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The biological activities of root exudates from Poa pratensis (donor) were examined in biotest in which germination and height and mass of seedlings of Dactylis glomerata, Festuca pratensis and Phleum pratense (acceptors) were evaluated. The experiment was performed using root exudate recirculating system (RERS). It was documented that root secretion of Poa pratensis circulating in a closed cycle considerably limited germination of Dactylis glomerata and Phleum pratense, but only slightly limited germination of Festuca pratensis. It also negatively influenced the height of Phleum pratense seedlings, in the first growth as well as during regrowth after first cut; in case of Dactylis glomerata only the height of the plants after first cut was influenced. They had no pronounced influence on the height of Festuca pratensis seedlings. The application of amberlit XAD-4 reduced negative influence of root secretion of Poa pratensis on the height of Phleum pratense and Dactylis glomerata seedlings. Dry matter accumulation by tested grass species was reduced significantly at the presence of Poa pratensis root exudate as compared to the control; exception was Festuca pratensis, which was not influenced. The highest effectiveness of XAD-4 in limiting negative influence of Poa pratensis secretion on biomass of the tested species was found in the case of Phleum pratense.
The aim of the study was to recognise of thousand seed weight (TSW) of 44 breeding forms of Poa pratensis L. and its relationship to seed yield, leaf width, number of generative shoots, plants height, heading time. The forms of Poa pratensis including 7 cultivars, 13 breeding strains and 24 ecotypes were tested during 1997-98 in Radzików (central Poland). The forms were divided according to average of TSW in three groups: small seeds <0,300 g, medium seeds 0,300-0,350 g, and large seeds >0,350 g. Generally range of TSW was from 0,245 g to 0,425 g. The TSW of most forms was stable by years and replications. Range of coefficient variability value was from 2,4% to 15,1% for ecotypes and 4,0-6,0% for cultivars. Not significant correlation were found between TSW and seed yield, leaf width, number of generative shoots and heading time. Significant correlation between TSW and plants height was found (r = -0,40***).
The grazing studies were conducted in two experiments established in 1996 and located on peat-muck soil. A randomised block design with four replications was used. The investigations with two sward types in every trial aimed to compare the maintenance of Lolium perenne and Poa pratensis in the pasture under postboggy habitat. The mentioned species were the main grass components in grass-clover mixtures, fertilized with 40 kg ha⁻¹ N and also in grass mixtures, fertilised with 40, 80 and 120 kg ha⁻¹ N. Seven cultivars or Trifolium repens were included to grass mixtures. As the white clover cultivar was never significant then the results from the seven grass-clover treatments were pooled in the data presentation. The pasture swards were grazed rotationally with Limousine cattle four times a grazing season. Samples of the herbage were analysed for the botanical composition by manual separation and expressed on a weight basis. Lolium perenne grew well in postboggy habitat and became rapidly predominant species in grass and grass-clover sward. Low resistance to frost in December and January in 1996 to 1997 was the most important reason of Lolium perenne content variation in the pasture sward. However, during the vegetative season of 1997 proceeded good regeneration of this species. Development of Poa pratensis in the sward also depended on climatic conditions. High rainfalls in late autumn of 1996 and 1997 influenced negatively stability of this specics in the grass community. Presence of Trifolium repens in the pasture sward affected beneficially the wintering of Lolium perenne and favoured the expansion of Poo pratensis.
Poa pratensis is a grass species characterised by a wide range of utilisation possibilities. As a fodder grass, it is considered as an irreplaceable element of grassland sward. Moreover, this grass species is gaining in importance as lawn grass. In recent years, it has been increasingly viewed as a turf-forming grass species appropriate for difficult sites, including industrial sites. One of the most valuable advantages of Poa pratensis is its persistence. In this regard, it is comparable with Lolium perenne. Its other asset is its considerable turf-forming capability, albeit somewhat delayed. A good evidence of its growing importance is the breeding work carried out on this species with a collection of developed cultivars quite different with regard to their utilisation potentials. It is interesting to note that it is increasingly dominated by fodder cultivars and, therefore, any appearance of a new fodder cultivar, especially one suitable for pastures, deserves attention. On the other hand, such creations raise concern of evaluation criteria. The objective of the research project was to determine the importance of biological and chemical properties of Poa pratensis in the development of cultivars designed for pasture utilisation. The performed investigations were conducted on the following four fodder cultivars of this species: 'Skrzeszowicka' [PL], 'Skiz' [PL], 'Balin' [DK] and 'Slezanka' [CZ]. The multi-cut experiment was situated at a Cultivar Evaluation Station in Śrem. The following assessment criteria were applied: concentrations of total nitrogen anp nitrates, sugars and carbohydrate complex (lignin, chlorophyll and carotene dyes), selected mineral components as weil as the abundance of foliage and yields. It turned out that a moderate and systematic fertilisation allows obtaining sward characterised by an optimal - from the nutritional point of view - chemical composition. Another important feature deserving attention is a considerable phytochemical stability of the cultivars. The application of such a wide spectrum of evaluation criteria allowed determining numerous correlations. The most interesting of them were those, which indicate the existence of relationships between the chemical composition and the assimilation area of leaf blades, and cultivar yields. The observed correlations can be utilised in the process of developing new, improved cultivars, better than those used in the performed experiments.
The studies were carried out in laboratory conditions. Poa pratensis root exudates were obtained in the CRETS (continuous root exudate trapping system) and then in glass platter experiment was determined their biological activity in biotest on seed germination, length of roots and height of Phleum pratense seedlings. In the experiment were used the following concentrations of Poa pratensis root exudates: 0,80%, 0,40% and 0,20%. Conducted studies showed that higher concentrations of Poa pratensis root exudates (0,80% and 0,40%) caused total inhibition of germination. Lower concentrations of exudates significantly limited number of germinated seeds and inhibited of root elongation and growth of tested species seedlings. These results indicate that Poa pratensis root exudates seem to include chemical compounds of allelopathic nature.
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