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Notes: [Auszug] Monoamine oxidase exists in at least four molecular forms in different areas of the human brain. Variations in their enzymatic properties may have important clinical implications, perhaps reflecting their relative ability to degrade different monoamine substrates in ...

Notes: Seeds of Agropyron repens (L.) Beauv, have little innate dormancy and germinate mainly during autumn, but germination may be delayed by cold, inadequate moisture or deep burial. Seedlings emerged from all viable seeds sown 5 cm deep but from only 4% of those 10 cm deep. Many seeds are viable when green and immature. At Rothamsted, spike emergence and flowering were earlier in 1970 than in 1968 and 1969 but more seeds became viable more rapidly in 1969. Higher temperatures in May and early June in 1970, and after flowering in 1969, probably account for most of these differences. Germination is facilitated by a diurnal alternation of temperature, but more old than young seeds can germinate at a constant temperature.

Notes: Summary. Spikes oi Agropyron repens (L.) Beauv. were collected from field crops (mostly spring barley and winter wheat) in England and Wales near the time of crop harvest. Seeds per spike were counted and their germination tested in soil in the glasshouse.About 95% of the samples contained viable seeds; about one third of the samples had fewer than 5 viable seeds/spike, a third between 6 and 15 and a third more than 15. The average number of viable seeds/spike for all samples was 13. Spikes from spring barley (152 samples) had an average of 11 and a maximum of 51 viable seeds and those from winter wheat (42 samples), 20 and 48 respectively. Samples collected within 3 weeks after mid-July had fewer viable seeds/spike than those collected later. Samples containing morphologically-different spikes had more viable seeds/spike than apparently uniform samples, and spikes from dense field populations more seeds than those from sparse populations.

Notes: Summary. Small plots of Agropyron repens (L.) Beauv, were shaded with ‘Tygan’ screening fabric which transmitted approximately 46% of daylight. In 1968, plots were either shaded or unshaded throughout the experiment (from mid-May until September) and in 1969, some plots were also shaded early (mid-May to mid-July) or late (mid-July to September). In both experiments continuous shading halved rhizome dry weight but had a much smaller effect on shoot dry weight. It also decreased rhizome dry matter by 5%. With early shading there were fewer shoots and ears until mid-July but this difference disappeared by September, because plants shaded early produced more shoots and ears after mid-July than unshaded plants. Early shading slightly decreased the final percentage of shoots that developed ears. Early shading increased shoot height by mid-July and late shading increased it by the end of the experiment. Effets de la diminution de l'intensié lumineuse sur la croissance de l'Agropyron repens (L.) Beauv, au champ Résumé. De petites parcelles d'Agropyron repens (L.) Beauv. ont été ombragiés avec du ‘Tygan’écran en treillis qui ne laisse passer que 46% environ de la lumère du jour. En 1968, les parcelles furent ombragées ou non pendant toute la durée de l'expérience (de mi-mai à septembre); en 1969 certaines parcelles furent aussi ombragées précocement (de mi-mai à mi-julliet) ou tardivement (de mi-jmllet à septembre). Dans les deux expériences, l'ombrage continu réduisit de moitié le poids sec des rhizomes mais eut un effet beaucoup plus faible sur le poids sec de la partie aérienne. II réduisit également de 5% la matière sèche des rhizomes. Avec un ombrage précoce, il y eut moins de tiges et d'épis jusquà mi-juillet, mais cette différence n'existait plus en septembre paree que les plantes ombragées précocement produisirent après la mi-juillet, plus de tiges et d'épis que les plantes non ombragées. L'ombrage précoce diminua le pourcentage final des tiges qui produisirent des épis. L'ombrage précoce augmenta la hauteur des tiges à la mi-juillet et l'ombrage tardif eut le même effet à la fin de I'expérience. Auswirkungen verringerter Lichtintensität auf das Wachstum von Agropyron repens (L.) Beauv. Im FeldZusammenfassung. Kleine Parzellen mit Agropyron repens (L.) Beauv. wurden mit ‘Tygan’ Abschirmmaterial, das etwa 46% des Tageslichts durchliess, beschattet. Im Jahre 1968 wurden die Parzellen während der gesamten Versuchadauer (von Mitte Mai bis September) entweder beschattet oder nicht beschattet; 1969 wurden auch einige Parzellen früh (von Mitte Mai bis Mitte Juli) oder spät (von Mittc Juli bis September) beschattet. In beiden Experimenten reduzierte durchgehende Beschattung das Rhizom-trockengewicht um die Hälfte, hatte jedoch eine weit geringere Auswirkung auf das Trockengewicht der oberirdischen Teile. Die Rhizomtrockensubstanz war um 5% vermindert, Bei früher Beschattung würden bis Mitte Juli weniger Schosse und Ahren gebildet; dieser Unterschied war jedoch bis September wieder verschwunden, da beschattete Pflanzen ab Mitte Juli mehr Schosse und Ähren produzierten als unbeschattete. Frühe Besehattung führte zu einer leiehten Verringerung des Prozentsatzes der Schosse, die Ähren bildeten. Die Länge der Sehosse war Mitte Juli durch frühe Beschattung vergrössert und am Ende des Experiments durch späte Besehattung.

Notes: Summary. The growth of seedlings of Agropyron repens (L.) Beauv. and Agrostis gigantea Roth, in pots was studied in two experiments in 1968 and 1969. In Experiment 1 their growth was compared with that of wheat and in Experiment 2 they were grown in sandy loam (Woburn) and silt loam (Rothamsted) soil at four levels of nitrogen.Both species grew faster than wheat, mainly because they had a larger leaf area ratio. Tillering began earlier in wheat, but continued longer in the grasses, which eventually had many more shoots. Ears emerged in the order: wheat before Agropyron before Agrostis. Although Agrostis had much lighter seeds than Agropyron, it grew faster, but Agropyron initiated rhizomes sooner, usually when it had 1–2 tillers and 4 leaves. Agrostis did not initiate rhizomes until it had at least 10 tillers and 6 leaves. In Experiment 2 the seedlings at first grew more in Woburn than in Rothamsted soil but later more in Rothamsted than in Woburn soil. There was no evidence of a species/soil interaction but nitrogen had more effect on both species in Woburn than in Rothamsted soil. Neither soil type nor nitrogen affected the time at which rhizomes were initiated.Etude de la croissance de plantules d'Agropyron repens (L.) Beauv. et d'Agrostis gigantea Roth.Résumé. La croissance de plantules A'Agropyron repens (L.) Beauv. et d'Agrostis gigantea Roth, cultivdes en pots a étéétudiée au cours de deux expériences en 1968 et 1969. Dans la premiére experience, leur croissance fut compareée à celle du blé et dans une seconde experiénce, ces deux espéces furent cultivées sur un sol sablo-limoneux (Woburn) et sur un sol argilo-limoneux (Rothamsted) á quatre niveaux d'azote.Les deux mauvaises herbes poussérent plus vite que le blé, principalement en raison de leur rapport plus éalevé de surface foliaire. Le tallage commenga plus tot chez le bié, mais se poursuivit plus longtemps chez les deux mauvaises herbes qui, en fin de compte, eurent plus de tiges. L'épiaison se produisit dans l'ordre suivant: bléa, Agropyron, Agrostis. Bien que I'Agrostis ait des semences plus petites que I'Agropyron, il poussa plus vite, mais I'Agropyron émit des rhizomes plus tôt, habituellement au stade 1 à 2 talles et 4 feuilles. L'Agrostis n'émit pas de rhizome avant d'atteindre au moins le stade 10 talles et 6 feuilles. Dans la deuxième experience, les plantules poussérent d'abord plus dans le sol de Woburn que dans celui de Rothamsted mais, plus tard, plus dans le sol de Rothamsted que dans Celui de Woburn. II ne fut pas décelé d'interaction entre le sol et les espéces, mais I'azote fit un effet plus marqué sur les deux espéces dans le sol de Woburn que dans celui de Rothamsted. Ni le type de sol, ni le niveau d'azote n'eurent d'influence sur l'époque à laquelle les rhizomes commencérent de croître.Untersuchungen zum Wachstum von Keirnpjlanzen von Agropyron repens (L.) Beauv. Und Agrostis gigantea Roih.Zusammenfassung. Das Wachstum von Keimpfianzen von Agropyron repens (L.) Beauv. und Agrostis gigantea Roth, in Töpfen wurde 1968 und 1969 in zwei Versuchen untersucht. In Versuch II wurde das Wachstum mit dem von Weizen verglichen. In Versuch II wurden sie in sandigen Lehmboden (Woburn) und Silt-Lehm-(Rothamsted) Boden bei vier Stickstoffstufen angezogen.Beide Arten wuchsen in erster Linie wegen ihres grösseren Blattflächenanteils schneller als Weizen. Die Bestockung begann fruher bei Weizen, zog sich jedoch bei den Gräsern, die schliesslich wesentlich mehr Halme hatten, langer hin. Ahrenschieben erfolgte am frühesten bei Weizen, dann bei Agropyron und schliesslich bei Agrostis. Obgleich Agrostis viel leichtere Samen hatte als Agropyron, wuchs es schneller, doch entwickelte Agropyron fruher Rhizome, nornialerweise bei 1–2 Bestockungstriebe und 4 Blättern. Agrostis entwickelte Rhizome nicht ehe es mindestens 10 Bestockungstriebe und 6 Blätter hatte. In Versuch II wuchsen die Keimpflanzen zunächst besser in Woburn- als in Rothamsted-Boden, später wieder besser in Rothamsted als in Woburn-Boden. Es gab keine Anhalts-punkte für eine Interaktion zwisehen den Arten und dem Boden, doch wirkte Stickstoff bei beiden Arten besser in Woburn- als in Rothamsted-Boden. Weder Bodentyp noch Stickstoffmenge beeinflussten den Beginn der Rhizombfldung.

Notes: Summary. The growth of Agropyron repens seedlings, or of clones derived from them, raised from seeds collected from different areas was compared; the growth of seedlings raised from seeds from single spikes and from seeds of a cross of two clones was also compared.The number and length of shoots and the amount of rhizome produced differed between seedlings from different areas. Seedlings with a large weight of rhizomes often had a small weight of shoots. Many of the differences found between seedlings from different areas were confirmed by comparing clones established from some of them. Comparisons of both seedlings and clones showed that the percentage of shoots that developed spikes differed between genotypes; clones with the least weight of rhizome tended to have most weight of spikes. Large variations also occurred between clones established from seedlings from a given area, particularly in the way their dry weight was partitioned between primary and secondary shoots and in the time the spikes emerged.The amount of rhizome per seedling varied greatly between seedlings from seeds from single spikes and from seeds from a cross of two clones. There was some evidence of a negative correlation between per cent shoot and per cent rhizome dry weight with seedlings from single spikes and between number of shoots and number of rhizomes per seedling with seedlings from a cross of two clones. Variation en croissance de plantules issues de semences et de clones d' Agropyron repens (L) Beauv.

Notes: Summary. Seedlings and plants derived from single-node rhizome fragments of Agropyron repens and Agrostis gigantea were grown in au unheated glasshouse, separately or together with wheat (cv. Kolibri), in sandy loam soil in well-spaced pots, adequately watered and moderately fertilized. Samples of crop and weeds were taken for growth analysis in mid- May, late June and early August (when the wheat was ripe).On average, wheat decreased the weight of weed shoots by 84% and of rhizomes by 77%, but the weeds decreased the weight of wheat shoots by only 7% and of grain by 13%. Without wheat, seedlings of both weed species had, by late June, grown as much as plants from rhizomes, but with wheat, the weed seedlings were throughout most of the experiment more susceptible to competition than were plants from rhizomes. There was no simple relationship between the final dry weights of the weeds and the amount they decreased wheat yield: although Agropyron seedlings in competition with wheat were much lighter than Agrostis from rhizomes, they decreased grain yield of wheat as much, suggesting that they competed more intensely for a limiting factor, possibly nitrogen.It is concluded that the faster initial growth rate of wheat seedlings relative to the weeds from rhizomes and a larger initial seed reserve relative to the weed seedlings enabled the wheat to dominate the weeds. Comparaison de la croissance et comportement compétitif de plantules et de plantes issues de rhizomes d'Agropyron repens (L.) Beauv. et d' Agrostis gigantea Roth

Notes: Summary. To assess the role of seed production and seedling behaviour in the biology of the perennial grass weed Agrostis gigantea Roth, seed germination and seedling emergence of the species were investigated in the glasshouse and in the laboratory. These studies showed that the species may produce a large number of seeds: panicles collected from a cereal field in 1971 and 1972 contained about a thousand viable seeds in both years. Mature seeds of the species are mostly non-dormant and germinate readily on moist soil surfaces. Freshly-harvested seeds require light and alternating tempratures for germination, but older seeds can germinate in constant temparature in the dark. Covering seeds with 0·6 cm soil halved the percentage emergence and few seedlings emerged from seeds sown deeper than 3±8 cm, but many seeds survived under enforced dormancy. A. gigantea seeds may also persist long in frequently cultivated shallow soil. The species flowers late but its seeds become viable quickly—in 1969 a third of the number that were finally viable became so within a week of flowering. Germination des semenes d' Agrostis gigantean Roth.

Notes: Summary. Seeding of Agropyron repens (L.) Beauv. und Agrostis gigantea Roth were grown in two photoperiods and with amounts of nitrogen. On two occasions plants transferred between photoperiods.The early growth of the seedlings was increased most by increasing the light intensity, but later nitrogen had the greatest effect. In short photoperiods, plants of both species were decumbent and had many more shoots than in long photoperiods. At the end of the experiment, plants of both species responded more to nitrogen in bright than in dim light, and the dry weight of Agropyron was increased more than that of Agrostis by increased photoperiod and nitrogen. Agropyron initiated rhizomes sooner than Agrostis; it had fewer rhizomes but they were longer and thicker and weighed more. Brighter light, longer photoperiod and nitrogen all increased rhizome weight. Photoperiod did this mainly by producing more rhizomes, light by increasing thickness or density, and nitrogen by both. The effects of photoperiod and nitrogen on the rhizome dry weight of Agropyron, but not of Agrostis, were additive.Transferring plants from short to long photoperiods or from long to short, respectively increased or decreased total growth, but had an opposite effect on the rhizomes.