Rostromysis bacescuii gen. et sp. nov. and Megalopsis den-ticauda gen. et sp. nov. (Crustacea -- Mysidacea) from the south-west coast of Australia

Rostromysis bacescuii gen. et sp. nov. and Megalopsis denlicaudagen. et sp. nov. belonging to the tribe Leptomysini are describedfrom the south-west coast of Australia. The characters uniqueto the genus Rostromysis are the unusually long club-shapedrostrum and the large delicate lamella-like pleopods of thefemale, thus easily distinguishing it from the allied generaTenagomysis and Doxomysis. The genus Megalopsis is closely alliedto Leptomysis, Prionomysis and Promysis but is readily distinguishablein having a short linguiform uncleft telson with a pair of medianplumose setae.     

Karyological Anatomy of Fibre Development in the Leaves of Agave americana L. var. marginata alba Trel.

From a study of 100 metaphase plates in root-tip squashes and75 fibre-cells in leaf-base squashes, it is found that the chromosomenumber, although having an irregular type of variation, commonlytend to occur as multiples of 15, the haploid number. In developingfibre-cells the tendency of complete endomitosis (resultingin 2n, 4n, and 8n numbers) is stronger than the partial endomitosis(resulting in 5n, 6n, 7n, etc.). Nuclear volumes of fibre-cellsalso roughly correspond to 2K, 4K, and 8K. Significant linearcorrelations between chromosome number and nuclear volume andbetween nuclear volume and fibre-cell volume has been obtained.Thus the development and differentiation of fibres involve completeand partial endomitoses, accompanied by somatic non-disjunctionphenomena.     

Morphogenetic Potential of Embryo- and Seedling-Derived Callus of Elaeis guineensis Jacq. var. pisifera Becc.

The oil palm of commerce, Elaeis guineensis (tenera), derivesfrom hybridization of variety dura x pisifera. Germ plasm ofpisifera is limited, however, because of varying degrees offemale sterility. Efforts to increase the range of availablepisifera male germ plasm have thus far been limited to fertilepisiferas but it is anticipated that clonal multiplication ofembryos and explanted organs from less female-fertile, but nonethelessfertile, male, plants could play a significant role in breedingprogrammes. Callus has been produced from mature pisifera embryosand leaf explants from young plantlets using a half-strengthMurashige and Skoog medium supplemented with inositol, caseinhydrolysate, activated charcoal and varying concentrations ofauxins. After sub-culture on media of similar composition, organizedstructures can develop. Those which form in stale nutrient media(e.g. left in the same medium for up to 3 months) give riseto embryonal structures which do not readily develop furtherand can be regarded as neomorphs. If callus once formed is transferredto media with lower auxin concentrations (40–0 mg l^–1)embryonal buds and well-formed shoots are produced; additionof gibberellic acid (GA₃) fosters the production of well-organizedshoots accompanied by roots. Elaeis guineensis var pisifera, oil palm, tissue culture, micropropagation, embryo development, morphogenetic potential, callus     

Induction of Near-vessellessness in Ephedra campylopoda C. A. Mey.

Near-vessellessness was induced in the secondary xylem of Ephedracampylopoda C. A. Mey. by mechanical bark blocking or by wounding.Both treatments resulted in regions of near-vesselless xylem.Xylem formed after the mechanical bark blocking also had regionsin which the orientation of the axial components was changedfrom axial to lateral. Since either mechanical arrest of phloemand cambial transport or wounding of the cambium almost stoppeddifferentiation into vessels, and instead induced differentiationinto tracheids, it seems that the developmental signal for tracheiddifferentiation is not the same as that for vessels. The possibleregulation of near-vessellessness in Ephedra is discussed.Copyright1994, 1999 Academic Press Differentiation, Ephedra campylopoda, near-vessellessness, wood formation, xylem     

Somatic Hybrids of the Forage Legumes Medicago sativa L. and M. falcata L.

Protoplasts isolated from embryogenic cell suspensions of tetraploidMedicago sativa cv. Europe (2n= 4? = 32) and M. falcata (2n=4? = 32) were fused using polyethylene glycol (PEG). Heterokaryonswere isolated by micromanipulation and cultured in the presenceof nurse protoplasts from albino or embryogenic cell suspensionsof M. sativa, to give free-floating embryos and embryogeniccalli. Ninety-nine plants were regenerated from somatic embryos.Fifteen of the plants exhibited leaf abnormalities and did notsurvive transfer from culture to the glasshouse. The remainingphenotypically normal plants were established ex vitro and floweredat maturity. Morphological and biochemical analyses confirmedthat 12 of the phenotypically normal plants were somatic hybrids.Morphological characteristics of the hybrids, including plantstature, internode length, leaf size, flower colour, and podshape, were intermediate compared with those of the purple floweredM. sativa and yellow flowered M. falcata parents. Flowers ofthe hybrids were yellow traced with purple-blue veins. Isoenzymebanding patterns for esterase showed bands additional to thoseof M. sativa and M. falcata. The chromosome complements of individualhybrids varied from (2n= 4? = 32) to 58.     

Studies in the Bangioideae III. The Life-history of Porphyra umbilicalis (L.) Kutz. var. lociniata (Lightf.) J. Ag.: A. The Conchocelis-Phase in culture

As the first step in an investigation of the life-history ofPorphyra umbilicalis (L.) Kütz. var. laciniata (Lightf.)J. Ag., spores which have originated as a result of the repeateddivision of the mother-cells have been germinated. When grownon glass their method of germination and growth agrees withthat described by previous investigators, but when germinatedon sterile shell the germ-tubes penetrate the shell and developinto growths identical with Conchocelis rosea Batters. This‘species’, therefore, is a phase in the life-historyof P. umbilicalis var. laciniata and not an autonomous species.The development of the ‘Conchocelis’-phase in cultureis described and also the formation of fertile cell-rows and‘plantlets’. Until the significance of these structuresis understood and a cytological investigation completed, therelationship of the intertidal leafy Porphyra-thallua to thefilamentous, shell-inhabiting, deep-water Conchocelis cannotbe expressed in the terms usually employed to denote the variousphases of the life-histories of algae.     

Psammodiscus nov. gen. Based on Coscinodiscus nitidus

The epipsammic diatom Coscinodiscus nitidus differs from typicalCoscinodiscus species in areola arrangement and structure, closingmembrane structure, rimoportula arrangement, and habitat. Severalsimilarities exist between it and Rhaphoneis species but, whilethe relationship between these is close, the two cannot be consideredcongeneric. A new genus, Psammodiscus, is created to includeC. nitidus. Coscinodiscus nitidus, Rhaphoneis, Psammodiscus nov. gen., epipsammic diatom, diatom taxonomy     

Aspects of the Comparative Physiology of Ranunculus bulbosus L. and Ranunculus repens L.: I. Response to Nitrogen

Ranunculus bulbosus and R. repens are closely related taxonomicallyand coexist in the same general habitat but differ in that R.bulbosus only exceptionally shows vegetative multiplicationcontrasting with R. repens which reproduces extensively by meansof long branched stolons which root and form new daughter plantsat the nodes. The response of these two species to nitrogen was similar inthat an increase from 10 to 50 ppm nitrogen gave rise to greatlyincreased total dry weight and higher shoot to root ratios,whereas further nitrogen increase from 50 to 200 ppm had littleeffect. However, they differed in that at low nitrogen levelsthe perennating organ (corm) took priority in R. bulbosus withsexual reproduction assuming greater importance at the highernitrogen levels, whereas in R. repens the main storage organ(the stock) was not especially favoured at low nitrogen levelsreflecting perhaps the differences between this structure andthe corm in R. bulbosus. In R. repens the greatest responseto nitrogen was shown by the stolons although this was due toincreased branching and a higher dry weight per unit lengthat the higher levels of nitrogen (50 and 200 ppm). Primary stolonlength was not greatly affected by nitrogen level. Dry weightsof flowers and fruits in R. repens were very much lower thanin R. bulbosus. It is suggested that in R. bulbosus the emphasis lies firstin replacement of the parent at approximately the same siteby a daughter from the new corm and secondly in sexual reproductivespread. In R. repens lateral spread by vegetative propagationtakes precedence over all else and under low nitrogen conditionsbranching is sacrificed and energy is diverted to maintaininglong primary stolons. These, in turn, have the potential forproducing daughter plants at some distance from the parent andthis may be of considerable importance in field situations sincethe daughter may come to occupy more favourable sites than theparent.     

Addenda Clavariacea. III

1. The following noveltiea are described, with notes on otherspecies of their genera : Aphelaria subgen. Tremellodendropsis for the A. tuberosa alliancewith subtremellaceous basidia: A. amboinensis (Lév.)comb. nov. Chaetotyphula gelatinosa sp. nov. and C. tetraspora sp. nov.from Tropical America, whence C. hyalina (Jungh.) Corner isalso recorded. Clavariadelphus junceus (Fr.) Corner is recorded from Brazil. Mucronella flava sp. nov. from Iowa. Phaeoapheloria austra1iensis gen. et sp. nov. is intermediatebetween Aphelaria and stereoid fungi. Pistillaria trispora sp. nov. from Iowa: P. tucumanensis (Speg.)comb. nov. for Typhula tucumanensis Speg. Phistillina calyx Heim is excluded as marasmioid. 2. The Physalacria-subseriea is reviewed, and the followingare described aa new: Hormomitaria albidula sp. nov. from Brazil Pseudotyhula gen. nov. from West Africa: P. ochracea sp. nov.as the typespecies : P. tenuipes (Lloyd) comb. nov. (= Mucronellatenuipes Lloyd).     

The Genus Hantzschia with Particular Reference to H. virgata v. intermedia (Grun.) comb. nov.

The diatom genus Hantzschia and its closely associated generaare discussed briefly. From a study of one variety of Hantzschiavirgata by light and scanning electron microscopy the morphologyof the siliceous components has been determined. The new combinationH. virgata v. intermedia has been proposed. The possible originof Hantzschia from Nitzschia by a displacement of the raphesystem at cell division is discussed.     

Growth of Lettuce, Onion and Red Beet. 2. Growth Modelling

Data from a field experiment carried out on growth of lettuce,onion, and red beet were used: (a) to fit logistic, Gompertz,expolinear and ‘Scaife and Jones’ (Journal of AgriculturalScience, Cambridge86 : 83–91, 1976) functions using time,day-degrees and effective day-degrees; and (b) to test a mechanistically-basedmodel that combines the effects of potentially limiting variables,such as temperature and light, and allows for plant zone areain light interception (Aikman and Benjamin,Annals of Botany73 : 185–194, 1994). The use of day-degrees and effective day-degrees instead oftime, in general, improved the fit and gave a better estimateof growth parameters. The best fit was obtained by the Gompertzfunction for lettuce, and by the expolinear function for redbeet and for onion. The expolinear function seemed the mostreliable function in estimating the early relative growth ratewhich is the crucial value in all the mechanistic models. Thezone area model showed very good simulations for lettuce andred beet, but it requires a modification for canopy senescencein onion. Lettuce; Lactuca sativa L. var.crispa ; onion; Allium cepa L.; red beet; Beta vulgaris L. var.conditiva ; growth modelling; logistic; expolinear; Gompertz; zone area; time; day-degrees; effective day-degrees     

Pollination Ecology ofChloranthus serratus(Thunb.) Roem. et Schult. andCh. fortunei(A. Gray) Solms-Laub. (Chloranthaceae)

Flowering and pollination biology ofChloranthus serratusandChloranthusfortuneiwere studied. Flowering took place from early Marchto mid–April inCh. fortunei, and from April to September,the whole growth period, inCh. serratus.The flowering periodof an inflorescence ofCh. serratusaveraged about 8 d and anthesisof a single flower was 5–6 d. Flowers are slightly protogynous.The flower emitted fragrance when the androecium became white.Both species are entomophilous with thrips as exclusive pollinators.Under natural conditions, fruit set occurs mainly as a resultof cross-pollination, but self-pollination and agamospermy mayoccur in some cases. In flowers ofCh. fortuneiandCh. serratus,theincurved androecium, the carpel and the spike axis form a nearlyclosed chamber that contains the anthers and stigma. The developmentof a floral-axial chamber may be an important step towards amore economical and effective pollination system. Floral morphology,pollination biology and fossil evidence suggest that the mainevolutionary trend in the genusChloranthusis towards developmentof ‘closed’ flowers. The fidelity of the relationshipbetweenChloranthusand thrips is regarded as a specialized featureof pollination biology and this relationship may have originatedearly in the evolutionary lineage.Copyright 1999 Annals of BotanyCompany Chloranthaceae,Chloranthus, Thysanoptera,flowering, floral-axial chamber, pollination, evolution trends.     

Micromorphology of the labellum and floral spur of Cryptocentrum Benth. and Sepalosaccus Schltr. (Maxillariinae: Orchidaceae)

Background and Aims: Gross vegetative and floral morphology, as well as modern moleculartechniques, indicate that Cryptocentrum Benth. and SepalosaccusSchltr. are related to Maxillaria Ruiz & Pav. However, theydiffer from Maxillaria in their possession of floral spurs and,in this respect, are atypical of Maxillariinae. The labellarmicromorphology of Maxillaria, unlike that of the other twogenera, has been extensively studied. In the present report,the labellar micromorphology of Cryptocentrum and Sepalosaccusis compared with that of Maxillaria and, for the first time,the micromorphology of the floral spur as found in Maxillariinaeis described. Methods: Labella and dissected floral spurs of Cryptocentrum and Sepalosaccuswere examined using light microscopy (LM) and scanning electronmicroscopy (SEM). Key Results: In each case, the labellum consists of a papillose mid-lobe(epichile), a cymbiform region (hypochile) and, proximally,a spur, which is pronounced in Cryptocentrum but short and bluntin Sepalosaccus. The inner epidermal surface of the spur ofCryptocentrum is glabrous or pubescent, and the bicellular hairs,where present, are unlike any hitherto described for Maxillariinae.Similar but unicellular hairs also occur in the floral spurof Sepalosaccus, whereas the glabrous epidermis lining the spurof C. peruvianum contains putative nectar pores. Conclusions: The labellar micromorphology of Cryptocentrum and Sepalosaccusgenerally resembles that of Maxillaria. The floral spur of Cryptocentrumdisplays two types of organization in that the epidermal liningmay be glabrous (possibly with nectar pores) or pubescent. Thismay have taxonomic significance and perhaps reflects physiologicaldifferences relating to nectar secretion. The trichomes foundwithin the spurs of Cryptocentrum and Sepalosaccus more closelyresemble the hairs of certain unrelated, nectariferous orchidtaxa than those found in the largely nectarless genus Maxillaria,and this further supports the case for parallelism.     

Pollination Biology in a TropicalAcaciaHybrid (A. mangiumWilld. xA. auriculiformisA. Cunn. ex Benth.)

Floral biology and pollination mechanism of theAcaciahybrid(A. mangiumWilld. xA. auriculiformisA. Cunn. ex Benth.) growingin Thailand are investigated using light and electron microscopy.The hybrid is andromonoecious. A floral spike consists of about150 loosely arranged flowers. Flowers are cream coloured, fragrantand have no floral nectaries. The pistil has a solid style witha smooth, wet stigma and amphitropous ovules with immature integuments.The anther consists of eight loculi, each bearing only one 16-grainpolyad. The flowers are weakly protogynous. Anthesis is completeat 0500–0600 h but peak female receptivity begins at 0200–0300h and is completed that day. The stigmatic exudate is of thelipophilic type and is secreted from the stigmatic cells bya holocrine mechanism. Pollen is the main floral reward forthe insect pollinators. There are several floral characteristicswhich facilitate pollen transfer from anthers and depositionon stigmas.Apis melliferaandCeratinasp. are the most effectivepollinators because they are the most common visitors and carrya heavy load of hybrid polyads. However, their behaviour inforaging for pollen in the same tree and weak protogynous dichogamymay promote self-pollination in the hybrid. The hybrid has lowpollination success due to low pollinator number. An increasein exposure time of flowers to pollinators or pollinator numbermay increase pollination success but may not affect the rateof pollen deposition on stigmas due to the relatively smallsize of the stigma in relation to the polyad.Copyright 1998Annals of Botany Company Acaciahybrid,Acacia mangium, Acacia auriculiformis, pollination, pistil receptivity, anthesis, pollinators.     

Water Use Characteristics of Dactylis glomerata L., Lolium perenne L. and L. multiflorum Lam. Plants

Cocksfoot (Dactylis glomerata L.). perennial ryegrass (Loliumperenne L.) and Italian ryegrass (L. multiflorum Lam.) plantswere grown on deep (75–95 cm) columns of soil in glasshousesand growth rooms with and without irrigation. The species inwhich growth declined least rapidly after water had been withheldwere those which transpired most slowly. During early establishmentin the glasshouse cocksfoot transpired least because of slowroot growth. In the growth room, when root systems were deeperand denser, perennial ryegrass transpired least because of lowleaf water conductance. Results are discussed in relation to(a) drought resistance in the three species; (b) breeding forincreased drought resistance through modifying root distributionand leaf water conductance; and (c) the use of isolated soilcolumns in water relations studies. Dactylis glomerata L., Lolium perenne L., Lolium multiflorum Lam., cocksfoot, perennial ryegrass, Italian ryegrass, transpiration, roots, leaf water conductance     

Evidence of Three Subspecies in Trifolium nigrescens Viv.

Germplasm accessions of Trifolium nigrescens Viv. were foundto belong to three distinct taxa which differed in morphology,hybrid seed-set in crosses among themselves and with white clover(T. repens L.), chromosomal distribution of rDNA genes, andrDNA internally transcribed spacer (ITS) region sequences. Thesetaxonomic groups correspond with T. nigrescens ssp. nigrescens,T. nigrescens ssp. petrisavii var.petrisavii and var. meneghinianum.The existence of var. meneghinianum has been rejected or ignoredin recent taxonomic treatments. The present study indicatesthat it is very distinctive and warrants at least subspeciesstatus. Phylogenetic analysis based on ITS sequences and podmorphology placed ssp. nigrescens as progenitor to the others.ITS sequences placed white clover closer to ssp. petrisaviibut neither DNA sequences nor rDNA chromosome locations clearlyshowed whether var. petrisavii or var. meneghinianum was closerto white clover. In contrast, results of hybridization studiesshowed that ssp. nigrescens gave full seed-set when pollinatedwith T. repens whereas both ssp. petrisavii var. petrisaviiand ssp. petrisavii var. meneghinianum gave poor seed-set. Allthree taxa showed close relationships with white clover andnone can clearly be shown to be a direct ancestor of T. repens.Copyright 2001 Annals of Botany Company Fabaceae, Trifolium nigrescens, Trifolium repens, internal transcribed spacer region (ITS), nuclear ribosomal DNA, interspecific hybridization     

Study of Biomphalaria Tenagophila Tenagophila, B. t. Guaibensis and B. Occidentalis by Polymerase Chain Reaction Amplification and Restriction Enzyme Digestion of the Ribosomal RNA Intergenic Spacer Regions

Biomphalaria tenagophila tenagophila, B. tenagophila guaibensisand B. occidentalis are indistinguishable on the basis of shellmorphology and the majority of organs of the genital system.Only B. t. tenagophila is susceptible to infection with Schistosomamansoni. The identification of this species is important forepidemiological studies of schistosomiasis. Snails from differentsites in Brazil, Argentine and Uruguay were studied using thePolymerase Chain Reaction (PCR) and Restriction Fragment LengthPolymorphism (RFLP) of the Ribosomal RNA Internal TranscribedSpacers (ITS) using seven enzymes. Profiles resulting from digestionwith AluI showed some invariant species-specific products allowingcorrect identification of B. t. tenagophila, B. occidentalisand B. t. guaibensis. Profiles obtained with other enzymes didnot permit species identification as extensive intraspecificpolymorphism or invariant RFLP profiles were observed. Restriction profiles obtainedwith all enzymes were used to calculate the percentage of bandsharing between all individual snails and these data were usedfor a cluster analysis. A closer relationship between B. occidentalisand B. t. guaibensis than B. t. tenagophila and the subspeciesB. t. guaibensis was observed. Based on previous morphologicaldata and these molecular data, we propose grouping B. t. tenagophila,B. occidentalis and B. t. guaibensis into a B. tenagophila complex. (Received 22 December 1997; accepted 26 May 1998)     

Pollen-Derived Haploids of Nicotiana Knightiana, N. raimondii, and N. attenuata

Haploid plantlets were obtained in large numbers in three diploid,24-chromosome species of Nicotiana by culture of anthers ator just past the first pollen mitosis. The three species wereN. Knightiana, N. raimondii, and N. attentiata. Efficiency ofhaploid production varied from about 10 per cent in N. attenuatacultures to 30 and 38 per cent respectively in cultures of N.raimondii and N. Knightiana. H-medium without hormones and standardcultural conditions were used. N. Knightiana appeared to beespecially suitable for haploid studies on account of its highplantlet productivity, low chromosome number, and distinctivekaryotype.