Experiments on the germination of potato seeds. II

Summary The experiments reported fall into three groups: experiments on techniques of extraction and testing that reveal the maximal germination of which seed is capable; experiments on dormancy; and experiments on longevity. Dormancy is present in various degrees in most fresh potato seeds; it is preserved by dry or cool storage and broken by the application of gibberellic acid. Estimates of longevity vary widely from a few to many years, depending on plant material and storage conditions. A general review of the biology of potato seeds is presented in 4.Discussion.

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Zusammenfassung Einige Kartoffelbeeren (warscheinlich die meisten) sind im Alter von sechs Wochen reif. Samen von jüngeren Beeren zeigen eine herabgesetzte Lebensf?higkeit und eine kürzere Keimruhe-periode (Tab. 1). Mit Hilfe einer Mischmachine k?nnen die Samen auf sichere Art gewonnen werden, wenn auch dabei einige Samenschalen zerbrochen werden. Für Keimversuche eignen sich Petrischalen, die mit feuchtem Filterpapier ausgelegt und unter Licht bei ungef?hr 20 C gehalten werden; Schaumgummi kann ebenfalls verwendet werden, nicht aber Fliesspapier. Kleine Samenk?rner haben eine verminderte Lebensf?higkeit. Bei Samen, die sich nicht mehr im Stadium der Keimruhe befinden, wird die Keimung durch Dunkelheit etwas gehemmt (Abb. 1). Die meisten Kartoffelsamen sind noch im Zustand der Keimruhe, wenn sie aus den Beeren gewonnen werden. Die Keimung von Proben nach vier Wochen ergibt ein umgekehrtes Mass für die Keimruhe, vorausgesetzt dass die Muster wie oben erw?hnt behandelt werden. Die Keimruhe in heterogenen Samenmustern von diploiden und tetraploiden Gew?chsen nahm in 6 Monaten merklich ab, doch verschwand sie auch nach 18 monatiger luftiger Lagerung nicht vollst?ndig (Abb. 2) Bei Versuchen, die Keimruhe zu unterbrechen, blieben verschiedene physikalische Vorbehandlungen wirkungslos; Sch?len war teilweise. Gibberellins?ure sogar sehr wirksam. Gibberellins?ure, in suboptimaler Menge angewendet, erzeugte mit Cystein synergistische Wechselwirkung (Tab. 2, 3 und 6). Licht begünstigt das Heraustreten aus dem Zustand der Keimruhe und hat, zusammen mit chemischen Behandlungen, komplexe Wechsel-wirkungen zur Folge (Tab. 3). Die Aufbewahrung von Samen w?hrend 8 Monate unter kalten oder trockenen Lagerungsbedingungen verz?gert das Erwachen aus dem Ruhezustand, und trockene Lagerung scheint die Keimruhe sogar zu verst?rken (Tab. 4). Das Auswechseln des als Keimmedium gebrauchten Filterpapiers f?rdert die Keimung ruhender Samen (Abb. 3); dies deutet auf das Vorhandensein eines wasserl?slichen Hemmstoffes, aber die Anstrengungen zu Identifizierung endigten nur in der Feststellung, dass in allen geprüften Samen unspezifische Hemmstoffe vorhanden waren (Tab. 5). Es gibt keinen Beweis dafür, dass phenolische Stoffe für den Zustand der Keimruhe ausschlaggebend sind. Die Keimf?higkeit von luftig aufbewahrten Samenmustern von Wildarten dauerte 6–8 Jahre, nach 11–12 Jahren war sie nur noch gering (Tab. 7). Einige alte Samenmuster zeigten eine h?chst unregelm?ssige “sekund?re Keimruhe” unbekannter Natur. Eine übersicht bezüglich der Korngr?sse von Wildkartoffelsamen ergab eine Schwankung zwischen 22 und 96 mg pro 100 Samen. Die Unterschiede sind nicht fest an die Zahl der Erbs?tze oder die Artzugeh?rigkeit gebunden. Ein allgemeiner überblick über die Biologie der Kartoffelsamen wird in der Diskussion geboten.

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Résumé Certaines baies de pomme de terre (la plupart, probablement) sont m?res à l'age de six semaines, et les graines provenant de baies plus jeunes présentent une certaine réduction de la viabilité et de la dormance (Tableau 1). Les graines peuvent être extraites sans risque au moyen d'un malaxeur, bien qu'une certaine proportion ait le tégument endommagé par l'opération. Pour les tests de germination, des bo?tes de Pétri contenant du papier-filtre humide, conservées à la lumière à 20 C environ donnent satisfaction. Le plastiquemousse convient également comme milieu de germination, mais le papier buvard n'est pas approprié. Les graines de petite dimension se révèlent moins viables. La germination de graines non dormantes est légèrement inhibée par l'obscurité (fig. 1). La plupart des graines de pomme de terre sont en état de dormance au moment où elle sont récoltées, et la germination d'échantillons à quatre semaines suivant le procédé décrit ci-dessus fournit une mesure inverse de la dormance. La dormance de lots hétérogènes de graines de variétés cultivées diplo?des et tétraplo?des diminuait nettement en 6 mois, mais il en restait encore des traces jusque après 18 mois de conservation en plein air (fig. 2). Dans les essais de suppression de l'état de dormance, différents traitements physiques restèrent sans effet, l'enlèvement du tégument avait un effet partiel et l'administration d'acide gibérellique se révéla très efficace; ce dernier, administré à une dose inférieure à la dose optimale, produisait un effet synergique avec la cystéinc (Tableaux 2, 3 et 6). La lumière hate la fin de la dormance et présente des interactions complexes avec les traitements chimiques (Tableau 3). Le stockage des semences pendant huit mois dans un milieu froid ou sec retarde la fin de la dormance, et la sécheresse semble même rendre la dormance plus profonde pendant cette période (Tableau 4). Le renouvellement du papier-filtre servant de milieu de germination stimule la germination des graines en dormance (Fig. 3); cela implique la présence d'un substance inhibitrice hydrosoluble, mais les efforts tendant à l'identification de cette substance ont uniquement permis de démontrer la précence d'une ou de plusieurs, substances inhibitrices non specifiques dans toutes les semences étudiées (Tableau 5). Rien ne porte à croire que des corps phénoliques soient responsables de la dormance. La durée de vie des échantillons d'espèces sauvages conservées en plein air se trouva être de 6 à 8 ans, et on ne trouva que peu de faculté germinative après 11 à 12 ans (Tableau 7). Il existe très irrégulièrement une “seconde dormance” de nature inconnue dans certains lots de semences anciens. Un aper?u des grosseurs des graines de pommes de terre sauvages présente une variation de 22 à 96 mg les 100 graines, cette variabilité n'étant pas liée systématiquement à la plo?die ni à la taxonomie. La Discussion donne un aper?u général de la biologie des graines de pomme de terre.

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Continuation of —Fortserzung von —contiuation de: Europ. Potato J., Vol. 6 (1963) No. 1 (March) 45–60.     

A COMPARATIVE STUDY OF PAPER AND OIL AS CARRIERS OF CHROMIUM SESQUIOXIDE ADMINISTERED TO GRAZING STEERS TO DETERMINE THEIR FAECAL OUTPUT

Two steers excreting similar quantities of organic matter daily were grazed at pasture during the summer of 1961. The four experiments each involved a preliminary period of five days dosing with Cr₂O₃ to reach a fairly constant excretion. The steers received a daily dose of Cr₂O₃ either in oil suspension or in shredded paper. The carriers and steers were interchanged for each trial. For two of the trials each steer in turn was harnessed every other day and all its dung collected in a bag. Total faecal excretion of organic matter was measured from the bagged steer and estimated from the Cr₂O₃ concentration in a composite sample made up from all dung pats voided during the ten-day collection period. In the other two trials the steers were not harnessed and each dung pat was separately sampled and analysed for Cr₂O₃ in the organic matter. The average recovery of Cr₂O₃ in the first two trials was 99·1 (oil) or 94·4% (paper). Calculating the faecal organic matter excretion from the concentration of Cr₂O₃ in the faeces and the quantity given daily overestimated it by 3·5 to 8·0%. There was no significant difference between shredded paper and oil as carriers of Cr₂O₃ for estimating the quantity of organic matter excreted. There were 37% and 22% less variation between dung pats in Cr₂O₃ concentration when this was administered in shredded paper than when given in oil suspension.     

THE INFLUENCE OF FERTILIZER ON THE WINTER SURVIVAL OF INTERMEDIATE WHEATGRASS FOLLOWING A LONG PERIOD OF DROUGHT

In Saskatchewan, intermediate wheatgrass ( Agropyron intermedium Host. Beauv.) suffered severe winter injury during the 1961–2 winter season, which followed a series of drought years, the most severe being 1961. In two tests, designed to study fertilizer effects, the extent of severe winter injury increased with the rate of application. The killing ranged from 4% where no fertilizer was applied to 90% where 66 lb of N per acre were applied. Slightly more winter-killing occurred after applications of ammonium phosphate/sulphate (16-20-0) fertilizer than after ammonium nitrate (33·5-0-0).
The grass growing in rows 36 in. apart killed out to a greater extent than that growing in rows 18 in apart Less winter injury occurred after spring applications of fertilizer than after application in the fall.     

THE GRASSLANDS OF EAST ANGLIA

Because in the past the main emphasis was placed on arable farming, grassland husbandry has played a minor role in East Anglia. Now the increased efficiency exercised in the arable farming of the area is being applied to the grasslands. The main trends are discussed.     

THE EFFECT OF HISTAMINE ON SILAGE DRY-MATTER INTAKE

The oral introduction of 0·5 g histamine as the diphosphate into the rumen of sheep produced no effect on the physiological condition of the animals. The feeding of histamine, as the dihydrochloride, in levels up to 1 g/day to sheep on silage diets did not affect the dry-matter intake.     

THE POTENTIAL VALUE OF SILAGE EFFLUENT AS A FERTILIZER

Results of the analysis for dry-matter, nitrogen and major base content of 9 silage effluents obtained from farm silos and 3 effluents from experimental tower silos are presented. The mean values obtained for the principal plant nutrients in the 12 effluents examined were 0·19% N, 0·037% P and 0·38% K. The results indicate that effluents may be a useful source of plant nutrients, particularly when undiluted with rainwater, and that, in general, silage effluents appear to be superior to liquid manure in manurial value.     

WILD WHITE CLOVER SEED PRODUCTION

A survey, covering some 140 fields, totalling 1540 acres, in Kent was conducted in 1961 on the effect of different methods of management on yields of perennial ryegrass and white clover seed. The main results were: (a) the majority of seed growers harvested seed from short-term leys and only a limited acreage of permanent pasture was used for producing seed. Yields of both ryegrass and clover seed were considerably higher on the younger leys; (b) the highest seed yields in 1961 were obtained from fields where sheep grazing was stopped on 24 May. However, a large number of growers continued sheep grazing well after this date: (c) mechanical defoliation, especially when used to supplement sheep grazing, proved an effective method for producing high yields of clover seed; (d) honey bees are important in increasing seed yields, particularly on recently sown leys; (e) combine harvesting from the swath was the most common method of harvesting and no instance of the use of tripods was reported. Seed yields from baling methods were generally low, but direct combining produced a high average yield of clover seed. From these results it was concluded that there was much scope for raising the general level of clover seed yields, especially by giving greater attention to details of management.     

Chemical Aids in Forest Fire Control

Progress in development of chemical aids in suppressing andretarding forest fires and in drying vegetation to facilitatecontrolled burning is reviewed briefly. The main part of thepaper describes exploratory trials in 1958–61, using arange of fire-retardant compounds for control of grass and heathfires. All chemicals tested were markedly superior to plainwater in checking fire spread. Ammonium phosphate solution,and ‘viscous water’ prepared using sodium alginate,were the most promising retardants tested, the latter beingthe more effective on heavier fuels such as heather and gorse.The costs and mechanics of use are discussed. Subject to operationaltrials, it is concluded that these chemicals could be of practicalvalue in checking the front and hottest parts of vegetationfires. Recent trials suggest that herbicides, of those testednotably Paraquat, may be used to desiccate grass vegetationto permit safe and rapid controlled burning during summer months.