Search

Copyright of Canadian Journal of Plant Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A Texel sheep ear marginal tissue fibroblast cell line (named TSF19) was successfully established by using a primary explant technique and cell cryoconservation technology. TSF19 cells were adherent, with a population doubling time of 24.9 h. Chromosome analysis showed that >90% of cells were diploid prior to cell passage 4. Isoenzyme analyses of lactate dehydrogenase and malate dehydrogenase showed that the TSF19 cells had no cross-contamination with other species. Tests for cell line contamination with bacteria, fungi, or mycoplasmas were also negative. Plasmids encoding the fluorescent proteins pEGFP-N3, pECFP-N1, pDsRed1-N1, and pEYFP-N1 were transfected into cells to study exogenous gene expression in the cells. The plasmid transfection efficiency was between 21.8% and 46.5%. This newly established cell line will not only preserve the genetic resources of the important Texel sheep at the cell level but will also provide a valuable resource for genomic, postgenomic, somatic cloning research. [ABSTRACT FROM AUTHOR]

It is commonly assumed that plant establishment in the High Arctic is limited by severe abiotic conditions and by a paucity of propagules and seeds. Heavy reindeer grazing may reduce plant allocation to reproduction and removes significant proportions of flowers and seeds, thus reducing contributions to seed rain and seed bank. In contrast, foraging and trampling may break up existing mature plants, increasing the vegetative propagules in the soil. To determine the effect of grazing on colonization potential in the High Arctic, two studies were carried out: (i) a comparison of seed bank inside and outside three long-term reindeer (Rangifer tarandus platyrhnchus (Vrolic)) exclosures and (ii) an investigation of the germinable seed and propagule bank of two neighbouring peninsulas with contrasting reindeer grazing history in northwestern Svalbard (79°N, 12°E). Seed banks inside reindeer exclosures germinated significantly more seedlings (596 seedlings·m–2) than those outside (263 seedlings·m–2). Species composition and total plant cover was similar on both peninsulas, but forage-plant cover was lower on the heavily grazed peninsula (Brøggerhalvøya) than on the adjacent lightly grazed peninsula (Sarsøyra). Brøggerhalvøya had significantly lower species richness and density of seed and propagule bank (0.21 ± 0.02 germinating species per sample, 0.15 ± 0.02 propagule species per sample, 416 ± 103 seedlings·m–2, 283 ± 78 propagules·m–2) than did Sarsøyra (0.44 ± 0.40 germinating species per sample, 0.35 ± 0.03 propagule species per sample,1016 ± 188 seedlings·m–2, 782 ± 238 propagules·m–2). These results imply that reindeer depleted both the seed and the propagule banks, thus reducing the potential for colonization of disturbed areas. Grazing may, therefore, have a lasting impact on High Arctic plant communities. [ABSTRACT FROM AUTHOR]

Phalaris arundinacea L. (reed canary grass) is a major invader of wetlands in temperate North America; it creates monotypic stands and displaces native vegetation. In this study, the effect of plant canopies on the establishment of P. arundinacea from seed in a fen, fen-like mesocosms, and a fen restoration site was assessed. In Wingra Fen, canopies that were more resistant to P. arundinacea establishment had more species (eight or nine versus four to six species) and higher cover of Aster firmus. In mesocosms planted with Glyceria striata plus 1, 6, or 15 native species, all canopies closed rapidly and prevented P. arundinacea establishment from seed, regardless of the density of the matrix species or the number of added species. Only after gaps were created in the canopy was P. arundinacea able to establish seedlings; then, the 15-species treatment reduced establishment to 48% of that for single-species canopies. A similar experiment in the restoration site produced less cover of native plants, and P. arundinacea recruited more readily. Results suggest that, where conditions are favorable for native plant growth, even species-poor canopies can inhibit P. arundinacea establishment from seed, but when disturbances create gaps, species-rich canopies confer greater resistance to invasion.Key words: diversity, establishment, fen, invasion resistance, species richness, wetlands.Le Phalaris arundinacea L. (phalaris roseau) est un envahisseur majeur dans les terres humides de l'Amérique du nord tempérée; il crée des stations monotypiques et déplace les espèces indigènes de la végétation. Dans cette étude, les auteurs évaluent l'effet de la canopée des plantes sur l'établissement du P. arundinacea à partir de la graine, dans une tourbière basse, dans un mésocosme tourbeux et dans un site de tourbière basse restaurée. Dans la tourbière de Wingra, les canopées qui ont le mieux résisté à l'établissement du P. arundinacea comportent plus d'espèces (huit ou neuf contre quatre à six espèces) ainsi qu'un plus fort couvert en Aster firmus. Dans les mésocosmes plantés de Glyceria striata avec en plus 1, 6 ou 15 espèces indigènes, toutes les canopées se ferment rapidement et préviennent l'établissement du P. arundinacea à partir de graines, indépendamment du nombre d'espèces ajoutées. Ce n'est qu'après avoir créé des ouvertures dans la canopée que le P. arundinacea a pu établir ses plantules; dans ce cas, le traitement avec 15 espèces a réduit l'établissement de 48% par rapport aux canopées ne comportant qu'une espèce. Une expérience similaire conduite sur le site en restauration a produit moins de plantes indigènes, et le recrutement du P. arundinacea a été plus efficace. Les résultats suggèrent que là où les conditions sont favorables à la croissance des espèces indigènes, même les canopées pauvres en espèces peuvent inhiber l'établissement du P. arundinacea à partir de la graine, mais lorsque les perturbations créent des ouvertures, les canopées riches en espèces confèrent une plus grande résistance à l'invasion.Mots clés : diversité, établissement, tourbière basse, résistance à l'invasion, richesse en espèces, terres humides.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]