Changes in mass and chemical composition of grass roots during decomposition

The decomposition of dead roots of perennial grasses was examined in nylon litter bags not containing soil at two soil depths, 10 and 20 cm, and also in larger nylon bags containing soil at 020 cm depth. Bags were sampled three times during the growing season to determine weights of organic matter, crude protein, Klason lignin and non-structural and structural carbohydrates.
From 3 July to 5 October (94 days) the litter bags at 10 and 20 cm and the nylon bags lost, respectively, 35,38 and 65% of their organic mass of particle size < 1 mm.
Non-structural carbohydrates constituted 6% of the organic matter in the original sample but only 1% or less during the sampling period. Klason lignin increased from 22 to 29% and crude protein from 8 to 10% of the remaining organic matter, whereas structural carbohydrates changed very little.
The constituents were degraded at different rates. The non-structural carbohydrates had decomposed almost completely by the first sampling and of the other constituents the structural carbohydrates were degraded most rapidly. Before the first sampling unexpected amounts of structural carbohydrates, particularly glucans, had disappeared.
The results help to explain rapid declines in root mass (up to 50%) during summer in perennial grass leys observed in earlier experiments.     

Seed potato production in Northern Ireland

Summary With cool moist summer weather, Northern Ireland is suited for the production of vigorus healthy potato stocks. An export trade to Great Britain and countries in Europe, Asia and Africa has been developed during the last twenty years. As a result of research, particularly in plant pathology and nematology, and with the co-operation of both farmer and merchant methods have been developed to ensure that healthy stocks are propagated on land known to be free from potato root eelworm.

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Zusammenfassung Der kühle, feuchte Sommer Nordirlands begünstigt die Erzeugung kr?ftiger, gesunder Kartoffelbest?nde. Die Pflanzguterzeugung hat seit der Vorkriegszeit einen betr?chtlichen Aufschwung erfahren und in den letzten Jahren wurden j?hrlich nahezu 50 000 1 Saatkartoffeln nach Grossbritannien und eine gleiche Menge nach L?ndern in Europa, Asien und Afrika geliefert. Die Forschungsarbeiten auf dem Gebiet der Pflanzenpathologie werden besprochen. Die Züchtung erfolgt sowohl durch den Staat wie durch einen Privatzüchter, und viele der zur Zeit in Grossbritannien angebauten Sorten sind in Nordirland erzeugt worden. Die Verbreitung des Wurzel?lchens aus einigen wenigen befallenen G?rten und Feldern ist durch gesetzliche Massnahmen verhütet worden und die Züchtung nematodenfreier Sorten wird in die Hand genommen. Der gute Ruf, dessen sich das Pflanzgut aus Nordirland erfreut, ist mit der engen Zusammenarbeit der Forschungs- und Beratungsstellen des Ministeriums für Landwirtschaft mit Landwirt und H?ndler zu verdanken.

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Résumé Le temps d'été frais et humide de l'Irlande du Nord est favorable à la production de cultures saines et vigoureuses de pommes de terre. La production de plants a considérablement augmenté depui l'avant-guerre et des dernières années près de 50.000 tonnes de plants de pomme de terre ont été expédiées chaque année vers la Grande-Bretagne et une même quantité vers différents pays d'Europe, d'Asie et d'Afrique. Les recherches dans le domaine de la pathologie végétale, concernant entre autres les méthodes de lutte contre les malladies des tubercules et le mildiou, ainsi que la sélection et la multiplication de cultures exemptes de virus, sont discutées. Les travaux de sélection sont exécutés par le gouvernement et par un cultivateur privé; de nombreuses nouvelles variétés cultivées actuellement en Grande-Bretagne proviennent de l'Irlande du Nord. La propagation du nématode doré à partir d'un petit nombre de jardins et de champs infectés a été enrayéc par la législation et I'on s'occupe de la sélection de variétés résistantes aux nématodes. La renomméc des plants de pomme de terre de I'Irlande du Nord est due à l'étroite coopération des services de recherches et d'information du Ministère de l'Agriculture avec les cultivateurs aussi bien qu'avec le commerce.

     

A quick microtechnique for inspection of potato periderm or wound periderm formation

Summary A method for a quick inspection of wound periderm formation is described. Sections are freehand cut into a stain solution, and microscopic examination is accomplished with an epiplanatic lens.     

亚种间杂交稻产量源库特征

 对大量典型的籼粳亚种间杂交种组合的产量源库特征进行了研究，获得了如下如果：亚杂组合的物质生产的优势主要表现在出穗后经济产量形成期，这与籼型三系杂交稻物质生产的优势主要表现在出穗前迥然不同；亚杂组合的库容优势也十分明显，就其总体而言全生育期物质生产量与库容的比例高于汕优63；大多数亚杂组合的光合产物向穗的运转不良，这是部分亚杂组合籽粒充实不良的成因，也是限制亚种间杂种优势充分利用的带普遍性的问题。对这一问题的研究展望及提高亚种间杂交稻籽粒充实度的栽培途径进行了讨论。     

Advancing growth vigor of seed potatoes by a haulm application of gibberellic acid and storage temperature regimes

Seed tubers that are planted soon after their harvest give low yields because of dormancy and low growth vigor. In the research reported in this paper, we investigated the advancing effect of a haulm application of gibberellic acid (750 g GA/ha) 6 days before haulm pulling and its interaction with storage temperature regimes on the growth vigor of immaturely harvested seed tubers of three cultivars. The effects on tuber yield were also examined in one experiment. The storage regimes were: 18 C continuously, hot pre-treatments of different duration (different periods at 28 C and subsequently 18 C) and a cold pre-treatment (20 days at 2 C and subsequently 18 C). Both a foliar spray with GA and storage at 28 C enhanced physiological aging of the tubers and greatly advanced the growth vigor, without negative effects on the morphology of the plants. There was a clear interaction between the GA treatment and the storage temperature regime. At early planting, the effect of the treatments on tuber yield were small for Diamant (short dormancy), but strongly positive for Désirée and Draga (long dormancy).     

Relationships between numbers of main stems and yield components of potato (Solanum tuberosum L. cv. Erntestolz) as influenced by different daylengths

Summary The relationshops between numbers of main stems and some measures of growth and yield, as well as total tuber yield, were examined for potatoes grown under different daylengths. Leaf area, tuber number and tuber yield per plant increased significantly with increasing daylength and number of main stems. Numbers of main stems and leaf area were correlated positively with tuber number and tuber yield and negatively with average tuber weight. The correlations were stronger with stem number than with leaf area and were differently affected by daylength. Standard regression coefficients indicated that stem number has strong positive and negative relationships with tuber number and average tuber weight, respectively. Since tuber number was a better determinant of yeild than average tuber weight, the final relationship between the numbers of main stems and tuber yield remained positive for all daylengths. Determinants that will best explain variation in tuber total yield, tuber number, and average tuber weight are suggested.