Characterization of saline soil for the halophytes of largest inland saline wetland of India using geospatial technology

About 23%of the surface area and 44%of the volume of all the lakes are occupied by saline lakes in the world.Importantly,agricultural diversion,illegal encroachment,pollution,and invasive species could cause these lakes to dry up completely or partially by 2025.Illegal saltpan encroachment is causing Sambhar,India’s largest saline lake,to shrink by 4.23%every decade.This study aims to characterize the soil parameters where halophytes are growing.A literature survey was conducted for halophytes and soil characteristics.The study area was divided into four zones for stratified random sampling.Soil sampling was conducted in February 2021.The soil indicators for halophyte selected were pH,electrical conductivity,moisture,salinity,organic carbon,and organic matter.The obtained results were interpolated in the geospatial platform for soil characteristic mapping.It is found that no research is conducted on halophytes of the lake.Studies on soil are also inconsistent and only six common parameters could be identified.Results show that the pH ranged 9.37-7.66,electrical conductivity was 16.1-0.38,moisture 23.37%-1.2%,organic carbon 3.29%-0.15%,organic matter 5.6%-0.2%,and salinity 8.86%-0.72%.Though these results show improved condition as compared to last few years,in long term,the lake is desiccating.During the UN Decade of Ecosystem Restoration(2021-2030),if these causes are not addressed,the ecosystem may completely dry up.

Characteristics of mineral elements in shoots of three annual halophytes in a saline desert, Northern Xinjiang

Halophytes are valuable salt-, alkali- and drought-resistant germplasm resources. However, the char- acteristics of mineral elements in halophytes have not been investigated as intensively as those in crops. This study attempted to investigate the characteristics of mineral elements for annual halophytes during their growth period to reveal their possible physiological mechanisms of salt resistance. By using three native annual halophytes （Salsola subcrassa, Suaeda acuminate and Petrosimonia sibirica） distributed in the desert in Northern Xinjiang of China, the dynamic changes in the mineral element contents of annual halophytes were analyzed through field sampling and laboratory analyses. The results demonstrated that the annual halophytes were able to absorb water and mineral nutrients selectively. In the interaction between the annual halophytes and saline soil, the adaptability of the annual halophytes was manifested as the accumulation of S, Na and CI during the growth period and maintenance of water and salt balance in the plant, thus ensuring their selective absorption of N, P, K, Ca, Mg and other mineral nutrients according to their growth demand. By utilizing this property, halophyte planting and mowing （before the wilting and death periods） could bioremediate heavy saline-alkali soil.

Maternal salinity environment affects salt tolerance during germination in Anabasis setifera： A facultative desert halophyte

The effects of maternal salinity and light incubation on the salinity tolerance of the facultative halophyte Anabasis setifera during their germination stages were assessed. Seeds were collected from non-saline habitats in Egypt and saline habitats in the United Arab Emirates （UAE）. The seeds of the two populations were germinated in 0, 100, 200, 400, 600 and 800 mM NaCI, and incubated at 25℃/15℃ in both 12-h light and 12-h darkness regimes and continuous darkness. Significantly more seeds germinated in the Egyptian population than in the UAE population. Salinity tolerance was significantly greater with the Egyptian population than with the UAE population, especially under the conditions of higher salinities. The difference in salinity tolerance between the seeds of two populations was attributed to their seed mass. In addition, germination was significantly faster for the Egyptian population than for the UAE population. Most of the saline treated seeds were able to recover their germination when transferred to distilled water, but this depended on their maternal salinity and light incubation. Recovery from higher salinities was significantly better for the seeds under darkness than for those under light in the UAE population, but the reverse was true for the seeds in the Egyptian population. The higher salinity tolerance for the A. setifera seeds from the non-saline Egyptian population and the lower salinity tolerance for the seeds from the saline UAE population cannot explain their natural distribution. Further studies about other possible roles, such as levels of different promoting and inhibiting phytohormones, are needed to understand the importance of salinity as an environmentally induced maternal effect.

Vertical Migrating and Cluster Analysis of Soil Mesofauna at Dongying Halophytes Garden in Yellow River Delta

For the first time, we used Tullgren method made a study on vertical migrating and cluster analysis of the soil mesofauna in Dongying Halophytes Garden in the Yellow River Delta （YRD）, Shandong Province. The results showed that the soil mesofauna tended to gather on soil surface in most samples at most times, but the vertical migrating greatly varied in different seasons or environment conditions. Acari was the dominant group. The index of diversity of the soil fauna was correlated with the index of evenness. The Acari＇s number of individuals infected other species and numbers. Dominant group-Aeari made greater contribution to the result of cluster analysis, and there were significant differences between communities in different habitats by cluster analysis with both Bray-Curtis and Jaccard similarity coefficient.

Diversity of cultivable endophytic bacteria associated with halophytes in Xinjiang of China and their plant beneficial traits

Endophytic bacteria from halophytes have a wide range of application prospects in various fields,such as plant growth-promoting,biocontrol activity and stress resistance.The current study aimed to identify cultivable endophytic bacteria associated with halophytes grown in the salt-affected soil in Xinjiang Uygur Autonomous Region,China and to evaluate their plant beneficial traits and enzyme-producing activity.Endophytic bacteria were isolated from Reaumuria soongorica(PalL Maxim.),Artemisia carvifolia(Buch.-Ham.ex Roxb.Hort.Beng.),Peganum harmala L.and Suaeda dendroides(C.A.Mey.Moq.)by using the cultural-dependent method.Then we classified these bacteria based on the difference between their sequences of 16S rRNA(16S ribosomal RNA)gene.Results showed that the isolated bacteria from R.soongorica belonged to the genera Brucella,Bacillus and Variovorax.The bacteria from A.carvifolia belonged to the genera Micromonospora and Brucella.The bacteria from P.harmala belonged to the genera Paramesorhizobium,Bacillus and Peribacillus.The bacteria from S.dendroides belonged to the genus Bacillus.Notably,the genus Bacillus was detected in the three above plants,indicating that Bacillus is a common taxon of endophytic bacteria in halophytes.And,our results found that about 37.50%of the tested strains showed strong protease-producing activity,6.25%of the tested strains showed strong cellulase-producing activity and 12.50%of the tested strains showed moderate lipase-producing activity.Besides,all isolated strains were positive for IAA(3-Indoleacetic acid)production,31.25%of isolated strains exhibited a moderate phosphate solubilization activity and 50.00%of isolated strains exhibited a weak siderophore production activity.Our findings suggest that halophytes are valuable resources for identifying microbes with the ability to increase host plant growth and health in salt-affected soils.

Unlocking the in vitro anti-Trypanosoma cruzi activity of halophyte plants from the southern Portugal

Objective:To evaluate the in vitro anti-Trypanosoma cruzi（T.cruzi） activity of organic extracts prepared from halophyte species collected in the southern coast of Portugal（Algarve）,and chemically characterize the most active samples.Methods:Acetone,dichloromethane and methanol extracts were prepared from 31 halophyte species and tested in vitro against trypomastigotes and intracellular amastigotes of the Tulahuen strain of T.cruzi.The most active extract was fractionated by preparative HPLC-DAD,affording 11 fractions.The most selective fraction was fully characterized by 1H-NMR.Results:From 94 samples tested,one was active,namely the root dichloromethane extract of Juncus acutus(IC50 < 20 μg/mL).This extract was fractionated by HPLC,affording 11 fractions,one of them containing only a pure compound（juncunol）,and tested for anti-parasitic activity.Fraction 8(IC50 = 4.1 μg/mL) was the most active,and was further characterized by 1H-NMR.The major compounds were phenanthrenes,9,10-dihydrophenanthrenes and benzocoumarins.Conclusion:Our results suggest that the compounds identified in fraction 8 are likely responsible for the observed anti parasitic activity.Further research is in progress aiming to isolate and identify the specific active molecules.To the best of our knowledge,this is the first report on the in vitro anti T.cruzi activity of halophyte species.

Homologous cloning, characterization and expression of a new halophyte phytochelatin synthase gene in Suaeda salsa

The halophyte Suaeda salsa can grow in heavy metal-polluted areas along intertidal zones having high salinity.Since phytochelatins can effectively chelate heavy metals,it was hypothesized that S.salsa possessed a phytochelatin synthase(PCS) gene.In the present study,the cDNA of PCS was obtained from S.salsa(designated as SsPCS) using homologous cloning and the rapid amplification of cDNA ends(RACE).A sequence analysis revealed that SsPCS consisted of 1 916 bp nucleotides,encoding a polypeptide of 492 amino acids with one phytochelatin domain and one phytochelatin C domain.A similarity analysis suggested that SsPCS shared up to a 58.6%identity with other PCS proteins and clustered with PCS proteins from eudicots.There was a new kind of metal ion sensor motif in its C-terminal domain.The SsPCS transcript was more highly expressed in elongated and fibered roots and stems(P<0.05) than in leaves.Lead and mercury exposure significantly enhanced the mRNA expression of SsPCS(P<0.05).To the best of our knowledge,SsPCS is the second PCS gene cloned from a halophyte,and it might contain a different metal sensing capability than the first PCS from Thellungiella halophila.This study provided a new view of halophyte PCS genes in heavy metal tolerance.

Endophytic bacteria associated with halophyte Seidlitzia rosmarinus Ehrenb.ex Boiss.from saline soil of Uzbekistan and their plant beneficial traits

Endophytic bacteria of halophytic plants play essential roles in salt stress tolerance.Therefore,an understanding of the true nature of plant-microbe interactions under extreme conditions is essential.The current study aimed to identify cultivable endophytic bacteria associated with the roots and shoots of Seidlitzia rosmarinus Ehrenb.ex Boiss.grown in the salt-affected soil in Uzbekistan and to evaluate their plant beneficial traits related to plant growth stimulation and stress tolerance.Bacteria were isolated from the roots and the shoots of S.rosmarinus using culture-dependent techniques and identified by the 16S rRNA gene.RFLP(Restriction Fragment Length Polymorphism)analysis was conducted to eliminate similar isolates.Results showed that the isolates from the roots of S.rosmarinus belonged to the genera Rothia,Kocuria,Pseudomonas,Staphylococcus,Paenibacillus and Brevibacterium.The bacterial isolates from the shoots of S.rosmarinus belonged to the genera Staphylococcus,Rothia,Stenotrophomonas,Brevibacterium,Halomonas,Planococcus,Planomicrobium and Pseudomonas,which differed from those of the roots.Notably,Staphylococcus,Rothia and Brevibacterium were detected in both roots and shoots,indicating possible migration of some species from roots to shoots.The root-associated bacteria showed higher levels of IAA(indole-3-acetic acid)synthesis compared with those isolated from the shoots,as well as the higher production of ACC(1-aminocyclopropane-1-carboxylate)deaminase.Our findings suggest that halophytic plants are valuable sources for the selection of microbes with a potential to improve plant fitness under saline soils.

Evaluating germinability of eight desert halophytes under long-term seed storage: Implications for conservation

Ex situ conservation in seed banks is a potential complementary conservation strategy for native plant species.It is well established that ex situ seed banking of native wild plants prolongs seed viability and thereby preserves genetic and species diversity for future use.We evaluated ex situ storage potential of eight halophytic species from deserts in the United Arab Emirates(UAE)by studying seed germination.Specifically,we examined the germinability of freshly collected seeds and seeds stored for three years in a seed bank.We also examined the effect of light conditions on fresh and stored seed germination.Fresh seeds of seven of the eight species tested had a higher germination rates under 12/12 h light/dark fluctuations than did those exposed to total darkness.Storage reduced light sensitivity in Halocnemum strobilaceum,Suaeda aegyptiaca,Salsola drummondii and Salsola imbricata,but increased the requirement for light in Arthrocnemum macrostachyum.In Anabasis setifera,storage decreased germination percentage when there was a 12-hour light/dark fluctuation,but increased germination rate when exposed to the dark treatment.Storage significantly reduced germination in both the light/dark and dark treatments in Suaeda vermiculata and S.aegyptiaca.Germination speed also responded differently to storage;whereas Timson's index significantly increased in A.macrostachyum and H.strobilaceum,it significantly decreased for S.drummondii,S.aegyptiaca and S.vermiculata.Germination of these species at a range of temperatures requires further testing;additionally,we strongly suggest that these laboratory findings be complemented by field studies.

Effects of Different Halophytes on Soil Microflora and Enzyme Acti-vities of Saline-alkali Soil

In the pot experiment,seven varieties of halophytes were grown in saline-alkali soil to investigate the responses of microflora and soil enzymes in the rhizosphere.The results showed that compared to the control,the population of bacterial colony(84.8%-95.6%),actinomycetes colony(12.0%-14.5%)and fungi colony(0.5%-1.1%)increased significantly(P<0.05).The population of ammonia bacteria,aerobic cellulose decomposition bacteria in the soil of Vicia sativa L.(201.99%and 395.49%),Medicago sativa(152.43%and 319.90%)and Sesbania cannabina(Retz.)Pori(193.14%and 396.08%)were higher significantly than that of Panicum virgatum L.(49%and 60%),Sorghum bicolor(L.)Moench(99%and 210%),Amaranthus hypochondriacus L.(75%and 36%)and Aneurotepidimu chinense(75%and 77%)(P<0.05).However,Sorghum bicolor(L.)Moench was evidently higher than Panicum virgatum L.,Amaranthus hypochondriacus L.and Aneurotepidimu chinense(P<0.05)in the soil.The population of ammonia bacteria and aerobic cellulose-decomposing bacteria was significantly correlated with the five enzymes(P<0.05),which could improve the microenvironment in saline-alkali soil to accelerate the element cycling and promote the sustainable development of agriculture through cultivating Medicago sativa,Vicia sativa L.,Sesbania cannabina(Retz.)Pori and Sorghum bicolor(L.)Moench.

Mesocosm Assessment of Stability Habitat for Halophyte

In this paper, we constructed the halophyte Mesocosm experimental group which was used as a substrate material that consisted of tidal flat and dredged sediment. Depending on whether the ingredients of vegetation and substrate material of Mesocosm, we constructed Mesocosm A (tidal flat sediment + Salicornia herbecea), Mesocosm B (only dredged sediment), Mesocosm C (dredged sediment + Salicornia herbecea). Monitoring was carried out of seawater quality factors (Chemical Oxygen Demand (COD), Total Nitrogen (T-N), Total Phosphorus (T-P), temperature, salinity), sediment factors (Chemical Oxygen Demand (COD), Total (T-N), Total Phosphorus (T-P) and growth of Salricornia herbecea) in each Mesocosm. Habitat Stability Index of vegetation was calculating by using the monitoring results. HSI of Mesocosm C was calculated from 0.87 to 0.95 as compared to the relatively high HSI Mesocosm A, it was evaluated to be able to be used in the restoration of the coastal salt marsh with dredged sediment.

Study of Halophytes Dispersion in the North-West Region of Algeria

To know the mode of distribution of halophytes species in the western region of Algeria, it was considered useful to undertake a study based on the achievement of identified linear. Two areas were considered, Northern Tlemcen (Beni Saf and Rachgoun) and Northwest Oran (Sabkha). The trend of climate aridity which is more pronounced in the study area may have influences on floristic halophytes. The study of the floristic composition showed the importance of indicator halophitisation species such as Atriplex halimus, Tamarix gallica, Salicornia fruticosa, Arthrocnemum glaucum and was accompanied by various therophytes such as Sinapis arvensis, Erodium moschatum, Malva sylvestris and Plantago lagopus. ANOVA (analysis of variance) has highlighted the factors that influence the spatial distribution of some halophytes species at five stations studied;some are dispersed aggregates (Tamarix gallica, Suaeda fruticosa) with a coefficient of variation (Cv) greater than 10%;others are regularly dispersed (Atriplex halimus) with a coefficient of variation (Cv) less than 10%.

Climate and topography regulate the spatial pattern of soil salinization and its effects on shrub community structure in Northwest China

Soil salinization may affect biodiversity and species composition,leading to changes in the plant community structure.However,few studies have explored the spatial pattern of soil salinization and its effects on shrub community structure at the ecosystem scale.Therefore,we conducted a transect sampling of desert shrublands in Northwest China during the growing season(June–September)in 2021.Soil salinization(both the degree and type),shrub community structure(e.g.,shrub density and height),and biodiversity parameters(e.g.,Simpson diversity,Margalf abundance,Shannon-Wiener diversity,and Pielou evenness indices)were used to assess the effects of soil salinization on shrub community structure.The results showed that the primary degree of soil salinization in the study area was light salinization,with the area proportion of 69.8%.Whereas the main type of soil salinization was characterized as sulfate saline soil,also accounting for 69.8%of the total area.Notably,there was a significant reduction in the degree of soil salinization and a shift in the type of soil salinization from chloride saline soil to sulfate saline soil,with an increase in longitude.Regional mean annual precipitation(MAP),mean annual evapotranspiration(MAE),elevation,and slope significantly contributed to soil salinization and its geochemical differentiation.As soil salinization intensified,shrub community structure displayed increased diversity and evenness,as indicated by the increases in the Simpson diversity,Shannon-Wiener diversity,and Pielou evenness indices.Moreover,the succulent stems and leaves of Chenopodiaceae and Tamaricaceae exhibited clear advantages under these conditions.Furthermore,regional climate and topography,such as MAP,MAE,and elevation,had greater effects on the distribution of shrub plants than soil salinization.These results provide a reference for the origin and pattern of soil salinization in drylands and their effects on the community structure of halophyte shrub species.

Comparison of biochar properties from 5 kinds of halophyte produced by slow pyrolysis at 500℃

Glycophyte biomass-derived biochars are currently concerned in most studies.However,little attention is given to the char-acteristics of halophyte-derived biochars.In this study,five typical halophytes of euhalophytes(Suaeda altissima,Suaeda salsa,and Kalidium foliatum),recretohalophytes(Phragmites australis),and pseudohalophytes(Tamarix chinensis)which are widely distributed in the arid and semiarid regions of northwestern China were selected for producing biochars with a slow pyrolysis process at 500℃for 1 h.The harvested biochars were characterized in elemental content,pores,surface area,and surface charges,and then their potential value as a soil conditioner was evaluated.The results showed that the halophyte-derived biochars had variable ash and Na+contents,ranging from 7.26 to 23.64%and 1.06 to 33.93 g kg^(−1)respectively.The EC value of the biochars ranged from 1.76 to 23.45 mS cm^(−1).The biochar derived from Suaeda altissima had a very low specific surface area(SSA),3.50 m^(2)g^(−1),while that derived from Phragmites australis(BPA)had a very high SSA,344.02 m^(2)g^(−1).All the biochars carried both positive and negative charges.Kalidium foliatum biochar(BKF)possessed more nega-tive charges,while Suaeda altissima biochar(BSA)contained more positive charges.In general,the halophyte biochars had a higher ash content and lower point of zero net charge(PZNC)value,compared with the biochars derived from glycophytes,which would imply their higher potential value as an acidic soil conditioner.

Kinetics of the Anti-oxidant Response to Salinity in the Halophyte Cakile maritima

The effects of NaCl stress on the activity of anti-oxidant enzymes （superoxide dismutase, catalase （CAT）, peroxidase （POD）, ascorbate peroxidase （APX）, monodehydroascorbate reductase, dehydroascorbate reductase （DHAR）, and glutathione reductase （GR））, anti-oxidant molecules （ascorbate and glutathione）, and parameters of oxidative stress （malondialdehyde （MDA）, electrolyte leakage, and H2O2 concentrations） were investigated in Cakile maritima, a halophyte frequent along the Tunisian seashore. Seedlings were grown in the presence of salt （100, 200, and 400 mmol/L NaCl）. Plants were harvested periodically over 20 days. Growth was maximal in the presence of 0-100 mmol/L NaCl. At 400 mmol/L NaCl, growth decreased significantly. The salt tolerance of C. maritima, at moderate salinities, was associated with the lowest values of the parameters indicative of oxidative stress, namely the highest activities of POD, CAT, APX, DHAR, and GR and high tissue content of ascorbate and glutathione. However, prolonged exposure to high salinity resulted in a decrease in anti-oxidant activities and high MDA content, electrolyte leakage, and H2O2 concentrations. These results suggest that anti-oxidant systems participate in the tolerance of C. maritima to moderate salinities.

Expression Analysis of Proline Metabolism-related Genes From Halophyte Arabis stelleri under Osmotic Stress Conditions

Arabis stelleri var. japonica evidenced stronger osmotic stress tolerance than Arabidopsis thaliana. Using an A. thaliana microarray chip, we determined changes in the expression of approximately 2 800 genes between A. stelleri plants treated with 0.2 M mannitol versus mock-treated plants. The most significant changes in the gene expression patterns were in genes defining cellular components or in genes associated with the endomembrane system, stimulus response, stress response, chemical stimulus response, and defense response. The expression patterns of three de novo proline biosynthesis enzymes were evaluated in A. stelleri var. japonica seedlings treated with 0.2 M mannitol, 0.2 M sorbitol, and 0.2 M NaCI. The expression of At-pyrroline-5-carboxylate synthetase was not affected by NaCI stress but was similarly induced by mannitol and sorbitol. The proline dehydrogenase gene, which is known to be repressed by dehydration stress and induced by free L-proline, was induced at an early stage by mannitol treatment, but the level of proline dehydrogenase was increased later by treatment with both mannitol and NaCI. The level of free L-proline accumulation increased progressively in response to treatments with mannitol, sorbitol, and NaCI. Mannitol induced L-proline accumulation more rapidly than NaCI or sorbitol. These findings demonstrate that the osmotic tolerance of the novel halophyte, Arabis stelleri, is associated with the accumulation of L-proline.

Effect of Nitrate on Root Development and Nitrogen Uptake of Suaeda physophora Under NaCl Salinity

The effects of NaCl salinity and NO^-3 on growth, root morphology, and nitrogen uptake of a halophyte Suaeda physophora were evaluated in a factorial experiment with four concentrations of NaCl （1, 150, 300, and 450 mmol L^-1） and three NO^-3 levels （0.05, 5, and 10 mmol L^-1） in solution culture for 30 d. Addition of NO^-3 at 10 mmol L^-1 significantly improved the shoot （P 〈 0.001） and root （P 〈 0.001） growth and the promotive effect of NO^-3 was more pronounced on root dry weight despite the high NaCl concentration in the culture solution, leading to a significant increase in the root：shoot ratio （P 〈 0.01）. Lateral root length, but not primary root length, considerably increased with increasing NaCl salinity and NO^-3 levels （P 〈 0.001）, implying that Na^＋ and NO3^- in the culture solution simultaneously stimulated lateral root growth. Concentrations of Na^＋ in plant tissues were also significantly increased by higher NaCl treatments （P 〈 0.001）. At 10 mmol L^-1 NO^-3, the concentrations of NO^-3 and total nitrogen and nitrate reductase activities in the roots were remarkably reduced by increasing salinity （P 〈 0.001）, but were unaffected in the shoots. The results indicated that the fine lateral root development and effective nitrogen uptake of the shoots might contribute to high salt tolerance of S. physophora under adequate NO^-3 supply.

Detecting soil salinity with arid fraction integrated index and salinity index in feature space using Landsat TM imagery

Modeling soil salinity in an arid salt-affected ecosystem is a difficult task when using remote sensing data because of the complicated soil context （vegetation cover, moisture, surface roughness, and organic matter） and the weak spectral features of salinized soil. Therefore, an index such as the salinity index （SI） that only uses soil spectra may not detect soil salinity effectively and quantitatively. The use of vegetation reflectance as an indirect indicator can avoid limitations associated with the direct use of soil reflectance. The normalized difference vegetation index （NDVI）, as the most common vegetation index, was found to be responsive to salinity but may not be available for retrieving sparse vegetation due to its sensitivity to background soil in arid areas. Therefore, the arid fraction integrated index （AFⅡ） was created as supported by the spectral mixture analysis （SMA）, which is more appropriate for analyzing variations in vegetation cover （particularly halophytes） than NDVI in the study area. Using soil and vegetation separately for detecting salinity perhaps is not feasible. Then, we developed a new and operational model, the soil salinity detecting model （SDM） that combines AFⅡ and SI to quantitatively estimate the salt content in the surface soil. SDMs, including SDM1 and SDM2, were constructed through analyzing the spatial characteristics of soils with different salinization degree by integrating AFⅡ and SI using a scatterplot. The SDMs were then compared to the combined spectral response index （COSRI） from field measurements with respect to the soil salt content. The results indicate that the SDM values are highly correlated with soil salinity, in contrast to the performance of COSRI. Strong exponential relationships were observed between soil salinity and SDMs （R2〉0.86, RMSE〈6.86） compared to COSRI （R2=0.71, RMSE=16.21）. These results suggest that the feature space related to biophysical properties combined with AFII and SI can effectively provide information on soil salinity.

Effects of salinity and desalination on seed germination of six annual weed species

The effects of various salinities and desalination on seed germination of six annual glycophytes （Artemisia sieversiana, A. scoparia, Chloris virgata, Eragrostis pilosa, Chenopodium acuminatum and Chenopodium glaucum） were studied in Horqin Sandy Land, Inner Mongolia, China. NaCl solutions of five concentrations （0 mM, as the control, and 50, 100, 200 and 300 mM） were used for saline stress and desalination treatments. Increasing salinity significantly reduced germination percentages of A. sieversiana, A. scoparia, Ch.virgata and Ch. acuminatum, but had no effect on the germination percentages of E. pilosa. Lower salinity levels （50 mM） significantly increased germination percentage of Ch. glaucum. High salinity might be a precondition for germi- nation after desalination for five of the six species, excepting E. pilosa at NaCl concentration of 300 mM in comparison with non-primed seeds. Higher salinity （200 mM） led to some specific ion toxicity and reduced seed viability of A. sieversiana. No specific ion toxicity but an osmotic effect limited the germination of other five species was observed The final germination percentages （salinity stress and desalination） of the six species showed three variations in comparison with the controls, namely, indiscrimination, stimulation, and reduction. Germination responses to salinity and desalination suggested that the six species were separated into three categories. Three species （A. sieversiana, Ch. virgata and Ch. acuminatum） showed similar germination responses to salinity with those of halophyte, but also showed a lower tolerance limit than most halophytes, although this was not always the case. A. scoparia and Ch. glaucum exhibited some ‘salt stimulation’ in seed germination percentages after desalination, whereas E. pilosa did not show any obvious responseto salinity. Therefore, salinity usually induces dormancy of seeds with strong germination capacity in fresh water, but has few, or even positive, effects on seeds with strong innate dormancy.

Photosynthetic Behaviour and Mineral Nutrition of Tamarix gallica Cultivated Under Aluminum and NaCl Combined Stress

The lack of knowledge of plant tolerance and differential response to aluminum(Al)encouraged many researchers,in the last decade,to elucidate Al toxicity and tolerance mechanisms.The current study reported the impact of Al,a toxic element with negative effects on plant growth and development,in halophytic plant Tamarix gallica.Plants were subjected to different Al concentrations(0,200,500 and 800μM)with or without NaCl(200 mM)supplementation.Growth,photosynthesis and mineral content were assessed.Al stress had a significant decrease on shoots’biomass production between 19 to 41%,and a little variation on chlorophyll content and photosynthetic efficiency(Fo,Fm,Fv fluorescence’s and Fv/Fm).Furthermore,the Al-treatments did not affect significantly the content of potassium,calcium,and magnesium in different plant parts,whereas NaCl addition to the medium induced a decrease in these elements’concentrations.Our results have shown that T.gallica is able to accumulate the high levels of Al in shoots and roots,6288μg.g^(-1) DW and 7834μg.g^(-1) DW respectively.It is considered as a hyperaccumulator plant of Al.In addition,Na+contents in shoots and roots exceed 23000μg.g^(-1) DW.Therefore,T.gallica presents a high tolerance at the same time to Al and NaCl phytotoxicity,so it is interesting to use in phytoremediation programs.