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.

Effects of Salinity and Potassium Application on Antioxidant Enzyme Activities and Physiological Parameters in Pearl Millet

A plot culture experiment was conducted in a greenhouse at University of Zabol,Iran,to study the effects of different salinity levels and potassium supply on pearl millet.The experiment was laid out in a completely randomized factorial design with three replicates.Potassium sulfate was used as the potassium source.The rates of potassium treatments were 0,100,and 200 kg ha-1.Pearl millet was subjected to different salinity levels（0,4,8,and 12 ds m-1） through addition of NaCl to irrigation water.Results showed that the increase in the salt concentration from control to 12 ds m-1 decreased grain yield（38.7%） of millet plants.In this study,we found a negative relationship between potassium and proline accumulation at vegetative（r2=-0.75＊＊） and reproductive stage（r2=-0.66＊＊） in millet plants.Salt stress remarkably elevated the activities of CAT and GPX antioxidant enzymes at vegetative and reproductive stages.Furthermore,potassium application had significant effect on grain yield and increased it about 10.6% at the highest salinity treatment（12 ds m-1）.Though,potassium treatment increased antioxidant activity in millet plants,it had no significant effect on proline content in leaves.Salinity treatment decreased potassium uptake but application potassium increased potassium content in leaves at two stages.

Effects of parasitic plant Cistanche deserticola on chlorophyll a fluorescence and nutrient accumulation of host plant Haloxylon ammodendron in the Taklimakan Desert

The parasitic plant Cistanche deserticola attaches to Haloxylon ammodendron, a perennial shrub with high tolerance to salinity and drought. However, little was known about the parasite-host relation between the two species. Effects of the parasite on chlorophyll a fluorescence and nutrient accumulation in the host plant （H. am- modendron） were investigated in the Taklimakan Desert. Some photosynthetic parameters of both host and non-host H. ammodendron plants were measured by in vivo chlorophyll a fluorescence technology in the field. The assimilating branches of host and non-host plants were collected and nutrient and inorganic ion contents were analyzed. The results from field experiments showed that the infection of C. deserticola reduced the non-photochemical quenching of the variable chlorophyll fluorescence （NPQ） and the potential maximum quantum yield for primary photochemistry （Fv/Fm） of the host. Compared with non-host plants, the host H. ammodendron had low nutrient, low inorganic ion contents （Na~ and K~） and low K~/Na~ ratios in the assimilating branches. It suggested that C. deserticola infection reduced the nutrient acquisition and caused damage to the photoprotection through thermal dissipation of the energy of the photosystem II in the host, resulting in a decrease in the tolerance to salinity and high radiation. It was concluded that the attachment of the parasite plant （C. deserticola） had negative effects on the growth of its host.

Experimental Study on Fatigue Performance of Reinforced Concrete Beams in Corrosive Environment with Cyclic Loads

In marine environments,reinforced concrete bridge structures are sub-jected to cyclic loads and chloride ingress,which results in corrosion of the rein-forcing bars,early deterioration,durability loss,and a considerable reduction in the fatigue strength.Owing to the complexity of the problem and the difficulty of testing,there are few studies on the fatigue performance of concrete structures under the combined action of corrosion environment and cyclic load.Therefore,a coupling test device for corrosion and cyclic load is designed and fatigue tests of reinforced concrete beams in air environments and chlorine salt corrosive envir-onments are carried out.The fatigue corrosion process,damage mode,and corro-sion features of the test beams as well as chloride ion content in concrete are analyzed.The relationships of deflection,crack,and number of cycles in the dif-ferent environments are given.Results show that the fatigue life of the beam is.greatly reduced under coupled effects of the cyclic load and corrosive environ-ment,the failure fom of the beam is corrosion fatigue damage.The deflection and crack keeps growing with the increase in loading cycles.Under the coupling of cyclic load and corrosion env ironment,the content of chloride ion in concrete is low and there is less variety along the direction of penetration.

Potato Responds to Salt Stress by Increased Activity of Antioxidant Enzymes

To understand the response of potato to salt stress, antioxidant enzyme activities and ion content were analyzed for a sensitive and a tolerant cultivar. Nodal cuttings of the tolerant cultivar, Kennebec, and the sensitive cultivar, Concord, were exposed to media without or with 30, 60, 90 or 120 mmol/L NaCI for 4 weeks. On exposure to NaCI, the length and fresh and dry weight of both shoots and roots of Concord showed greater decrease than those of Kennebec. The decrease in shoot growth was more severe than that of the root for both cultivars. The K^＋ content of shoots and roots of both cultivars was reduced in a dose-dependent manner by exposure to NaCl; the Na^＋ content increased. Activities of ascorbate peroxidase, catalase and glutathione reductase were increased in NaCl-exposed shoots of Kennebec; the corresponding activities in NaCI-exposed shoots of Concord were decreased. Roots of both cultivars showed similar changes in the activities of these enzymes on exposure to NaCI. These studies established that enzyme activities in Concord shoots are inversely related to the NaCI concentration, whereas those in Kennebec do not show a dose dependency, which is also the case for the roots of both cultivars. Our findings suggest that an increase in activity of antioxidant enzymes, such as ascorbate peroxidase, catalase and glutathione reductase, can contribute to salt tolerance in Kennebec, a salt resistant cultivar of potato.

Effects of coarse and fine aggregates on long-term mechanical properties of sea sand recycled aggregate concrete

Typical effects of coarse and fine aggregates on the long-term properties of sea sand recycled aggregate concrete(SSRAC)are analyzed by a series of axial compression tests.Two different types of fine(coarse)aggregates are considered:sea sand and river sand(natural and recycled coarse aggregates).Variations in SSRAC properties at different ages are investigated.A novel test system is developed via axial compression experiments and the digital image correlation method to obtain the deformation field and crack development of concrete.Supportive results show that the compressive strength of SSRAC increase with decreasing recycled coarse aggregate replacement percentage and increasing sea sand chloride ion content.The elastic modulus of SSRAC increases with age.However,the Poisson’s ratio reduces after 2 years.Typical axial stress-strain curves of SSRAC vary with age.Generally,the effect of coarse aggregates on the axial deformation of SSRAC is clear;however,the deformation differences between coarse aggregate and cement mortar reduce by adopting sea sand.The aggregate type changes the crack characteristics and propagation of SSRAC.Finally,an analytical expression is suggested to construct the long-term stress-strain curve of SSRAC.

Effects of water-salt coordinated regulation technique on ion distribution and antioxidant enzyme activities in tomato

In order to explore the effects of brackish water combined with regulated deficit irrigation of different growth periods,different levels of water,and salt synergistic stress on the characteristics of ion absorption,distribution,transport,and antioxidant enzyme activity of tomatoes,a greenhouse pot experiment was applied.The influencing factors were set as:irrigation water salinity(local shallow groundwater S01.1 g/L,S12.0 g/L,S24.0 g/L),different water deficit levels(W170%-80%field capacity(FC),W260%-70%FC,W350%-60%FC),and three growth stages(T1 seedling stage,T2 blossoming and bearing fruits stage,T3 mature picking stage).Monitoring and analyzing the dynamic changes of K^(+)and Na^(+)content in tomato root stems and leaves under water-salt stress and antioxidant enzyme activities of leaves at the seedling stage.The results showed the coordinated regulation of water and salt can significantly change the ion absorption of roots and the transfer between stems and leaves at different growth stages.The roots and leaves of tomatoes mainly accumulated K^(+),and the stems mainly accumulate Na^(+).The increase of irrigation salinity can reduce the ratio of K^(+)/Na^(+)ratio in leaves.Under the coordinated regulation of water and salt,K^(+)became the main osmotic adjustment ion of the leaves again.The activities of catalase,superoxide dismutase,and peroxidase in tomato leaves increased with the increase of water-salt stress.The results have great significance to the response of crops and to meet the requirements for water quality and quantity of brackish water under water-salt stress at different growth stages of tomatoes.

Modifying effects and mechanisms of superfine stainless wires on microstructures and mechanical properties of ultra-high performance seawater sea-sand concrete

Ultra-high-performance seawater sea-sand concrete(UHPSSC)presents a prospective solution to address the natural resource shortage in marine infrastructure construction.To eliminate the corrosion risk of steel fibers and broaden the applicability of UHPSSC,this study investigates the mechanical properties and free chloride ion content as well as microstructures of UHPSSC reinforced with superfine stainless wires(SSWs)under natural curing.The results indicate that 1.5%SSWs can remarkably improve the flexural strength and toughness of UHPSSC by 127%and 1724%,respectively,and mitigate the long-term strength degradation of UHPSSC.The strong interfacial bond between SSW and UHPSSC improves the compactness of UHPSSC,thus reducing the growth space for Ca(OH)_(2) crystals and swelling hydration products generated by sulfate and magnesium ions.This can be supported by the observed reduction in the Ca/Si ratio of C–S–H gels,CH crystal orientation index,and porosity.Moreover,through mechanisms such as pull-out,rupture,overlapping network,and internal anchor interface,SSWs effectively prevent microcrack growth and propagation,transforming single long-connected microcracks into multiple-emission microcracks centered on SSW.Additionally,the free chloride ion content of the composites at 28 and 180 d meets the ACI 318-19 standard requirements for concrete exposed to seawater.This compliance is attributed to the chloride immobilization facilitated by Friedel’s salt and C–S–H gels within the interfaces around SSWs and sea-sand.Consequently,SSWs-reinforced UHPSSC exhibits considerable potential for applications in sustainable marine infrastructures,demanding long-term mechanical properties and high durability.