Some Aspects of the Growth and Spread of Fire in the Open

This paper describes some recent experimental and theoreticalwork on the growth and spread of fire in the open and discussessome examples of field data in terms of the theoretical calculationspresented. The lengths of flames from laboratory fires have been relatedto the size and rate of burning of the fuel by formulae derivedfrom a simplified dimensional analysis. The effects of a windblowing across a long fuel bed on the length and orientationof flames are also described. The scaling laws for flame heightsuggest that in the horizontal spread of fire, heat transferfrom the flames above the fuel bed is important primarily withshallow fuel beds. It is suggested that the main effect of a wind on crib firesis aerodynamic. The wind deflects the advancing fire front fromthe vertical, but perpendicular to this deflected front therate of spread of fire, at least for cribs, is roughly the sameas in still air. However, a theory of spread allowing for heattransfer through the fuel bed and radiation from the flamespredicts that there can be a stable ‘fast‘ spreadas well as a ‘slow’ spread. In ‘fast’spread the flames are thick and control the spread. In ‘slow’ spread radiant heat transfer from theburning zone is usually responsible for the spread. The flamesare thin and of low emissivity. The most important factors determiningthe rate of ‘slow’ spread R are ^pb the bulk densityof the fuel bed and ø the deflection from the verticalof the front of burning fuel which varies with wind speed. Rpb cos ø is approximately constant over a wide rangeof conditions with an order of magnitude of 5–10 mg cm^–2s^–1.     

Nachteilige Wirkungen eines Herbizids auf Gesundheit und Wuchsleistung von Pappeljungpflanzen

Ohne Zusammenfassung     

Prüfung vonSaco undSaco-Kreuzungen auf Resistenz Gegen das S-virus der Kartoffel

Zusammenfassung Die SorteSaco blieb bei allen Versuchen. das S-Virus mit Safteinreibungen zu übertragen, virusfrei. Nach 6 Wochen dauernden Pfropfungen mit S-haltigen Reisern war das Virus jedoch in zwei von 42 Pflanzen zur Vermehrung gelangt und wurde im Nachbau festgestellt. DieSaco-Resistenz wird als hohe Infektionsresistenz gegen das S-Virus bezeichnet. 204 S?mlinge und Klone der KombinationSaco selbst liessen sich ausnahmslos nicht mit dem S-Virus infizieren, gleichgültig, ob Pfropfungen oder Pressafteinreibungen selbst im jüngsten S?mlingsstadium durchgeführt wurden. Der Nachbau war ebenfalls S-frei. Nach den bisherigen Erfahrungen scheint sich die hohe Infektionsresistenz derSaco auf 100% ihrer Selbstungsnachkommenschaft zu vererben. Nur 10% von 704 pfropfinfizierten Klonen aus zwei verschiedenen Kombinationen derSaco mit S-anf?lligem Material brachten einen ganz oder teilweise S-freien Nachbau. Ihr Resistenzgrad war von dem derSaco nicht zu unterscheiden. 86–88% der Klone hatten ausschliesslich S-haltige Nachbaupflanzen. Bei Einreibung von S-haltigem Pressaft auf 6 Wochen alte Pflanzen der gleichen Kombinationen blieb der Nachbau von 34% der Klone ganz oder teilweise S-frei.

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Summary The American varietySaco is commonly assumed to be S-immune. Several attempts to induce infection by sap inoculation failed. Two out of 42 plants on which S-infected scions had been grafted for 6 weeks each yielded one S-infected tuber out of a total of 3. This indicates thatSaco is highly resistant but not immune to infection. Attempts to infect 202Saco selfs by grafting or sap inoculation failed (Table 1); no virus was detected in the tuber progeny. The high level of resistance inSaco seems, therefore, to be transmitted to 100% of the selfed progeny. Tests were made on two families ofSaco pollinated with S-susceptible Max-Planck-Institute clones (49.540/2 and44.1004/5), which possess other resistance and quality characters rendering them particularly suitable for use in European breeding programmes involvingSaco. The method of testing mainly used is shown in Fig. 1: serological tests were done on mature leaves from shoots which had been subjected for 6 weeks to the effects of S-infected scions below them. In addition, tubers from these plants were grown on and the resulting plants tested serologically. 704 clones of 2 families were grafted but only 564 and 75, respectively, formed tubers. The results of S-tests on the tuber progenies, given in Table 2, show that 86–88% of the clones were readily infected but about 10% produced few or no infected tubers and did not behave significantly differently fromSaco. No results were obtained from about 3% of the clones on account of secondary virus infection, early death etc. Sap inoculation of 110 six-week-old F₁ plants produced 36 plants with S-free or partially S-free tuber progenies (Table 3). Sap inoculation of very young seedlings produced only 7.9% healthy plants. We can conclude from the relatively poor transmission of S-resistance to F₁ progenies thatSaco is not an ideal source. The 34% of resistant or partially resistant plants selected by sap inoculation may, however, allow the production of a reasonable amount of breeding material with adequate resistance under field conditions. Howeyer, the faults, agronomic and otherwise, of the F₁ clones suggest that a second breeding step is necessary, i.e.Saco F₁.

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Résumé La variété américaineSaco est réputée être immune au virus S. Nous aussi n’avons trouvé aucune infection par virus S dans différents essais par inoculation de jus, mais à la suite de greffe de scions malades de S durant 6 semaines, deux plantesSaco récoltées étaient infectées de S sur un total de 42 plantes testées. Chacune de ces deux plantes produisaient trois tubercules dont un était infecté, les deux autres étaient libres de S. II résulte de cette expérience que le type de résistance deSaco est la plus haute résistance à l’infection. Les essais d’infection d’autofécondations deSaco par greffes ou transmission de jus ne donnaient aucune multiplication du virus dans 202 plantes (Tableau 1). De même les descendances des tubercules ne montraient pas de virus S. Par conséquent, la haute résistance à l’infection deSaco semble se transmettre à 100% à la descendance autofécondée. Deux familles deSaco pollinisée par des clonesgéniteurs du Max-Planck-Institut (49.540/2 et44.1004/5) furent testées pour la présence du virus S. Ces clones-géniteurs étaient susceptibles au virus S mais possédaient d’autres résistances et des caractères de bonne qualité qui les destinaient à des programmes prometteurs d’amélioration européenne basée surSaco. La technique de test la plus utilisée est montrée dans Fig. 1: des tests sérologiques sont effectués sur des feuilles m?res de branches qui ont poussé durant 6 semaines sous l’influence d’un scion infecté de S placé en-dessous En outre, les tubercules de telles plantes furent plantés et les plantes de la descendance furent également testées sérologiquement. 704 clones des deux familles furent greffés. mais seulement 564 et 75 donnèrent des tubercules. Les résultats de tests S sur les descendances par tubercules sont donnés dans Tableau 2. Coneluant sur la base des descendances par tubercules totalement infectées, 86–88% des clones étaient susceptibles. Environ 10% seulement des clones donnaient des tubercules sains ou quelques tubercules sains. Ces clones étaient catalogués comme hautement ou faiblement résistants et ne montraient aucune diffétence significative avecSaco dans les conditions des essais. Environ 3% des clones ne donnaient aucun résultat à la suite d’infection virologique secondaire, mort précòce, etc. A la suite de la transmission par jus à 110 plantes F₁ à l’age d’environ 6 semaines, 36 plantes donnaient des tubercules totalement ou partiellement libres de virus (Tableau 3). Cependant à la suite de la transmission par jus à de très jeunes plantules, on rècoltait seulement 7,9% de plantes saines. Des résultats relativement pauvres de la transmission de la résistance deSaco à sa descendace F₁ dans des tests de greffe, nous concluons queSaco n’est pas la source idéale de résistance au S dans des programmes d’amélioration. Le taux de quelque 34% de plantes saines à la suite d’inoculation par jus permet néanmoins la production d’une quantité raisonnable de matériel d’amélioration avec résistance suffisante dans les conditions du champ. La faible qualité des clones F₁ semble toutefois exiger une seconde étape d’amélioration, par ex.Saco-F₂.

     

THE EFFECT OF SEVERITY OF DEFOLIATION AND NITROGEN FERTILIZER ON THE GROWTH OF PHALARIS TUBEROSA L.

The responses of Phalaris tuberosa L. to cutting to 1/2- and to 3-in. at 3 levels of nitrogen (0, 23 and 92 lb/ac after each cut) were investigated in two irrigated, small-plot trials. A technique involving the use of sheet-iron borders embedded in the soil to contain root systems, irrigation water and fertilizer was developed. The 3-in. cutting height gave greater dry-matter yields than J in., the difference reaching significance only with applied N. Plant mortality was significantly greater for the 1/2-in. cutting height at each N level. N significantly increased DM yield at both cutting heights, the greatest yield being at the higher application rate. Plant mortality at both cutting heights was significantly reduced by applied N. The results are discussed in relation to the most suitable grazing management for sustained growth of irrigated Phalaris swards.     

THE EFFECT OF CUTTING AND NITROGEN TREATMENTS ON YIELD, PROTEIN CONTENT AND CERTAIN MORPHOLOGICAL CHARACTERISTICS OF TIMOTHY AND SMOOTH BROMEGRASS

Timothy and bromegrass were studied in pure sowings in a glasshouse, and each in a mixture with lucerne, dominated by the grass–fraction in the first crop year, in the field. In the glasshouse both species were cut 3, 5, or 6 times at a 2–in. and 6 times at a 3/4–in. stubble height. In timothy, cutting 6 times gave lower DM but higher protein yields than less frequent cutting. In bromegrass close cutting gave higher DM yields than lax cutting. The following results applied to both species: root weight decreased with increasing severity of defoliation, final tiller density was very low under close cutting, and a complete application of N at the time of sowing was superior to a split application.
In the field, the first cut was taken on 5 dates at intervals of 1 week, the second cut 6 or 8 weeks after the first cut, and the third cut 7 weeks after the second cut (for bromegrass mixture only). DM yield was generally the higher the later the first cut was taken and the longer the subsequent rest period. However, the opposite applied for best sustainment of yield. The 1 1/2–in. stubble treatments outyielded the 3 1/2–in. treatments. Generally, production of CP was influenced more by DM yield than by % content. Reduced removal of tiller primordia in the second cut led to higher third–cut yields, but at the cost of total yield. Difficulties in the control of shoot apex removal encountered in both glasshouse and field are discussed.     

Induction of adventitious buds on roots of the potato

Auxin treatment of de-eyed potato slices induced root formation. When the roots were exposed to light, adventitious buds were formed.This method for bud formation may be used to produce non-chimerical potato mutants, when the buds can be obtained from mutagenically treated tissue. An additional purpose is the investigation of the L₃ of existing mutants.This investigation was supported by the EURATOM-ITAL Association, Wageningen, The Netherlands.     

Entwicklungslinien der forstlichen Meteorologie

Ohne ZusammenfassungErweiterte Fassung der Antrittsvorlesung als Privatdozent an der Ludwig-Maximilians-Universität München am 13. Februar 1967     

Entwicklungslinien der forstlichen Meteorologie

Ohne ZusammenfassungErweiterte Fassung der Antrittsvorlesung als Privatdozent an der Ludwig-Maximilians-Universität München am 13. Februar 1967