Scapania praetervisa Meyl., not S. mucronata Buch in Britain

Abstract

The protonema of Orthotrichum obtusifolium, regenerated from leafy shoots, comprises a dense mass of largely unbranched exclusively upright filaments. All the cells have transverse cross-walls and contain numerous chloroplasts which become larger and discoidal in older filaments. Differentiation into chloro- and caulonema is absent. When upright filaments are transplanted onto an agar surface, they act as the main axes for a further set of upright branches. Buds and side branches are produced symmetrically at right angles to the mother cells. Protonemal morphogenesis hardly changes on nutrientfree medium and spherical brood cells are not produced after prolonged culture or in the presence of abscisic acid. Rhizoids with oblique septa and pigmented walls arise from the base of gametophores. These revert to protonemata when in contact with nutrient agar.

The upright filaments produce terminal and intercalary filamentous gemmae with well defined abscission cells. The latter swell and lose their contents prior to liberation. Cells immediately below the abscission cells produce side branches in acropetal succession. Secondary gemmae arise by percurrent proliferation and gemmae frequently germinate in situ.     

Protonemal gemmae on Amblystegium serpens (Hedw.) B., S. & G. from Macquarie Island

Abstract

Amblystegium serpens, collected on Macquarie Island, formed protonemal gemmae in laboratory culture. The gemmae germinated to form leafy shoots. They are presumed to be vegetative reproductive structures.     

Development and germination of rhizoidal gemmae of Bryum violaceum

Approximately four to six weeks after transferring gametophores of Bryum violaceum Crundwell & Nyholm to fresh soil, abundant new rhizoids with stalked gemmae were present at the bases of the gametophores. The development of gemmae on rhizoids was followed from single cell initials to multicellular, three-dimensional forms. Mature gemmae, the vegetative diaspores, were pale orange, purple or reddish brown and each had a uniseriate stalk of two to four cells. While remaining on soil, the rhizoidal gemmae showed no in situ germination. However, following the removal of gametophores with rhizoidal gemmae, or rhizoids alone with gemmae, and their placement upon wet filter paper in Petri dishes in light, the gemmae germinated. During germination, the protonemata emerged consistently from mature gemmae at their distal ends, revealing the existence of gemma polarity. In the case of immature gemmae, on the other hand, the protonemata emerged from any surface cell indicating that gemma polarity had not yet been established.     

Hormonal Regulation of Gametangial Formation in the Moss Bryum argenteum Hedw

Phytohormones such as auxins, cytokinins, gibberellins, andabscisic acid differentially affect gametangial induction inmale and female clones of Bryum argenteum. Both IAA and GA³increased the percentage of fertile gametophores in the maleclone, and inhibited the response in the female clone. GA₃ wasmore effective than IAA in eliciting the response in the maleclone. Cytokinins, on the other hand, increased the productionof fertile gametophores in the female clone, and inhibited itslightly in the male clone. The two cytokinins tested (kinetinand DMAAP) were almost equally effective for the female clone. An Interaction of IAA and kinetin nullified their individualinhibitory effects on the female and male clones, respectively.Cyclic AMP prevented the inhibitory effect of kinetin in themale clone; whereas, in the female clone, it stimulated theresponse elicited by kinetin. Abscisic acid (ABA) acted as ageneral inhibitor of vegetative growth and gametangial inductionin this moss. However, the inhibition of gametangial inductionwas greater in the female clone which is also more sensitiveto ABA than the male clone.     

Development of gametophores from isolated protoplasts of the mossAnoectangium thomsvnii Mitt.

Summary Protoplasts of the mossAnoectangium thomsonii Mitt. were isolated from preplasmolyzed protonemal filaments, grown in suspension cultures, after the digestion of the cell wall by the enzymes cellulase and macerozyme or driselase. Driselase was more effective than cellulase and macerozyme. After purification these protoplasts were plated in the form of small agar drops in modified Kofler's medium without hormones and incubated in the dark at 26 ± 2 °C. Cell walls regenerated within three days and cell divisions started seven days after the initiation of the cultures. When the regenerants were transferred to normal protonemal culture medium and illuminated by 3,000 lux continuous light, a multi-cellular protonema developed which formed leafy gametophores on salicylic acid supplemented medium.     

A review of the Gymnostomum calcareum Nees & Hornsch. complex (Bryopsida: Pottiaceae) in southern Europe and the Macaronesian Islands,including G. calcareum var. atlanticum var. nov.

Abstract

New taxonomic observations, based on rhizoidal and protonemal gemmae of material from southern Europe and the Macaronesian Islands, are given in this work for sibling taxa of the Gymnostomum calcareum Nees & Hornsch. complex. Gymnostomum calcareum var. atlanticum Sérgio from the Iberian Peninsula, Madeira and Azores is described as a new variety, and its diagnostic characters are described and illustrated. This moss has a bistratose margin in the upper parts of the perichaetial and vegetative leaves, and the perichaetial leaves are markedly acute. It is closely related to Gymnostomum lanceolatum Cano, Ros & J. Guerra, here reduced to a variety of G. calcareum. The occurrence of fusiform or claviform protonemal gemmae provides a diagnostic feature for the different taxa.     

Gibberellins and the Growth of Excised Tomato Roots: Comparison of gib-1 Mutant and Wild Type and Responses to Applied GA3 and 2S, 3S Paclobutrazol

Clones of excised roots of wild type tomato (Lycopersicon esculentum,Mill., cv. Moneymaker) and a near-isogenic GA-deficient mutant(gib-1/gib-1) were cultured in modified White's medium containing1.5% w/v sucrose. The linear elongation rate of the main axisof the gib-1 mutant was 40% less than that of the wild type.In addition, the main axis of the gib-1 mutant was thicker thanthat of the wild type but main axis volume growth was the samein both genotypes, indicating that the gib-1 allele was affectingthe orientation of root expansion. There was no evidence tosuggest that the gib-1 allele affected either the pattern ofemergence or the density of lateral roots. Elongation rate andthickness of gib-1 mutant roots were restored to those of thewild type by the addition of low concentrations (0.1–1.0µM) of gibberellic acid (GA3). These concentrations ofGA3 caused a slight reduction in extension growth of wild typeroots, indicating that endogenous GAs were not limiting elongationof normal roots in culture. The GA biosynthesis inhibitor, 2S,3S paclobutrazol, at 0.1 µM, significantly reduced elongationof wild type roots and this inhibition was counteracted by 0.1µM GA₃. It is concluded that the difference in growthbetween the gib-1 mutant and the wild type represented GA-dependentgrowth. Low concentrations of 2S, 3S paclobutrazol caused onlya small (5%) reduction in growth of the gib-1 mutant and thisgrowth inhibition was not reversed by GA₃. This observation,and the fact that gib-1 mutant roots grow in the absence ofadded GA₃, suggested that part of root growth was GA-independent.However, the possibilities that the gib-1 mutant is ‘leaky’and that paclobutrazol does not inhibit GA biosynthesis completelycannot be excluded. Key words: gib-1 mutant, gibberellic acid, Lycopersicon esculentum, 2S, 3S paclobutrazol, root growth     

The Formation of Catenate Foliar Gemmae and the Origin of Oil Bodies in the Liverwort Odontoschisma denudatum (Mart.) Dum. (Jungermanniales): a Light and Electron Microscope Study

This article describes the ultrastructural events associatedwith the differentiation and liberation of the exogenous gemmaeproduced in branched acropetal chains along the margins of theleaves in the liverwort Odontoschisma denudatum. Formation ofa dorsal protrusion from young leaf cells containing a largecentral nucleus, small vacuoles, starch-free chloroplasts, scatteredcytoplasmic lipid droplets but no oil bodies, signals the onsetof the formation of the initial cell of a gemmiferous filament.The protrusion enlarges and the nucleus migrates into its base,therein dividing with the equator of the spindle virtually fillingthe central isthmus between the leaf surface and the now swollentip of the initial cell. Subsequent divisions of the initialcell produce a chain of cells in atropetal succession. Transverselyorientated microtubules line the cortical cytoplasm along thelateral walls of the terminal cells of the gemmiferous filaments,but are absent from the tips, thus suggesting that these cellselongate by intercalary, rather than by tip, growth. Duringmitosis microtubules are closely associated with the envelopesof spindle-shaped prophase nuclei, radiate from ill-definedspindle poles surrounded by plastids at metaphase and anaphaseand form a dense phragmoplast array during telophase. Pre-prophasebands are absent and it may be that the nuclear equator determinesthe plane of division in gemmiferous filaments. Chloroplastdivision, associated with extremely transient plastid-dividingrings, takes place during interphase. Lateral branches of thegrowing filaments arise from subapical cells by reiterationof the first division mechanism. Immediately following the proliferative divisions, which takeplace in cells measuring only 5-6 µm in diameter, oilbodies suddenly appear as flat pleomorphic cisternae associatedwith endoplasmic reticulum and occasional microtubules. Theircontents are electron-transparent apart from scattered osmiophilicdroplets. Throughout their ontogeny the oil bodies are closelyassociated with cytoplasmic lipid bodies but there is no evidenceof fusion. The nascent oil bodies swell rapidly to their finaldiameter, become ovoid to spherical in outline and are eventuallysuspended by fine cytoplasmic bridges within the vacuoles. Thelatter rapidly increase in size together with an expansion ofthe cells themselves until these reach their final diameterand length. The final event in gemma maturation is an endogenousdivision with the formation of a new internal wall along a phragmosome.Separation of the bicellular gemmae proceeds basipetally andinvolves the appearance of an electron-transparent line alongthe middle lamella in the cross walls, which often develop convexthickenings, and severing of the plasmodesmata. After theirliberation shallow scars are visible on the leaf surface underthe SEM. Gemma maturation sees a marked increase in the electron-opacityof the walls and dense staining of these together with Golgivesicles with the periodic acid/thiocarbohydrazide/silver proteinatetest for non-cellulosic carbohydrates. This change in wall chemistryand ultrastructure may be related to the fact that the maturinggemmae become extremely water repellant and are probably dispersedeither on the surface of water films or in the air.Copyright1995, 1999 Academic Press Bryophyta, gemmae, liverwort, microtubules, morphogenesis, oil bodies, polar growth, vegetative reproduction     

Effect of Lead and Colchicine on Morphogenesis in Protonemata of the Moss Funaria hygrometrica

Protonemata of Funaria hygrometrica grown in artificial mediacontaining different lead concentrations grow more slowly thancontrols and show a disturbance of polar growth, changed arrangementof chloroplasts, alterations of nucleus and septa position.Morphological effects are dose-dependent. At the lowest leadconcentration (10^-6 M), only a delay in development was observed,but no cellular alterations, At 10^-5 M Pb nuclear migration,cellular shape, size and position of plastids, were alteredand a variety of aberrant forms were present. At 10^-4 M, besidesthese alterations, a drastic reduction of the protonemal system,high vacuolation and the growth of protonemal filaments fromleaves were evident. The highest concentration, (10^-3 M), causeddeath. Patterns of protonemal development and cellular arrangementin lead-treated samples showed similarities as well as differences,if compared to alterations induced by colchicine. Indirect immunofluorescencedemonstrated a correlation between lead concentration and alterationof cytoskeletal organization (alterations similar to those inducedby colchicine). Hypotheses are raised to account for effects of lead on microtubulestructure, arrangement and cytoplasm organization.Copyright1995, 1999 Academic Press Funaria hygrometrica, lead, protonemal development, cytomorphogenesis, microtubules     

2-Trans-Abscisic Acid Biosynthesis and Metabolism of ABA-Aldehyde and Xanthoxin in Wild Type and the aba Mutant of Arabidopsis thaliana

Abscisic acid (ABA) and 2-trans-ABA (t-ABA) biosynthesis werestudied in wild type Landsberg erecta and the three allelicaba mutants of Arabidopsis thaliana (L.) Heynh., which are impairedin epoxy-carotenoid biosynthesis. Labelling experiments with¹⁸O₂and mass spectrometric analysis of [¹⁸O]ABA and its catabolitesABA-glucose ester (ABA-GE) and phaseic acid (PA), and t- ABAand t-ABA-GE, showed that t-ABA biosynthesis was less affectedthan ABA biosynthesis by mutations at the ABA locus. The aba-4allele caused the most severe impairment of ABA biosynthesiscompared with the other two mutant alleles aba-1 and aba-3,yet aba-4 plants synthesized as much t-ABA as wild type Landsbergerecta plants. Feeding experiments with RS- [²H₆]ABA-aldehydeisomers and unlabelled xanthoxin isomers suggest that t-xanthoxinand t-ABA-aldehyde are precursors to ABA and t-ABA in Arabidopsis Key words: ABA-alcohol, ABA-aldehyde, ABA-glucose ester, ¹⁸O₂ labelling, phaseic acid     

Effects of fatty acids on BK channels in GH(3) cells

Ca²⁺-activated K⁺ (BK) channels inGH₃ cells are activated by arachidonic acid (AA). Becausecytosolic phospholipase A₂ can produce other unsaturatedfree fatty acids (FFA), we examined the effects of FFA on BK channelsin excised patches. Control recordings were made at several holdingpotentials. The desired FFA was added to the bath solution, and thevoltage paradigm was repeated. AA increased the activity of BK channelsby 3.6 ± 1.6-fold. The cis FFA, palmitoleic, oleic,linoleic, linolenic, eicosapentaenoic, and the triple bond analog ofAA, eicosatetraynoic acid, all increased BK channel activity, whereasstearic (saturated) or the trans isomers elaidic,linolelaidic, and linolenelaidic had no effect. The cisunsaturated FFA shifted the open probability vs. voltage relationshipsto the left without a change in slope, suggesting no change in thesensitivity of the voltage sensor. Measurements of membrane fluidityshowed no correlation between the change of membrane fluidity and thechange in BK channel activation. In addition, AA effects on BK channelswere unaffected in the presence of N-acetylcysteine.Arachidonyl-CoA, a membrane impermeable analog of AA, activateschannels when applied to the cytosolic surface of excised patches,suggesting an effect of FFAs from the cytosolic surface of BK channels.Our data imply a direct interaction between cis FFA and theBK channel protein.

     

The role of gibberellins in the growth of floral organs of Pharbitis nil

Evidence that the synthesis of GA₃ is involved in the growthof floral orga'ns of Pharbitis nil is presented. GAs in floralorgans at different developmental stages were surveyed usingTLC followed by the bioassay with two dwarf rice seedlings,‘Tanginbozu’ and ‘Waito-C’. The amountof GAs in the petal and stamen increased rapidly after the petalemerged from calyx, reached a maximum 12 hr before anthesis,then declined markedly thereafter. The GA content in the calyxremained unchanged before and after anthesis, and that in thepistil increased after anthesis. Pharbitis flowers containedat least two active GAs, one of which was probably GA₃, theother appeared to be GA₁₉. GA₃ was detected in relatively largeamounts in both the petal and stamen during their rapid elongation.In the calyx, which showed little increase in fresh weight duringrapid flower growth, GA₉ was the dominant GA. Exogenously suppliedGA₃ promoted elongation of sections in excised young filaments.Sucrose was necessary for definite growth promotion by GA₃.GA₁₉ had little effect on filament elongation, and IAA was ratherinhibitive. (Received July 29, 1972; )     

The In Vitro Flowering of Kalanchoe blossfeldiana Poellniz: I. ROLE OF CULTURE CONDITIONS AND NUTRIENTS

Dickens, C. W. S. and Van Staden, J. 1988. The in vitro floweringof Kalanchoe blossfeldiana Poellniz. 1. Role of culture conditions.—J.exp. Bot. 39: 461—471. Nodal explants of Kalanchöe blossfeldiana Poellniz. werecultured in vitro on a low nutrient hormone-free medium. Floweringwas achieved in response to short-day inductive cycles. Thissystem was used to test the influence, on the flowering response,of a variety of culture conditions and media. Reduced vesseland medium volume both inhibited flowering, as did renderingthe vessel impervious to gasses. Nitrogen in the form of NH₄NO₃and KNO₃ promoted flowering and vegetative growth in differentways. Increasing sucrose content in the medium caused some increasein the flowering response and in leaf anthocyanin production,but inhibited most aspects of vegetative growth. All of theseaspects are discussed in relation to the induction and evocationof flowering. Key words: Kalanche, flowering, in vitro     

Focal central chemoreceptor sensitivity in the RTN studied with a CO2 diffusion pipette in vivo

Li, Aihua, and Eugene E. Nattie. Focal centralchemoreceptor sensitivity in the RTN studied with aCO₂ diffusion pipette in vivo.J. Appl. Physiol. 83(2): 420-428, 1997.We describe and use a CO₂diffusion pipette to produce a quickly reversible focal acidosis in theretrotrapezoid nucleus region of the rat brain stem. No tissueinjection is made. Instead, artificial cerebrospinal fluid (aCSF)equilibrated with CO₂ circulateswithin the micropipette, providing a source for continuedCO₂ diffusion into the tissue fromthe pipette tip. Tissue pH electrodes show the acidosis is limited to500 µm from the tip. In controls (aCSF equilibrated with air), 1-minpipette perfusions increased tissue pH slightly and decreased phrenicnerve amplitude. In moderate- andhigh-CO₂ groups (aCSF equilibratedwith 50 or 100% CO₂), 1-minperfusions significantly decreased tissue pH and increased phrenicnerve amplitude in a dose-dependent manner. The responses developed andreversed within minutes. Compared with our prior use of medullary acetazolamide injections to produce a focal acidosis, in this approachthe acidosis 1) arises and reversesquickly and 2) its intensity can bevaried. This allows study of sensitivity and mechanism. We concludefrom this initial experiment that retrotrapezoid nucleus regionchemoreceptors operate within the normal physiological range ofCO₂-induced tissue pH changes.

     

Serial Development of Foliar Gemmae in Tortula (Pottiales, Musci), an Ultrastructural Study

The development and liberation mechanism of foliar gemmae havebeen studied by electron microscopy in two mosses, Tortula latifoliaBruch and Tortula papillosa Wils. The gemmae develop on theadaxial surface of mature leaves from single initial cells onboth the lamina and costa in T. latifolia but only on the costain T. papillosa . Elongation of the initial cell is associatedwith the deposition of a highly extensible new wall whilst theold wall and cuticle in the apical dome rupture. The first divisionis transverse and separates a short basal cell embedded in thefoliar tissue and a distal cell, or gemma primordium, protrudingfrom the leaf surface. Subsequent divisions of the gemma primordiumgive rise to a six-to-eight-celled globose gemma with mucilaginousouter walls. During gemma development the basal cell producesa new wall and elongates again whilst the common wall with thegemma splits apart centripetally along the boundary betweenthe old and new wall in the basal cell; plasmodesmal connectionsare gradually severed and eventually the young gemma remainsconnected to the basal cell only by mucilage. After separationof the first-formed gemma, the basal cell may expand and producea second gemma by the same mechanism. The whole process maybe repeated several times resulting in the formation of a chainof gemmae stuck together by mucilage and which are liberatedonly when the leaves are fully hydrated. Accumulation of abundantlipid deposits in the gemmae after symplasmic isolation reflectsconsiderable photosynthetic autonomy. Abscission; bryophytes; cell wall formation; plasmodesmata; vegetative reproduction     

Scanning Electron Microscope Studies of Multiple Shoot Production by Meristem Tip Cultures of Solarium x curtilobum

A meristem tip culture isolated from Solatium x curtilobum cv.Mallku produced a limited amount of callus at the cut surfaceof the explant when cultured on Murashige and Skoog medium containing1 mg dm³ 6--{dimethylallylamino)purine and O.01 mg dm³ naphthaleneacetic acid. A single sheet of cuticle-like material develops on localizedregions of the callus surface and the cells beneath it decreasein mean cell size. These meristematic centres develop into fullyorganized shoot meristems, and each will grow out into a leafyshoot when the culture is transferred to growth medium containingo.1 mg dm³ gibberellic acid (GA₃) as the only growth hormone.This system has considerable value in the rapid clonal propogationof Solanum species, since as many as fifty shoots can be producedfrom a single meristem tip culture.     

Inhibition of Ion Transport in Excised Barley Roots by Abscisic Acid; Relation to Water Permeability of the Roots

Previous papers have shown that abscisic acid can inhibit transportof ions across the root to the xylem vessels, resulting in reducedexudation from excised roots or inhibiting guttation from intactplants. However, it has not been established whether the inhibitionwas due to a reduction in salt transport (J_s) or in permeabilityof the roots to water (L_p). This paper investigates the effectof ABA on L_p and J_s separately. It is shown that L_p increasedin ABA and then fell, but was about the same as in control rootswhen transport was inhibited. The effect of ABA on exudationtherefore appeared to be mainly due to reduction in J_s. Inhibitionof J_s was also present in intact, transpiring plants and sowas not due to reduced water flow. The inhibition of ion releaseto the xylem affected Na⁺, Mg²⁺, Ca²⁺, and phosphate as wellas the major ion in the exudate, K⁺. It is concluded that ABAinhibits salt transport to the shoot by acting on ion transportinto the xylem, and not by reducing water flow coupled withsalt transport.     

Studies on the Development of the Air Pores and Air Chambers of Marchantia paleacea: 1. Light Microscopy

The ontogeny of the air pores and air chambers of Marchantiapaleacea begins with the schizogenous development of protodermalintercellular spaces of the initial apertures, and is completedwith the formation of the air pores and giant sub-epidermalair chambers bearing numerous photosynthetic filaments. Intercellularspace formation commences from the thallus surface and proceedsinwards to the first internal layer of cells. The cells amongwhich spaces develop do not originate from one mother cell.Spaces are formed only in the regions of the intersection ofthe anticlinal walls of three, four, or sometimes more successivederivatives of S₁, S₃ and S₄ segments of the apical cell, oneor two of which have been divided periclinally and the restanticlinally. Protodermal intercellular spaces appear in mostor all the corners of these cells, the anticlinal walls of whichexhibit an opposite disposition. The S₁, S₂, S₃ and S₄ segmentsare produced by definite divisions of a five-sided apical celland by a series of divisions give rise to initial cells of theinternal layers of the thallus and initial cells of the protodermaland sub-protodermal layers. The concept of a quiescent apicalcell cannot be accepted, since dividing apical cells have beenobserved, and the pattern of wall disposition of the thallusapex cannot be explained without the active participation ofthe apical cell. The air chambers are apparently of exogenous origin. They resultfrom the broadening of the bottom of the initial apertures bythe coordination of the rate of anticlinal divisions and growthof the protodermal and sub-protodermal cells surrounding theintercellular spaces of the initial apertures. The ontogenyof the pore rings starts at an advanced stage of air chamberformation not from a mother cell but from the cells which surroundthe closed entrance of the air chamber, by a shift of the planeof division from anticlinal to periclinal. Before the periclinaldivisions a new axis of growth perpendicular to the thallussurface is established in the mother cells of the pore. By a polarized growth into the air chamber followed by periclinaldivisions, the cells of the floor form initial cells of thephotosynthetic filaments. The latter divide again to form singleor branched photosynthetic filaments. Marchantia paleacea, air pore, air chamber     

Immunological Reactions of Single Pollen Grains, Electrophoresis and Enzymology of Pollen Protein Exudates

Single intact pollen grains of Oenothera organensis, when placedupon a thin layer of agar containing pollen antiserum, producecircular areas of precipitate. Pollen grains from an S₂S₂ plantdo not produce precipitate in S₆ antiserum. Pollen grains froman S₆S₆ plant and an S₂'S₄' self-compatible plant produce precipitatesin S₆ antiserum. Fifty per cent of the pollen grains from anS₂S₆ plant produce precipitate in S₆ antiserum. Protein diffusesinto buffer solutions from intact pollen grains within 212 min.As much as 40 per cent of the total protein diffuses out inan hour. Amylase and invertase were detected in the diffusatefrom pollen grains. Alkaline and acid phosphatases were confinedto the pollen grains and did not diffuse out. The serologicalprecipitates are specific to the incompatibility system.