Effects of Nutrient Supply on Pre-emergence Growth and Nutrient Absorption in Wheat (Triticum aestivumL.) and Sugarbeet (Beta vulgarisL.)

Nutrient absorption in wheat and sugarbeet was studied duringpre-emergence growth by adding 0, 7, 10.5 or 14 mol m^-3nitrogen(N) to the growth medium. Seedling growth and carbon, N and¹⁵Ncontents of the seedling parts were measured. Differences betweenthe natural abundance of¹⁵N in seeds and in nutrient solutionwere used to determine the proportion of N in the organs originatingfrom seed reserves and from absorption. Absorption began laterfor wheat than for sugarbeet and had less effect on seedlinggrowth. The absorbed N was found mainly in roots. Compared towheat, sugarbeet seedling N content was greatly altered andthe hypocotyl showed increased elongation when nutrients wereadded. Most of the absorbed N was found in the radicle and hypocotylwith less in the cotyledons. Sugarbeet seedling emergence andearly growth could be decreased by adverse conditions occurringafter sowing by affecting mineral availability in the soil orthrough altered root absorption.Copyright 1998 Annals of BotanyCompany Triticum aestivumL., wheat,Beta vulgarisL., emergence, natural isotopic composition, seedling, seed reserves     

瓢虫和草蛉对小麦挥发物组分的行为及电生理反应

利用触角电位（electroantennogram, EAG）和嗅觉测定技术,比较分析了4种捕食性天敌昆虫七星瓢虫Coccinella septempunctata、龟纹瓢虫Propylaea japonica、中华通草蛉Chrysoperla sinica和大草蛉Chrysopa septempunctata对麦蚜取食诱导小麦挥发物的行为和电生理反应,揭示了瓢虫及草蛉类天敌昆虫的嗅觉反应特点。4种捕食性天敌昆虫对麦蚜取食诱导挥发物都有较高的EAG反应值,七星瓢虫和龟纹瓢虫对6-甲基-5_庚烯-2-酮、6-甲基-5-庚烯-2-醇的反应值较大;中华通草蛉和大草蛉对6-甲基-5-庚烯-2-醇和水杨酸甲酯的反应值较大,七星瓢虫对6-甲基-5-庚烯-2-醇的反应值最大,为0.96±0.18 mV;4种天敌昆虫对苯甲醛的EAG反应值较低,对反-2-己烯醛无反应。“Y”型管嗅觉测定结果表明,4种天敌昆虫对2-莰烯、6-甲基-5-庚烯-2-酮、6-甲基-5-庚烯-2-醇和水杨酸甲酯具有正趋性。说明4种多食性的捕食性天敌昆虫对麦蚜取食诱导挥发物各组分的嗅觉与行为反应各具特点;寄主麦蚜生境中的嗅觉线索在这4种捕食性天敌昆虫的寄主定位和生境选择中起重要作用。     

The Influence of the Rht1 and Rht2 Alleles on the Deposition and Use of Stem Reserves in Wheat

A field experiment was undertaken with a set of near-isogenicspring wheat lines (cv. Triple Dirk) to determine the influenceof the Rht₁ and Rht₂ alleles on the deposition of carbon inthe stem, and the subsequent use of these reserves during graingrowth. The amount of dry matter stored and mobilized was estimatedby the measurement of changes in masses of stem from frequentharvests. Deposition or absolute reserve was defined as thesum of the increments in mass in each segment of the large culmbetween the time that the segment ceased extending and the timethat it reached maximum mass. The incorporation of the Rht₁and Rht₂ alleles into a Triple Dirk background reduced the absoluteamount of stored carbon in the stem by 35 and 39%, respectively.This was a consequence of the 21% reduction of stem height inRht₁ and Rht₂ lines. Use or mobilization of reserve was definedas the sum of the decrements in mass in each segment of thelarge culm between maximum and maturity. The alleles did notconfer an ability to mobilize more of the stored stem reservesin absolute terms, although the efficiency of use of stem reserves(i.e. use as a proportion of deposition) was higher in Rht₁than in rht or Rht₂ . The possible contribution of stored carbonin the stem to final grain yield was estimated to be 22, 18and 14% in the rht, Rht₁ and Rht₂ lines. In these estimates,the loss of mass was adjusted by 33% to allow for respiration.It was concluded that the larger stem reserves in rht wheatsare of no real advantage under favourable environmental conditions,and may in fact be a disadvantage if the accumulation of thatextra dry matter results in a reduction of sink size.Copyright1993, 1999 Academic Press Triticum aestivum L., Rht genes, stem reserves, deposition, mobilization, grain growth     

Proteins Associated with Specific Host-Pathogen Relationships in Infections with Wheat Rust

The specific relationship between host and pathogen was studiedusing a criss-cross genetic system of well characterized, nearisogenic mutants of Triticum aestivum that differed in theircompatibility reaction to two genetically related mutant clonesof Puccinia recondita tritici. Specific and non-specific pathogenesis-relatedchanges in proteins were followed by pulse-labelling with [³⁵S]methionineof rust-inoculated and mock-inoculated wheat leaves, combinedwith SDS-PAGE and subsequent fluorography. Detectable changesin the patterns of the polypeptides synthesized "de novo" werenoted as early as 3 days after infection. Synthesis of a 39-kDapolypeptide was enhanced in incompatible reactions while synthesisof an 85-kDa and a 15-kDa polypeptide were enhanced in compatiblereactions. Synthesis of polypeptides present in the mock-inoculatedleaves was suppressed in both the compatible (52-kDa band) andincompatible interaction systems (37-kDa band). Comparisonswith a third mutant clone of rust, which elicits an inversecriss-cross relationship with the same wheat lines, indicatedthat most of the detected changes are likely to be associatedwith gene-for-gene relationships. (Received January 16, 1990; Accepted October 1, 1990)     

Nitrate Stimulation of Mobilization of Seed Reserves in Temperate Cereals: Importance of Water Uptake

Relationships between nitrate (NO^-₃) supply, uptake and assimilation,water uptake and the rate of mobilization of seed reserves wereexamined for the five main temperate cereals prior to emergencefrom the substrate. For all species, 21 d after sowing (DAS),residual seed dry weight (d.wt) decreased while shoot plus rootd.wt increased (15–30%) with increased applied NO^-₃concentrationfrom 0 to 5–20 mM . Nitrogen (N) uptake and assimilationwere as great with addition of 5 mM ammonium (NH⁺₄) or 5 mMNO^-₃but NH⁺₄did not affect the rate of mobilization of seedreserves. Chloride (Cl^-) was similar to NO^-₃in its effect onmobilization of seed reserves of barley (Hordeum vulgare L.).Increased rate of mobilization of seed reserves with additionalNO^-₃or Cl^-was associated with increases in shoot, root and residualseed anion content, total seedling water and residual seed watercontent (% water) 21 DAS. Addition of NH⁺₄did not affect totalseedling water or residual seed water content. For barley suppliedwith different concentrations of NO^-₃or mannitol, the rate ofmobilization of seed reserves was positively correlated (r >0.95)with total seedling water and residual seed water content. Therate of mobilization of seed reserves of barley was greaterfor high N content seed than for low N content seed. Seed watercontent was greater for high N seed than for low N seed, 2 DAS.Additional NO^-₃did not affect total seedling water or residualseed water content until 10–14 DAS. The effects of seedN and NO^-₃on mobilization of seed reserves were detected 10and 14 DAS, respectively. It is proposed that the increasedrate of mobilization of seed reserves of temperate cereals withadditional NO^-₃is due to increased water uptake by the seedlingwhile the seed N effect is due to increased water uptake bythe seed directly. Avena sativa L.; oat; Hordeum vulgare L.; barley; Secale cereale L.; rye; xTriticosecale Wittm.; triticale; Triticum aestivum L.; wheat; nitrate; seed; germination; seed reserve mobilization     

Partitioning of Dry Matter and the Deposition and Use of Stem Reserves in a Semi-dwarf Wheat Crop

An experiment was carried out within a crop of spring wheat(cv. Condor) to examine dry matter partitioning between thedeveloping stem and ear, and to estimate the magnitude of carbonstored in the stem both before and after anthesis, and the subsequentutilization of these reserves during grain growth. The amount of reserve laid down and mobilized was estimatedfrom analysis of data for changes in masses of stem and leaffrom frequent harvests. The rate of change of the dry mass ofthe individual plant organs was expressed as a proportion ofthe rate of change of the total dry mass of the large culm.This value was called the Allocation Ratio (AR). It was assumedthat assimilate was transferred directly from the stem intothe growing ear, and not into other organs. This paper providesevidence for the idea that the stem intemodes of wheat are ableto accumulate and subsequently mobilize a dry matter reserve.The accumulation and subsequent mobilization of fructans inthe stem was demonstrated using ascending thinlayer chromatography.On a dry matter basis the large culms of the wheat crop accumulatedall of their stem reserves after anthesis (0–41 g perlarge culm; 98·4 g m^–1). After adjusting the lossof mass by 33% to allow for respiration, it was concluded thatpost-anthesis stem reserves may have contributed at least 21%of the final grain yield of this crop. Triticum aestivum L., semi-dwarf spring wheat, dry matter partitioning, stem reserves, fructans     

Root-Shoot Interaction in the Turnover of Reserves in Tea (Camellia sinensis L.) Roots

Root–shoot interaction in the tea plant, in relation toturnover of root reserves, following pruning and manuring, wereinvestigated by ring barking the roots or severing mature rootsin both unpruned and pruned plants. Translocation of leaf assimilatesto the root system appears to be dependent on a feeder rootstimulus, and nitrogen assimilation by the root system seemsto depend on replenishment of root reserves by leaf activity,both of which were interrupted by ring barking. Camellia sinensis, root–shoot interaction, tea, root reserves, translocation     

Growth Analysis of Solution Culture-grown Winter Rye, Wheat and Triticale at Different Relative Rates of Nitrogen Supply

At low nitrogen (N) supply, it is well known that rye has ahigher biomass production than wheat. This study investigateswhether these species differences can be explained by differencesin dry matter and nitrogen partitioning, specific leaf area,specific root length and net assimilation rate, which determineboth N acquisition and carbon assimilation during vegetativegrowth. Winter rye (Secale cereale L.), wheat (Triticum aestivumL.) and triticale (X Triticosecale) were grown in solution cultureat relative addition rates (R_N) of nitrate-N supply rangingfrom 0.03–0.18 d^-1and at non-limiting N supply under controlledconditions. The relative growth rate (R_W) was closely equalto R_Nin the range 0.03–0.15 d^-1. The maximalR_W at non-limitingnitrate nutrition was approx. 0.18 d^-1. The biomass allocationto the roots showed a considerable plasticity but did not differbetween species. There were no interspecific differences ineither net assimilation rate or specific leaf area. Higher accumulationof N in the plant, despite the same relative growth rate atnon-limiting N supplies, suggests that rye has a greater abilityto accumulate reserves of nitrogen. Rye had a higher specificroot length over a wide range of sub-optimal N rates than wheat,especially at extreme N deficiency (R_N=0.03–0.06 d^-1).Triticale had a similar specific root length as that of wheatbut had the ability to accumulate N to the same amount as ryeunder conditions of free N access. It is concluded that thebetter adaptation of rye to low N availability compared to wheatis related to higher specific root length in rye. Additionally,the greater ability to accumulate nitrogen under conditionsof free N access for rye and triticale compared to wheat maybe useful for subsequent N utilization during plant growth.In general, species differences are explained by growth componentsresponsible for nitrogen acquisition rather than carbon assimilation.Copyright 1999 Annals of Botany Company Growth analysis, nitrogen, nitrogen productivity, partitioning, specific root length, Secale cereale L.,Triticum aestivum L., X Triticosecale, winter rye, winter wheat, winter triticale.     

Temperature Response of Early Foliar Expansion of Potato and Wheat

We studied the course of early leaf area expansion and specificleaf area (S_LA) in potato (Solanum tuberosum L.) and wheat (Triticumaestivum L.) genotypes and tested whether air temperature explainsdifferences in these courses within different environments.Such knowledge can be used to improve crop growth modelling.The relative rate of leaf area expansion (R_L) of potato andwheat decreased with thermal time, but was nearly linear upto a leaf area index (L) of 1.0. TheR_L (L < 1; mean: 17.9x 10^-3°C^-1 d^-1) of potato showed an interaction betweengenotype and environment, and varied with year. TheR_L (L <1; mean: 7.1 x 10^-3°C^-1 d^-1) of winter wheat was lower thanthat of spring wheat (mean: 10.9 x 10^-3°C^-1 d^-1), and bothvaried with year. S_LAof potato increased nearly linearly withthermal time from 5 to 15 m² kg^-1at 50% emergence, to 20 to25 m² kg^-1at 155°Cd, and then decreased slightly. The S_LAofboth winter and spring wheat began at 16 to 23 m² kg^-1and inmost cases increased slightly with thermal time. In potato,regression parameters of S_LAwith thermal time were affectedby environment (management conditions and year) and genotype;in wheat they were affected by environment (year and site).Treatment effects on R_Lof potato were not correlated with thoseon S_LA , and were only partly correlated for wheat. Thereforewe conclude that the early foliar expansion of potato is associatedwith a strong increase in S_LA , and not so for wheat. For bothcrops the course of early leaf area expansion and ofS_LA withair temperature is not robust over environments and genotypes.The consequences of these results for modelling are discussed.Copyright 2000 Annals of Botany Company Triticum aestivum, spring wheat, winter wheat, Solanum tuberosum, leaf area expansion, specific leaf area, early growth, genotype, environment, modelling     

The benefits of stealing from a predator: foraging rates, predation risk, and intraspecific aggression in the kleptoparasitic spider Argyrodes antipodiana

In the trade-off between food and safety, the role of aggressiveintraspecific interactions has not been extensively examined.Here I present information on this system using a kleptoparasiticspider, Argyrodts antipodiana, and its host spider and potentialpredator, Eriophora pustulosa. A. antipodiana can feed eitherat a potentially dangerous site (the hub of its host's web withthe host), or at a relatively safe site (on food bundles aroundthe edge of the host's web). I found that A. antipodiana cangain food very quickly when feeding with the host, apparentlyby exploiting the host's ability to digest the prey. Thus A.antipodiana follows predictions based on foraging models inthat it accepts a higher predation risk at the hub because ofthe higher food payoff. A. antipodiana also aggressively competesfor access to more food. However, aggressive competition increasesthe predation risk from the host, especially at tile hub wherethe host is very close. Consequently, A. antipodiana modifiesits level of intraspecific aggressiveness in accordance withits position on the web: at the hub, where the cost of aggressionis high (due to predation risk), A. antipodiana reduces itsaggressiveness, but it is aggressive away from the hub whencompeting for food bundles. The ability of A. antipodiana tochange interaction intensity as a function of its position onthe web enables it to exploit a rich, but risky, food sourceand provides a new angle for examining food and safety tradeoffs in light of intraspecific competition for food     

Effects of Ageing on Amylase Activity and Scutellar Cell Structure during Imbibition in Wheat Seed

In wheat seed the scutellum plays an important role in the hydrolysisof stored substrate during germination. This layer is activatedfirst, whilst the aleurone becomes activated later. A good correlationexists between the initiation of visible germination and theappearance of enzyme activity in the scutellum. Enzyme activityin the aleurone becomes apparent only when the germinating seedlingreaches the rapid growth phase. Electron microscopic observationsshow that during the later stages of germination the scutellarcells develop finger like projections. These may serve to absorbendospermic reserves hydrolysed by aleurone amylase. The scutellumof aged non-germinating seeds showed no amylase activity andno finger like projections were produced even after prolongedimbibition.Copyright 1993, 1999 Academic Press Wheat (Triticum aestivum L.), deteriorated, germination, scutellum, scanning electron microscopy, aleurone     

不同寄主植物上灰飞虱种群生命表的比较

为比较不同寄主植物上灰飞虱种群发展趋势,通过室内实验,组建了灰飞虱Laodelphax striatellus Fallèn在武育粳3号、盐稻8号、徐稻3号、Ⅱ优084、Ⅱ优42、扬麦12、稗草和千金子这8种寄主植物上的实验种群生命表;通过田间调查,比较了粳稻武运粳7号和籼稻Ⅱ优084上灰飞虱自然种群发生动态。不同寄主植物上灰飞虱实验种群生命表的比较结果表明,灰飞虱的若虫发育历期在稗草上最短,其次为扬麦12和粳稻上,而在杂交籼稻Ⅱ优084、Ⅱ优42和杂草千金子上的发育历期长达近30 d;灰飞虱在稗草上的种群趋势指数亦最高,为45.57,其次为粳稻品种盐稻8号（39.36）、徐稻3号（34.54）和武育粳3号(31.70)上,其中盐稻8号与稗草上无显著差异;杂交稻Ⅱ优084和Ⅱ优42上灰飞虱的种群趋势指数显著低于粳稻上的;而灰飞虱在千金子上的种群趋势指数最低,仅为11.04。大田调查则表明,一定时期粳稻武运粳7号上灰飞虱种群个体数量显著高于籼稻Ⅱ优084上。研究表明灰飞虱的适宜寄主植物依次为稗草、粳稻品种和小麦。     

Interactions between Hydrotropism and Gravitropism in the Primary Seminal Roots of Triticum eastivum L.

It has been proposed that hydrotropism interacts with gravitropismin seedling roots; that is, roots which are highly gravitropicshow less hydrotropism (Takahashi and Suge, 1991 PhysiologiaPlantarum 82: 24-31; Takahashi and Scott, 1993 Plant, Cell andEnvironment 16: 99-103). Here, we examine varietal differencesin the hydrotropic response and its interaction with gravitropismin wheat roots. Primary seminal roots of wheat (Triticum aestivumL.) were hydrotropically stimulated by different moisture gradientsestablished by placing wet cheesecloth and saturated solutionsof different salts in closed chambers. From equations obtainedby relative humidity (RH) at different distances from the wetcheesecloth, moisture gradients at the root-tip level were estimatedto be 0·03 to 1·84% RH mm^-1, depending upon thesalt introduced into the chamber. The roots showed positivehydrotropism in response to 0·67% RH mm^-1, and the responseapparently increased as the gradient was strengthened. Whenthe primary seminal roots of 12 cultivars were exposed to amoisture gradient of 1·84% RH mm-1, hydrotropic responsesignificantly differed depending upon the cultivar tested. Amongthe cultivars, the roots of Norin 11, Norin 15, Norin 117, andNorin 125 responded hydrotropically more strongly than the others.These roots, with the exception of Norin 11, showed a less vigorousresponse to gravity compared to the remaining cultivars. However,the roots of Norin 20, Norin 38, and Norin 107 were relativelyunresponsive to both a moisture gradient and to gravity. Thus,the primary seminal roots of wheat respond hydrotropically,and the responsiveness differs among cultivars. However, thevarietal difference in hydrotropic response cannot be explainedsolely by converse differences in responsiveness to gravity.Copyright1995, 1999 Academic Press Cultivar, gravitropism, hydrotropism, primary seminal roots, Triticum aestivum L., wheat     

Carbon Supply From Starch Reserves to Spring Growth: Modelling Spatial Patterns in Kiwifruit Canes

The remobilization and transport of reserve carbon from a kiwifruit(Actinidia deliciosa)cane to developing axillary shoots wasmodelled using a simple pool structure and mass flow process.Manipulative experiments with mature kiwifruit plants are comparedwith simulation results. The model uses detailed architecturalinformation rather than explicit partitioning functions, achievingcarbon partitioning as emergent behaviour of a spatial organization.The model successfully simulated shoot growth and starch distributionpatterns.Copyright 1999 Annals of Botany Company Carbon reserves, starch reserves, plant architecture,Actinidia deliciosa,kiwifruit.     

Comparative mapping of HKT genes in wheat, barley, and rice, key determinants of Na+ transport, and salt tolerance

Salt tolerance of plants depends on HKT transporters (High-affinityK⁺ Transporter), which mediate Na⁺-specific transport or Na⁺-K⁺co-transport. Gene sequences closely related to rice HKT geneswere isolated from hexaploid bread wheat (Triticum aestivum)or barley (Hordeum vulgare) for genomic DNA southern hybridizationanalysis. HKT gene sequences were mapped on chromosomal armsof wheat and barley using wheat chromosome substitution linesand barley–wheat chromosome addition lines. In addition,HKT gene members in the wild diploid wheat ancestors, T. monococcum(A^m genome), T. urartu (A^u genome), and Ae. tauschii (D^t genome)were investigated. Variation in copy number for individual HKTgene members was observed between the barley, wheat, and ricegenomes, and between the different wheat genomes. HKT2;1/2-like,HKT2;3/4-like, HKT1;1/2-like, HKT1;3-like, HKT1;4-like, andHKT1;5-like genes were mapped to the wheat–barley chromosomegroups 7, 7, 2, 6, 2, and 4, respectively. Chromosomal regionscontaining HKT genes were syntenic between wheat and rice exceptfor the chromosome regions containing the HKT1;5-like gene.Potential roles of HKT genes in Na⁺ transport in rice, wheat,and barley are discussed. Determination of the chromosome locationsof HKT genes provides a framework for future physiological andgenetic studies investigating the relationships between HKTgenes and salt tolerance in wheat and barley. Key words: Barley, comparative mapping, HKT, rice, salt tolerance, sodium transport, wheat     

Impacts of a native parasitic plant on an introduced and a native host species: implications for the control of an invasive weed

Background and Aims: While invasive species may escape from natural enemies in thenew range, the establishment of novel biotic interactions withspecies native to the invaded range can determine their success.Biological control of plant populations can be achieved by manipulationof a species' enemies in the invaded range. Interactions weretherefore investigated between a native parasitic plant andan invasive legume in Mediterranean-type woodlands of SouthAustralia. Methods: The effects of the native stem parasite, Cassytha pubescens,on the introduced host, Cytisus scoparius, and a co-occurringnative host, Leptospermum myrsinoides, were compared. The hypothesisthat the parasitic plant would have a greater impact on theintroduced host than the native host was tested. In a fieldstudy, photosynthesis, growth and survival of hosts and parasitewere examined. Key Results: As predicted, Cassytha had greater impacts on the introducedhost than the native host. Dead Cytisus were associated withdense Cassytha infections but mortality of Leptospermum wasnot correlated with parasite infection. Cassytha infection reducedthe photosynthetic rates of both hosts. Infected Cytisus showedslower recovery of photosystem II efficiency, lower transpirationrates and reduced photosynthetic biomass in comparison withuninfected plants. Parasite photosynthetic rates and growthrates were higher when growing on the introduced host Cytisus,than on Leptospermum. Conclusions: Infection by a native parasitic plant had strong negative effectson the physiology and above-ground biomass allocation of anintroduced species and was correlated with increased plant mortality.The greater impact of the parasite on the introduced host maybe due to either the greater resources that this host providesor increased resistance to infection by the native host. Thisdisparity of effects between introduced host and native hostindicates the potential for Cassytha to be exploited as a controltool.     

Localization of Purothionins and Genome Expression in Wheat Plants

The leaves, steins and ears of tetraploidal wheat, Triticumdurum (genomes AABB) harvested two weeks after heading wereanalyzed for purothionins. There were considerable amounts oftwo iso-purothionins (Pu-1 and Pu-2) in the young kernels ofthe ears, but not in the leaves and stems. The amino acid compositionsof Pu-1 and Pu-2 were in good agreement with those of Pu I andPu II from hexaploidal wheat. As diploidal wheat, T. monococcum(genome AA) is known to produce only Pu I [Fernandez de Caleyaet al. (1976) Genetics 83: 687], we conclude that the threeiso-purothionins, Pu I, Pu II and Pu III in hexaploidal wheat,T. aestivum (genomes AABBDD), are encoded by the genes of genomesA, B and D, respectively. (Received June 28, 1982; Accepted September 24, 1982)     

麦双尾蚜及其天敌在不同海拔高度的分布

在新疆塔城,麦双尾蚜Diuraphis noxia (Mordvilko) 在春麦田最集中分布于海拔600～800 m 高度,在冬麦田最集中分布于700～800 m 高度;冬麦田和同海拔高度的春麦田麦双尾蚜数量密切相关(r=0.91, P<0.01)。麦双尾蚜寄生性天敌蚜茧蜂类和蚜小蜂类,在春麦田最集中分布的高度为500～600 m,随着时间的延后,分布的高度范围逐渐扩展;冬麦田最集中分布的高度为600～800 m,略高于春小麦田。捕食麦双尾蚜的斑腹蝇幼虫在春麦田前期最集中分布的高度为500 m处,后期分布高度上升;冬麦田较集中分布的高度为600～800 m,也随着时间的延后也上升。     

Effects of Soil Flooding on Growth and Grain Yield of Populations of Tetraploid and Hexaploid Species of Wheat

Single populations of three hexaploid species of wheat, Triticumaestivum, Triticum spelta and Triticum macha, and two populationsof the tetraploid wheat, Triticum dicoccum (Pontus and Bordeaux),were grown in a greenhouse experiment at a range of soil floodingregimes: free draining, two levels of transient flooding andcontinuous flooding. Increasing severity of flooding treatment resulted in increasedsoil reduction and an increase in the concentration of reducediron and manganese in the experimental soil, and also resultedin a reduction in vegetative growth, number of inflorescences,grain number and grain weight. There were, however, large differencesbetween the wheat populations in the degree of reduction inyield caused by flooding. The population of T. macha was muchmore flooding-tolerant than the other hexaploid species andthe ‘Pontus’ population of the emmer wheat, T. dicoccum,was more tolerant than the ‘Bordeaux’ populationof this species and than T. spelta and T. aestivum. The results are discussed in relation to the origin of the populations. Soil flooding, Triticum aeslivum, Triticum macha, Triticum spelta, Triticum dicoccum