ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00213.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ZusammenfassungDie Sippen der terrestrischen Bryophytengesellschaften entlang eines Transektes durch die Judäische Wüste vom Toten Meer nach Jerusalem weisen verschiedene Lebensstrategien auf: die der Besiedler mit generativem Reproduktionsverhalten (“generative” Besiedler), der Besiedler mit vegetativem Reproduktionsverhalten (“vegetative” Besiedler), der Besiedler mit basitonen Innovationen (“innovative” Besiedler), der einjährigen und der kurzlebigen und/oder ausdauernden Pendler und die geophytische Lebensstrategie.Arbeitstechnische Grundlage für die gewichtete Analyse des Lebensstrategiengefüges entlang des klimatischen und des edaphischen Gradienten in diesem Transekt war die Ermittlung der mittleren Gruppenmenge für die jeweilige Lebensstrategie. Damit war es möglich, den Anteil der jeweiligen Lebensstrategie am Gesamtspektrum stärker zu gewichten und ihre Verteilung und ihre Position in den Gesellschaften und Vegetationsstufen aufzuzeigen.Unter den extrem ariden Bedingungen und auf den salzhaltigen instabilen Böden der saharo‐arabischen Stufe scheinen “innovative” Besiedler und kurzlebige und/oder ausdauernde Pendler entscheidende Vorteile zu haben.In der semi‐ariden irano‐turanischen Stufe, in der klimatisch etwas günstigere Bedingungen und stabilere Bodenverhältnisse herrschen, geht die Bedeutung dieser Lebensstrategien zurück und “generative” Besiedler werden mitbestimmend. Außerdem treten in dieser Stufe zwei weitere Lebensstrategien, die der geophytischen und der ausdauernden Besiedler auf.In der subhumiden, mediterranen Stufe der Judäischen Berge dominieren fast ausschließlich “generative” Besiedler. Dies ist auf die günstigen makroklimatischen Bedingungen der mediterranen Stufe und die mikroklimatischen Bedingungen in den Zwergstrauchgesellschaften zurückzuführen. Hier erreichen Sippen mit der Lebensform Kurzrasen und mittelhoher Rasen hohe Artmächtigkeiten und bestimmen das Bild der Bryophytenvegetation. Die anderen Lebensstrategien sind in dieser Höhenstufe untergeordnet.AbstractSpecies found in the terrestrial bryophyte communities along a transect across the Judean Desert from the Dead Sea to Jerusalem are classified under seven life strategies, that is, the colonists with generative reproduction (“generative” colonists), colonists with vegetative reproduction (“vegetative” colonists), colonists with basitone innovations (“innovative” colonists), and perennial colonists, the annual and short‐lived and/or perennial shuttle species and the geophytes.The strategy of the “innovative” colonists is characterized by solitary plants crowded together, by regular basitone innovation of the plants and by the characteristics of the xeropottioid life syndrome. “Generative”, “vegetative” and perennial colonists occur within the short turf or medium turf life forms. In “generative” colonists there is frequent sporophyte production and dispersal by small spores, while in “vegetative” colonists reproduction is by vegetative diaspores. Monoicy, regular sporophyte production and a high mortality rate are characteristic of the perennial colonist life strategy. Large spores obviously destined to prevent long distance dispersal (atelechorous mechanisms) are characteristic of the annual and/or short‐lived shuttle life strategies. Taxa are differentiated into annual and perennial ones depending on their lifespan. In the geophyte life strategy, so far only known inGigaspermum mouretii, there are subterranean creeping stems, with bud‐like leafy secondary axes growing above the soil.Determination of the mean percentage cover for the respective life strategies was the working basis for the weighted analysis of the life strategy pattern along an ecological gradient in this transect. From application of this analysis it will be possible to weight life strategies more strongly and to demonstrate their distribution and their occurrence within the communities and vegetation zones.Within this life strategy spectrum we recognize a distinct adaptation of life strategy in relation to the climatic and edaphical conditions. Under the extreme arid conditions of the Saharo‐Arabian zone and on the instable soils rich in salt, taxa with the “innovative” colonist and short‐lived and/or perennial shuttle life strategies seem to have decisive advantages.The importance of the above life strategies decreases in the semi‐arid Irano‐Turanian zone with its somewhat more favourable climatic conditions and with its more stable pedological conditions and the “generative” colonist life strategy also becomes a critical factor. Additional life strategies, such as the geophyte and the perennial colonist ones are a result of the ecologically broader conditions in this zone.The subhumid Mediterranean zone of the Judean Mountains is dominated nearly exclusively by species with the “generative” colonist life strategy. This results from the favourable macroclimatic conditions and the microclimatic ones of the mediterranean dwarf shrub communities where taxa with the short turf and medium turf life forms attain a high cover abundance, deter

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00214.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ZusammenfassungDer Bestäubungsmechanismus der Blüte vonThalia geniculatawird im Zusammenhang mit speziellen Blütenstrukturen (schiefe Leiste, Schwiele, Häutchen, Trigger, Narbenfortsatz) erläutert. Im Gegensatz zu anderen Marantaceen‐Gattungen verläuft die Griffelbewegung nicht bogen‐, sondern S‐förmig. Der Griffel steht aktiv unter Spannung und ist nur an einer Stelle reizbar. Mittels Zeitlupenaufnahmen wird die Bewegung rekonstruiert: Sie verläuft in 3 Phasen und dauert etwa 0,03 Sek. Die enorm hohe Geschwindigkeit der Griffelbewegung und die Tatsache, daß die Blüte nur eine einzige Bestäubungschance besitzt, verlangen präzise Synorganisations‐ und Synchronisationsprozesse, die im einzelnen dargestellt werden.AbstractThe pollination mechanism of the flower,Thalia geniculata, and the unusual construction of the style and staminodes is illustrated. As early as the bud stage, pollen of the single stamen is deposited onto the pollen tray at the top of the style. Special structures of the staminodes — “oblique ledge” (schiefe Leiste, sL), “callosity” (Schwiele, Schw) and “hood” (Kapuze, Ka) — are in the optimal position for pollination. The style functions only as a secondary pollen presenter. It is under active tension and only sensitive at a defined site. The proboscis of a visiting insect is guided into the flower by special structures: “callosity”, “pellicle” (Häutchen, H) and an appendage to the stigma (Narbenfortsatz, Nf). The insect touches the style and starts its explosive S‐shaped movement via a trigger mechanism. Slow motion pictures (5000 pictures/s) show that the revolving movement occurs in 3 phases in approximately 0.03 s. During this very short time the style becomes erect, scrapes the pollen from the proboscis into its stigmatic cave and deposits its own pollen onto the proboscis in the form of a sticky paste.InTh. geniculatathe 2 flowers of a partial inflorescence together form one attractive symmetrical, melittophilous blossom. They are pollinated, by Xylocopidae (even in SE Asia, where the plant is not indigenous). Each flower has only a single chance to be pollinated. I

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00215.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe early effects of penconazole (PCZ) at relatively high concentration (10−4to 5 × 10−4M) on changes in pH and in titratable acidity of the medium, transmembrane electrical potential difference (Em), electrolyte leakage and cell morphology were investigated inEgeria densaleaves. At the lowest (10−4M) concentration and in the presence of a very low (10 μM) K+concentration, triazole induced an early, moderate hyperpolarization of Em, associated with a decrease of net K+uptake, suggesting some increase in the passive permeability to K+. This Em hyperpolarization was no longer detectable at high (2 mM) K+outconcentration. At high PCZ concentrations (3 × 10−4M and 5 × 10−4M) the early hyperpolarization detectable in the presence of a low K+outconcentration became transient, and was followed by a marked depolarization. PCZ, at these concentrations, suppressed acidification of the medium, stimulated electrolyte leakage and, in the mesophyll cells, induced some shrinking of the cytoplasm and its disconnection from the cell walls. These results are interpreted as due to an early effect of this triazole leading to the disorganization of the pl

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00216.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe movement responses of the cellular slime moldDictyostelium discoideumto multiple stimuli were investigated. The responses were found to differ depending on the developmental stage of the organism. A novel response, positive gravitaxis, was found inDictyosteliumslugs but not in amoebae. In the presence of a simultaneous light stimulus, gravitaxis is effective only at low fluence rates. Slugs showed positive thermotaxis in a thermal gradient (0.2 °C cm−1) and ignored the simultaneous light stimulus at low fluence rates (<10−3W m−2), while at higher fluence rates they moved toward the light source. With a combination of a thermal gradient and gravityDictyosteliumslugs clearly oriented thermotactically ignoring the gravist

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00217.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractDynamic changes of microtubule (MT) configuration have been examined during the cell cycle progression in tobacco BY‐2 cells, which have been highly synchronized by aphidicolin treatment. Although it has been shown previously that four cell cycle stages display characteristic features of MTs (Hasezawa et al., 1991), distinct changes of MT configuration were observed at the interfaces of G2/M, M/G1and G1/S, and the frequency of appearance of such distinct structures were quantitatively examined. Among others, it is the first observation that at M/G1disintegrating phragmoplasts coexisted with short MTs in the perinuclear envelopes, but the MTs disappeared in the later stage, when cortical MTs were organizing. Thus it is supposed that cortical MTs originate from the transiently observed short MTs in the perinuclear region. This observation offered also an experimental system to analyze the molecular changes of MTs at the three interfaces during cell cycle progression in plant cells, as the mass culture of tobacco BY‐2 cells is readily availa

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00218.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractExperiments on transient gene expression were performed with mesophyll protoplasts isolated from young leaves of the sunflower (Helianthus annuusL.). Both PEG‐mediated DNA transfer as well as electroporation, were shown to be suitable for the introduction of a foreign gene. The expression of the reporter gene β‐glucuronidase was measured by a fluorimetric GUS assay. Inhibiting RNA synthesis by cordycepine (3‐deoxyadenosine) or translation of mRNA by cycloheximide suggests that biologically active plasmid‐DNA as well as functional mRNA transcripts are available for only short time periods in transfected protoplasts. Electroporation was carried out using rather high pulses in the microsecond range. Results indicate, that DNA uptake is more efficient using PEG, while electroporation causes less damage in DNA treated mesophyll pro

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00219.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractMembrane lipid degradation of plant protoplasts ofVicia fabawas characterized by the determination of ethane formation after electrofusion and electropermeabilization. Incubation of protoplasts with ascorbate or α‐tocopherol before electromanipulation led to a decrease in ethane production. Fusion product yield could be increased by incubation with α‐tocopherol.Using a simple model system, we investigated the active species involved in lipid peroxidation under conditions typically used for electromanipulation. The formation of lipid free radicals by electric pulses could be demonst

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00220.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractRhizoids ofCharafragilisDesv. were iontophoretically loaded with the Ca2+‐sensitive ratio dye indo‐1. After loading, the rhizoids regained their preinjection‐membrane potential within 2 to 5 min and survived the procedure for more than 24 h, but their growth in length was permanently inhibited. Microfluorimetric measurements of the indo‐1 fluorescence‐ratio showed spontaneous fluctuations of the cytoplasmic Ca2+‐concentration, usually declining from high values after loading to 425 ± 80 nM (± SD, n = 7) as determined byin‐vitrocalibration. Increasing the extracellular K+‐concentration (0.1 mM to 10 mM) or Ca2+‐concentration (1 mM to 10 mM) led to increases of 100 to 200 nM in cytoplasmic Ca2+‐concentration. The spatial distribution of cytosolic Ca2+in the rhizoid tips was visualised in ratio images computed from low‐light video‐pictures. These images showed a fairly homogeneous distribution of Ca2+throughout the tip cytoplasm with concentrations being in the same range as determined by microfluorimetry. A tip‐to‐base gradient in cytoplasmic Ca2+, thought to be a prerequisite for cell polarity and tip growth, was found in only 1 out of 16 successfully microinjected cells. Additionally, a progressive compartmentalization of the fluorochrome indo‐1, probably in the proplastids and the very abundant endoplasmic reticulu

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00221.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryYoung plants ofPhaseolusandCanavaliawere grown in nutrient solutions where calcium had been partially or totally replaced by either strontium or sodium. The deleterious effect of this replacement on growth and development was greater with strontium than with sodium. As the calcium content of the nutrient solution was decreased fewer calcium oxalate crystals were formed in leaf tissues. There were fewer crystals formed when calcium was replaced by strontium than by sodium. Changes in solubility characteristics of the crystals indicated that they had incorporated strontium.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1991.tb00222.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY