Catalase Activity and Post-anoxic Injury in Monocotyledonous Species

Three anoxia-intolerant species, Glyceria maxima, Juncus effususand Iris germanica (var. Quechei), and three anoxia-tolerantspecies Schoenoplectus lacustris, Acorus calamus and Iris pseudacoruswere chosen for investigation. Rhizomes of anoxia-intolerantspecies show increased catalase activities when returned toair after periods of prolonged anoxia. Levels of catalase remainedfairly constant in anoxia-tolerant species under the same conditions.In the anoxia intolerant G. maxima, the post-anoxic increasein catalase activity was reduced by circulating the anaerobicatmosphere. This treatment also reduced the ethanol contentof the tissue under incubation, and increased the survival ofthe rhizomes as seen in their ability to resume growth in thepost-anoxic phase. Exposure of anaerobic G. maxima rhizomesto ethanol vapour increased post-anoxic levels of catalase activityand when this produced a 5-fold increase always resulted indeath of the rhizomes. Acetaldehyde vapour applied in the sameway gave rise to increases in catalase activity followed byrapid death of the rhizomes. It is suggested that post-anoxic oxidation of anaerobicallyaccumulated ethanol may result in a surge of acetaldehyde production,which could exert a toxic effect on the recovering tissues.The possible role of catalase in an ethanol-oxidation reaction,which is well documented in animals, is discussed in the lightof the association between the natural accumulation of largeconcentrations of ethanol and subsequent post-anoxic death insome plant tissues. Key words: Catalase, post-anoxia, ethanol     

Variation in the Structure and Response to Flooding of Root Aerenchyma in some Wetland Plants

The structure and response to flooding of root cortical aerenchyma(air space tissue) in a variety of wetland (flood-tolerant)species was investigated and compared with some flood-intolerantspecies. In some species aerenchyma consisted of enlarged schizogenousintercellular spaces and in others aerenchyma formation involvedlysigeny. Two types of lysigenous aerenchyma were distinguished.In the first the diaphragms between lacunae were arranged radiallyand consisted of both collapsed and intact cells. In the secondtype, which was confined to the Cyperaceae, the radial diaphragmscontained intact cells, and stretched between them were tangentially-arrangeddiaphragms of collapsed cells. Flooding in sand culture generally increased root porosity (airspace content) although there were exceptions. The flood-intolerantspecies Senecio jacobaea produced aerenchyma but did not survivelong-term flooding. Among the flood-tolerant species, Filipendulaulmaria did not produce extensive aerenchyma even when flooded.Eriophorum angustifolium and E. vaginatum produced extensiveaerenchyma under drained conditions which was not increasedby flooding. In Nardus stricta root porosity was increased bylow nutrient levels as well as by flooding. Aerenchyma, root cortex, wetland plants, waterlogging, flooding-tolerance, Ammophila arenaria, Brachypodium sylvalicum, Caltha palustris, Carex curia, Eriophorum vaginatum, Filipendula ulmaria, Glyceria maxima, Hieracium pilosella, Juncus effusus, Myosotis scorpioides, Nardus stricta, Narthecium ossifragum, Phalaris arundinacea, Senecio jacobaea, Trichophorum cespitosum     

Superoxide Dismutase as an Anaerobic Polypeptide : A Key Factor in Recovery from Oxygen Deprivation in Iris pseudacorus?

The perennating organ, the rhizome, was chosen for examination of response to anoxia in the species Iris pseudacorus L., Iris germanica L. var Quechei, and Glyceria maxima (Hartm.) Holmberg. These monocots are known to differ in their tolerance of anoxia. Intact rhizomes were subjected to periods of prolonged anoxia of up to 28 days and superoxide dismutase (SOD) activity was determined in a 48 hour postanoxic recovery phase. Tests were performed to ensure the accuracy of the measured enzyme activities. In the most anoxia tolerant species, I. pseudacorus, SOD activity rose continuously during the period of imposed anoxia, and levels were maintained in the postanoxic recovery phases: 28 days brought about a 13-fold increase to 1576 U SOD per milligram protein. Small increases were found in the less anoxia tolerant I. germanica during anoxic/postanoxic phases, while a drop in activity was recorded in the least anoxia tolerant G. maxima. However, initial levels in G. maxima were more than twice as high as in the other two species. Experiments applying cycloheximide to anoxic rhizome slices of I. pseudacorus inhibited the increase in SOD activity. This indicates that SOD is, paradoxically, induced under anoxia and we suggest that in this species SOD is one of the enzymes identified as anaerobic polypeptides. The significance of the induction of an `oxygen-protecting' enzyme during complete oxygen deprivation is discussed with regard to a possible critical role during recovery from anoxic stress.     

Mitochondrial Ultrastructure of Three Hygrophyte Species at Anoxia and in Anoxic Glucose-Supplemented Medium

Mitochondrial ultrastructure of excised roots of Alisma plantago-aqisaticaL., Lycopus europaeus L and Glyceria fluitans L. were electron-microscopicallystudied at anoxia and in anoxic glucose- supplemented mediumin order to find Out if the roots of the three hygrophytes growingon water-logged anaerobic soils have an increased resistanceto anoxia. Irreversible destruction of mitochondrial membranes and othersubcellular structures was shown to occur in the above plants'roots after 24 h at anoxia or in anoxic glucose-supplementedmedium. Only in roots of Glyceria had exogenous glucose a protectiveaction, yet in this case, too, a 48 h anacrobic exposure resultedin a deep-going degradation of cell ultrastructure. It is concluded that though the plants in question grow on soilsdevoid of O₂ their roots avoid anaerobiosis through translocationof O₂ from aerated parts, which appears to explain why theseplants have not developed a biochemical mechanism of adaptationto anaerobiosis in the process of evolution. Key words: Anaerobiosis, hygrophytes, mitochondrial ultrastructure     

Effects of anoxia and flooding on alcohol dehydrogenase in roots of Glyceria maxima and Pisum sativum

Flood tolerant Glyceria maxima and intolerant Pisum sativum were compared in respect of the effects of anoxia and flooding on the maximum catalytic activities of alcohol dehydrogenase in their roots. Small (<73%) increases in enzyme activity occurred when excised roots of both species were incubated in nitrogen for up to 2 days. Further incubation in nitrogen rapidly and permanently damaged the roots of both species. Enzyme activity in flooded roots of Glyceria was about double that in corresponding non-flooded roots. A marginally greater difference was found for roots of Pisum. It was concluded that the two species respond so similarly to the above treatments that variation in the extent of induction of alcohol dehydrogenase is unlikely to be a significant factor in determining their ability to tolerate flooding.     

Relationship between Coleoptile Elongation and Alcoholic Fermentation in Rice Exposed to Anoxia. II. Cultivar Differences

The relationship between coleoptile elongation and survivalvs. alcoholic fermentation of rice under anoxia is examinedusing eight cultivars differing in submergence tolerance. Anoxiawas imposed on either 1 or 4 d aerated seeds either by N₂ flushingsubmerged tissues or by incubating tissues in stagnant deoxygenatedagar at 0·1% w/v; the latter simulated the stagnant conditionsof waterlogged soil. Two cultivars that were most tolerant tosubmergence also had the greatest tolerance to anoxia, whilea submergence intolerant cultivar was also intolerant to anoxia. Coleoptile growth under anoxia was related to rates of ethanolsynthesis (R_E), however differences between growth during anoxiaand survival after anoxia indicated that post-anoxic injurymay also be important in rice seeds exposed to anoxia. The correlationbetween coleoptile growth and R_E measured on a tissue basisusing intact seeds was r² = 0·67 among six varietiesover 0-3 d anoxia. This correlation improved to about r² = 0·85using R_E of (embryos plus coleoptiles) over 0-3 d, or coleoptilesat 3 d after anoxia. Coleoptile growth of individual seeds wasusually poorly correlated to R_E in these cultivars at 2-3 dafter anoxia. When coleoptiles of similar lengths were obtainedfrom different cultivars using 4 d aerated seeds, there weredifferences in R_E and coleoptile growth which were related tocoleoptile growth during 3 or 5 d anoxia, either on a tissue(r² = 0·85) or a fresh weight basis (r² = 0·70-0·97respectively). Results are discussed in relation to factorswhich may limit ethanol synthesis in rice exposed to anoxiaand the importance of growth to the survival of seeds and matureplants during submergence in the natural environment.Copyright1994, 1999 Academic Press Anoxia, ethanol, alcoholic fermentation, Oryza sativa L., rice, submergence     

Causes and consequences of thermal tolerance limits in rocky intertidal porcelain crabs, genus petrolisthes

Vertical zonation of intertidal organisms, from the shallowsubtidal to the supralittoral zones, is a ubiquitous featureof temperate and tropical rocky shores. Organisms that livehigher on the shore experience larger daily and seasonal fluctuationsin microhabitat conditions, due to their greater exposure toterrestrial conditions during emersion. Comparative analysesof the adaptive linkage between physiological tolerance limitsand vertical distribution are the most powerful when the studyspecies are closely related and occur in discrete vertical zonesthroughout the intertidal range. Here, I summarize work on thephysiological tolerance limits of rocky intertidal zone porcelaincrab species of the genus Petrolisthes to emersion-related heatstress. In the eastern Pacific, Petrolisthes species live throughouttemperate and tropical regions, and are found in discrete verticalintertidal zones in each region. Whole organism thermal tolerancelimits of Petrolisthes species, and thermal limits of heartand nerve function reflect microhabitat conditions. Speciesliving higher in the intertidal zone are more eurythermal thanlow-intertidal congeners, tropical species have the highestthermal limits, and the differences in thermal tolerance betweenlow- and high-intertidal species is greatest for temperate crabs.Acclimation of thermal limits of high-intertidal species isrestricted as compared to low-intertidal species. Thus, becausethermal limits of high-intertidal species are near current habitattemperature maxima, global warming could most strongly impactintertidal species.     

Dynamics of Nitrification and Denitrification in Root-Oxygenated Sediments and Adaptation of Ammonia-Oxidizing Bacteria to Low-Oxygen or Anoxic Habitats

Oxygen-releasing plants may provide aerobic niches in anoxic sediments and soils for ammonia-oxidizing bacteria. The oxygen-releasing, aerenchymatous emergent macrophyte Glyceria maxima had a strong positive effect on numbers and activities of the nitrifying bacteria in its root zone in spring and early summer. The stimulation of the aerobic nitrifying bacteria in the freshwater sediment, ascribed to oxygen release by the roots of G. maxima, disappeared in late summer. Numbers and activities of the nitrifying bacteria were positively correlated, and a positive relationship with denitrification activities also was found. To assess possible adaptations of ammonia-oxidizing bacteria to low-oxygen or anoxic habitats, a comparison was made between the freshwater lake sediment and three soils differing in oxicity profiles. Oxygen kinetics and tolerance to anoxia of the ammonia-oxidizing communities from these habitats were determined. The apparent K(infm) values for oxygen of the ammonia-oxidizing community in the lake sediment were in the range of 5 to 15 (mu)M, which was substantially lower than the range of K(infm) values for oxygen of the ammonia-oxidizing community from a permanently oxic dune location. Upon anoxic incubation, the ammonia-oxidizing communities of dune, chalk grassland, and calcareous grassland soils lost 99, 95, and 92% of their initial nitrifying capacity, respectively. In contrast, the ammonia-oxidizing community in the lake sediment started to nitrify within 1 h upon exposure to oxygen at the level of the initial capacity. It is argued that the conservation of the nitrifying capacity during anoxic periods and the ability to react instantaneously to the presence of oxygen are important traits of nitrifiers in fluctuating oxic-anoxic environments such as the root zone of aerenchymatous plant species.     

Variation in Tolerance and Metabolic Responses to Flooding in some Tropical Trees

The effect of flooding on aerobic and anaerobic respirationas well as on the internal levels of ethanol, lactic, succinicand malic acids were compared in three flood-tolerant and twonon-flood-tolerant species. In the non-flood-tolerant speciesKielmeyera coriacea and Pseudobombax marginatum, which comefrom the ‘ cerrado’ vegetation, there was a uniformityof response with ethanol being the only one of the above productsto accumulate substantially during flooding. In the flood-tolerantspecies, Sebastiana klotzchyana, Hymenaea courbaril var. stilbocarpaand Chorisia speciosa, flooding induced a variety of responseswhich indicate that the tolerant species have evolved differingstrategies to overcome flooding stress.     

Supply and partitioning of assimilates to roots of Medicago sativa L. and Lotus corniculatus L. under anoxia

Abstract A current explanation of the mechanism of flooding injury to roots suggests that oxygen deficiency depresses the supply of respirable carbohydrates sufficiently to inhibit fermentation. However, even though it has been shown that phloem transport of assimilate is sharply reduced to anaerobic roots, inhibition of assimilate metabolism has also been suggested to be an important factor. This study examines these hypotheses by relating assimilate supply and metabolic activity in anoxic roots of alfalfa (Medicago sativa L.), a flood-intolerant species, and birdsfoot trefoil (Lotus corniculatus L.), a flood-tolerant plant. Roots were made anoxic (severe O₂ deficiency) for 2, 4 or 6 d and shoots were labelled with ¹⁴CO₂. Assimilate transport to the roots and metabolism to structural components were significantly decreased in both species in response to anoxia. Trefoil exhibited significantly greater ¹⁴C incorporation into the residue fraction at 4 d anoxia than did alfalfa, and this was consistent with the greater flooding tolerance of trefoil. When assimilate supply to O₂-deficient roots was decreased by shoot shading, shoot fresh weight was reduced by both anoxia and light treatments. Root-soluble sugars were significantly decreased by shading but were greatly increased in response to anoxia. Root starch concentration also increased under anoxia. Root K⁺ concentration was reduced by anoxia only. The energy status (ATP/ADP) of roots was significantly decreased by shading; however, anoxia reduced the energy status only in unshaded plants. The data indicate that carbohydrate supply to anaerobic roots does not appear to be a limiting factor in the metabolic response of alfalfa roots. Alternatively, metabolism of assimilate in anoxic roots may be an important determinant of survival.     

Copepod succession in two South African estuaries

The seasonal succession of copepod species was studied fromNovember 1976 through October 1978 in the Swartkops and Sundaysriver estuaries. South Africa. Acartia natalensis appeared inthe plankton in spring and reaches maximum abundance duringsummer and autumn. It was replaced by A. longipatella in lateautumn which reached maximum abundance in winter and spring.Cycles of dominance are regulated by the interaction of temperature,salinity and competition between the two species. A natalensis a more tolerant of low salinity and the replacementof A. longipatella by A. natalensis starts in the upper estuaryand spreads seawards. Maximum abundance of A. natalensis isattained in water of lower salinity than in the case of A. longipatella.In the Sundays estuary A. natalensis appeared briefly in thelatter half of the study and in the upper and middle estuaryonly. In the lower estuary A. longipatella was present duringall seasons. This was due to the absence of competition fromA. natalensis, high salinity and lower summer temperatures dueto marine influence. A third species of copepod, Pseudodiaptomushessei functions as a pioneer species, exploiting "new water"after flooding or strong fresh water inflow. High abundancemay therefore occur during any season and no competition betweenP. hessei and either species of Acartia was observed.     

Life cycle strategies and seasonal variations in distribution and population structure of four dominant calanoid copepod species in the eastern Weddell Sea, Antarctica

The dominant Antarctic copepod species Calanoides acutus, Calanuspropinquus, Rhincalanus gigas and Metridia gerlachei were investigatedwith respect to their abundance, vertical distribution, developmentalstage composition, dry weight and lipid content. The specimenswere sampled during three expeditions to the eastern WeddellSea in summer (January/February 1985), late winter/early spring(October/November 1986) and autumn (April/May 1992) between0 and 1000 m depth to follow the seasonal development of thepopulations. Three species were most abundant in April, onlyC.propinquus reached highest concentrations in February. A seasonalmigration pattern was evident in all four species, but was mostpronounced in C.acutus. In October/November, they inhabiteddeeper water layers, their ascent started by mid-November andin mid-February the species concentrated in the upper 50 m,except for M.gerlachei (50–100 m). Their descent was observedin April/May. The stage composition changed dramatically withseason, the older developmental stages (CIII–CVI) dominatedthe populations in late winter/early spring, whereas youngerstages (CI and CII) prevailed during summer (C.acutus, C.propinquus)or autumn (R.gigas, M.gerlachei). Only C.acutus ceased feedingin autumn and diapaused at depth. Strong differences betweenseasons were also detected in dry weight and lipid levels, withminima in late winter/early spring and maxima in summer (C.acutus,R.gigas) or autumn (C.propinquus, M.gerlachei). Lipid reservesseem to be most important for the older stages of C.acutus andC.propinquus. Based on these seasonal data, different life cyclestrategies are suggested for the four species.     

The calanoid copepod Acartia italica Steuer, phenomenon in the small saline Lake Rogoznica (Eastern Adriatic coast)

Lake Rogoznica, near ibenik, Croatia, is a salt coastal lakewith a maximum depth of about 15 m. During most of the year,this small, naturally eutrophied lake is highly stratified,with hypoxia/anoxia occurring in the bottom layer. Total anoxia,with the presence of hydrogen sulphide, was recorded on September27, 1997. At that moment, massive mortality of all planktonicand benthic organisms was observed. After the anoxia, Acartiaitalica, the only planktonic copepod species of the lake, re-establishedquickly. Before anoxia, the population dynamics of the A.italicapopulation depended primarily on predator/prey relationships.However, in the post-anoxic period, nutrient–phytoplankton–copepodrelationships became more important, as there was no longerany predation pressure. From all accounts, it would appear thatonly A.italica is adapted to the extreme conditions which appearfrom time to time in the lake, and that this species has animportant role in the functioning of the lake ecosystem. Acartiaitalica was very important for the gradual normalization oflife in the lake after total anoxia.     

Macrozooplankton studies in Kuwait Bay (Arabian Gulf). II. Distribution and composition of planktonic penaeidea

Six penaeideans were identified during a 12-month investigationof macrozooplankton in Kuwait Bay. The numerically dominantspecies included two sergestids, Lucifer hanseni and Acetesjaponicus. Of the two, L.hanseni appears to spawn in the bayduring summer months while, A.japonicus may concentrate itsspawning in coastal waters during late spring through fall.The most abundant penaeids were Parapenaeopsis stylifera andMetapenaeus spp., although Kuwait Bay may not be a major spawningarea for these species. However, the Khor al Sabiya, a river-likechannel northeast of Kuwait Bay, may serve as a nursery forat least two of the penaeids (Metapenaeus spp. and Penaeus semisulcatus)as well as for A.japonicus. Both P.stylifera and Metapenaeusspp. larvae were most abundant during late spring. Penaeus semisulcatuslarvae exhibited fall and spring-summer maxima but were neverlocally abundant.     

The Effects of Rootzone Salinity and Hypoxia on Shoot and Root Growth in Trifolium Species

The effect of concurrent salinity (0-60 mM NaCl) and rootzonehypoxia (flooding for up to 15 d) on shoot and root growth andshoot ion concentrations of six species of Trifolium (T. subterraneumL., T. fragiferum L., T. michelianum Savi., T. isthmocarpumBot., T. purpureum Lois., and T. repens L.), was studied intwo greenhouse experiments. There was a significant salinityx flooding effect for shoot yield but no significant salinityx flooding x species interaction although individual speciesdiffered significantly (P < 0·001) in their growthresponse to the saline or flooded conditions separately. Concentrationsof Na and Cl in the shoots of all species increased with increasingperiods of saline flooding and there was a significant salinityx flooding interaction. Sodium and Cl concentrations were significantlyhigher (P < 0·001) in T. purpureum, the species inwhich shoot growth was most depressed by saline flooding, thanother species. In T. michelianum, T. fragiferum and T. repens,fresh and dry weight of roots increased with flooding underboth saline and non-saline conditions while in T. subterraneumroot growth decreased. A significant proportion of the increasedroot growth in the first three species occurred as new adventitiousroots. These roots had higher percentages of internal gas spaceswithin the root tissue even in the presence of salinity comparedwith roots from non-flooded conditions. There were also significantlymore gas spaces in the total root tissue in T. fragiferum andT. repens under saline-flooding than in roots of T. subterraneum.Electron micrographs of the root cross sections illustratedthe presence of these gas spaces or aerenchyma. Trifolium fragiferum, T. repens and T. michelianum are morelikely to be suited to growth in soils prone to high salinityand to flooding than are T. subterraneum, T. purpureum and T.ishmocarpum.Copyright 1993, 1999 Academic Press Trifolium subterraneum, Trifolium fragiferum, Trifolium michelianum, Trifolium isthmocarpum, Trifolium purpureum, Trifolium repens, salinity, flooding, hypoxia, adventitious roots, aerenchyma, subterranean clover, white clover, strawberry clover, purple clover, balansa clover     

Discrimination of American Cranberry Cultivars and Assessment of Clonal Heterogeneity Using Microsatellite Markers

Cranberries (Vaccinium macrocarpon Ait.) are an economically important fruit crop derived from a North American native species. We report the application of 12 simple sequence repeats (SSR) or microsatellite markers to assess the genetic diversity of cranberry cultivars. We studied 164 samples of 21 different cranberry cultivars, 11 experimental hybrids, and 6 representative accessions of wild species. Genetic cluster analysis, based on 117 SSR alleles, differentiated the major cranberry cultivars. However, some cranberry cultivar subclone variants and mislabeled samples were observed. Consensus genetic profiles identified the most likely clonal representatives of several important cranberry cultivars (e.g., “Ben Lear,” “Howes,” and “Stevens”). The markers were further used to confirm putative parents of several hybrid progenies. The long-term goal of our studies is to identify, preserve, and utilize unique genetic materials to breed improved cranberries. Attaining this goal will help growers maintain sustainability under changing economic and environmental conditions.     

Clonal diversity and genetic differentiation revealed by SSR markers in wild Vaccinium macrocarpon and Vaccinium oxycoccos

American cranberry (Vaccinium macrocarpon) is a perennial, woody plant species, native to North American bogs and wetlands. Cranberries represent one of the few agriculturally important native plants in which wild gene pools are still readily available within the undeveloped wetlands of the northern US and Canada. Earlier studies have reported low genetic variation in V. macrocarpon at the species and population level. However, in this study, we characterised 229 individuals of wild V. macrocarpon and V. oxycoccos (small cranberry) from Wisconsin and 22 accessions using microsatellite markers and observed substantial genetic variation and differentiation within and among populations and species. While V. macrocarpon was analysed using 108 alleles from 11 microsatellite loci revealing 42 unique genotypes, V. oxycoccos was analysed using 156 alleles from eight loci revealing 28 unique genotypes. There were a total of 182 alleles found in both species combined with 156 of those alleles present in V. oxycoccos and 84 alleles found in V. macrocarpon. All eight loci possessed species‐specific alleles with V. oxycoccos possessing 98 private alleles versus 26 private alleles found V. macrocarpon, and 58 alleles were found in common between both species. Our data will be valuable not only for future wild cranberry diversity and population genetics research, but for other cranberry breeding and genetics studies.     

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