摘要:

AbstractPlastids of non‐photosynthetic cells or tissues, such as chromoplasts or leukoplasts, which develop during the course of ontogenetic differentiation contain DNA which is identical to chloroplast DNA with respect to size, organization and gene content. Also in ribosome‐deficient bleached plastids, produced in leaves by experimental treatments or mutation, chloroplast DNA remains unaltered. The chloroplast DNA of various bleached mutant strains ofEuglenahas suffered major deletions or rearrangements, but is, however, never totally lost. Also leukoplasts of parasitic higher plants contain DNA. In the organellar DNA of several parasitic plants photosynthetic genes are conserved. In the heterotrophic flagellateAstasiaand in the holoparasiteEpifagus virginiana(Orobanchaceae) the size of the plastid DNA is greatly reduced by major deletions and most or all photosynthetic genes or genes related to the chloroplastic respiratory chain are lost. The residual plastid genomes have, however, retained genes for RNAs, tRNAs and ribosomal polypeptides and these are transcribed, although plastidic RNA‐polymerase genes are lost inEpifagus. These findings demand the existence of a nuclear‐encoded RNA‐polymerase. The relevance of the conservation of plastid DNA and of plastidic gene expression in non‐photosynthetic cells is discussed, remains, however, at present elusive. Open reading frames of unknown function might be of particular significance for non‐photosynth

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00292.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe vacuole is the largest compartment of a mature plant cell and serves as an internal reservoir of metabolites and nutrients. In the last years transport of solutes across the tonoplast has been intensively investigated. It was shown that two different proton pumps reside in the tonoplast. These pumps generate an electrochemical gradient which can be used as an energy‐source to accumulate solutes. Cation uptake is driven by an H+antiport mechanism. Anions are accumulated in response to the inside positive membrane potential. In addition, the existence of ion channels was shown using the patch clamp technique. The aim of this review is to compare and to discuss the present state of our knowledge of solute transport across the tonoplas

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00293.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe peripheral cell wall(s) of stems and coleoptiles are 6 to 20 times thicker than the walls of the inner tissues. In coleoptiles, the outer wall of the outer epidermis shows a multilayered, helicoidal cellulose architecture, whereas the walls of the parenchyma and the outer wall of the inner epidermis are unilayered. In hypocotyls and epicotyls both the epidermal and some subepidermal walls are multilayered, helicoidal structures. The walls of the internal tissues (inner cortex, pith) are unilayered, with cellulose microfibrils oriented primarily transversely. Peeled inner tissues rapidly extend in water, whereas the outer cell layer(s) contract on isolation. This indicates that the peripheral walls limit elongation of the intact organ. Experiments with the pressure microprobe indicate that the entire organ can be viewed as a giant, turgid cell: the extensible inner tissues exert a pressure (turgor) on the peripheral wall(s), which bear the longitudinal wall stress of the epidermal and internal cells. Numerous studies have shown that auxin induces elongation of isolated, intact sections by loosening of the growth‐limiting peripheral cell wall(s). Likewise, the effect of light on reduction of stem elongation and cell wall extensibility in etiolated seedlings is restricted to the peripheral cell layers of the organ. The extensible inner tissues provide the driving force (turgor pressure), whereas the rigid peripheral wall(s) limit, and hence control, the rate of organ elongatio

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00294.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe distribution of intracellular pH was studied in cultured cells ofGossypium hirsutumby con‐focal pH topography using the fluorescent probe car‐boxy SNARF1 and a ratio imaging procedure. The resulting pH maps can visualize pH differences with an accuracy of 0.1 unit in the investigated range between 7.5 and 5.6. They reveal the following characteristic features of theGossypiumcells:– the pH of the cytoplasmic core regions ranges from near 7.4 in younger to near 6.0 in older cells;– vacuoles show the expected acidity with pH<5.6;– the cell wall/apoplastic region is acidic with a pH near 5.6 or below, especially in young, growing cells;– interestingly, acidic areas appear also at the periphery of the cytoplasm, i.e. beneath the plasma membrane. They remain stable in the presence of 5/μmol/I of the protonophore CCCP.Acidic layers of peripheral cytoplasm were also detected in protoplasts ofPenicillium cyclopium, i.e. eukaryotic cells of simpler structure, which served as a reference object. This ronfirms earlier findings obtained with classical fluorescence microscopy and another fluoroprobe (fluorescein diacetate). Though additional experimental support is needed, low pH regions at the cytoplasm/plasma membrane interface should be considered a real contribution to the pH control of plant and fungal cells, facilitating e.g. the maintenance of cytosolic pH in acidic

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00295.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIA detergent removal technique was used to reconstitute solubilized tonoplast proteins of mesophyll cells of the CAM plantKalanchoë daigremontianainto phosphatidylcholine liposomes. The proteoliposomes were able to hydrolyse ATP and to pump protons across the vesicle membrane. Both activities were inhibited by nitrate, an inhibitor of V‐type ATPases. Freeze‐fracture micrographs confirmed the incorporation of membrane proteins into liposomes. Increase of specific ATP‐hydrolysis activity compared to solubilized tonoplast proteins and SDS‐PAGE analysis of reconstituted proteins in comparison with the polypeptide pattern of the purified tonoplast H+‐ATPase from the same plant source indicated a highly selective reconstitution of the tonoplast

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00296.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractMany growing leaves of tulips show subtle undulations of their surface, oriented mostly transversely to the leaf axis. The undulations move acropetally with respect to cells. The epidermal peels from the leaves with the undulations placed on agar plates containing a pH indicator dye produce band patterns of more acid and less acid zones. Similar patterns also appear when the agar‐indicator is applied to the abraded leaf surface. This indicates that there is spatially variable H+efflux from the epidermis into agar. No variation of the colour appears when the agar‐indicator is applied to the mesophyll surface formed by peeling off the epidermis, which indicates that the pH pattern is a feature of the epidermis only. The pattern of pH bands correlates closely with the pattern of undulation; more acid bands correspond to the convex zones of the surface. The movement of the undulations also indicates that the pH pattern moves, which means that in the epidermal apoplast the pH oscillates at a particular locat

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00297.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe ion currents, activated by depolarizations, across the plasma membrane ofArabidopsis thalianacultured cells were studied by means of the patch‐clamp technique in the whole‐cell configuration. The electrical conductance of the membrane could be shifted from a cation to an anion conducting state by changes in the [K+]: [Cl−] ratio in the external medium. For ratios between 1:1 and 1:5 the currents were due to K+efflux and for a ratio of 1:10 to Cl−influx. In the cation conducting state the permeability ratio of K+over NH+4and the alkali metal ions was: K+≅ NH>Na+≅ Li+>Cs+. In the anion conducting state the permeability of NO−3was the same as that of Cl−. These channels were activated by depolarizations in the range of physiological potentials (‐70/‐80mV) and, either by mediating the efflux of cations or the influx of anions, they could function to re‐hyperpolarize the membrane potential after depolarizations due to the influx of cations or of solutes cotransported with protons and/or to the inhibition

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIn different marine red algae (Chondrus crispus, Delesseria sanguinea, Membranoptera alata, Phycodrys rubens, Phyllophora truncata, Polyneura hilliae) photoinhibition of photosynthesis has been investigated by means of both fluorescence and oxygen measurements. Measurements of absolute oxygen production show that photoinhibition causes a decline in the initial slope and in the rate of bending of the fluence rate‐response curve (i.e. the photosynthetic efficiency at non‐saturating fluence rates), as well as a decline in the photosynthetic capacity (Pm) at saturating fluence rates. Fluorescence data (Fv/Fm) were consistent with the results of oxygen measurements. Under excessive light photoinhibition protects photosynthesis against photo‐damage in red algae. However, an increase in the initial fluorescence (Fo) after photoinhibitory treatment indicates that it could not prevent photodamage entirely.Action spectra of photoinhibition demonstrate that the main photoinhibition site inPolyneura hiliaeis PS II, because far red light absorbed by PS I was ineffective. The strong increase of Fo in the blue wavelength range and the slight and partial recovery in weak blue light indicate that blue light especially causes photodamage.Recovery of photosynthesis requires dim white light conditions. Experiments with monochromatic light also show a wavelength dependence of recovery. Moreover, the recovery of photosynthesis after a photoinhibitory treatment is strongly temperature dependent, indicating participation of enzymatic processes. The comparison of fluorescence and oxygen measurement of the recovery shows different results in some species. The rate of oxygen production in red control light increased immediately after photoinhibited algae were exposed to weak light conditions. Surprisingly, the ratio of variable to maximum fluorescence (Fv/Fm) ofPhyllophora truncataand the maximum fluorescence (Fm) ofPolyneura hilliaeshow first a delay of the recovery under weak light conditions. Thus, in recovery experiments fluorescence and oxygen data are not quite consi

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryEquiproportional mixtures and monocultures of two roadside grass species (Elymus repens(L.) Gould andPuccinellia distans(L.) Pari.) were grown in experimental field plots under non‐limiting water and nutrient conditions. During the course of the season,E. repensincreasingly overgrew and shaded plants ofP. distanswhich eventually died. A multispecies canopy photosynthesis model was parameterized using measurements of structural and physiological characteristics from three different stages of canopy development. Results of simulations clearly revealed that canopy photosynthesis ofP. distanswas highly dependent on the degree of light competition caused byE. repens. SinceP. distanshas recently invaded stands of roadside vegetation throughout Central Europe where it has replaced the native and highly competitiveE. repens, it is hypothesized that this success is due to disturbance factors that keepE. repensfrom growing tall and shadingP. distan

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00300.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractNectar secretion pattern and effects of nectar removal were analyzed in six hummingbird‐pollinated Argentinean Pitcairnioideae:Abromeitiella brevifolia. A. lorentziana, Deuterocohnia longipetala. Dyckia floribunda, D. ragoneseiandPuya spathacea. Flower lifetime was determined in each case. Nectar volume, concentration and sugar production were measured from bud opening till fading of flowers at different time intervals according to the species' flower life‐span. Nectar volume varies while nectar concentration and cumulative sugar production increase as a function of flower age in all the studied species. In general, total nectar volume and concentration values can be affected by periodic removal, but total sugar production is unaffected. Only inPuya spathaceadid periodic nectar harvesting reduce the total amount of sugar produ

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1992.tb00301.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY