Library

Notes: Summary During a treatment that lasted approximately 100 days beginning at fledging time, four groups of pigeons were kept for ten 3-day periods in an aviary of wire-netting located in Arnino. Here they could acquire a visual experience of the landmarks and leave for exercise flights. During these 3-day sojourns, the birds wore masks which prevented or limited their breathing through the nostrils. For the remaining time the pigeons were unmasked and closed in four cages outdoors that prevented them from seeing the country-side. The cages were of two types, ones with walls of horizontal strips that allowed the flow of air (pervious cages) and ones with vertical walls impervious to air currents (impervious cages). The four groups were kept under different conditions: 1) RP-birds were kept in a pervious cage in Arnino; 2) RI-birds, in an impervious cage in Arnino; 3) CP-birds, in a pervious cage in Miemo, 42 km SW of Arnino; 4) CI-birds, in an impervious cage in Miemo. The results of the test releases, carried out in a location 24.5 km SW of Arnino and 17.8 km NE of Miemo were the following: 1) The RP-birds were home oriented, all returning to Arnino; 2) the RI-birds were erroneously oriented towards SW, 20 out of 24 returning to Arnino but more slowly than the RP-birds with 4 lost; 3) the CP-birds were oriented towards the site of the cage (Miemo), 4 returning to Arnino, 5 to Miemo with 8 lost; 4) the CI-birds are oriented at random, 5 returning to Arnino with 8 lost. The results indicate that the initial orientation is correct only in pigeons which have been exposed to winds with their nostrils free. They can return to their cage even if they have no visual experience of the surroundings. However, return to a location where the pigeons had visual experience but no olfactory experience is also possible.

Notes: Summary From fledging time, two groups of homing pigeons were protected for most of the time from wind exposure. Instead, they were subjected to artificial odorous winds. One of the two groups was subjected to an odorous wind of olive oil from the S and an odorous wind of a solvents' mixture (“synthetic turpentine”) from the N. The other group underwent the opposite treatment (odorous wind of olive oil from the N and odorous wind of synthetic turpentine from the S). The birds of the first group, released from two points 21.0 and 26.5 km W of the aviary flew in a northerly direction when olive oil was applied to their nostrils and in a southerly direction when synthetic turpentine was applied. Under the same conditions, the birds of the second group flew in the opposite directions. These results support the olfaction hypothesis of pigeon navigation (Papiet al., 1972).

Notes: Summary From fledging time up to the test releases, two groups of experimental pigeons were housed in two cubic cages supplied with deflectors which deviated the winds through to the inside approximately 70° clockwise (CW-birds) or counter-clockwise (CCW-birds). Test releases were made at 9.0, 23.5, and 105.3 km from the loft. With respect to that of control birds, the mean bearing of CW-birds was always deflected clockwise, and that of CCW-birds was always deflected counter-clockwise. Control birds performed better than CW-birds in homing from the first release site, and better than both experimental groups from the second release site. These results agree with the olfactory hypothesis of pigeon navigation (Papiet al., 1972).

Notes: Summary Beginning from fledging time up to the time of homing experiments, 33 experimental pigeons were kept alternatively for three days in a wire-netting aviary which they could leave for spontaneous flights (O-aviary), and for three days in a closed aviary fenced with plastic sheeting (C-aviary). In the O-aviary they wore masks which prevented or limited their breathing through the nostrils. As controls, 31 birds were kept for three days in the O-aviary without masks and for three days in the C-aviary wearing masks. In eight releases from places situated between 10 and 61 km from the aviary, the experimental birds gave worse homing performances than the control birds. Besides, contrary to the control birds, the initial orientation is mostly either wrong or at random in the experimental ones. These results support the hypothesis of olfactory navigation (Papiet al., 1972), which supposes that the pigeons, during their first months of life, gather information on smells prevailing in surrounding regions through the winds.

Notes: Summary A number of studies have demonstrated the pivotal role of collagen molecules in modulating cell growth and differentiation. In order to analyze the direct effects of collagen type I on the osteoblastic phenotype, we have devised an in vitro culture system for studying the interactions between bovine collagen type I and Saos-2 cells, a human osteoblastic cell line. Saos-2 cells were cultured both on top of collagen-coated culture dishes as well as inside a three-dimensional collagen network. Plating on dishes treated with collagen induced maximal adhesion of Saos-2 cells after 24-hour incubation. Cells cultured on collagen gel matrix expressed about 2.5-fold more alkaline phosphatase when compared with untreated plastic dishes. On collagen-coated dishes the responsiveness of Saos-2 cells to parathyroid hormone was decreased, whereas no modifications were observed in the effect of vasoactive intestinal peptide on these cells. Using a microfluorimetric measurement of DNA, an increase of proliferation was observed in Saos-2 cells cultured on collagen gel Saos-2 cells were also able to colonize collagen sponges and in this three-dimensional network they were able to synthesize osteocalcin, as assessed both by immunocytochemistry and radioimmunoassay. In this study we have demonstrated that bovine collagen type I exhibits favorable effects on attachment and functional and growth activities of a human osteoblastic cell line, encouraging its use as a bone graft material.

Notes: Relations between availability of light and reproductive activity in several of the most damaging summer weeds (Abutilon theophrasti Medicus, Datura stramonium L., Sorghum halepense L. Pers.) were studied, in order to investigate seed production capacity of these weed species in the unfavourable conditions occurring under a crop canopy simulated by shade cloths. Decrease in seed production under shading appeared to be due to a decrease in the number of fruits per plant, while the quantity of seed per fruit proved to be fairly stable. Biomass partitioning within the plant reduced the percentage of dry matter accumulated in reproductive organs, leading to a marked decrease in the harvest index. Further-more, shading caused a species-dependent delay in onset of the flowering and ripening stages. In Datura stramonium shading led to a greater de-crease in seed production and, consequently, in the harvest index than in the other species examined. Finally, laboratory tests demonstrated that the percentage of dormant seeds remained unmodified in all species examined. Effet de l'ombragesur la reproduction et quelques caracteristiques morphologiques de Abutilon theophrasti Medicus, Datura stramonium E. et Sorghum halepense L. Pers. Les relations entre la fourniture de lumière et l'activité reproductrice de quelques unes des mauvaises herbes les plus importantes (Abutilon tiieophrasti Medicus, Datura stramonium L., Sorghum halepense L. Pers.) ont étéétudiées en vue de déterminer leur capacitéà produire des graines dans les conditions défavorables qui prévalent sous les couverts végétaux. La diminution de la production de graines était due à une diminution du nombre de fruit par plante, alors que la quantité de graines par fruits restait à peu près stable. La distribution de la biomasse dans la plante conduisait à une diminution du pour-centage de matière seche accumulée dans les organes reproducteurs, ce qui se traduisait par une diminution de l'indice de récolte. De plus, l'ombrage causait un retard (variable selon l'espece) du début de la floraison et de la maturation. Chez Datura stramonium, l'ombrage conduisait à la réduction la plus importante de la production de graines (et par conséquent de l'indice de récolte). Enfin, des tests en laboratoire ont montré que le pourcentage de graines dormantes n'était modifie chez aucune des espèces testées. Einfluß von Beschattung auf Vermehrung und morphologische Eigenschaften von Abutilon theophrasti Medicus, Datura stramonium E. und Sorghum halepense (E.) Pers. An einigen sommerannuellen Unkräutem (Abutilon theophrasti Medicus, Datura stramonium L. und Sorghum halepense (L.) Pers.) wurde die Beziehung zwischen der Lichtverfügbarkeit und der Samenproduktion dieser Arten unter den ungünstigen Bedingungen der Beschattung in einem Kulturpflanzenbestand, die durch Beschattungsgewebe simuliert wurde, untersucht. Die Abnahme der Samenproduktion bei Beschattung ist durch die geringere Fruchtzahl pro Pflanze bedingt; die Samenzahl pro Frucht erwies sich als ziemlich stabil. Die Biomasseverteilung in den Pflanzen führte zu einer Abnahme der Trockenmasse der Reproduktionsorgane und damit zu einem deutlich kleineren Ertragsindex. Außerdem wurden durch die Beschattung der Blühbeginn und das Reifestadium verzögert. Bei Datura stramonitim war die Abnahme der Samenbildung und somit des Ertragsindex stärker als bei den anderen Arten. Der Anteil dormanter Samen blieb bei alien Arten durch die Beschattung einbeeinflußt.

Notes: Trials were carried out to investigate the effects of light and temperature on germination of Rumex obtusifolius L. After several months of storage, seeds gradually lost dormancy and became photosensitive. Thermal optima for germination were between 20 °C and 25 °C in light or in darkness. At lower temperatures there was a greater demand for light, so that the greatest differences in germination percentage (between low and high temperatures) were found within the 10–15 °C temperature range. The calculated thermal minima (x-intercept method) in light and darkness were 8.3 °C and 6.1 °C respectively. Daily temperature fluctuation increased germination even after seed irradiation with far-red light, suggesting a lower demand for the far-red-absorbing form of phytochrome. Seed burial inhibited germination in proportion to depth; however, germination inhibition was independent of seed phytochrome photo-equilibrium, which had been diversified by seed pretreatment with light. Seedlings did not emerge when seeds were buried 〉8 cm deep. Recovery of ungerminated seeds showed that excessive burial did not impede seedling emergence but rather prevented seed germination. However, this induction of dormancy was lost once germination processes were activated (24–48 h at 20 °C) that made germination irreversible. Temperature was also involved in inhibition, and low temperature (〈15 °C) induced the least inhibition. This is discussed in terms of processes of respiration and fermentation in buried seeds.

Notes: Trials were carried out in order to investigate the effect of hypoxia on seed germination of Datura stramonium L. in Petri dishes and when buried at various depths in soil. Hypoxia was found to cause a decrease in germination capacity and germination rate. This inhibition was partially alleviated by daily exchange of hypoxic gas surrounding the seeds during incubation. Similarly, seed scarification allowed maintenance of a higher germination capacity under conditions of low oxygen availability, showing that the seed coat was only partially gas permeable. Oxygen deficiency led to a decrease in respiratory capacity. However, this was probably compensated for by induction of fermentation metabolism. The possibility of removing the final products of fermentation exerts a decisive influence on seed germination, especially in an environment such as soil, where their diffusion into the surrounding environment is restricted. Thus daily nitrogen flushing partially eliminated this inhibition, even under conditions of low external oxygen availability. It was therefore postulated that the main depth–derived inhibition was not caused directly by oxygen deficiency but by the increasing difficulty in eliminating toxic fermentation products, which was found to be proportional to the degree of hypoxia. Finally, incubation for several days under completely anaerobic conditions induced secondary dormancy. This was probably due to an ecological adaptation mechanism that prevents germination under conditions that are unfavourable for survival.

Notes: Trials were carried out to study the germination and dormancy of Cuscuta campestris Y. (dodder) seeds and factors influencing the success of early parasitisation of sugarbeet. Primary dormancy can be removed by seed scarification. Germination was negligible at 10°C and optimal at 30°C, while it was not influenced by light. Seed burial induced a cycle of induction and breaking of secondary dormancy. Seedling emergence was inversely proportional to the depth of seed burial and only seed buried within 5 cm of the soil surface emerged. Storage of C. campestris seeds in a laboratory for 12 years resulted in the loss of primary dormancy, enabling the germination of all viable seeds. Host infection (i.e. protrusion of parasite haustoria from host tissue) was heavily influenced by host growth stage. Tropism towards a host was due to the perception of light transmitted by green parts of sugarbeet plants. Insertion of a transparent glass sheet between host leaves and parasite seedlings did not modify this response. This phototropism permitted Cuscuta to identify host plants with high chlorophyll content as a function of the lower red/far red ratio of transmitted light.