Root Regeneration of Transplanted Trees in Relation to the Status of Carbohydrate Levels and Root Invading Fungi
Watson, Gary William
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https://hdl.handle.net/2142/70580
Description
Title
Root Regeneration of Transplanted Trees in Relation to the Status of Carbohydrate Levels and Root Invading Fungi
Author(s)
Watson, Gary William
Issue Date
1981
Department of Study
Plant Pathology
Discipline
Plant Pathology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Plant Pathology
Abstract
The natural root distributions of 7 species of shade trees (Norway, red and sugar maple, green ash, redbud, ginkgo and pin oak), growing under nursery conditions were characterized. In general, the vertical distribution of the major roots showed the greatest development at the soil depth of 13-38 cm, with limited growth in the top 12 cm, and decreasing development at depths below 38 cm. The north quadrant of the root systems of these trees was more developed than any other quadrant. Fine roots that develop in rather shallow soil appear to constitute a large portion of the early root system that develops the first year after transplanting. Regenerated roots originate primarily at the severed ends of the roots cut during transplanting.
Root systems of approximately 96 trees, 5-10 cm in diameter, (Norway, sugar and red maple, green ash, ginkgo, constituting the majority of these) were wholly or partially excavated 1-3 years after transplanting. Isolations were made from root sections exhibiting mechanical damage, wood discoloration and dieback. Selected fungal isolates were tested for their ability to colonize root and stem tissue of Norway maple, green ash, and ginkgo saplings. Isolates of Geotrichum candidum Link ex Pers. and Fusarium oxysporum Schlecht were successful invaders of root and stem wood tissue. Norway maple was the tree species most susceptible to colonization, with dormant Norway maples more susceptible than nondormant plants.
Assays of the total carbohydrate content show an increase in both roots and twigs of transplanted trees over controls. Total sugar content increased in Norway maple and green ash roots while decreasing slightly in ginkgo roots. Sucrose and galactose levels were highest in Norway maple. Glucose and fructose levels were similar in transplants and controls for species tested.
Root regeneration was decreased in Norway maples transplanted in early spring. This group of trees was transplanted during the spring period of shoot growth, a time when carbohydrates are in highest demand. This was the only case where season of transplanting appeared to have an impact on root regeneration. Transplanting during this period is not advised.
In vitro tests indicate that carbohydrate content of host tissue may be a factor affecting root colonization by soil borne fungi. Growth rate of F. oxysporum was directly related to the amount of sucrose added to the media. G. candidum showed a significant growth response to starch and galactose. The higher carbohydrate content of transplanted tree roots, especially the high sucrose levels in Norway maple, is believed to be partially responsible for the ability of these common soil fungi to colonize the severed roots, so readily.
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