolic pathways including photosynthesis, sucrose and starch metabolism, and oxidative phosphorylation, while in roots genes involved in membrane transport, phenylpropanoid biosynthesis, purine, thiamine, and tryptophan metabolism, and casparian strip development were enriched. Differentially expressed genes (DEGs) common to both tissues included the auxin responsive gene, GH3, a putative potassium transporter 8 and vacuolar membrane proton pump.ConclusionsLeaf and root tissues respond differentially to salinity stress and this study has revealed genes and pathways that are associated with responses to elevated NaCl levels and thus may play important roles in salt tolerance providing a foundation for functional characterization of salt stress-responsive genes in the date palm.

Soil characteristics and plant distribution in saline wetlands of Oued Righ, northeastern Algeria

Saline wetlands are rare ecosystems in Saharan areas, which are important for conservation of many endemic and rare plant species. In this study, we investigated five saline wetland sites of the Oued Righ region, located in the northeastern Algeria, to determine the environmental factors controlling the composition and distribution of plant communities. We established a total of 20 transects to measure the vegetation parameters (density and cover) and soil characteristics (electrical conductivity, moisture, pH, CaSO4, CaCO3, organic matter, Na+, K+, Mg2+, Ca2+, SO4 2–, Cl–, NO3 – and HCO3 –). A total of 17 plant species belonging to seven families were identified. The natural vegetation was composed of halophytic and hydro-halophytic plant communities, presented specially by the species of Amaranthaceae family. Soils in the studied wetlands were moist, gypsiferous, alkaline, salty to very salty with dominance of chloride and calcium. Results of the Canonical Correspondence Analysis (CCA) showed that community structure and species distribution patterns of vegetation were mainly dependent on soil characteristics, mainly being soil salinity (CaSO4, K+, Ca2+ and Cl–) and moisture. The distribution of plant species was found to follow a specific zonal pattern. Halocnemum strobilaceum was observed to grow in highly salt-affected soils, thus being the more salt-tolerant species. Phragmites communis plants were widely distributed in the study area with a high density at the edges of accumulated water body. Juncus maritimus, Tamarix gallica and Salicornia fructicosa grew in soils that are partially or completely flooded in winter. Suaeda fructicosa, Traganum nudatum, Arthrocnemum glaucum, Aeluropus littoralis, Cressa cretica and Cynodon dactylon were distributed in salty and moist soils away from the open water body. Plants of Zygophyllum album, Limonastrirum guyonianum, Cornulaca monacantha, Cistanche tinctoria, Mollugo nudicaulis and Sonchus maritimus were found in soils with less salty and moisture. They constituted the outermost belt of vegetation in the studied wetlands. This study will provide a reference on introducing the salt-tolerant plant species as a fodder resource in saline habitats and regenerating the degraded saline wetlands.

Effect of salinity on seed germination, growth and ion content in dimorphic seeds of Salicornia europaea L. (Chenopodiaceae)

The halophyte Salicornia europaea L. is a widely distributed salt-tolerant plant species that produces numerous dimorphic seeds. We studied germination and recovery in dimorphic seeds of Central Asian S. europaea under various salinity conditions. We also tested the effects of various salts on Na+ and K+ accumulation during plant development from germination to anthesis under greenhouse conditions. We found good germination (close to control) of large seeds under NaCl between 0.5 and 2%, Na2SO4 and 2NaCl + KCl + CaCl between 0.5 and 3%, and 2Na2SO4 + K2SO4 + MgSO4 between 0.5 and 5%. For the small seeds, we found stimulating effects of chloride salts (both pure and mixed) under 0.5–1% concentrations, and sulfate salts under 0.5–3%. Both types of seeds showed high germination recovery potential. Salt tolerance limits of the two seed types during germination and at the later stages of development were very similar (4–5%). During plant growth the optimal concentrations of mixed chloride and sulfate salts ranged from 0.5 to 2%. The mechanisms of salt tolerance in the two seed types of S. europaea appear to differ, but complement each other, improving overall adaptation of this species to high salinity.

GDP-D-mannose pyrophosphorylase from Pogonatherum paniceum enhances salinity and drought tolerance of transgenic tobacco.

Pogonatherum paniceum is a highly drought- and salt-tolerant plant species that is typically used for ecological restoration and the conservation of soil and water in many countries. Understanding the molecular mechanisms underlying plant abiotic stress responses, especially to salinity and drought stresses, in species such as P. paniceum could be important to broader crop improvement efforts. GDP-D-mannose pyrophosphorylase (GMPase) is the limiting enzyme in the synthesis of L-ascorbic acid (AsA), which plays a crucial role in the detoxification of reactive oxygen species (ROS). We have cloned and characterized the cDNA of the PpGMP gene of P. paniceum encoding a GMPase. The full-length cDNA sequence contains 1411 nucleotides encoding a putative protein with 361 amino acid residues and an approximate molecular mass of 39.68 kDa. The GMPase transcript was up-regulated in P. paniceum plants subjected to salinity and drought stress, respectively. Transgenic tobacco expressing PpGMPase exhibited enhanced salinity and drought resistance, a higher seed germination rate, better growth performance, a higher AsA content, a more stable redox state, higher superoxide dismutase (SOD) activity, and lower levels of malonaldehyde (MDA) and H2O2 under drought and salinity stress. Taken together, expression of PpGMPase in tobacco conferred salinity and drought stress tolerance by increasing the content of AsA, thereby enhancing ROS-detoxifying functions. Thus, PpGMP is a potential candidate gene for crop improvement.

Time-integrated measurements of seed germination for salttolerant plant species

Time-integrated measurements of seed germination for salttolerant plant species

Yeast functional screen to identify genes conferring salt stress tolerance in Salicornia europaea

Salinity is a critical environmental factor that adversely affects crop productivity. Halophytes have evolved various mechanisms to adapt to saline environments. Salicornia europaea L. is one of the most salt-tolerant plant species. It does not have special salt-secreting structures like a salt gland or salt bladder, and is therefore a good model for studying the common mechanisms underlying plant salt tolerance. To identify candidate genes encoding key proteins in the mediation of salt tolerance in S. europaea, we performed a functional screen of a cDNA library in yeast. The library was screened for genes that allowed the yeast to grow in the presence of 1.3 M NaCl. We obtained three full-length S. europaea genes that confer salt tolerance. The genes are predicted to encode (1) a novel protein highly homologous to thaumatin-like proteins, (2) a novel coiled-coil protein of unknown function, and (3) a novel short peptide of 32 residues. Exogenous application of a synthetic peptide corresponding to the 32 residues improved salt tolerance of Arabidopsis. The approach described in this report provides a rapid assay system for large-scale screening of S. europaea genes involved in salt stress tolerance and supports the identification of genes responsible for such mechanisms. These genes may be useful candidates for improving crop salt tolerance by genetic transformation.