Water-storing and Cavitation-preventing Adaptations in Wood of Cacti

Ancestral cacti presumably had abundant, fibrous, heavily lignifiedwood, similar to that present in the relictual, leaf-bearinggenus Pereskia. During the evolutionary radiation of the subfamilyCactoideae, diverse types of bodies and woods arose. Severalevolutionary lines have retained an abundant, fibrous wood:all wood cells, even ray cells, have thick lignified walls,and axial parenchyma is only scanty paratracheal. Aside froma diversity of vessel diameters, there seems to be little protectionagainst cavitation during water-stress, and little water-storagecapacity. This strong wood permits the plants to be tall andto compete for light in their tree-shaded semi-arid habitats.In other evolutionary lines, the wood lacks fibres, and almostall cells have thin, unlignified walls. Vessels occur in anextensive matrix of water-storing parenchyma, and tracheidsare also abundant, constituting over half the axial tissue insome species. There is excellent protection against cavitation,but little mechanical support for the plant body; however, theseplants are short and occur in extremely arid, unshaded sites.Scandent, vinelike plants of two genera produce a dimorphicwood—while their shoots are extending without externalsupport, they produce fibrous, lignified wood, but after leaningagainst a host branch, they produce a parenchymatous, unlignifiedwood.Copyright 1993, 1999 Academic Press Cactaceae, cactus, water-stress, wood, evolution, xylem     

UPPER BARREMIAN (CRETACEOUS) HETEROCERATID AMMONITES FROM SOUTH AFRICA AND THE CAUCASUS AND THEIR -PALAEOBIOGEOGRAPHIC SIGNIFICANCE

Heleroceratid ammonites are abundant in the Upper Barremiansediments of Zululand, South Africa, and representatives ofthe genera Heteroceras, Colchidites and Paraimerites are describedbelow. This assemblage shows strong similarities to faunas knownfrom the Caucasus region of the USSR, a similarity that persistedinto the succeeding Aptian. This similarity presents somethingof a paradox, because the genera concerned are among the leasthydrodynamically streamlined of ammonites. Their distributionsuggests an open marine connection between the Mediterraneanparts of Tethys and the eastern coast of Africa, linked, inthe Barremian — early Aptian at least, to Patagonia. Theirwide distribution also supports the view that climatic gradientswerelow during the Barremian and that the climate was generallywarmer than at present. (Received 12 January 1983;     

COMPETITION BETWEEN TWO LAND GASTROPODS ALONG ALTITUDINAL GRADIENTS IN SOUTH-EASTERN FRANCE: NEONTOLOGICAL AND PALAEONTOLOGICAL EVIDENCE

In south-eastern France, Trochoidea geyeri (Soós) todaycharacterizes open upland environments from about 1000 m abovesea level. At lower altitude it is replaced by Candidula unifasciata(Poiret)—another member of the Helicellinae—whilethe other members of the community remain almost the same. Duringthe cold stages of the Quaternary, T. geyeri was also an importantelement of lowland gastropod communities in Provence, whileit was always replaced by C. unifasciata during the interglacialstages. Thus, T. geyeri seems to be a valuable cold indicatorspecies for palaeoclimatic reconstructions. Some anomalies in this pattern, however, show that each of thesespecies can live in bioclimatic conditions which characterizethe area of the other. This suggests a competitive dominancephenomenon from a threshold situated around 1000 m on the altitudinalgradient. The influence of competitive interaction is demonstratedusing similar altitudinal gradients in which T. geyeri is missingbecause of historical factors: in such cases, C. unifasciataoccupies the entire gradient, up to 2250 m. Quaternary climaticchanges produced altitudinal shifts of the contact zone betweenT. geyeri and C. unifasciata, and, correlatively, repeated isolationsof T. geyeri populations. (Received 26 December 1992; accepted 4 February 1993)     

Cues in the Web-Building Process

SYNOPSIS. Sensory events presumably guide the orb-weaver inthe sequence of placing radii. However, at a given stage ofconstruction, several sectors of the web may be equivalent inthe sense that they possess features capable of eliciting radius-building.Observation of the natural progress of construction cannot revealthese characteristics. Some delineation of the problem may beobtained by compelling the spider to identify equivalent sectors.This procedure was followed for Araneus diademntus by selectivelydestroying threads, in effect repeatedly forcing the spiderinto the same web-array. The "candidate" sectors—thoseregions which are placed and replaced by the spider—aresufficiently described by the size of their central angles inearly stages of radius-building, but not in later stages. Anglesof relatively large size are left open in the upper half ofthe web. Sensory guidance in construction of radii may dependupon response to a complex array of forces in the web.     

A twin Gliwicz--Haney in situ zooplankton grazing chamber: design, operation and potential applications

The design and operation of a twin-chambered modification ofthe Gliwicz — Haney in situ grazing vessel is described.Grazing rates are determined in one chamber, while the secondfunctions as a self-draining plankton trap.     

Fine Structure of Hydrolysed Primary Walls in Tracheary Elements of Petiolar Xylem in Eucalyptus delegatensis

The hydrolysed lateral primary walls of tracheary elements ofthe petiolar xylem of Eucalyptus delegatensis were examinedby electron microscopy. Vessel-vessel and vessel—tracheidhydrolysed walls were strikingly different in appearance fromtracheid—tracheid walls. The difference seemed to be inthe degree to which the primary walls were hydrolysed. The observationssuggest the wall hydrolysis to be an ordered and controlledprocess. Eucalyptus delegatensis, hydrolysed wall, petiolar xylem, tracheary elements     

Society for Molecular Biology and Evolution (SMBE) Council and Business Meetings, 2004 State College, Pennsylvania, USA

Council Meeting

1. Call to order.—President John Avise called the meetingto order at 9:00 AM, 17 June 2004. In attendance were PresidentJohn Avise, Treasurer Marta L. Wayne, Editorial Advisory Boardmember Stanley A. Sawyer, Editor William Martin, Past- PresidentNaoyuki Takahata, Secretary Sudhir Kumar, and Councillors G.Brian Golding, Laura A. Katz, and Jody Hey. President-ElectJeffrey R. Powell arrived later due to flight delays. The meetingbegan with Introductions.
2. Approval of minutes.—Councilapproved the minutes of the2003 Council and Business meetings,published in the December2003 issue of the journal MolecularBiology and Evolution (MBE).
3. Editor's report.—Most ofthe meeting addressed a discussionconcerning the Journal'sfuture and dealings with the OxfordUniversity Press (OUP) (seereport).
4. Treasurer's report.—Treasurer Marta L. Waynesummarizedthe financial state of the Society (see report).The fiscalyear has now changed to January–December (coincidentwith     

Cellular Aspects of the Control of Physiological Color Changes in Amphibians

SYNOPSIS. The present paper is concerned mainly with the melanin-dispersingeffect of melanocyte-stimulating hormones (MSH's) on the skinmelanophores of amphibians. In addition, some of the more recentevidence for the unihumoral theory of the control of color changeis reviewed. The mechanism of dispersion of melanin is stillunknown, but evidence is accumulating that the action of MSHmay be mediated by an increase in the melanophoric content ofadenosine 3', 5'-monophosphate (cyclic AMP). For example, cyclicAMP has a specific, reversible melanin-dispersing effect onthe melanophores of the isolated skin of R. pipiens and Xenopuslaevis. It also has a reversible "melanophore—expanding"effect on the tissue—cultured embryonic melanophores ofthe spotted salamander, Ambystoma maculatum. The effect of cyclicAMP on melanophores of R. pipiens does not require sodium butis inhibited by hypertonicity. Finally, new evidence is presented that confirms that the melanin-dispersingeffect of catecholamines on melanophores of X. laevis is mediatedby beta adrenergic receptors,because it is blocked by the highlyspecific ß—blocking agent, propranolol. On theother hand, the melanin-aggregating effect of catecholamineson amphibian melanophores appears to be mediated by alpha adrenergicreceptors. There is even a possibility that the effects of catecholaminesare also mediated through a control of cyclic AMP levels inmelanophores, with beta adrenergic stimulation producing anincrease in cyclic AMP levels, followed by dispersion of melanin,and alpha adrenergic stimulation producing a decrease in cyclicAMP levels, followed by aggregation of melanin.     

Structure of the Nemertine Integument with Consideration of Its Ecological and Phylogenetic Significance

The phylum Nemertina, with more than 800 described species,occupies a wide range of habitats and figures prominently intheories of bilaterian evolution. Integuments of nemertines,from a number of habitats and representing the major orders,are compared and the general cell types constituting the epidermisare reviewed and defined. The general construction and celldemography of the integument are more or less characteristicfor each order, but are not readily generalized to lower taxonomiclevels. Similarly, the general structure of the integument hascorrelations with broad environments, but there are few conspicuous,uniquely adaptive, morphological specializations; e.g., theadhesive plate and ciliary bristles of interstitial nemertines,the tube-forming cells of Carcinonemertes epialti and variouspalaeonemertines, the epidermis of the pilidium larva. It isproposed that there are three generalized types of integumentaryglandular cells, mucous, serous and bacillary, and that theseand the ciliated cells vary only modestly across taxonomic andenvironmental lines. However, it is also proposed that the majorstructural variations of the integument not only are diagnosticfor the orders but also suggest and correlate with two majorevolutionary radiations of the extant nemertines, one epibenthic,the other infaunal—in that sequence. Similarities of thenemertine integument to that of turbellarians are superficialor at best plesiomorphous; i.e., they are also found in othertaxa.     

Physiological and Ecological Studies in the Analysis of Plant Environment: VII. An Analysis of the Differential Effects of Light Intensity on the Net Assimilation Rate, Leaf-Area Ratio, and Relative Growth Rate of Different Species

Since relative growth rate is the product of net assimilationrate and leaf-area ratio (leaf area/plant weight), it followsthat if the effects of shading on both net assimilation rateand leaf-area ratio can be expressed mathematically, then therelationship between light intensity and relative growth ratecan be derived from the product of the two mathematical expressions. For all the ten species investigated in field and pot cultureexperiments, it has been found that during the early vegetativephase both the changes in leaf-area ratio and net assimilationrate, over the range of 0·1 to full daylight, are linearlyrelated to the logarithm of the light intensity. In consequence,the relationship between relative growth rate and the logarithmof light intensity—being the product of the two linearregressions—is curvilinear. For species of shady habitats (Geum urbanum, Solamun dulcamara)neither the levels of assimilation rate nor the ‘compensation-point’values are very different from those of the eight species fromopen situations (e.g. Hordeum vulgare, Pisum sativum, Fagopyrumesculentum). Nevertheless the intensity at which growth rateis maximal varies between species: it is 0•5 for G. urbanum,0•7 for H. annuus, full daylight for F. esculentum, whilefor Trifolium subterraneum the calculated value is 1·8daylight. Such specific differences can be largely accountedfor in terms of the differences in leaf-area ratio at the differentlight levels. On the basis of this analysis of the light factor, a ‘shade’plant is best redefined as a species in which a reduction ofthe light intensity causes a rapid rise in the leaf-area ratiofrom an initial low value in full daylight: for a ‘sun’plant the converse definition holds.     

Growth and Dry-weight Distribution in Callistephus chinensis as Influenced by Lighting Treatment

Plants of two cultivars of Callistephus chinensis (Queen ofthe Market and Johannistag) were grown in 8 h of daylight perday with one of the following treatments given during the 16h dark period: (a) darkness—‘uninterrupted night’,(b) I h of light in the middle of the dark period—a ‘nightbreak’, (c) I min of light in every hour of the dark period—‘cycliclighting’, (d) light throughout—‘continuouslight’. The plants receiving uninterrupted dark periods remained compactand rosetted in habit with small leaves, while leaf expansion,stem extension, and flower initiation were promoted in all threeillumination treatments (b, c, d). Although these three treatmentsproduced similar increases in leaf area, continuous light wasthe most effective for the promotion of both stem growth andflower initiation while cyclic lighting was generally more effectivethan a I-h night break. Continuous light also caused more dry matter to be divertedto stems at any given vegetative dry weight and it was shownthat the stem weight ratio of both varieties was correlatedwith stem length.     

Microbial Symbiosis: Patterns of Diversity in the Marine Environment

SYNOPSIS. Symbiotic associations expand both the diversity ofpotential ecological niches and metabolic capabilities of thehost—symbiont combinations. Symbioses can also be consideredto have evolutionary potential in that the partnership can resultin a "new organism." Associations between chemoautotrophic bacteriaand marine invertebrates, discovered only 10 years ago, arenow found widely in nature, in habitats ranging from deep-seahydrothermal vents to coastal sediments. Here I review chemoautotroph—invertebrateassociations and discuss the benefits inferred for both partnerswith regard to the diversity of these symbioses in nature.     

Development of Air Blisters in Pilea cadierei Gagnep. and Guillaumin

An ultrastructural study was conducted to determine the originand development of the air blisters in leaves of Pilea cadierei.At early developmental stages (characterized visually by ananthocyanin flush to the blistered region, in leaves 0.5–1.8cm long) two epidermal layers separated by a small intracellularspace from a sub-epidermal layer of phenolic cells are observed.Osmiophilic phenol aggregates occur in the central vacuole,minivacuoles (or provacuoles) and in the endoplasmic reticulaof the phenol cells. Plastids in the phenol-containing cellshave extremely osmiophilic thylakoids, perhaps indicative ofphenol—caffeine complexes in the plastid. Later developmentalstages (characterized by a silver coloration in the air blisters)show an increase in the intracellular space, due at least inpart to the apparent collapse of the second epidermal layerand breaking of cell connexions. Phenol-containing cells havetwo different types of electron-opaque deposit: a grey granulardeposit and a continuous caffeine—phenol agglutination.Plastids are shade type and are much less opaque than in earlierstages. Several possible reasons for the presence of air blistersin many genera are discussed. Pilea cadierei, air blisters, ultrastructure, phenolics, tannin     

Crocodylian Snouts in Space and Time: Phylogenetic Approaches Toward Adaptive Radiation

Recent phylogenetic analyses of fossil and living crocodyliansallow us to compare the taxonomic, geographic, and temporaldistributions of morphological features, such as snout shapes.A few basic snout morphotypes—generalized, blunt, slender,deep, and excessively broad ("duck-faced")—occur multipletimes in distantly-related lineages. Some clades—especiallythose found in the Northern Hemisphere or with minimum originationdates in the Cretaceous or lower Tertiary—are morphologicallyuniform, but geographically widespread; crocodylian faunas ofthe early Tertiary tend to be composite, with sympatric taxabeing distantly related, and similar-looking taxa on differentcontinents being close relatives. In contrast, crocodylian faunasof the later Tertiary tend to be more endemic, with local adaptiveradiations occurring in Africa and Australia containing membersof most basic snout shapes. Endemic radiations in Africa andAustralia have largely been replaced by Crocodylus, which canbe divided into subclades that may individually represent endemicadaptive radiations.     

Freezing avoidance mechanism of primordial shoots of conifer buds

Excised winter buds of very hardy fir supercooled to —30or — 35?C, though primordial shoots excised from thesewinter buds (freezing point: about —5.5?C) supercooledonly to —12 to — 14?C. Also, excised primordialshoots did not tolerate freezing, but were rather resistantto desiccation. Differential thermal analysis (DTA) of primordialshoots revealed that the capability of supercooling increasedwith decreasing water content and that no exotherm could bedetected in the primordial shoots with a water content belowabout 20%. When excised whole buds were cooled very slowly,the exotherm temperature shifted markedly to a lower value andthe exotherm became much smaller. Also, masses of needle icewere observed, mainly beneath the crown of the primordial shoot.From these results, it may be concluded that most of the waterin primordial shoots gradually migrates out through the crownand freezes as the temperature decreases (extraorgan freezing),which enables primordial shoots to survive at very low temperatures.Winter buds of Abies balsamea held at — 20?C for 30 daysand then slowly cooled down to —50 or —60?C remainedalive. Thus, there seems to be no low temperature limit to thisfrost avoidance mechanism, if the primordial shoots can resistintensive freeze-dehydration. Low temperature exotherms wereobserved in all genera which belong to Abietoideae and Laricoideaeof Pinaceae, all of which have a crown in the primordial shoots,but not in other conifers. ¹ Contribution No. 2037 from the Institute of Low TemperatureScience. (Received June 25, 1979; )     

Origin and diversification of the soldier meadow springsnails (Hydrobiidae: Pyrgulopsis), a species flock in the northwestern Great Basin, United States

The large, western North American hydrobiid gastropod genusPyrgulopsis (commonly known as springsnails) includes a seriesof locally endemic faunas that are thought to be species flocks.Although these assemblages are of interest from the evolutionary,biogeographic and conservation perspectives, their monophylyand phylogenetic relationships have yet to be rigorously evaluated.Here we present a molecular phylogeny (based on mitochondrialsequence data) of a putative flock of four thermal spring-dwellingspringsnails that is distributed in many sites in Soldier Meadowand a single locality in Bog Hot Valley (northwestern Nevada).Our analyses support monophyly of this assemblage (‘SoldierMeadow clade’) and a close relationship with other regionalspecies and suggest that the invasion of thermal habitats bythese springsnails occurred independently of other such radiationswithin the genus. The divergence of the Soldier Meadow claderelative to its sister group is substantial (6.79–10.36%for COI, 10.35–15.88% for NDI), suggesting a split inthe early Pliocene, based on the application of a COI clockfor Pyrgulopsis. The splits within the Soldier Meadow cladeinto three main subunits also appear to be old events, basedon their 5.78–8.54% COI divergence relative to each other.These findings are consistent with a long history of springsnailevolution in Soldier Meadow, which is intriguing given thatthis basin was flooded by Lake Lahontan during periods of theearly and middle Pleistocene. We suggest that progenitors ofthe contemporary fauna survived in high elevation springs thatmay have been present in the basin during these pluvial periodsand subsequently colonized contemporary habitats following thetermination of the extreme Lake Lahontan highstands. We speculatethat the broadly disjunct population (of P. militaris) in BogHot Valley, which is consistently nested within the SoldierMeadow clade in our phylogenetic analyses, is either a vicariantrelict of a spring zone that may have once extended betweenthese two areas; or was founded by a past ‘jump’dispersal event from Soldier Meadow. Phylogeographic structureof springsnail populations in Soldier Meadow bears the strongstamp of geologically recent, allopatric diversification, perhapsreflecting the short time that basin floor habitats have beenoccupied. We describe a new species (P. varneri) for a seriesof recently discovered populations that are monophyletic, substantiallydivergent and morphologically distinctive. Additional studieswill be necessary to confidently assess the taxonomic statusof morphologically distinctive P. limaria and P. umbilicata,which are shown herein to be little divergent genetically; anda recently discovered minute springsnail that is morphologicallydivergent yet closely similar genetically to P. notidicola. (Received 20 December 2006; accepted 22 February 2007)     

The response of tomato roots (Lycopersicon esculentum Mill.) to iron deficiency stress: alterations in the pattern of protein synthesis

Dicotyledon plants adapt to iron (Fe) deficiency through a seriesof reactions that increase the ability of the plant to assimilateFe and to increase the efficiency of Fe utilization. In an attemptto gain an insight into these adaptive processes, the specificchanges in protein synthesis associated with the onset of theFe deficiency response in tomato roots (Lycopersicon esculentumMill cv. Rutgers) have been investigated. Roots were grown underFe—sufficient and —deficient conditions, and thepattern of protein synthesis was analysed by in vitro translationof root mRNA and by in vivo labelling of root proteins. Polypeptideswere resolved by two—dimensional polyacrylamide gel elec—trophoresis.Seven polypeptides were identified by in vitro translation,whose synthesis was significantly increased during Fe deficiency.The increase was probably specific to Fe deficiency in thatthe polypep—tide synthesis was not increased during phosphatedeficiency stress, was less prominent following prolonged Fedeficiency and was decreased following re—supply of Feto the hydroponic medium. The pattern of in vitro translation of mRNA isolated from Fe—deficientroots was compared to the results obtainedin vivo followingradiolabelling of proteins. In these analyses, eight polypeptideswere identified, tentatively including the seven polypeptidespreviously identified by in vitro translation. All polypeptideswere characterized with regard to molecular mass and pl andtheir localization in the cell, whether being membrane boundor soluble. It is suggested that members of this group of polypeptidesare involved in the response of the root to Fe deficiency: althoughtheir functions remain to be identified. Key words: In vitro protein synthesis, iron, iron deficiency, root, 2-dimensional PAGE     

Studies on the vegetative life cycle of Chlamydomonas reinhardi Dangeard in synchronous culture II. Effects of chloramphenicol and cycloheximide on the length of cell cycle

Cells of Chlamydomonas reinhardi Dangeard were synchronouslygrown under a 12 hr light— 12 hr dark regime. When thesecells were brought into contact with chloramphenicol for a shortperiod at early stages in the cell cycle, zoospore liberationwas delayed for a period which was nearly the same as that ofthe duration of contact with the antibiotic. When given at laterstages, the antibiotic caused no such effect. Cycloheximide,on the other hand, caused—when provided at some intermediatestage of the cell cycle— two different prolonging effectson the length of the cell cycle: one doubled the normal length(observed when the drug was administered at certain stages)and the other caused a delay similar to that caused by chloramphenicol.Interestingly, no prolonging effect was observed when cycloheximidewas given either at early stages or at later stages, such asduring the last 1/4 period of the cell cycle preceding zoosporeliberation. Based on these results, three phases were distinguishedin the algal cell cycle: "chloramphenicolsensitive", "cycloheximide-sensitive"and "insensitive" phases. Considering the known facts aboutthe modes of action of the two antibiotics inhibiting proteinsynthesis, discussions were made on the significance of proteinsynthesis in chloroplasts and in cytoplasm in determining thelength of the cell cycle. (Received October 12, 1970; )     

Resupination Studies of Flowers and Leaves

The torsion performed by zygomorphic flowers borne on pendulousracemes-such as Wistaria, Laburnum, &c.-is described andexamples are given of the torsions which such zygomorphic flowerswill exhibit if normally erect spikes are turned verticallydownwards or normally pendent ones tied erect. An account is given of orchid flowers which normally are non-resupinate—speciesof Epidendrum, &.—and of those which are resupinateand of the further torsions which are involved when inflorescencesbearing resupinate flowers are pendent. The torsions exhibitedare illustrated by reference to the pendulous racemes of Cycnochesand to the flowers of Mormodes tigrina. The complete inversionof the flowers of Malaxis, which thus become ‘nonresupinate’,is mentioned and a full account of the similar inversion ofthe flowers of Angraecum eburneum is given, where the complicatedtorsions in three different planes result in a torsion through630°. The leaf torsions of Bomarea, Luzuriaga, Pharus, and Leptaspis,where the morphologically lower side of the leaf becomes theupper surface owing to the twisting of the petiole, is describedand an account is given of the two different types of pitcherin Nepenthes—those of the climbing stems being reversedowing to the twisting of their petioles. The physiological stateinto which the pitcher plant appears to pass when it reachesthe adult condition, is compared with the production of TreeIvy, which is propagated from the short, flowering shoots ofthe climbing plant. My thanks are due to Dr. C. R. Metcalfe for his assistance inexamining the anatomy of the leaves of Leptaspis and Luzuriaga;to Mr. L. Stenning and Mr. W. E. Everett for their help in connexionwith the orchid studies; to Miss Ross-Craig and Mr. G. Atkinsonfor their drawings, and to Mr. S. F. Ormsby for taking numerousphotographs to show the twisting of the flower buds of Angraecumeburneum and other plants which have been reproduced as drawingsfor the text figures. Mr. V. S. Summerhayes kindly furnishedme with the particulars relating to the Merent species of Catasetumand other orchids.