Studies on the Growth of Basidiomycetes in Soil

Fructifications of basidiomycetes have been collected at LakenheathWarren, and thirty-nine species have been obtained from fivegrassland soils. The different soils have been found to havedifferent species growing upon them and most species occur onthe alkaline-slightly acid grasslands. Highly acid grasslandat Lakenheath has a poor fungus flora. Studies have been made of the regions in the soil in which themycelia of certain of these basidiomycetes occur, and attemptshave been made to isolate these fungi from soil. Some specieshave been found to inhabit the litter zone rather than the minerallayers of the soil. A few form extensive rhizomorph systemswhich may penetrate deeply into the soil. A few species of ringfungi, such as Marasmius oreades, Psalliota arvensis, and Tricholomanudum, have been found to possess a well-defined mycelial zonein the soil, from which the fungus could be isolated. Profile studies have shown that the mycelial zones of thesespecies contain a restricted population of microfungi, bothfewer species and fewer colonies, as compared with the normalsoil around. Ascomycetes, such as Arachniotus, Chaetomium, Gymnoascus,and Penicillium, have been isolated more frequently from mycelialzones than from normal soil.     

Observations on the Life History of the Haptophycean Alga Pleurochrysis scherffelii with Special Reference to the Microanatomy of the Different Types of Motile Cells

The coccolith-bearing phase of Pleurochrysis scherffelii hasbeen examined with the electron microscope for the first time.Coccolith and scale structure, haptonema morphology, and themicroanatomy of the protoplast have been recorded and shownto agree closely with those of Hymenomonas carterae and theHymenomonas stage of Apistonema previously investigated by thepresent author. Comparative observations have been made on thevegetative phase and non-coccolith-bearing swarmers of Pleurochrysisscherffelii and these differ significantly in scale morphologyfrom the coccolith-bearing phase although the haptonema of theswarmers is similar. Certain developmental observations havebeen included in the investigation and the taxonomic significanceof the findings is discussed in a preliminary way.     

The Diatom Genus Tabellaria: II. Taxonomy and Morphology of the Plankton Varieties

Plankton samples of Tabellaria from all the lakes of the EnglishLake District have been examined and evidence of morphologicallydistinct populations has been found in samples from (a) a singlelake at one time, (b) different lakes, and (c) a single lakeat different times. Clone cultures have been used to study thenature of these differences. Fifteen characters have been foundto show quantitative or qualitative variation in plankton populationsof Tabellaria, and the morphological diversity of differentpopulations is largely due to different combinations of thesecharacters. All known plankton populations of Tabellaria arereferred to the species T. flocculosa.     

A Step in the Biosynthesis of Gibberellins that Is Controlled by the Mutation in the Semi-Dwarf Rice Cultivar Tan-Ginbozu

Genetic analysis and a comparison of endogenous levels of gibberellinsbetween the semi-dwarf rice cultivar Tan-ginbozu and the correspondingnormal cultivar Ginbozu have confirmed that Tan-ginbozu is agibberellin deficient mutant and that the semi-dwarfism of Tan-ginbozuis controlled by a single recessive gene. A step in the biosynthesisof gibberellins that is blocked by the mutation in Tan-ginbozuhad been considered to be the synthesis of ent-kaurene or anearlier step. However, the rate of production of ent-kaureneby Tan-ginbozu was almost the same as that by Ginbozu. By contrast,accumulation of only a small amount of ent-kaurene was detectedin Tan-ginbozu, and the amount that accumulated was similarto that in Ginbozu that had been treated with 6.9 x 10^-8 M uniconazole-P(an effective inhibitor of three oxidative steps in the pathwayfrom ent-kaurene to ent-kaurenoic acid via entkaurenol and ent-kaurenal).The height of the treated Ginbozu plants was reduced to thesame as that of Tanginbozu plants. Resembling Tan-ginbozu plants,Ginbozu plants that had been treated with uniconazole-P respondedwell to ent-kaurenoic acid and slightly to ent-kaurene and ent-kaurenol.Since the growth-promoting activity of enf-kaurenal in Tan-ginbozuwas similar to that of ent-kaurene, our results suggest thatthe mutation in Tan-ginbozu blocks the three oxidative stepswhereby ent-kaurene is converted to ent-kaurenoic acid. (Received June 9, 1995; Accepted February 15, 1996)     

Electron Microscopic Observations of the Structure of Sieve-connexions in the Phloem of Angiosperms and Gymnosperms

The sieve elements of Pinus silvestris L., Sorbus aucupariaL., Vitis vinifera L., and Cucurbita pepo L. have been examinedelectron microscopically in ultra-thin section, and the structuresof the corresponding sieve areas or sieve plates have been describedand compared. In Pinus the sieve areas contain groups of connectingstrands which enter the wall from the lumen side as individualsbut coalesce within it in the median cavity. This cavity hasdeveloped by wall breakdown in the middle lamella and primarywall region and corresponds to the median nodule visible undera light microscope. Neither in this nor in the other speciesobserved is there any visible closing membrane. Structural differences between the four species are shown tosuggest that the major evolutionary trend in the evolution ofspecialized conducting strands has been the enlargement of theconnecting strands from groups of small separate strands toa smaller number of larger strands as the median cavity becomesenlarged to form a canal through the wall. The connecting strands appear invariably to be dense, highlyosmiophilic and continuous with the cytoplasmic surface of thecell. No signs of micropores or of other tubular structure inthe strands have been found. The structures thus revealed aremore nearly compatible with active transport of materials acrossthe sieve plate than they are with any purely physical mechanism.It is suggested that they are incompatible with any mass flowhypothesis.     

The Olfactory System as a Model for the Analysis of the Contribution of Gene Expression to Programmed Cell Death

The process of programmed cell death is frequently attenuatedby inhibitors of protein and RNA synthesis. This implies thatgene expression is necessary for the active elimination of somecell types. Genes such as bcl-2 and bax have been implicatedin the direct control of cell death, while cellular immediate-earlygenes (clEGs), such as c-fos and c-jun have been repeatedlyassociated with neuronal degeneration. We are using the olfactoryneuroepithelium as a model system to investigate the role thatexpression of such genes might play in cell death. The advantagesof this system is that even in the adult, there is spontaneousdegeneration of olfactory receptor neurons followed by theirreplacement by the division and differentiation of precursors.Futhermore, the receptor neurons can be induced to die synchronouslyby removal of the olfactory bulb or intranasal administrationof toxic agents. We have generated fos-lacZ and jun-lacZ transgenicmice that can be used to assess expression of c-fos and c-junfollowing these various manipulations. In addition, a line oftransgenic mice has been derived that express Bcl-2 under thecontrol of the olfactory receptor protein promoter. These micehave high levels of Bcl-2 selectively in receptor neurons ofthe primary neuro-epithelium and vomeronasal organ. Since insome circumstances, Bcl-2 can protect against programmed celldeath these mice are being assessed for neuronal turnover underbasal conditions and following olfactory bulbectomy.     

Purification and characterization of novel glycosidases from the bacterial genus Xanthomonas

Enzymatic analysis of oligosaccharides using exoglycosidaseshas become a powerful tool for determining the sequence andstructure of sugar chains. The principal limitation to thesemethods has been the lack of highly purified and wellcharacterizedenzymes. Using fluorescently labelled carbohydrate substratesand TLC, we have developed a method to identify glycosidaseswith novel specificities. This screening method led to the discoverythat bacteria of the genus Xanthomonas are a rich source ofexoglycosidases. From Xanthomonas manihotis, eight novel exoglyccosidaseshave been isolated and characterized. A novel ß-N-acetylglucosaminidasehas been purified that, unlike those previously described, willcleave N-acetylglactosamine without cleaving N-acetylgalactosamineresidues. A novel ß-galactosidase has been isolatedthat preferentially hydrolyses ß(1     

The Identification of the Seeds and Achenes of the British Plantaginaceae

The morphology of seeds and achenes of the British members ofthe Plantaginaceae has been examined. Keys to the identificationof seeds in the genera Plantago and Littorella are presented.Quantitative data on size and weight, as well as informationabout shape, colour and surface features of the seeds are givenfor: Plantago major L., P. media L., P. lanceolata L., P. martimaL., P. coronopus L., P. indica L., P. sempervirens Crantz, andLittorella uniflora (L.) Aschers. A representative sample ofeach seed is illustrated.     

A Rapid Method for the Determination of the Leaf Area of Oxalis corniculata L. and Tephrosia purpurea (Linn.) pers.

A rapid simple method has been described for the determinationof leaf area of Oxalis corniculata L. (Oxalidaceae) and Tephrosiapurpurea (Linn.) pers. (Leguminoseae) by evaluating area = a²x0.866and a²x0.335 respectively for the two plants, where a representsa single linear measurement. The relation has been derived afterintegrating the equation of the curve r² = a² cos 2 coveringthe area of each leaflet. Areas of a large number of leaflets have been determined withthe help of two methods (1) Planimeter method, (2) Evaluationmethod. The significance of the difference between the two valuesfor a particular leaf has been statistically examined and itappears that the former method can be replaced by the latterin the case of these plants.     

Descriptions of some planktonic larvae of the Calappidae (Crustacea: Decapoda; Brachyura)

Some unidentified planktonic larval stages have been assignedto the Calappidae using Rice's key of Brachyura families. Zoeastage I from the eastern region of the Algerian coast (westernMediterranean Sea) has been attributed, according to Manningand Holthuis (1980), to Calappa granulata (L.), the only recordedrepresentative of the family from the Mediterranean Sea. Zoealstages 1-lV from the Jordanian coast of the Gulf of Aqaba, NorthernRed Sea, have been reported to the subfamily Matutinae. Comparisonsof larvae of Calappa and of Hepatus and then, of larvae of Hepatusand of Matuta, show that Hepatus larvae are more closely relatedto those of Calappa, while those of Matuta are clearly distinct.It s suggested to place the genus Hepatus with the Calappinae.Guinot (1966. 1978) placed some genera, including Hepatus. ina 'unit parthenoxystomienne, lea Aethrinae'. Larval developmentis unknown for Aethra, Actaeomorpha. Hepatella andOsachila.However, comparison of Hepatus larvae with those of Parthenopidaeshows that larval characters, particularly the setation of theendopod of the first maxilliped, are not conclusive for supportingsuch a regrouping. Moreover, the Calappidae have a combinationof primitive and advanced features which suggest that theirgrouping in the Oxystomata seems more likely to be an adaptationto a similar way of life. The morphotypal taxon Oxystornatahas been definitively rejected by Guinot (1978).     

Development of the diatom-Phaeocystis spring bloom in the Dutch coastal zone of the North Sea: the silicon depletion versus the daily irradiance threshold hypothesis

The Dutch coastal zone of the North Sea is characterized byhigh nutrient inputs and low water column irradiance due tohigh concentrations of suspended matter. The vernal phytoplanktonblooms are dominated by diatoms and the flagellate Phaeocystis(Haptophyta). Two hypotheses that predict the timing of thePhaeocystzs bloom were tested with field data collected in 1992.The first one, stating that the Phaeocystis bloom starts whensilicon has been depleted by a preceding diatom bloom, couldnot be bracketed with observations. The second hypothesis, predictingthat Phaeocysus blooms under nitrogen- and phosphorus-repleteconditions after a daily irradiance threshold has been passedcould be supported by field observations. Furthermore, it isshown that the Dutch coastal zone is not continuously homogeneouslymixed. It is argued that this is an important factor in thelife cycle of Phaeocystis and in foam formation on nearby shores.Grazing by the ciliate Strombidium sulcatum and heterotrophicgymnodinoid flagellates accounted for 92% of Phaeocystis cellloss after the bloom.     

On the Megaspores of Four Species of Lepidostrobus

This paper is an account of the megaspores borne by four speciesof Carboniferous Lycopod cones, referred to the genus Lepidostrobus.The megaspores (assigned to the genus Triletes) have been knownisolated for more than twenty years, but the identities of theirparent cone species have not previously been established. Thisstudy suggests the limits of variation that can reasonably beallowed in a ‘spore species’. Three of the conespecies are emended in the light of their spore content, anda new species (Lepidostrobus allantonensis) is described. Usingthe megaspores as a diagnostic cone character, it has provedpossible to correlate a species of isolated cone (Lepidostrobusdudius Binney) with the tree which bore it (Lepidodendron smileKidst.). A cone previously attributed on doubtful evidence toBothrodendron is shown to bear megaspores indistinguishablefrom those of a species reliably attributed to Lepidodendron,suggesting that the attribution to Bothrodendron is incorrect.     

The Identification of the Seeds of the British Papaveraceae

The morphology of seeds of British wild, introduced, and commonlycultivated members of the Papaveraceae has been examined, anda key to the identification of the seeds is presented. Quantitative data on size and weight as well as informationabout shape, colour and surface features of the seeds are givenfor Papaver rhoeas L., P. dubium L., P. lecoqii lamotte, P.hybridum L., P. argemone L., P. somniferum L., P. lateritiumC. Koch, P. atlanticum (Ball) Coss., P. orientale L., P. nudicauleL., Meconopsis cambrica (L.) Vig., M. betonicifolia French,Roemeria hybrida (L.) DC., Glaucium flavum Crantz., G. corniculatum(L.) Rudolph, Chelidonium majus L., Eschscholzia californicaCham., E. erecta cv. compacta and E. erecta cv. miniature. Arepresentative sample of each seed is illustrated.     

Physiologic Races of the Brown Rust of Brome Grasses

A number of cultures of the brown rust of Brome grasses havebeen isolated and maintained as single-spore strains. By theirinfection reactions on a representative selection of Brormusspp. at least five physiologic races have been characterized.Two of these have host-ranges confined to a single section ofthe genus, but others have a much wider host-range within thegenus. The uredospore stage of all was identical. Studies ofthe teleutospores have been limited and knowledge of the speciesof rust involved is incomplete. All belong to the group-speciesPuccinia dispersa Erikss. & Henn.; the species P. brominaErikss. and P. symphyti-bromorum Müller were included amongthe cultures studied, possibly also P. bromi-maximi Guyot. Ina large series of inoculations, over a period of in all 14 years,all physiologic races have been remarkably stable in their infectiontypes and host-range, and no confirmation of Marshall Ward's‘bridging-host’ theory has been obtained. Cultivationof two physiologic races for 164 generations on Bromus arduennensis,a species considered by Ward to have special significance asa bridging-host, induced no changes in their host-range.     

A Comparative Study of Certain Seed Isoenzymes in the Ten Chromosome Complex of Brassica Campestris and its Allies

A gel electrophoretic study has been carried out on the seedisoenzymes of n = 10 members of the genus Brassica. Eleven isoenzymesystems have been studied and the distribution of the isoenzymesused to indicate a possible relationship between the major recognizedtaxa. Three basic centres of the complex have been indicated:Indo-European, China and Mediterranean as exemplified by B.campestris (turnip/turnip-rape), B. chinensis and B. tournefortii(wild turnip) respectively.     

Hugo de Vries and the Development of Seed Aging Theory

Although work published in 1901 by de Vries has helped shapeour current understanding of the relationship between seed agingand genetic mutation, it has been fundamentally misinterpreted.Upon sowing 5 year-old Oenothera erythrosepala seed, de Vriesobtained an emergence of about 1 per cent. A relatively highproportion of the seedlings (about 40 per cent) displayed mutantphenotypes, mostly albida or lata. De Vries concluded that thesephenotypes, which were already present to a minor extent (about1 per cent) in unaged seed lots, were more resistant to agingthan the erythrosepala norm. Later opinion has dismissed DeVries' hypothesis, contending instead that the mutant phenotypesarose as a consequence of seed aging. A reconsideration of thesedata suggests that the De Vries' explanation remains more convincing;paradoxically, his work on seed aging has been influential becauseit has been consistently misunderstood. Mutation, Oenothera, seed aging     

Chemical Properties and the Physiological and Pharmacological Actions of Urophysial Peptides

Recent advances in urophysial research are reported and currentresearch in this laboratory on the urophysial peptides (urotensinI, urotensin II) of Catostomxts commersoni is summarized. UrotensinI has been purified by gel filtration, electrofocussing, ultrafiltrationand ion exchange chromatography. Three similar utotensin I peptideswere found. The main peptide was shown to be a straight chainpeptide with about 36 amino acid residues. Pressor-diureticeffects in fish have been observed. The peptide produces a long-lastinglowering of mammalian blood pressure by peripheral vasodilatation.Urotensin II has been isolated and purified. It appears to contain23 amino acids including two disulphidebridges. It is a potentpressor-diuretic-smooth muscle contracting agent in the fish,without any known pharmacological actions in mammals. UrotensinIII: the existence of this activity as a separate chemical entityhas not been established, but urophysectomy was shown to lowerblood Na⁺ without an increase in renal excretion. UrotensinIV has been shown to be similar to, or identical with, argininevasotocin. Urotensin IV could not be found in the urophysisof Catostomus (gel filtration, bioassays, immunohistochemistry).Similarities and differences between the hypothalamic and caudalneurosecretory systems and their active principles are analysed.     

Mutations in the Arabidopsis SWC6 gene, encoding a component of the SWR1 chromatin remodelling complex, accelerate flowering time and alter leaf and flower development

Mutations affecting the Arabidopsis SWC6 gene encoding a putativeorthologue of a component of the SWR1 chromatin remodellingcomplex in plants have been characterized. swc6 mutations causeearly flowering, shortened inflorescence internodes, and alteredleaf and flower development. These phenotypic defects resemblethose of the photoperiod independent early flowering 1 (pie1)and early in short days 1 (esd1) mutants, also affected in homologuesof the SWR1 complex subunits. SWC6 is a ubiquitously expressednuclear HIT-Zn finger-containing protein, with the highest levelsfound in pollen. Double mutant analyses suggest that swc6 abolishesthe FLC-mediated late-flowering phenotype of plants carryingactive alleles of FRI and of mutants of the autonomous pathway.It was found that SWC6 is required for the expression of theFLC repressor to levels that inhibit flowering. However, theeffect of swc6 in an flc null background and the down-regulationof other FLC-like/MAF genes in swc6 mutants suggest that floweringinhibition mediated by SWC6 occurs through both FLC- and FLC-likegene-dependent pathways. Both genetic and physical interactionsbetween SWC6 and ESD1 have been demonstrated, suggesting thatboth proteins act in the same complex. Using chromatin immunoprecipitation,it has been determined that SWC6, as previously shown for ESD1,is required for both histone H3 acetylation and H3K4 trimethylationof the FLC chromatin. Altogether, these results suggest thatSWC6 and ESD1 are part of an Arabidopsis SWR1 chromatin remodellingcomplex involved in the regulation of diverse aspects of plantdevelopment, including floral repression through the activationof FLC and FLC-like genes. Key words: Arabidopsis, chromatin remodelling, floral repression, HIT-Zn finger, phase transition, SWR1 complex     

Effects of the Photoperiod Genes Ppd1 and Ppd2 on Growth and Development of the Shoot Apex in Wheat

Two major genes influencing the photoperiod response in wheat,Ppd1 and Ppd2, have been identified on the group 2 chromosomes.Substitution lines, which had been characterized on the basisof time of ear emergence as carrying either the insensitiveor sensitive alleles of the two Ppd genes, were used to investigatethe effect of these genes on development. They were grown undershort photoperiods, and growth and development of the shootapex was measured. The primary influence of the Ppd genes was on ear growth. Inthe plants carrying the insensitive alleles, Ppd1 and Ppd2,the relative growth rate of the floral apex was faster thanthat of plants with the sensitive alleles, ppd1 and ppd2. Therewere no differences in the rate of spikelet initiation, butthe spikelets of the ppd lines grew and developed more slowly. The Ppd2 material segregated for another gene located on chromosome2B affecting duration of the life cycle. This gene also affectedthe relative growth rate of the ear. It was considered that the major effect of the Ppd1, Ppd2 andthe second genetic factor on chromosome 2B is on floral growthrate. Differences in apex morphology, stem growth and ear emergenceare thought to be due to the differences in floral apex growthand size. Wheat, photoperiod genes, shoot apex development, shoot apex growth     

Ontogeny and Marginal Growth in the Leaf of Eubrachion ambiguum

Marginal growth in the leaf of Eubrachion ambiguum, a viscaceoushemiparasite, has been investigated. This growth is accomplishedby the marginal meristem comprising the marginal initials aloneas has been described earlier by Hara (1957) in Daphne odora.To the best of the author's knowledge the present communicationis the second report of such a type of marginal growth in thedicotyledons. Phylogenetically, at least in Eubrachion ambiguum, it probablyrepresents a reduced rather than a primitive feature.