THE EFFECT OF DEFOLIATION ON THE SEED-PRODUCING CAPACITY OF BRED VARIETIES OF GRASSES

Leafy grass varieties S24 perennial ryegrass, S26 cocksfoot, S215 meadow fescue and S51 timothy were cut in October and at various growth stages in spring; S53 meadow fescue was grazed at similar periods. Sub-plots were given different applications of N. The control plots had similar manurial treatments but were not defoliated. The seed yield of S24 following October cutting was significantly lower than the control in the first harvest year and significantly higher in the second; the mean yields over 2 years, as a result of cutting at this stage and before ear formation in March, were very similar to those of the control treatment. The mean yields from 3 harvest years for S26, S215 and S51 were generally improved by cutting in October and before ear formation, but cutting after ear formation reduced the number of heads and the seed yields. Extra N applied in conjunction with the defoliation had no significant effect on the number of seed heads or on seed yield. Double grazing of S53 in Sept. and Dec. reduced significantly its seed production in both harvest years. Application of N in spring gave a greater response than a similar application in autumn.     

Experimental hybridization in certain diploid mexican solanum species

S. bulbocastanum is highly interfertile with S. cardiophyllum. Through the F₁ to F₅ little breakdown due to sterility or lack of plant vigour occurred. F₁ plants of a 5-species hybrid involving S. pinnatisectum, S. trifidum, S. jamesii, S. bulbocastanum, and S. cardiophyllum could also be intercrossed. One-way compatibility was frequently expressed in progenies of these interspecific crosses. It appears to be cytoplasmically controlled, although nuclear factors may be present which interact with cytoplasmic factors. The group of Mexican diploid potatoes represented by these species is potentially interbreeding and shows evidence of introgression throughout its range in central and Western Mexico.Contribution No. 169, Canada Department of Agriculture Research Station, Fredericton, New Brunswick, Canada     

Germinal pore number in pollen grains as a selection basis in the production of tetraploid clover

Experiments with the variety Fahl of Berseem clover and with different material of red clover have shown that the occurrence of tetraploid and diploid tissues can be detected in a rapid and reliable way by determining the number and arrangement of germinal pores of the pollen. The advantages over the conventional methods are mentioned and described.The determination of the germinal pore pattern, which is combined with pair crossing of the tetraploid heads, makes it possible to obtain in an efficient way completely tetraploid material with a great genetic variability.Samenvatting Proeven met het ras Fahl van Alexandrijnse klaver en met verschillend materiaal van rode klaver hebben uitgewezen dat het voorkomen van tetraploide en diploide weefsels op een snelle en betrouwbare wijze aangetoond kan worden door middel van bepaling van het kiemporiënbeeld van het stuifmeel.De bepaling van het kiemporiënbeeld gevolgd door paarsgewijze kruising van de tetraploide hoofdjes maakt het mogelijk op een efficiënte wijze te komen tot zuiver tetraploid materiaal met een grote genetische variabiliteit.     

LOSSES IN THE CONSERVATION OF HEAVILY-WILTED HERBAGE SEALED IN POLYTHENE FILM IN LINED TRENCH SILOS

A conservation experiment is described in which the losses in ensiling heavily-wilted herbage, of approximately 50% dry matter, in lined trench silos, with and without a polyethylene film seal, are compared. The composition and digestibility of the silages produced in the sealed silos were comparable with those of the original herbage. The content of organic acids in the sealed silos was low, suggesting that fermentation was suppressed by the partially gas-tight seal. In the unsealed silos there was considerable spoilage, 70% of the material being inedible. In the 2 sealed silos losses of dry matter were 8·2 and 5·2% and losses of SE 11·5 and 7·8%, respectively. The losses recorded are compared with those usually encountered in lined trench silos.     

III. Buchbesprechungen

Ohne Zusammenfassung     

The respiration of developing potato tubers

Summary The rate of O₂-uptake and CO₂-output, at 10°C., of tubers (var.Majestic) soon after they were formed at the end of June was about 50 ml/kg/hr, and fell during development to final values, before the death of the foliage, of the order of 4–5 ml/kg/hr. The quotient CO₂/O₂ remained within the range 0,85–1,19. The respiration of the tubers per plant calculated for field temperature, rose from about 6–7 ml/hr at the end of June to a peak value of 25–30 ml/hr in mid-August and thereafter fell. The results given here, coupled with observations on foliage respiration, and on the effect of temperature on respiration, suggest that increased respiration plays only a minor part in the reduction in yield which is observed at high temperatures. The mechanism of this reduction is discussed.

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Zusammenfassung Die O₂-Aufnahme und CO₂-Abgabe bei 10°C durch Knollen der SorteMajestic belief sich kurz nach ihrer Bildung am Ende Juni auf ungef?hr 50 ml/kg/Std. und field w?hrend der Weiterentwicklung bis zum Absterben des Krautes auf den Endwert 4–5 ml/kg/Std. (abb, 1 und 2). Der Quotient CO₂/O₂ blieb innerhalb des Bereiches von 0,85–1,19. Die Atmung aller Knollen pro Pflanze — berechnet für Feldtemperaturen — stieg von ungef?hr 6–7 ml/Std. Ende Juni auf einen H?chstwert von 25–30 ml/Std. um Mitte August, wenn die Knollen sich ihrer maximalen Gr?sse n?herten oder sie erreicht hatten, aber immer noch mit dem Blattwerk verbunden waren. Nachher fielen die Werte für die Atmung der Knollen pro Pflanze. Die Erstellung einer Kohlenstoffbilanz ergab ungef?hr, dass in der Mitte der aktivsten Periode des Knollenwachstums im Jahr 1961 die durchschnittliche t?gliche, von der Pflanze assimilierte Menge von CO₂ etwa 14 g betrug. Davon wurden zirka 13% in die Trockensubstanz des Krautes eingebaut, etwa 7% wurden durch das Kraut veratmet und der Rest in die unterirdischen Teile abgeführt, wo weitere 2% für das Wachstum und die Atmung der Wurzeln und ungef?hr 7% für die Atmung der Knollen verbraucht wurden. Etwas mehr als 70% gelangten in die Trockensubstanz der Knollen. Die hier wiedergegebenen Resultate, verbunden mit Beobachtungen über die Wirkung der Temperatur auf die Atmung, deuten an, dass erh?hte Atmung nur von geringerer Bedeutung ist für die bei hohen Temperaturen beobachtete Verminderung des Ertrags. Die Art und Weise dieser Ertragseinbusse wird besprochen.

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Résumé Les quantités d'oxygène (O₂) absorbées et d'anhydride carbonique (CO₂) exhalées à 10°C, par des tubercules de la variétéMajestic sit?t après leur formation à la fin juin est d'environ 50 ml/kg/h; ces quantités tombent durant le développement, avant la mort du feuillage, à des valeurs finales de l'ordre de 4–5 ml/kg/h (fig. 1 et 2). Le rapport CO₂/O₂ restait dans les limites 0,85–1,19. La respiration des tubercules d'une plante, calculée à la température du champ, s'élevait de quelque 6–7 ml/h à la fin juin, à la valeur maximum de 25–30 ml/h à la mi-ao?t, au moment où les tubercules avaient atteint ou presque leur grosseur maximum mais étaient encore attachés à un feuillage en fonctionnement. Après cela, la respiration des tubercules d'une plante diminuait. Un bilan approximatif du carbone indiquait qu'à la moitié de la période la plus active de croissance du tubercule, en 1961, la quantité moyenne journalière de CO₂ assimilée par la plante était d'environ 14 g. De ceux-ci, 13% environ sont incorporés dans la matière sèche des fanes, quelque 7% sont utilisés dans la respiration des fanes, le restant étant transféré dans la partie souterraine; 2% sont alors utilisés dans la croissance et la respiration des racines, 7% environ dans la respiration des tubercules et 70% au moins sont incorporés dans la matière sèche des tubercules. Ces résultats et ceux provenant d'observations sur l'effet de la température sur la respiration suggèrent que l'accroissement de la respiration joue seulement un r?le mineur dans la réduction de rendement observée à hautes températures. Le mécanisme de cette diminution de rendement est discuté.