The following developments were apparent:
- 1.
The outer shore zone changed from a Cakile -dominated vegetation to a sparse and less diverse vegetation.
- 2.
The inner shore zone maintained spontaneous Ammophila as dominant and developed into a mobile dune with changing species.
- 3.
The outer dune slope with planted Ammophila developed into a mobile dune dominated by vigorous Ammophila.
- 4.
The dune zone with planted Ammophila: The outer part developed towards a somewhat fixed dune with increasing diversity. The inner part developed into a diverse and more fixed dune community with mainly Festuca rubra.
- 5.
The inner dune slope developed into a vegetation comprising few species.
- 1.
The grassland zone, initially sown with Festuca rubra and Lolium perenne , changed into a grass-herb-vegetation dominated by Festuca rubra , with a slowly increasing number of immigrating species, changing from annuals to perennials, in particular species of Fabaceae and Hippophaë.
- (1)
Using nested analysis of variance techniques, statistically significant variation was detected between species for several of the flight parameters measured: mean angular velocity; pronation/supination ratio; upstroke/downstroke ratio; and wing beat frequency. In each case this is discussed in terms of variation in flight behaviour.
- (2)
Beneficial aerodynamic forces are generated during the upstroke and the downstroke, in both fast forward and rising flight.
- (3).
When the insects change from level, forward flight to near vertical, rising flight, the following parameters are altered in most of the sequences analysed:
- (a).
the stroke plane angle becomes steeply, negatively inclined, associated with an increase in body angle;
- (b).
the stroke amplitude is reduced;
- (c).
wing beat frequency is lowered, associated with a drop in mean angular velocity;
- (d).
the speed of stroke reversal (rotational velocity) is increased. This may be associated with increased wing torsion and tip flexion which in turn could improve any beneficial unsteady aerodynamic effects generated at stroke reversal.
The reasons for this change in flight performance and the deviations from that seen in other insects are discussed.
It is shown that Heteroptera may make use of wing drag in flight, particularly during rising flight. 相似文献
- 1.
Some growth substances such as vitamins slightly promote the geotropic response of germinating spores in darkness.
- 2.
Glucose, even in concentrations as low as 10 mg./L, strongly stimulates the geotropic response.
- 3.
Light (at an intensity of 1000 lux and more) strongly inhibits the geotropic response. This effect is probably phototonic and can be partly counteracted by glucose.
- 4.
The nature of the phototropic and geotropic reactions of chloronema is variable, and depends to a certain extent on environmental influences.
- (1)
That both substances are involved in an oscillatory process induced by nerve stimulation.
- (2)
Both substances are present in synaptic vesicles; the size of the bound pool of ACh is Ca
2 -dependent and is large when Ca2+ is low. Free ACh and transmission are restored when Ca2+ is present in the incubation medium. - (3)
The amount of ATP in the tissue is also Ca
2+ -dependent but is low when Ca2+ is omitted. The addition of Ca2+ to the physiological medium restores the amount of ATP in the tissue. - (4)
There is a postsynaptic release of ATP triggered by transmitter depolarization. This release was measured after single nerve impulses.
- (5)
When added to the incubation medium, nucleotides strongly inhibit transmitter release. It is suggested that the postsynaptic release of ATP regulates transmitter release.
- (1)
Chitinolytic enzyme of high activity is present in enzyme solutions from the stomach contents, gastric mucosa and intestinal contents.
- (2)
Lower chitinase activities are found in samples of the intestinal mucosa and the pyloric caeca.
- (3)
The optimum pH ranges for the action of the enzymes in the stomach and the intestine differ: 4.5–5.1 and 5.1–6.5, respectively.
- (4)
The role of chitin-decomposing bacteria is discussed, based on bacterial numbers and pH conditions in the digestive tract. The existence of two different enzyme systems is indicated.
The following procedure was developed to suppress dormancy and to induce uniform germination:
- 1.
Imbibition of the seeds and moist treatment at 20°C for 2–3 months;
- 2.
stratification for 3 months;
- 3.
treatment at low temperature and low water potential for at least 4 months, this treatment should not exceed 6 months;
- 4.
complete rehydration of the seeds at 16°C.
- 1.
Implantation of the blastocyst into the uterine wall triggers a rapid loss of hyaluronan from the extracellular matrix of decidual cells on the anti-mesometrial side of the uterus.
- 2.
Hyaluronan appears early in development in the yolk cavity, and the basement membranes of primitive ectoderm and primitive endoderm.
- 3.
During gastrulation, mesodermal cells enter a hyaluronan-rich environment, but lack a pericellular hyaluronan coat themselves.
- 4.
In limb bud embryos, hyaluronan is present throughout the cranial mesenchyme, but is generally not present in the branchial bars, somites, or limb buds.
- 5.
At mid-gestation, hyaluronan is present in the axial skeleton, craniofacial mesenchyme, endocardial cushions of the heart, smooth muscle of the gastrointestinal tract, and connective tissue throughout the body.
The pattern of hyaluronan expression in the day 13 fetus is nearly identical to the published distribution of transforming growth factor β (TGF β ), suggesting a close functional relationship between these molecules. Together, the results suggest that hyaluronan is involved in the formation of early mesoderm, differentiation of craniofacial mesenchyme, and morphogenesis of the axial skeleton. 相似文献
- (1)
A reduction in mean stock densities for Bagrus docmac, Clarias mossambicus, Haplochromis spp., Protopterus aethiopicus, Schilbe mystus and Synodontis spp.
- (2)
An increase in mean stock densities for Lates niloticus, Tilapia nilotica and T. variabilis .
- (3)
No change in mean stock density for Labeo victorianus .
- (4)
No T. esculenta or Mormyrus kannume collected in 1977.
- (1)
A reduction in mean total catch rates at all seven depth intervals from 1970–1976.
- (2)
Reductions of 6.8, 6.1, 3.9, 6.2, 1.5, 2.9 and 5.9 times from shallow to deepest 10m depths respectively.
- (3)
No Tilapiu esculenfu were collected in 1976.
The trend that emerges shows a marked reduction in mean total trawl catch rates in the Kenya waters of Lake Victoria which should sound a note of caution for proponents of a mechanized fishing industry. 相似文献
- 1.
Competition experiments between
125 I-insulin (1 nM) and an excess of native insulin (30 μM) indicate a specific hormone fixation to membrane crude extracts from unfertilized and fertilized eggs. The magnitude of "specific binding'is comparable to values recorded for mammalian cells. - 2.
Inhibition of insulin fixation by concanavalin A (100 μg/ml) suggests the glycoprotein composition of plasma membrane receptors.
- 3.
A 30-min incubation of unfertilized and fertilized eggs in the presence of insulin leads to a significant increase in cyclic AMP content.
- 4.
An immunocytochemical method demonstrates that insulin is selectively and specifically bound to the plasma membrane of eggs incubated in the presence of insulin before fixation.
It can be concluded that insulin receptor sites are components of sea urchin eggs plasma membrane. Insulin binding which leads to cyclic AMP accumulation is not deeply modified by fertilization and does not induce visible morphological changes in the eggs. 相似文献
- –
with a continuous reproductive period from spring to autumn,
- –
with several variable breeding periods, part of the population overwintering as adults, part as larvae,
- –
with a breeding period that begins facultatively in autumn and continues the next spring,
- –
with a winter reproduction.
Comparison of life cycles in Scandinavia and In Belgium also shows their variability in relation to climate. More flexible and varied cycles are made possible by the milder winters further south. Existing classifications of life cycles of carabids appear unable to account for such a diversity and variability. 相似文献
- •
High rainfall at 3000 m altitude on Mount Kenya was expected to accelerate dung pile decay but no significant difference was found between 3000 and 2500 m where less rain falls, possibly because high rainfall at 3000 m is counteracted by lower temperatures;
- •
Physical obstacles make it difficult to walk long, straight transects in Montane forests. Deviating from a straight line pushes the distribution of distance measurements from dung piles to the transect centre line (pdist) towards a negative exponential (NE), which complicates data analysis and may give inaccurate estimates. Using short transects largely alleviate this problem;
- •
Analysis of dung count simulations shows that the expected sightability curve of pdist pushes towards a NE with increasing numbers of obstacles blocking the view, even along perfectly straight transects;
- •
Extrapolating measured dung density to map area on Mount Kenya resulted in an underestimate of c. 13%. An unstratified correction of map area to ground area for Montane areas would be biased because of the strong tendency for elephants to avoid steeply sloping areas.
- –
a Pseudochermes fraxini (Homoptera) community found on Fraxinus during the summer, and "trophically" different from others;
- –
a Vertagopus arborea (Collembola) community observed in foliose lichens in St. Mard mainly in winter.
The three other classes are directly related to the epiphytic cover, viz.
- –
a Dometorina plantivaga (Oribatida) community found in crustose epiphytes;
- –
an Eueremaeus oblongus/Trichoribates trimaculatus (Oribatida) community sheltered by foliose lichens;
- –
an Entomobrya nivalis (Collembola)/Cerobasis guestfalicus (Psocoptera) community observed in fruticose lichens.
The ecological meaning of those microcommunities (mosaic and stratification patterns, seasonal variation, succession) is discussed. The results support the hypothesis that corticolous microcoenoses are associated with the epiphyte type and that their composition is greatly affected by the vegetation stratification pattern on bark. 相似文献
- 1.
It is the result of successive loading of the concentric root cell layers centripetally from the epidermis.
- 2.
It is the result of successive loading of the root basipetally from the apex.
- 3.
It is the result of induction of the mechanism(s) responsible for upward translocation.
All three hypotheses are rejected. Within the whole root radial as well as longitudinal equilibration appears to be very rapid. The simple model of compartmentation is rejected. A more complex compartmentation of the cytoplasm (symplasm) in which the endopiasmic reticulum could play a predominant role is suggested. The mechanisms of vacuolar accumulation and upward translocation appear biochemically related. 相似文献
- 1.
Good progress has been made in bringing the importance of high-nature-conservation-value farming systems to the attention of a wider audience. However, simply having a broad appreciation of which farming systems are good for certain species or species assemblages is of little use without a detailed understanding of how each particular farming system functions and integrates with the species reliant upon that system as a whole.
- 2.
Many species have intimate and complex interactions with the annual farming cycle, and their presence on any one piece of farmland is determined not only by the farm management occurring at that time but also by the management practised over the previous weeks and months. Since their exact farm management requirements are not fully understood, it would currently be difficult (if not impossible) to put in place the exact set of conditions necessary to ensure the continued occurrence of many desired species.
- 3.
Consequently, a detailed understanding of the ecological relationships involved is essential before advice can be provided on how best to develop any individual farming system (and the associated policies) so that the ecological characteristics of the system of value to the wildlife assemblages are maintained.
- 4.
These issues are highlighted and illustrated with reference to the findings from research into the ecology and requirements of the chough Pyrrhocorax pyrrhocorax and the effects of farm management practices on ground beetles (Coleoptera: Carabidae) and leatherjackets (Diptera: Tipulidae), which together can form important prey items for birds associated with grassland habitats.
Nevertheless, the experiments presented here indicate that TPP
- 1.
Much of the incorporated TPP
+ -14 C could not be exchanged against unlabelled TPP+ . - 2.
The uptake of TPP
+ -14 C was very slow and exhibited complex rather than simple saturation kinetics. - 3.
A large adsorption of TPP
+ -14 C took place even after the cells were killed; the adsorption by living cells was only 20–60% higher than with killed cells. Furthermore, the adsorption by killed cells showed kinetics similar to living cells.
- 1
The extent of protochlorophyllide reduction in vivo was rapidly reduced as a function of the preillumination period. In 24 h preilluminated plants only a small fraction of the radioactively labelled protochlorophyllide was reduced during the subsequent light period.
- 2
The amount of NADPH-protochlorophyllide oxidoreductase (EC 1.6.99.-) present in plastids of fully-green plants was drastically reduced relative to levels in plastids of dark-grown plants as estimated by the methods of immunoblotting of plastid proteins and immunogold labelling of ultrathin sections of the leaf tissue.
- 3
In etiolated plants light seemed to affect the reduction of protochlorophyllide directly through the excitation of protochlorophyllide. In fully green plants, however, light also affected chlorophyll formation indirectly by the supply of NADPH via photosynthetic electron transport.
- (I)
Cell wall consisting of a peptidoglycanlayer
- (II)
Two-layered cell wall consisting of a peptidoglycan-layer and an S-layer
- (III)
Three-layered cell wall consisting of a peptidoglycan-layer and two S-layers
Group I and group II cell walls have not been described yet for protein-producing bacteria. The S-layers observed in this study all had hexagonal symmetry and lattice constants of approximately 18 nm. The immunological relation between the S-layer proteins of the newly isolated B. brevis strains and those of B. brevis 47 has been examined using antisera against both S-layer-proteins of B. brevis 47. S-layers from protein-producing B. brevis strains, which were adjacent to the peptidoglycan-layer, were similar to each other, whether they were the outermost cell wall layer (group II) or not (group III). However, no similarity was found between these layers and the outermost S-layer of B. brevis 47 (group III). 相似文献
- i.
transport of H
2 CO3 by diffusion - ii.
transport of CO
2 by diffusion; or - iii.
co-transport of HCO
3 and H+ .
The decision amongst these mechanisms is not yet possible. There are parallels between the charophytes and aquatic angiosperms that are indicated, and contrasts with the chlorophytes. 相似文献