Phosphorus utilization and microbial community in response to lead/iron addition to a waterlogged soil

Constructed wetlands have emerged as a viable option for helping to solve a wide range of water quality problems. However, heavy metals adsorbed by substrates would decrease the growth of plants, impair the functions of wetlands and eventually result in a failure of contaminant removal. Typha latifolia L., tolerant to heavy metals, has been widely used for phytoremediation of Pb/Zn mine tailings under waterlogged conditions. This study examined effects of iron as ferrous sulfate （100 and 500 mg/kg） and lead as lead nitrate （0, 100, 500 and 1000 mg/kg） on phosphorus utilization and microbial community structure in a constructed wetland. Wetland plants （T. latifolia） were grown for 8 weeks in rhizobags filled with a paddy soil under waterlogged conditions. The results showed that both the amount of iron plaque on the roots and phosphorus adsorbed on the plaque decreased with the amount of lead addition. When the ratio of added iron to lead was 1：1, phosphorus utilized by plants was the maximum. Total amount of phospholipids fatty acids （PLFAs） was 23%-59% higher in the rhizosphere soil than in bulk soil. The relative abundance of Gram-negative bacteria, aerobic bacteria, and methane oxidizing bacteria was also higher in the rhizosphere soil than in bulk soil, but opposite was observed for other bacteria and fungi. Based on cluster analysis, microbial communities were mostly controlled by the addition of ferrous sulfate and lead nitrate in rhizosphere and bulk soil, respectively.

Monitoring Perennial Sub-Surface Waterlogged Croplands Based on MODIS in Jianghan Plain, Middle Reaches of the Yangtze River

Perennial waterlogged soil（PWS） is induced by the high level of groundwater, and has a persistent impact on natural ecosystems and agricultural production. Traditionally, distribution information regarding PWS is mainly collected from in situ measurements through groundwater level surveys and physicochemical property analyses. However, in situ measurements of PWS are costly and time-consuming, only rough estimates of PWS areas are available in some regions. In this paper, we developed a method to monitor the perennial waterlogged cropland using time-series moderate resolution imaging spectroradiometer（MODIS） data. The Jianghan Plain, a floodplain located in the middle reaches of the Yangtze River, was selected as the study area. Temporal variations of the enhanced vegetation index（EVI）, night land surface temperature（LST）, diurnal LST differences（ΔLST）, albedo, and the apparent thermal inertia（ATI） were used to analyze the ecological and thermodynamic characteristics of the waterlogged croplands. To obtain pure remote sensing signatures of the waterlogged cropland from mixed pixels, the croplands were classified into different types according to soil and land cover types in this paper, and a linear mixing model was developed by fitting the signatures using the multiple linear regression approach. Afterwards, another linear spectral mixing model was used to get the proportions of waterlogged croplands in each 1 km×1 km pixel. The result showed an acceptable accuracy with a root-mean-square error of 0.093. As a tentative method, the procedure described in this paper works efficiently as a method to monitor the spatial patterns of perennial sub-surface waterlogged croplands at a wide scale.

Application of unsteady flow simulation technology to lightening urban storm waterlogged disaster

The application of unsteady simulation to lightening urban storm waterlogged disaster involves six blocks: the main program, the database of drainage networks, the abstractions and losses block, the calculating inflow of sewer block, the drainage networks routing block and the waterlogged areas calculating block. This model can be used for simulating sewer surcharge and calculating area and water depth of waterlogged areas under storm conditions. The best design of rebuilding storm sewer system or combined sewer system can be provided by simulating existing state of built drainage pipeline. The model was used for rebuilding Shenyang drainage works last year, and the good results were obtained.

Characteristics Research of Immersed and Waterlogged Subterranean River System of Reservoir Areas of Hydroelectric Stations

The karst immersion and waterlogging is one of the typical and the m os t harmful natural disasters in southern karst areas of China. It is threat to th e local production and life for a long time. In recent years, due to the constru ction of more reservoirs, the disaster became serious. This article takes immers ion and waterlogging of Banwen's subterranean rivers in Yantan reservoir area as an example, researches the daily rainfall's reflection to the water level of re servoir depression, discusses characteristics of immersion and waterlogging of t he valley, analyzes the disaster index in detail, such as water level process, t he highest water level, sensitive rainfall, original waterlogged rainfall and de layed day numbers etc., and provides the reference as a basis to the disaster an alysis.

Evaluation of Waterlogged Areas in El-Farafra Oasis, Egypt

A geographic information system (GIS) is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographical data. The key word to this technology is Geography—this means that some portion of the data is spatial. In other words, data that is in some way referenced to locations on the earth. The goal of this study is to evaluate how precisely waterlogging can be identified from medium-goals satellite pictures utilizing EWIS list. The point is to distinguish and mapping of the waterlogged territories in the piece of Farafra Desert Oasis of Egypt. To complete this identification, Landsat-8 symbolism and geographical sheets (1:50,000) have been utilized and handling through Envi 5.3 and Circular segment GIS 10.3, with field perceptions. The waterlogged regions have positive change (+), anyway grounds have negative change (−). Land has been diminished while water bodies have upward pattern. These waterlogged zones have been mapped at a general exactness of 99.22%. The primary explanations behind this descending rate are mostly improvement and anthropogenic mediations. The investigation shows utility of reconciliation of remote detecting and GIS systems for evaluation of waterlogged territories especially in districts where waterlogging conditions happen both because of over the top water system and poor waste. This investigation is recommended that an appraisal of water logging utilizing remotely detected information ought to be completed at customary interims.

Effects of urea mixed with nitrapyrin on leaf photosynthetic and senescence characteristics of summer maize(Zea mays L.)waterlogged in the field

Waterlogging is one of the major abiotic stresses in agricultural crop production.However,the application of 2-chloro-6-(trichloromethyl)pyridine(nitrapyrin)can effectually mitigate the losses of nitrogen efficiency and grain yield of summer maize induced by waterlogging.In order to explore its role to alleviate waterlogging stress on leaf antioxidative system and photosynthetic characteristics of summer maize,a field experiment was executed to research effects of nitrapyrin application on leaf photosynthetic and senescent characteristics of waterlogged summer maize Denghai 605(DH605)and Zhengdan 958(ZD958).Experimental treatments consisted of waterlogging treatment that was applying only urea(WL),waterlogging treatment that was applying urea mixing with nitrapyrin(WL-N),and no waterlogging treatment that was only applying urea(NWL).Results showed that WL significantly decreased leaf area index(LAI),SPAD,photosynthetic rate(Pn),and protective enzyme activities,accelerated leaf aging,eventually led to a remarkable yield reduction by 38 and 42%for DH605 and ZD958,respectively,compared to NWL.However,the application of nitrapyrin was useful for relieving waterlogging damages on leaf photosynthetic ability.LAI,SPAD and Pn of WL-N for DH605 were 10,19 and 12-24%higher,and for ZD958 were 12,23 and 7-25%higher,compared to those of WL,respectively.Moreover,application of nitrapyrin effectually relieved waterlogging losses on antioxidative enzyme activities.Leaf superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)activities of WL-N were averagely increased by 24,15 and 30%,respectively,while malondialdehyde(MDA)content was averagely decreased by 13%,compared to those of WL.Visibly,nitrapyrin application could improve leaf photosynthetic characteristics and retard leaf aging induced by waterlogging,thereby leading to a yield increase of waterlogged maize.

Melatonin and dopamine alleviate waterlogging stress in apples by recruiting beneficial endophytes to enhance physiological resilience

Melatonin and dopamine can potentially prevent waterlogging stress in apples.The current study investigated the mechanism by which melatonin and dopamine alleviate apple waterlogging stress.This study demonstrated that melatonin and dopamine alleviated waterlogging by removing reactive oxygen species(ROS),and that the nitric oxide(NO)content and nitrate reductase(NR)activity were significantly correlated.Melatonin and dopamine were also found to recruit different candidate beneficial endophytes(melatonin:Novosphingobium,Propionivibrio,and Cellvibrio;dopamine:Hydrogenophaga,Simplicispira,Methyloversatilis,Candidatus_Kaiserbacteria,and Humicola),and these endophytes were significantly and positively correlated with plant growth.Network analyses showed that melatonin and dopamine significantly affected the endophytic bacterial and fungal communities under waterlogging stress.The metabolomic results showed that melatonin and dopamine led to waterlogging resistance by upregulating the abundance of beneficial substances such as amino acids,flavonoids,coumarins,and organic acids.In addition,melatonin and dopamine regulated the physicochemical properties of the soil,which altered the endophyte community and affected plant growth.The co-occurrence network demonstrated close and complex relationships among endophytes,metabolites,soil,and the plants.Our results demonstrate that melatonin and dopamine alleviate waterlogging stress in apples by recruiting beneficial endophytes to enhance physiological resilience.This study provides new insights into how melatonin and dopamine alleviate stress and a theoretical basis for synergistic beneficial microbial resistance to waterlogging stress.

SiRAP2-12,a Positive Regulatory Factor,Effectively Improves the Waterlogging Tolerance of Foxtail Millet(Setaria italica)

Foxtail millet(Setaria italica)growth was inhibited because of waterlogging stress,which has caused yield reduc-tion.ERF family plays an important role to plant adversity tolerance.In our study,we obtained 19,819 differential expressed genes(DEGs)between the two treatments based on the RNA-seq sequencing of foxtail millet of water-logging stress.Furthermore,a total of 28 ERF family members were obtained,which have a complete open read-ing frame.We studied the evolution and function of SiERF family and how they affected the waterlogging tolerance.It was found that SiERF1A/B/C(GenBank ID:OR775217,OR775219,OR775218)and SiRAP2-12(GenBank ID:OR775216)have similar functions to the known waterlogging tolerance genes of other plants.Among them,the SiRAP2-12 expression was obviously significantly up-regulated in foxtail millet after 5d water-logging stress.After SiRAP2-12 was silenced,the activity of defense enzymes in millet decreased significantly.In details,superoxide dismutase(SOD),catalase(CAT)and peroxidase(POD),the osmotic regulator proline(Pro),and the activity of the anaerobic respiratory enzyme alcohol dehydrogenase(ADH)content were decreased by 78.61%,29.52%,79.95%,19.41%and 54.77%,respectively.In contrast,the relative electrical conductivity contents(REC),malondialdehyde(MDA),and hydrogen peroxide(H_(2)O_(2))of the foxtail millet subjected to virus-induced gene silencing clearly increased by 1.03-fold,36.09%,and 15.21%,respectively.The content of sodium(Na^(+))in the SiRAP2-12-silenced foxtail millet also increased,but that of potassium(K^(+))decreased.Interestingly,we found that ethylene content was significantly reduced.Further,the SiAOC1 expression,an essential gene for ethylene synthesis,was inhibited in SiRAP2-12-silenced foxtail millet after waterlogging stress.Taken together,we hypothesized that SiRAP2-12 might be a positive regulator of millet tolerance to waterlogging stress.

Responses of photosynthetic characteristics and leaf senescence in summer maize to simultaneous stresses of waterlogging and shading

A field experiment was performed to investigate the physiological mechanism of the simultaneous stresses of waterlogging and shading on leaf photosynthetic and senescence during three growth stages of summer maize.The responses of leaf gas exchange parameters and antioxidant enzyme activities of the summer maize hybrids Denghai 605(DH605)to waterlogging(W),shading(S),and their combination(W+S)for 6 days at the third leaf stage(V3),the sixth leaf stage(V6),and the tasseling stage(VT)were recorded.Shading,waterlogging,and their combination disturbed the activities of protective enzymes and increased the contents of H2O2and O-2,accelerating leaf senescence and disordering photosynthetic characteristics.Under waterlogging,shading and their combination,leaf Pn,the photo-assimilates and grain yield was decreased.The greatest reduction for waterlogging and the combined stresses occurred at V3 and that for shading stress occurred at VT.The individual and combined stresses reduced the activities of protective enzymes and inhibited photosynthesis,reducing the accumulation of photosynthetic compounds and thereby yield.Waterlogging and the combined stresses at the V3 stage showed the greatest effect on leaf photosynthetic and senescence,followed by the V6 and VT stages.The greatest effect for shading stress occurred at VT,followed by the V6 and V3 stages,and the combined influence of shading and waterlogging was greater than that of either single stress.

Root pruning is effective in alleviating the inhibition of soybean growth caused by anaerobic stress for a short period

Soybean is an important upland crop,but its productivity is often limited by anaerobic stress caused by waterlogging.The ability to adjust root growth under environmental constraints is an important physiological trait for adapting to an everchanging environment,and root pruning is an artificial technique for regenerating the root system.In the present study,we investigated whether root pruning in soybean can effectively alleviate the inhibitory effects of anaerobic stress.Soybean plants were affected by anaerobic stress at the germination,vegetative stage 1(V1),and reproductive stage 1(R1)stages,and then the plants were treated with root pruning just after the stress treatment.Soybean plants at the germination stage were treated with root cap and tip removals after hypoxia(N_(2)treatment).Root cap removal was more effective in suppressing the inhibitory effects of hypoxia than root tip removal(5 mm from the tip).The shoot dry weights of the soybean plants with and without root cap removal after hypoxia were 51.2 and 73.8%of the control,respectively,while the root dry weights of plants with and without root cap removal after hypoxia were 43.2 and 62.8%of the control,respectively.As root cap removal effectively enhanced soybean growth after anaerobic stress,the root cap may be the candidate tissue for the stress memory mechanism.When soybean plants at the V1 stage of growth were affected by anaerobic stress,the branch number,pod weight in the main stem,root length,and root surface area of the soybean plants treated with anaerobic stress at the R1 stage significantly decreased compared with those of the control.In contrast,root pruning(2 mm from the tip)immediately after the stress treatment enhanced root growth,branch number,and pod weight.The branch number,pod weight,root length,and root surface area of the plants treated with root pruning were 1.13,1.14,1.12,and 1.13 times higher than those of plants treated with anaerobic stress.Plasmolysis was observed in the root meristem,columella,and cortical cells in soybean roots subjected to anaerobic conditions.However,damage was not observed in the newly emerged roots after root pruning in plants treated with anaerobic stress.These results suggested that root pruning is effective in enhancing soybean growth after anaerobic stress.This effectiveness may be due to the regeneration and elongation of healthy lateral roots during the recovery period.When soybean plants were affected by anaerobic stress at the R1 stage,root pruning just after the stress treatment was ineffective.Thus,suppressing the growth reduction due to anaerobic stress at reproductive stages using only root pruning may be difficult.

Pore Characteristic Design Method of High-strength Pervious Concrete Based on the Mechanical Properties and Rainstorm Waterlogging Resistance

High-strength pervious concrete(HSPC) with porosity ranging from 0.08% to 2.011% was prepared. The mechanical properties and rainstorm waterlogging resistance of HSPC were evaluated,and a design method of HSPC pore characteristics(porosity and pore diameter) based on the mechanical properties and rainstorm waterlogging resistance was proposed. The results showed that the reduction of effective cross-sectional area caused by artificial channels was the main factor affecting flexural strength but had limited influence on compressive strength. Compared with the concrete matrix without artificial channels,the compressive strength of HSPC with porosity of 2.011% decreased by 7.4%, while the flexural strength decreased by 48.3%. The permeability coefficient of HSPC can reach 16.35 mm/s even at low porosity(2.011%).HSPC can meet the requirements of no rainstorm waterlogging, even if exposed to 100-year rainstorms. When the mechanical properties and rainstorm waterlogging resistance are compromised, the recommended porosity ranges from 1.1% to 3.5%, and the recommended pore diameter ranges from 0.8 to 2.7 mm.

Effect of Fatigue Loading on the Mechanical Properties and Resistance of High-strength Straight-hole Recycled Pervious Concrete to Rainstorm-based Waterlogging

A novel high-strength straight-hole recycled pervious concrete(HSRPC)for the secondary highway pavement was prepared in this paper.This study aimed to investigate the effect of porosity(0.126%,0.502%,and 1.13%),vehicle loading stress level(0.5 and 0.8)and service life on the resistance to rainstormbased waterlogging of HSRPC under fatigue loading.The mechanical properties of HSRPC in terms of flexural strength and dynamic elastic modulus were studied.The waterlogging resistance of HSRPC was described by surface water depth and drainage time.The microstructure of HSRPC were observed with scanning electron microscopy(SEM).Results showed that although the dynamic elastic modulus and flexural strength of HSRPC decreased with the increasing number of fatigue loading,the flexural strength of HSRPC was still greater than5 MPa after design service life of 20 years.After 2.5×10^(5)times of fatigue loading,the permeability coefficient of HSRPC with a porosity of 0.502%and 1.13%increased by 18.4%and 22.9%,respectively;while the permeability coefficient of HSRPC with 0.126%porosity dropped to 0.35 mm/s.The maximum surface water depth of HSRPC with a porosity of 0.126%,0.502%,and 1.13%were 8,5 and 4 mm,respectively.SEM results showed that fatigue loading expanded the number and width of cracks around the tiny pores in HSRPC.

Identification of stable quantitative trait loci underlying waterlogging tolerance post-anthesis in common wheat(Triticum aestivum)

Waterlogging is a growing threat to wheat production in high-rainfall areas.In this study,a doubled haploid(DH) population developed from a cross between Yangmai 16(waterlogging-tolerant) and Zhongmai895(waterlogging-sensitive) was used to map quantitative trait loci(QTL) for waterlogging tolerance using a high-density 660K single-nucleotide polymorphism(SNP) array.Two experimental designs,waterlogging concrete tank(CT) and waterlogging plastic tank(PT),were used to simulate waterlogging during anthesis in five environments across three growing seasons.Waterlogging significantly decreased thousand-kernel weight(TKW) relative to non-waterlogged controls,although the degree varied across lines.Three QTL for waterlogging tolerance were identified on chromosomes 4AL,5AS,and 7DL in at least two environments.All favorable alleles were contributed by the waterlogging-tolerant parent Yangmai16.QWTC.caas-4AL exhibited pleiotropic effects on both enhancing waterlogging tolerance and decreasing plant height.Six high-confidence genes were annotated within the QTL interval.The combined effects of QWTC.caas-4AL and QWTC.caas-5AS greatly improved waterlogging tolerance,while the combined effects of all three identified QTL(QWTC.caas-4AL,QWTC.caas-5AS,and QWTC.caas-7DL) exhibited the most significant effect on waterlogging tolerance.Breeder-friendly kompetitive allele-specific PCR(KASP) markers(K_AX_111523809,K_AX_108971224,and K_AX_110553316) flanking the interval of QWTC.caas-4AL,QWTC.caas-5AS,and QWTC.caas-7DL were produced.These markers were tested in a collection of 240 wheat accessions,and three superior polymorphisms of the markers distributed over 67elite cultivars in the test population,from the Chinese provinces of Jiangsu,Anhui,and Hubei.The three KASP markers could be used for marker-assisted selection(MAS) to improve waterlogging tolerance in wheat.

Enhancing waterlogging tolerance in cotton through agronomic practices

Recent publications have highlighted significant progress in utilizing agronomic interventions to alleviate waterlogging stress in cotton production.Based on these advancements,we provide a concise comment on the effects and underlying mechanisms of various strategies such as utilizing stress-tolerant cotton varieties,applying nitric oxide(NO),and implementing ridge intertillage.Finally,we recommend a combination of measures to enhance cotton’s ability to withstand waterlogging and reduce yield losses.

Research and Application of Ecological Outdoor Ground Structure with Composite Water Storage and Drainage Function

In order to solve the problems of surface runoff increase,water accumulation in rainy days and urban heat island effect,an ecological outdoor ground structure with composite water storage and drainage functions was studied and applied in this paper:Through the comprehensive design of road ground,road inspection well,garden inspection well and drainage pipe network,it can quickly store and drain ground water,alleviate the urban heat island effect,realize plant infiltration irrigation,and achieve the purpose of saving water and energy.

Cadmium Chemical Forms in Two Calcareous Soils Treated with Different Levels of Incubation Time and Moisture Regimes

Sequential extraction is used effectively to determine the chemical forms of heavy metals. Since few studies have been conducted in calcareous soils of Iran, the current research has been carried out to evaluate the effect of moisture regimes and incubation time on the chemical forms of cadmium in two calcareous soils. Treatments included three levels of cadmium (0, 30 and 60 mg/kg of soil as CdSo4), three incubation times (2, 4 and 8 weeks), two soils (clay and sandy clay loam) and two moisture regimes (Water-logged and Field capacity). The experiment was performed as factorial on the basis of randomized complete blocks design with two replications. At 2, 4, and 8 weeks after treatment, the Tessier et al. (1979) sequential extraction method was applied to measure the cadmium concentration in water soluble-exchangeable (WsEx.), iron and manganese oxide (Fe-MnOx.), carbonate (Car.), organic matter (Om.) and residual forms (Res.). The results showed depending on the soil texture, 68 to 72 percent of the cadmium was in water soluble-exchangeable and iron-manganese oxide forms. Flooding condition decreased the concentration of cadmium in water soluble + exchangeable form and increased the concentration of cadmium in the forms of Fe-Mn oxides, carbonate and organic matter. Concentration of cadmium in residual form was higher in clay soil. In sandy clay loam soil, water soluble-exchangeable, carbonate and organic matter forms were higher than clay soil. The iron-manganese oxides form showed no significant difference in two soils at field capacity regime. In flooding conditions, the concentration of the water soluble-exchangeable form decreased and the concentration of other forms increased. In contrast to the oxidizing conditions at the reduction conditions, no significant difference was observed in the residual and organic matter forms in two soils.

Drought and Waterlogging Characteristics during the Growth Period of Summer Maize in Luxi Plain Areas

In summer maize growth period,the water supply and demand ratio is regarded as the evaluation index of drought and waterlogging for the summer maize in Liaocheng City. Using GIS,statistics,agrometeorology and other methods,we analyze the precipitation during the summer maize growth period in Luxi Plains from 1961 to 2011. Through the calculation of drought and waterlogging index,it indicates that the disasters of drought and waterlogging frequently occur during the summer maize growth period,mainly affected by the drought; the frequency of occurrence of drought accounts for 80. 4%,that is,it is very prone to serious drought phenomenon,seriously affecting the normal growth and development of summer maize during the seedling period. With global warming,the industrial and domestic water demand is increasing year by year,so it is extremely difficult to increase the water diversion to solve the problem of water shortage for the growth of summer maize. Finally we put forth the following recommendations:( i) Selecting drought-resistant varieties,and improving the water resource use efficiency;( ii)Promoting the water and fertilizer coupling,sprinkler irrigation,drip irrigation,micro-irrigation and other water-saving irrigation technologies,and improving the water use efficiency;( iii) Promoting the ditch,ridge and laminating cultivation technology,reducing the field evapotranspiration,keeping warming and conserving moisture,and saving water resources;( iv) Strengthening the construction of water conservancy facilities,so that it can be irrigated during drought and drained during waterlogging;( v) During dry season,timely organizing artificial rainfall operation,and increasing precipitation in arid areas to ease drought;( vi) Rationally exploiting the groundwater,and improving the underground water use efficiency.

Influence of water logging time on the growth of Kandelia candel seedlings

Influence of waterlogging time on the growth of Kandelia candel(L.) Druce seedlings grown for 70 d in the artificial- tidal tanks' simulated semidiurnal tide under greenhouse is studied. Sand and soil act as the substrate and artificial seawater with salinity of 15 is used in cultivation. Shorter waterlogging time(inundated for about 2 ~ 4 h) promotes the growth of K. candel seedlings, while longer time(inundated more than 8 h) or no waterlogging(0 h) inhibits their growth. The number and length of aerating roots increase with the increase of waterlogging time. Under existing conditions, the optimal waterlogging time for the growth of K. candel seedlings is about 2 ~ 4 h in every tide cycle. Compared with other treatments, the 2 h sanded treatments obtain the highest biomass of seedlings, have the lowest mass loss of hypocotyl and broaden the photosynthetic area by increasing the area per leaf after 70-d cultivation. And the soil treatments have the similar tendency. However, waterlogging for 8 h in every tide cycle is critical for normal development of seedlings.K. candel seedlings are highly tolerant to waterlogging and a proper waterlogging is beneficial to the growth of K. candel seedlings.

Changes of Antioxidative Enzymes and Lipid Peroxidation in Leaves and Roots of Waterlogging-Tolerant and Waterlogging-Sensitive Maize Genotypes at Seedling Stage

To better understand the physiological and biochemical mechanisms of waterlogging tolerance, waterlogging effects on lipid peroxidation and the activity of antioxidative enzymes were investigated in leaves and roots of two maize genotypes, HZ32 （waterlogging-tolerant） and K12 （waterlogging-sensitive）. Potted maize plants were waterlogged at the second leaf stage under glasshouse conditions. Leaves and roots were harvested 1 d before and 2, 4, 6, 8 and 10 d after the start of waterlogging treatment. Through comparing the activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, glutathione reductase （GR）, catalase （CAT） and guaiacol peroxidase （POD） between waterlogging-tolerant and waterloggingsensitive genotype, we deduced that CAT was the most important H2O2 scavenging enzyme in leaves, while APX seemed to play a key role in roots. POD, APX, GR and CAT activities in conjunction with SOD seem to play an essential protective role in the O2^- and H2O2 scavenging process. Lipid peroxidation was enhanced significantly only in K12 （P 〈 0.001） and there was no difference （P 〉 0.05） in HZ32 up to 6 d after waterlogging stress. These results indicated that oxidative stress may play an important role in waterlogging-stressed maize plants and that the greater protection of HZ32 leaves and roots from waterlogging-induced oxidative damage results, at least in part, through the maintenance of increased antioxidant enzyme activity.

QTLs for Waterlogging Tolerance at Germination and Seedling Stages in Population of Recombinant Inbred Lines Derived from a Cross Between Synthetic and Cultivated Wheat Genotypes

Waterlogging is a widespread limiting factor for wheat production throughout the world. To identify quantitative trait loci （QTLs） associated with waterlogging tolerance at early stages of growth, survival rate （SR）, germination rate index （GRI）, leaf chlorophyll content index （CCI）, root length index （RLI）, plant height index （PHI）, root dry weight index （RDWI）, shoot dry weight index （SDWI）, and total dry weight index （DWI） were assessed using the International Triticeae Mapping Initiative （ITMI） population W7984/Opata85. Significant and positive correlations were detected for all traits in this population except RLI. A total of 32 QTLs were associated with waterlogging tolerance on all chromosomes except 3A, 3D, 4B, 5A, 5D, 6A, and 6D. Some of the QTLs explained large proportions of the phenotypic variance. One of these is the QTL for GRI on 7A, which explained 23.92% of the phenotypic variation. Of them, 22 alleles from the synthetic hexaploid wheat W7984 contributed positively. These results suggested that synthetic hexaploid wheat W7984 is an important genetic resource for waterlogging tolerance in wheat. These alleles conferring waterlogging tolerance at early stages of growth in wheat could be utilized in wheat breeding for improving waterlogging tolerance.