Populus tremuloides Michx. (trembling aspen) is a tree species native to much of North America and is normally ascribed to the architectural model of Rauh, characterized by an excurrent crown structure with a central main stem and orthotropic branches. A mutant clone of trembling aspen is located near Hafford, Saskatchewan, exhibiting an architecture with crooked and twisted tree trunks. It was the objective of the present study to determine how the architectural development of the crooked clone differed from the wild type. In a study conducted over a 5-year period, four mutant trees were compared with four young wild-type aspen in the Winnipeg, Manitoba, area. Based on detailed quantitative data, it was determined that the architecture of the crooked clone of aspen differs greatly from the wild type. The trees are built by the continuous superposition of vigorous relay shoots with a mixed orientation, that is, shoots that take over the main growth of the tree, and have a more or less upright basal part and a horizontal to pendulous distal part. The development of the crookedness starts with the bending of the relay shoots, mostly in relation to the gravitational direction, which is followed in the subsequent years by various gravimorphic responses. In particular, the longest lateral shoots on a parent relay shoot occur in the middle regions, and the tip of the parent relay shoot generally loses vigour over time. The parent shoot may die back to the junction with a daughter relay shoot, causing a sharp bend at that point. Moreover, the divergence angles of relay shoots with the parent shoots were shown to be greater than in wild-type aspen, and this appears to exacerbate the crookedness. The new relay shoot may actually grow back towards the centre of the crown, opposite to the direction of growth of the parent. The results of this study demonstrate how a quantitative change in one architectural character can set in motion a series of developmental processes that result in a vastly different crown structure from the wild type.Résumé : Le Populus tremuloides Michx. (peuplier faux-tremble) est une essence indigène qu'on retrouve dans une bonne partie de l'Amérique du nord et qui se conforme normalement au modèle architecturale de Rauh, caractérisé par une structure de la couronne ouverte, avec une tige centrale principale et des branches orthotropes. Près de Hafford, en Saskatchewan, on trouve un clone mutant de peuplier faux-tremble dont l'architecture montre des courbures et des torsions des troncs. Les auteurs ont cherché à déterminer comment le développement architectural, chez ce clone tordu, diffère de celui du type sauvage. Une étude ayant durée 5 ans a permis de comparer quatre arbres mutants avec quatre jeunes peupliers faux-tremble de type sauvage, dans la région de Winnipeg au Manitoba. Les données quantitatives montrent que l'architecture du clone tordu du peuplier faux-tremble diffère grandement de celle du type sauvage. Les arbres se développent par superposition continue de tiges à relais vigoureuses...

Remphrey, W. R. and Pearn, L. P. 2006. A comparison of seed-propagated and micropropagated Amelanchier alnifolia (saskatoon): Yield and yield components in relation to crown architecture characteristics. Can. J. Plant Sci. 86: [499][500][501][502][503][504][505][506][507][508][509][510]. A study of the architecture and yield components of young micropropagated and seed-propagated Smoky saskatoons over a 4-yr period revealed no differences in height, but the diameters and branchiness ratings of the seedling plants were greater. In the 3 yr of fruit harvest there were no differences in mean fruit weight or fruit number between propagation types, but there was a difference among years. The yield was considerably greater in the third year of harvest (1996), possibly reflecting the natural tendency for yield to increase as the plants develop. In all 3 yr, fruit ripening peaked in July, with most fruit harvested within about a week on either side of the peak. Although there were strong correlations between the number of infructescences and both fruit weight and fruit number, there was little difference between propagation types. There were no relationships between main-stem diameter and the weight or number of fruit that the plant bore. However, there was a positive linear relationship between yield parameters and the diameter of the shoots bearing that portion of the crop in 1994 and 1995. Although not different between propagation types, terminal shoots were longer and greater in diameter and in 1995 bore three times more fruit yield than did lateral shoots. There were no differences between propagation types in the weight of fruit per infructescence or in the mean weight (0.71 ± 0.02 g) or diameter (10.81 ± 0.11 mm) per fruit. 499-510. L'étude des paramètres du rendement et de la structure du collet de jeunes plants d'amélanchier Smoky obtenus par multiplication végétative in vitro et par la culture des semences durant une période de quatre ans n'a révélé aucune différence pour ce qui est de la hauteur, mais le diamètre et les ramifications étaient plus importants chez les plants issus des graines. Au cours des trois années de récolte, les auteurs n'ont noté aucun écart dans le poids ou le nombre moyen des fruits pour les deux types de plants, cependant il existait une variation annuelle. Le rendement a été considérablement plus élevé la troisième année de récolte (1996), peut-être à cause de la tendance naturelle qu'a le rendement d'augmenter à mesure que les plants prennent de l'âge. Les trois années, la maturation des fruits a atteint son maximum en juillet et la majorité des fruits ont été cueillis durant la semaine qui a précédé ou suivi ce pic. Bien qu'il existe d'étroites corrélations entre le nombre d'inflorescences et le poids des fruits ainsi que le nombre de fruits, le mode de multiplication n'entraîne pas de grandes fluctuations à ce niveau. Le diamètre de la tige principale ne présente aucun lien avec le poids ni le nombre des fruits récoltés. Toutefois, les auteurs ont observé une relation linéaire po...

This paper presents a longitudinal quantitative architectural study of Salix ‘Prairie Cascade’, a hardy pendulous willow cultivar developed for the Canadian Prairies. Trees were propagated from cuttings in 1993 and detailed measurements were obtained on amount of extension growth, orientation of shoots with respect to gravity, and the fate of buds and shoots until 2000. Instead of the mixed axis model of Champagnat typically ascribed to weeping willows, upright main-stem axes were constructed by vigorous, mostly distal shoots that remained more or less upright. The pendulous habit was largely the result of lateral shoots that were initially upright or semi-pendulous, drooping under their own weight to become pendulous. The pendulous habit was exacerbated by the weight of foliage. Sylleptic shoots were frequently incorporated into the main-stem axes. From original 1993 shoots, 40% of the buds developed into sylleptic shoots compared with 29% that developed into proleptic shoots. Two orders of sylleptic branching were often produced in one year. Willow is known for branch shedding but only 7% of ‘Prairie Cascade’ shoots were shed in the first year; however, more than half were gone by the third year and most of those remaining were located on the upper half of parent shoots.