Initial establishment of vegetation in a man-made coastal area in Denmark

A man-made coastal area (8 km long, 300 m wide), constructed from seed-free, marine sand was investigated from 1978 to 1983 as regards relief, soil properties, and establishment of vegetation.
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.

     

Comparison of bottom trawl stock densities in the inner Kavirondo Gulf of Lake Victoria

A comparison of mean bottom trawl stock densities (kg ha^-1) from 19 UNDP 1969/70 tows, 69 EAFFRO 1975 tows and 167 fourth quarter FFRI 1977 tows in the inner Kavirondo Gulf of Lake Victoria showed the following changes from 1969/70 to 1977.

• (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.

     

The kinematics of Heteroptera in free flight

The kinematics of six species of Heteroptera in free flight are analysed and compared.

• (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.     

Variations in the geotropic sensitivity of germinating Funaria spores in response to some external influences

Experiments on the germination of the spores of Funaria have established the following.

• 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.

     

Localization of hyaluronan in mouse embryos during implantation, gastrulation and organogenesis

Abstract. Hyaluronan was localized in postimplantation mouse embryos using CD44, the principal hyaluronan receptor. The specificity of CD44 receptor-globulin labelling was confirmed using Streptomyces hyaluronidase, anti-chondroitin sulfate antibody, and other receptor globulins. Our major findings are summarized as follows:

• 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.     

RELATED CHANGES IN AMOUNTS OF ACh AND ATP IN RESTING AND ACTIVE TORPEDO NERVE ELECTROPLAQUE SYNAPSES

Abstract— Closely related changes in the levels of acetylcholine (ACh) and adenosine triphosphate (ATP) in the electric organ of Torpedo exist during rest and synaptic activity. The present work clarifies these relations by showing:

• (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 Ca²-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 Ca²⁺-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.

     

Thoughts on the possible role of phytochrome destruction in phytochrome controlled responses

Abstract. Fluence-response curves for low-energy phytochrome responses show two steps at red light exposures c . two orders of magnitude apart. This Feature of the fluence-response relationship can be interpreted as the consequence of the following processes:

• 1. 

  Induction of a photoresponse by a very low level of Pfr.
• 2. 

  Activation of a Pfr-destroying enzyme above a threshold level of [Pfr].
• 3. 

  Dependency of the rate of Pfr destruction on [Pfr] once the threshold level is reached.

In this way, adaptation of the phytochrome control system to a broad range of light doses could be realized.     

Associations between corticolous microarthropod communities and epiphytic cover on bark

The discontinuous bark cover formed by epiphytic lichens and algae provides a mosaic of microhabitats for the fauna. Multivariate analyses applied to 1800 samples collected in Belgian Lorraine (southern Belgium) during each of the four seasons has made it possible to distinguish five major classes of arthropod microcommunities. Two of them are confined to special habitats or places at certain seasons, viz.

• –

  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.     

Annual activity and life cycles of carabid beetles in two forest communities

The annual activity and life cycles of thirteen species of carabid beetles coexisting in two forests in Belgium were studied by recording above-ground activity of adult and larval populations, and by examining the reproductive condition of adults in the course of the year. The cycles were far more complex and diversified than suggested by previous works. Besides typical "spring breeders" and "autumn breeders", species were found

• –

  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.     

Germination uniformity of Fraxinus excelsior controlled by seed water content during cold treatment

The seeds of Fraxinus excelsior L. are dormant after harvest, since they need a period of chilling for germination. Moist treatment at 20°C for 2–3 months followed by stratification at 4°C for 7 months breaks dormancy. We observed that germination occurred during stratification and was spread over a period of 3 months. Germination at low temperature was temporarily inhibited by a moderate reduction of the seed water content initiated after the third month of stratification. This allowed the afterripening process to continue.
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.

     

Chitinase activity in the digestive tract of the cod, Gadus morhua (L.)

The study was made to determine if enzymatic degradation of chitin occurs in the digestive tract of the cod, Gadus morhua . The method employed corresponds to the end product measurement of Jeuniaux (1966), using 'native' chitin as the substrate. The following results were obtained.

• (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.

     

Insulin Receptor Sites as Membrane Markers during Embryonic Development

Binding of insulin to sea urchin egg plasma membrane has been studied by biochemical and immunocytochemical methods. Unfertilized and fertilized eggs as well as embryos during the first cell division have been used.

• 1. 

  Competition experiments between ¹²⁵I-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.     

A comparison of bottom trawl catch rates in the Kenya waters of Lake Victoria

A comparison of mean trawl catch rates (kg/h) from 128 collections in 1969 and 1970 and 63 collections in the fourth quarter of 1976 showed the following changes.

• (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.     

Counting elephants in Montane forests: some sources of error

The dung count method is widely used to estimate elephant numbers in forests. It was developed in the lowland forests of Central Africa but it is also used in Montane forests in eastern Africa. Using data collected on Mount Kenya and computer simulations, this paper explores the following issues associated with dung surveys in Montane forests:

• • 

  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.

     

The lag-phase of potassium translocation from the root to the shoot of low-salt barley plants. Kinetic and localization studies

In roots of low-salt barley ( Hordeum vulgare L.), translocation of K⁺, as well as of several other ions, from the root to the shoot starts after a lag-time. Its length is independent of external concentration. The onset of upward translocation can be remarkably abrupt. Three hypotheses that could explain the lag-phase were tested:

• 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.     

UDP-Glucose level as a limiting factor for IAA-induced cell elongation in Avena coleoptile segments

The effects of galactose on IAA-induced elongation and endogenous level of UDP-glucose (UDPG) in oat ( Avena sativa L. cv. Victory) coleoptile segments were examined under various growth conditions to see if there was a correlation between the level of UDPG and auxin-induced growth. The following results were obtained:

• (1)

  Galactose (10 m M ) inhibited the auxin-induced cell elongation of oat coleoptile segments after a lag of ca 2 h. Determinations of cell wall polysaccharides and UDP-sugars indicated that galactose, when inhibiting the cell wall polysaccharide synthesis, decreased the level of UDPG but caused an increase in the levels of Gal-1-P and UDP-Gal.
• (2)

  When coleoptile segments treated with IAA and galactose were transferred to galactose-free IAA-solution, the segment elongation was restored and the amounts of cell wall polysaccharides increased. During this period, the amount of UDPG increased and the levels of Gal-1-P and UDP-Gal slightly decreased or leveled off. The UDP-pentoses changed similarly as UDPG did.
• (3)

  Addition of sucrose (30 m M ) enhanced IAA-induced cell elongation and removed growth inhibition by 1 m M galactose. Sucrose increased the amounts of the cell wall polysaccharides and the level of UDPG in the presence or absence of IAA and also counteracted the decrease in UDPG caused by galactose.

These results indicate that the level of UDPG is an important limiting factor for cell wall biosynthesis and, thus, for auxin-induced elongation.     

Applying the results of ecological studies to land-use policies and practices

Summary

• 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.

     

The uptake of inorganic carbon by freshwater plants

Abstract. The uptake of bicarbonate for photosynthetic assimilation by charophyte plants uses a chemiosmotic mechanism involving primary outward active transport of H⁺ in 'acid zones' of the membrane, and passive H⁺ re-entry in spatially separate 'alkaline' zones. In the process large electric currents circulate in the medium, and large local pH changes occur; bicarbonate ions, diffusing inwards across the unstirred layer of medium, encounter a number of competing mechanisms for the transfer of the carbon across the membrane. These are:

• i.

  transport of H₂CO₃ by diffusion
• ii.

  transport of CO₂ by diffusion; or
• iii.

  co-transport of HCO₃ 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.     

Tetraphenylphosphonium (TPP+) is not suitable for the assessment of electrical potentials in Chlorella emersonii

Abstract. For Chlorella emersonii , plausible membrane potentials between –80 and –120 mV were calculated from the distribution of the lipophilic cation tetraphenylphosphonium (TPP⁺) between the cells and the medium. Furthermore, these calculated membrane potentials were influenced in a way expected from the literature, by different metabolic conditions induced by light or dark, anaerobiosis, glucose, and by inhibition or uncoupling of electron transport.
Nevertheless, the experiments presented here indicate that TPP⁺ is unsuitable as a probe for electrical potentials, at least in Chlorella emersonii. The reasons for this conclusion are as follows:

• 1. 

  Much of the incorporated TPP⁺-¹⁴C could not be exchanged against unlabelled TPP⁺.
• 2. 

  The uptake of TPP⁺-¹⁴C was very slow and exhibited complex rather than simple saturation kinetics.
• 3. 

  A large adsorption of TPP⁺-¹⁴C 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.