Responses of antioxidant enzyme and photosynthesis in rape seedling to the combined stresses of acid rain and ultraviolet-B radiation

Effects of the simulated acid rain（AR） and ultraviolet-B（UV-B, 280-320 nm） radiation with a single or two ways simultaneously （AR ＋ UV-B） on the antioxidant enzyme and photosynthesis of the rape seedlings were investigated by the hydroponic culture. The results of static experiment indicated that the tolerance of rape seedling to single stress（AR or UV-B） is stronger than that to dual stresses（AR ＋ UV-B）. Furthermore, the dual stresses had additive effect on catalase activity, and a synergistic effect on MDA content, net photosynthesis rate, water use efficiency as well as intercellular CO2 concentration. Meanwhile, it has an independent effect on chlorophyll content, stomatal conductance, and transpiration rate as well as membrane permeability. During 64 h restoration course, the dynamic change in the curves of physiological and biochemical indices were not identical, and none of them show a simple linear variation. According to the static and dynamic experiments, it was found that a responsive sequence of catalase activity, membrane permeability, MDA content and photosynthetic characteristics to the above-mentioned stresses was as follows： AR ＋ UV-B 〉 UV-B 〉 AR.

Grain Yield,Biomass Accumulation,and Leaf Photosynthetic Characteristics of Rice under Combined Salinity-Drought Stress

Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.

Development of multi-functional anchorage support dynamic-static coupling performance test system and its application

In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.

Combined stress waves with phase transition in thin-walled tubes

The incremental constitutive relation and governing equations with combined stresses for phase transition wave propagation in a thin-walled tube are established based on the phase transition criterion considering both the hydrostatic pressure and the deviatoric stress. It is found that the centers of the initial and subsequent phase transition ellipses are shifted along the sigma-axis in the sigma tau-plane due to the tension-compression asymmetry induced by the hydrostatic pressure. The wave solution offers the 'fast' and 'slow' phase transition waves under combined longitudinal and torsional stresses in the phase transition region. The results show some new stress paths and wave structures in a thin-walled tube with phase transition, differing from those of conventional elastic-plastic materials.

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.

A STUDY ON THE EFFECT OF RADIAL INERTIA ON THE ELASTO-PLASTIC COMBINED STRESS WAVE PROPAGATION IN THIN-WALLED TUBES

An in-depth analysis of propagation characteristics ofelasto-plastic combined stress waves in circular thin-walled tubeshas been made. In obtaining the simple-wave solution, however, mostresearches have ignored the influence of the circumferential stressrelated to the radial inertial ef- fect in the tubes. In this paperthe incremental elasto-plastic constitutive relations which areconve- nient for dynamic numerical analysis are adopted, and thefinite-difference method is used to study the evolution adpropagation of elasto-plastic combined stress waves in a thin-walledtube with the radial inertial effect of the tube considered. Thecalculation results are compared with those obtained when the radialinertial effect is not considered. The calculation results show thatthe radial inertial effect of a tube has a fairly great influence onthe propagation of elasto-plastic combined stress waves.

Combined Drought and Heat Stress in Rice: Responses, Phenotyping and Strategies to Improve Tolerance

Simultaneous occurrence of drought and heat stress will have significant negative impact on rice yield,especially under upland conditions.The projected increase in global temperatures and reduced precipitation will increase the frequency of occurrence and intensity of these stresses,threatening rice production.Despite recognizing the importance of combined stress in rice,the knowledge generated in this area is very limited.Though complex,understanding combined stress tolerance of rice under water saving cultivation is more critical towards development of climate resilient rice cultivars.Here,we summarized the effects of combined stress on rice physiology with more emphasis on reproductive stage.Omics responses,phenotyping and physiology challenges and potential strategies for improving combined stress tolerance in rice are also discussed.

Metabolic responses to combined water deficit and salt stress in maize primary roots

Soil water deficit and salt stress are major limiting factors of plant growth and agricultural productivity. The primary root is the first organ to perceive the stress signals for drought and salt stress. In this study, maize plant subjected to drought, salt and combined stresses displayed a significantly reduced primary root length relative to the control plants. GC-MS was used to determine changes in the metabolites of the primary root of maize in response to salt, drought and combined stresses. A total of 86 metabolites were measured, including 29 amino acids and amines, 21 organic acids, four fatty acids, six phosphoric acids, 10 sugars, 10 polyols, and six others. Among these, 53 metabolites with a significant change under different stresses were identified in the primary root, and the content of most metabolites showed down-accumulation. A total of four and 18 metabolites showed significant up-and down-accumulation to all three treatments, respectively. The levels of several compatible solutes, including sugars and polyols, were increased to help maintain the osmotic balance. The levels of metabolites involved in the TCA cycle, including citric acid, ketoglutaric acid, fumaric acid, and malic acid, were reduced in the primary root. The contents of metabolites in the shikimate pathway, such as quinic acid and shikimic acid, were significantly decreased. This study reveals the complex metabolic responses of the primary root to combined drought and salt stresses and extends our understanding of the mechanisms involved in root responses to abiotic tolerance in maize.

Propagation of combined longitudinal and torsional stress waves in a functionally graded thin-walled tube

An analytical model for the propagation of combined stress waves in a functionally graded thin-walled tube subjected to combined longitudinal and torsional impact loading is established.The material properties of the tube are assumed to be continuously graded along the length according to a power law function with respect to the volume fractions of the constituents.The generalized characteristic theory is used to analyze the main features of the characteristic wave speeds and simple wave solutions in the functionally graded thin-walled tube.The finite difference method is used to discretize the governing equations.Two types of typical solutions are obtained for the functionally graded tube and the homogeneous tube subjected to combined longitudinal and torsional step loading.The numerical results reveal some abnormal phenomena in the stress path and wave process of the functionally graded thin-walled tube.

THE INVESTIGATION ON DYNAMIC FRACTURE BEHAVOUR OF MATERIALS UNDER COMPRESSIVE-SHEAR COMBINED STRESS WAVES

In this paper,an improved plate impact experimental technique is presented for studying dynamic fracture mechanism of materials,under the conditions that the impacting loading is provided by a single pulse and the loading time is in the sub-microsecond range.The impacting tests are carried out on the pressure-shear gas gun.The loading rate achieved is dK/dt～10~8 MPam^(1/2)s^(-1).With the elimination of influence of the specimen boundary,the plane strain state of a semi-infinite crack in an infinite elastic plate is used to simulate the deformation fields of crack tip. The single pulses are obtained by using the 'momentum trap'technique.Therefore, the one-time actions of the single pulse are achieved by eradicating the stress waves reflected from the specimen boundary or diffracted from the crack surfaces.In the current study,some important phenomena have been observed.The special loading of the single pulse can bring about material damage around crack tip,and affect the material behavior,such as kinking and branching of the crack propagation.Failure mode transitions from mode Ⅰ to mode Ⅱ crack are observed under asymmetrical impact conditions.The mechanisms of the dynamic crack propagation are consistent with the damage failure model.

热应力与电-热复合应力下油纸绝缘老化特性的比较研究(英文)

During the operation of power transformer,its oil-paper insulation is continuously subjected to various stresses,c.g.,the thermal,electrical,mechanical,and chemical stresses,which cause insulation aging gradually.It has been considered that the combined thermal and electrical stresses are the most important and unavoidable factors that induce insulation materials aging.In this work,accelerated aging experiments of oil-impregnated pressboards under combined thermal(130℃) and electrical stresses(4 kV/mm) are performed,while the aging experiments under single thermal stress are also carried out at the corresponding temperature(130℃).The electrical and physic-chemical properties of oil,including dielectric losses factor tanδ,resistivity,acid value and pH value etc.,are measured during the aging process.Dissolved gasses in oil and polymerization degree of cellulose are also measured.The relationship between these properties of oil-paper insulation and aging time is investigated.The results show that dissolved gases in oil,resistivity,tanδof oil under combined thermal and electrical stresses are obviously different from that tinder thermal stress during aging process while some other properties show similar changing trend.For cellulose, compared with the single thermal aging results,it even shows a slower degradation rate in the presence of electrical stress.

非比例加载下电镀铜箔的晶粒长大行为(英文)

Grain growth behavior in a copper foil under nonproportional loading was investigated. The grain growth density decreased with increasing phase shift between normal stress and shear stress. Moreover, under this condition, grains tended to grow in various directions. However, the relative frequency of the grain growth direction was slightly large in the maximum shear stress direction. Therefore, grain growth density is mainly dominated by the equivalent shear stress in Tresca theory in the case of nonproportional loading as well as proportional loading.

THE THREE-DIMENSIONAL STRESS INTENSITY FACTOR UNDER MOVING LOADS ON THE CRACK FACES

The dynamic stress intensity factor history for a half plane crack in an otherwise unbounded elastic body,with the crack faces subjected to a traction distribution consisting of two pairs of combined mode point loads that move in a direction perpendicular to the crack edge is considered.The analytic expression for the combined mode stress intensity factors as a function of time for any point along the crack edge is obtained.The method of solution is based on the application of integral transform together with the Wiener-Hopf technique and the Cagniard-de Hoop method. Some features of the solution are discussed and graphical results for various point load speeds are presented.

Different Responses of Plant Growth and Antioxidant System to the Combination of Cadmium and Heat Stress in Transgenic and Non-transgenic Rice

A comparative study of just cadmium （Cd） or heat and their combination treatments on some physiological parameters and the antioxidant systems in transgenic rice （Oryza sativa L. cv. Zhonghua No.11） carrying glutathione-S-transferase （GST, EC. 2.5.1.18） and catalasel （CAT1, EC. 1.11.1.6） and non-transgenics was conducted. The results revealed improved resistance in the transgenics to Cd and the combined Cd and heat stress than non-transgenics. Data showed that the activities of CAT, GST, superoxide dismutase （EC.1.15.1.1） and all components of the ascorbate-glutatbione cycle measured in the stressed transgenics shoots are significantly different from those of non-transgenics. Results indicated that co-expression of GST and CAT1 had an important effect on the antioxidant system, in particular, the whole ascorbate-glutathione cycle. The less oxidative damage induced by Cd and the stress combination in the transgenics resulted not only from the GST and CAT1 transgene but also from the coordination of the whole ascorbate-glutathione cycle.

Effect of contact forms on the wear of hard silicon surfaces by soft polymers

The mechanism of hard surfaces worn by soft polymers is not clearly understood.In this paper,a new hypothesis has been proposed,it holds that the stress acting on the hard surface under certain working conditions is the main reason for wear of the hard surface by a soft polymer.The hypothesis was investigated by changing the contact form between tribo-pairs.For this,friction tests between six polymer spheres and smooth,rough,and inclined monocrystalline silicon surfaces were carried out.The results show that for the same tribo-pair,the silicon surface will not be worn in some contact forms,but in other contact forms it will be worn.We believe the wear of hard surface by a soft polymer is the result of the combined stress state action on the hard surface.