01867nas a2200181   4500008004100000245014500041210006900186260001200255300001400267490000700281520121700288100001101505700001301516700001101529700001101540700001701551856011701568       2004                        eng d00aChromosome behavior during meiosis and development of spore mother cells in the Chinese quillwort Isoetes sinensis T. C. Palmer (Isoetaceae)0 aChromosome behavior during meiosis and development of spore moth  c2004///  a183 - 1950 v943 aChromosome behavior during meiosis of the tetraploid Isoetes sinensis was observed to be similar to that of basic diploid Isoetes species. This observation was consistent with the previous report that polyploid species of Isoetes are allopolyploids. Meiosis was generally similar in both megaspore and microspore mother cells, but differences were observed. Due to the smaller size of the microspore mother cells, during prophase I, chromosomes are not as dispersed as those in megaspore mother cells. Cytomixis was observed in all stages of meiosis in microspore mother cells, but it was not seen at any stage of meiosis in megaspore mother cells. Cytomixis, lagging chromosomes, chromosome bridges, chromosome fragments, and micronuclei, observed during meiosis in I. sinensis, can affect sexual reproduction, but it does not appear to be a major cause of population decline in this species. The major cause of decline is habitat degradation from human disturbance. The few remaining populations of the Chinese quillwort are fragmented and the numbers of individuals contained in these populations dwindle as a result of habitat degradation. Conservation efforts are needed to save I. sinensis from extinction.1 aHe, Z.1 aWang, H.1 aLi, J.1 aYe, Q.1 aTaylor, W.C.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-11444270683&partnerID=40&md5=e3b19a6dd117ccd20573e526dceb63bf01159nas a2200229   4500008004100000245008200041210006900123260001200192300001400204490000800218520044000226653001800666653001300684653002200697653001500719653001300734653002100747100001700768700001400785700001400799856011600813       2004                        eng d00aIsoetes fluitans sp. nov.: The identity of Spanish plants of 'I. longissimum'0 aIsoetes fluitans sp nov The identity of Spanish plants of I long  c2004///  a231 - 2360 v1463 aRecent revision of North African specimens of Isoetes velata A. Braun and the closely related taxon l. longissimum Bory, together with Spanish material conventionally designated I. longissimum, suggests that the Spanish specimens constitute a new species, I. fluitans. This is described and illustrated. The North African taxon I. longissimum is probably not specifically distinct from I. velata. © 2004 The Linnean Society of London.10aaquatic plant10aEndemism10aIberian peninsula10aIsoetaceae10ataxonomy10aThreatened plant1 aRomero, M.I.1 aAmigo, J.1 aRamil, P.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-6344262161&partnerID=40&md5=621cece2b24256d4cab656a85119d39501961nas a2200193   4500008004100000245017900041210007100220260001200291300001400303490000700317520123100324100001701555700001901572700001501591700001201606700001701618700001501635856011701650       2004                        eng d00aPhylogenetic relationships of Isoëtes (Isoëtaceae) in China as revealed by nucleotide sequences of the nuclear ribosomal ITS region and the second intron of a LEAFY homolog0 aPhylogenetic relationships of Isoëtes Isoëtaceae in China as rev  c2004///  a196 - 2050 v943 aIsoëtes is an ancient lycopod lineage with a highly conserved morphology that provides few morphological characters to resolve the phylogeny of its species. Species appear to have evolved by divergence and allopolyploidy. The basic diploids I. hypsophila, I. taiwanensis, and I. yunguiensis and the tetraploid I. sinensis occur in China. Analysis of ITS sequences indicates that the Chinese Isoëtes species are part of an Australasian clade including I. brevicula from Western Australia and I. kirkii from New Zealand. Two distinct cloned sequences of the second intron of a LEAFY homolog were recovered from I. sinensis supporting the hypothesis that I. sinensis is an allotetraploid. One of the I. sinensis cloned sequences was similar to the I. taiwanensis sequence and the other cloned sequence was similar to the I. yunguiensis sequence identifying I. taiwanensis and I. yunguiensis as the likely parents of I. sinensis. Other cloned sequences recovered from I. sinensis were recombined parts of the two distinct sequences. Morphological evidence supporting an allotetraploid origin of I. sinensis is found in its larger microspore size and intermediate megaspore texture compared to I. taiwanensis, and I. yunguiensis.1 aTaylor, W.C.1 aLekschas, A.R.1 aQing, F.W.1 aLiu, X.1 aNapier, N.S.1 aHoot, S.B.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-11444262662&partnerID=40&md5=7b7a2b568e139bee1b60bd62836ff6ef02382nas a2200229   4500008004100000245010700041210006900148260001200217300001600229490000700245520162100252653002601873653001101899653002401910653001601934653001201950653002101962653001901983653001602002100001802018856011602036       2004                        eng d00aRegulation of root anaerobiosis and carbon translocation by light and root aeration in Isoetes alpinus0 aRegulation of root anaerobiosis and carbon translocation by ligh  c2004///  a1102 - 11110 v273 aThe activity of alcohol dehydrogenase (ADH) was measured in corms and roots of the submerged freshwater macrophyte Isoetes alpinus Kirk. growing in situ, and related to its capacity for internal oxygen transport and to carbohydrate translocation. ADH activity was present in roots but not corms at uniform activity (0.15-0.35 × 10-6 mol g-1 fresh weight s-1) over the entire plant depth range (3-7 m depth), and was intermediate to that developed in excised roots after 1-week exposure to either dissolved oxygen at air-saturation or to anoxia. Responses of photosynthesis and root oxygen release to light intensity confirmed that shoot-to-root oxygen transport saturated at similar light intensities to photosynthetic oxygen evolution, but was positive in the dark and at irradiances below the compensation point for photosynthesis, due to contributions to transport by oxygen diffusion from the external medium. Transport of 14C-labelled photo-assimilates to roots nevertheless ceased when intact plants were exposed to a combination of leaf darkness and root external anoxia, even when high 14C concentrations were present in shoots, but remained high when the roots were provided with external oxygen. The lack of any control over permeability of the root surface to gases in this species suggested that ADH activity and reduced translocation is most likely caused by development of hypoxic tissues in the apical tissue. These results suggest that reductions in ambient light intensity may have indirect effects on I. alpinus viability by increasing the degree of root hypoxia and impairing carbon partitioning.10aAlcohol dehydrogenase10aAnoxia10aAquatic macrophytes10aAssimilates10aLacunae10aOxygen transport10aPhotosynthesis10aRespiration1 aSorrell, B.K.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-4544301436&partnerID=40&md5=3f174fe3d7839650597cfe52d3369b9102275nas a2200289   4500008004100000245011600041210006900157260001200226300001400238490000800252520133300260653002301593653002301616653001201639653002001651653002001671653001801691653003301709653002401742653001501766653002201781100001401803700001601817700002001833700001601853856011601869       2004                        eng d00aExperimental management of Mediterranean temporary pools for conservation of the rare quillwort Isoetes setacea0 aExperimental management of Mediterranean temporary pools for con  c2004///  a675 - 6840 v1183 aMediterranean temporary pools represent unique species-rich habitats with many rare and endangered species. The Roque-Haute Natural Reserve is one of the few sites in France with Isoetes setacea Lam., a very rare Mediterranean quillwort, considered as a keystone species determining a priority habitat for the European Union. Land uses changes have favoured the invasion of the pools by several shrub and tree species (e.g., Ulmus minor, Fraxinus angustifolia subsp. oxycarpa). Clearing shrubs in an experimental area of one pool resulted in the increase of I. setacea as compared to control, combining a higher cover in previously occupied quadrats and more quadrats occupied. Litter accumulation had a negative effect on the population of Isoetes but this effect was detectable only in the cleared area. Light attenuation was shown experimentally to be detrimental to the vegetative and regenerative production of I. setacea. Clearing of the shrubs and removal of the litter led to an increase in the I. setacea populations and therefore appears to be an effective technique for restoring these plant communities invaded by shrubs. Long-term shrub control should be ensured by reintroducing sheep grazing in order to enhance the sustainable conservation of this oligotrophic habitat. © 2003 Elsevier Ltd. All rights reserved.10aArtificial shading10aEndangered species10aGrazing10aIsoetes setacea10aLight reduction10aLitter effect10aMediterranean seasonal pools10aSexual reproduction10aSpore-bank10aVegetative growth1 aRhazi, M.1 aGrillas, P.1 aCharpentier, A.1 aMédail, F.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-2042522718&partnerID=40&md5=9b3e2127f0abc60df6e5407fa4e555ec02405nas a2200205   4500008004100000245014300041210006900184260001200253300001400265490000700279520168800286653000801974653001401982653001901996653000702015653002602022100001802048700001702066856011602083       2004                        eng d00aWater velocity and irradiance effects on internal transport and metabolism of methane in submerged Isoetes alpinus and Potamogeton crispus0 aWater velocity and irradiance effects on internal transport and   c2004///  a189 - 2020 v793 aSubmerged aquatic macrophytes are important methane (CH4) transport pathways, but little is known about how water velocity and illumination affect plant CH4 transport. We studied CH4 transport in vitro in fully-submerged plants of two aquatic macrophytes, Isoetes alpinus and Potamogeton crispus, comparing transport between two water velocities (0.5 and 90 mm s-1) and light versus dark treatments at the shoots. In I. alpinus, CH4 taken up by the roots accumulated in the lacunar system of the leaves at concentrations &gt;40 μmol l-1 at both flow rates, but there was no release from the shoots to the water at flow = 0.5 mm s-1, whereas at 90 mm s-1 release from the shoots to the water was always &gt;0.15 μmol (CH4 g-1 dry wt. h-1). Uptake of CH4 by the roots was 1.5 times greater at the higher than the lower water velocity. In P. crispus, a gradient in lacunar [CH4] developed from the base to the apex of the shoot and was steeper at the higher than the lower water velocity. CH4 release rates from the shoots were &lt;0.1 μmol (CH4 g-1 dry wt. h-1) at both water velocities in this species, due to CH 4 consumption by epiphytic methanotrophic bacteria. Irradiance and its associated root aeration had no effect on CH4 transport in I. alpinus, but decreased root to shoot CH4 transport and release more than 10-fold in P. crispus, apparently by alleviating effects of hypoxia on the root-associated methanotrophic bacteria. Our data support the view that plant-associated methanotrophs are important CH4 sinks in freshwater habitats, and demonstrate the importance of flow velocity in the CH4 dynamics of submerged macrophytes. © 2004 Elsevier B.V. All rights reserved.10aCH410aDiffusion10aLacunar system10aO210aSubmerged macrophytes1 aSorrell, B.K.1 aDownes, M.T.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-2642545092&partnerID=40&md5=9d9974a9e87e34dbe2225f98137ef82202291nas a2200205   4500008004100000245010500041210007100146260001200217300001400229490000700243520160200250653001901852653001901871653001201890653001701902100001501919700001701934700001701951856011701968       2004                        eng d00aRevealing unknown or extinct lineages within Isoëtes (Isoëtaceae) using DNA sequences from hybrids0 aRevealing unknown or extinct lineages within Isoëtes Isoëtaceae   c2004///  a899 - 9040 v913 aIsoëtes, a heterosporous lycopod with a fossil record dating back to the Paleozoic, has numerous putative allopolyploids (resulting from hybridization events coupled with doubling of chromosome number). By using the highly variable nucleotide sequences from the second intron of a LFY homologue in Isoëtes, species could be delimited and hybrid origins determined. The data suggest that reticulate evolution is both common and complex within a more derived species complex of Isoëtes. Sequences of identifiable parentage and sequences that are unlike any diploid species known were recovered, leading to the conclusion that one or both of the putative parents have not yet been discovered or are extinct. A range of observations concerning allopolyploid speciation were categorized as follows: (1) verification of previous hypotheses regarding parentage (e.g., I. riparia, I. appalachiana), (2) determination that two morphologically distinct allotetraploid species can share the same parentage (I. azorica and I. acadiensis), (3) recognition of a cryptic allotetraploid species, indicated by the presence of different parental genomes (I. "appalachiana" from Florida), and (4) identification of allotetraploid species with one or two unknown parents (e.g., I. tuckermanii, I. acadiensis, I. azorica, and I. hyemalis). Some sequences from diploid species are remarkably uniform among populations (e.g., I. echinospora from various locations in North America, Iceland, and Wales), while others are variable at the subspecies level (e.g., northern and southern populations within I. engelmannii).10aAllopolyploidy10aHybrid origins10aIsoetes10aLEAFY intron1 aHoot, S.B.1 aNapier, N.S.1 aTaylor, W.C.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-11444256350&partnerID=40&md5=420a4ad06820ce82f60d7a70e7db9dec01786nas a2200229   4500008004100000245008300041210006900124260001200193300001400205490000700219520106000226653001201286653001701298653001501315653002201330653001601352653002301368653002101391653001301412100001401425856011701439       2004                        eng d00aNon-destructive assessing and monitoring of populations of Isoetes lacustris L0 aNondestructive assessing and monitoring of populations of Isoete  c2004///  a147 - 1530 v343 aExtensive studies of Isoetes lacustris, performed throughout Europe, resulted in regressions between the number of leaves per rosette and (1) the number of spores per megasporangium, (2) length of seasonal growth, (3) Secchi depth and (4) water colour plus a relationship between pH and the number of spores per megasporangium. The evaluation of Isoetes populations requires measurements of the lake data Secchi depth, water colour, pH and conductivity, the establishment of climate data and leaf counts on 20-30 plants with the aid of SCUBA. The method may be applied to lakes in a range of situations, varying between lowland and highland, and between temperate and subarctic climate regions. The regressions are displayed graphically. The actual mean leaf number and corresponding megaspore number are compared with the numbers referred to in the environmental data. Consistent values point to the parameters which influence growth and vitality of the quillwort and to what extent, in a particular lake. Examples of evaluation and monitoring are given.10aClimate10aConductivity10aEvaluation10aIsoetes lacustris10aLeaf number10aLight availability10aMegaspore number10apH value1 aVöge, M.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-17944391690&partnerID=40&md5=bc81c2908849af47d9ff68a2cff5dbc9