Crooked Aspen
Graduate Students & Staff
Unpublished Papers

Woody Plants CD

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Biographical Notes
Plant Architecture and Development

Tree Modelling

Collaboration with Dr. P. Prusinkiewicz, Department of Computer Science, University of Calgary (and his graduate students). Development of simulation models for woody plants. We have also collaborated on modelling some theoretical aspects of tree development.



Crooked Aspen

Specimens of a clone of crooked Populus tremuloides that has been growing in central Saskatchewan since at least the 1940s were established in an experiment at the University of Manitoba. Currently working on a simulation model for crooked aspen development.


Green Ash

Fraxinus pennsylvanica var. subintegerrima (green ash) has been a major focus of my research program. In collaboration with Dr. Campbell Davidson, we have examined various aspects of the architecture and crown shape of green ash, as well as the response to pruning and fertilizing. Grant Bartlett, an M.Sc. student, also worked on the relation of architecture to light levels. We have done considerable work on preformation and neoformation in this species and I have also worked on the development of vegetative and floral buds. In a major collaboration with Dr. Prusinkiewicz, a simulation model of green ash shoot expansion was developed.


A comprehensive study of the crown architecture Larix laricina (tamarack) was conducted during my post-doc in the early 1980s in collaboration with Dr. Graham Powell, Department of Forest Resources, University of New Brunswick. We analyzed and modelled patterns, including the inclusion of syllepsis. We also analyzed the extent of shoot preformation and neoformation in relation to shoot vigour and crown location.



An analysis of the development and architecture of the prostrate boreal shrub, Arctostaphylos uva-ursi (bearberry) was the subject of my Ph.D. project at the University of Saskatchewan under the supervision of Dr. Taylor Steeves. A model simulating how the plant spread was developed and aspects of bud development were also examined.



Comparison of the architecture of an upright willow (Salix alba var. chermisina) and a pendulous willow developed by Dr. W. Ronald at the Morden Research Centre (Salix hydrid cv Prairie Cascade). There is little research on the architecture of pendulous trees.

Other Projects on Woody Plants

Saskatoon projects

Amelanchier alnifolia (known as the saskatoon) is a native fruit bearing shrub that has been valued for its flavourful berries since pre- and early settlement of the Canadian prairies. In the latter part of this century, the plant has been domesticated with the release of several cultivars, beginning with 'Smoky' in the 1950s.

a) Growth and yield studies - comparison of tissue cultured and traditionally propagated plants. Analysis of yield components in relation to shoot architecture.

b) Microspore and pollen development in saskatoons. A collaborative project with Dr. Michael Sumner, Department of Botany, University of Manitoba, using light and electron microscope techniques.

c) Epidemiology of Entomosporium leaf and berry spot disease and disease forecasting in Saskatoons using meteorological data. This work constituted the Ph.D project of Quinn Holtslag.


Bur oak decline in Winnipeg’s urban forest

Winnipeg is the only major western Canadian city in the native range of bur oak (Quercus macrocarpa), a species that forms an important component of the city’s urban forest in the form of both planted specimens and naturally occurring individuals. However, in recent years, the health profiles of many oak trees have been declining, resulting in concern about the sustainability of the urban oak population in Winnipeg. The goal of this study was to examine site conditions and history and attempt to correlate these with tree health. Part of the project has involved looking at declined trees by analyzing tree ring data. This research was conducted as an M.Sc. project by Haley Catton that was completed in 2005.


Research on Dutch Elm Disease

A vascular wilt disease known as Dutch elm disease (DED) (caused by Ophiostoma ulmi) has afflicted native stands of American elm (Ulmus americana) throughout North America. As a result of this disease Canada has lost many of its old stands of American elm. Moreover, American elm has also been removed from the recommended lists for urban tree planting. Our research has focused on mass selection to find disease resistance in the offspring of the remnant population. To date we have one tree propagated by seed in the mid 1990s that has survived 4 inoculations with Ophiostoma ulmi.

Another strategy has involved research on developing a rapid early screening method for genotypes of Ulmus americana for possible resistance to Dutch elm disease based on levels of mansonone, a phytoalexin considered to be a factor in the resistance to Dutch elm disease. Although it was possible to quantify mansonome from callus in culture, it was found that it was produced routinely after wounding and callus formation in general and was not specific enough to challenges from DED. Thus, it was concluded that its efficiency as a screening tool is tenuous at best.


Amur maple

Amur maple (Acer ginnala) is very prone to iron chlorosis, caused by the unavailability of iron to the plant. This results in leaves with veins that remain green and the region between the veins turns yellow to almost white. A project was undertaken by Ms. Martha Barwinsky as part of her M.Sc. thesis to examine and select genotypes with increased tolerance to chlorosis. We have selected 4 promising genotypes from her work and in collaboration with Jeffries Nurseries, Portage La Prairie, Manitoba, these genotypes are being multiplied for further chlorosis tolerance testing and examination of landscape characteristics such as form, leaf characteristics and fall colour.


Black knot disease

I was involved in a research initiative to address aspects of black knot disease caused by the fungus Apiosporina morbosa that affects members of the genus Prunus. This disease results in the formation of black, corky swellings around shoots and branches (galls). Increased incidence of this disease has resulted in serious economic losses in the nursery industry related to the sale of Shubert Chokecherry which is an extremely important purple-leaved street tree in the prairie regions of Canada. For this program I was involved in the research activities conducted by Dr. Jinxiu Zhang as a post-doctoral fellow, mainly under the supervision of Dr. Dilantha Fernando. The main thrust of the program was to assess genetic variability in the pathogen using molecular techniques.


Contact: Bill Remphrey

Last Updated: February 13, 2011
University of Manitoba AFS