Portland State University. Department of Biology
Robert O. Tinnin
Term of Graduation
Date of Publication
Master of Science (M.S.) in Biology
Dwarf mistletoes, Host-parasite relationships, Lodgepole pine -- Diseases and pests
1 online resource (2, viii, 92 pages)
Arceuthobium americanum is a vascular plant which is parasitic upon Pinus contorta var. murrayana. Its documented effects include reductions in host growth, vigor and wood quality. The specific physiological changes that occur in the host are, for the most part, unknown.
In an attempt to understand the manner in which the mistletoe alters its host's carbon budget, a model is proposed which states that the host plant has priorities for carbon allocation. The model proposes that the parasite will access the host's carbon initially in terms of carbon intended for storage, next, in terms of carbon intended for growth, and finally, in terms of carbon allocated for respiration. If the model is accurate, then the presence of the parasite will initially be reflected in decreased amounts of stored carbon (i.e. starch), next, in decreased host growth (i.e. biomass allocation), and finally, by the death of the host.
To determine the accuracy of the proposed model, starch concentrations and several physical characteristics of uninfected and variously infected host trees were examined.
Physical characteristics which were altered as a result of dwarf mistletoe infection include needle number, mean needle length, needle biomass, mass per needle, total needle length and surface area, twig length, twig biomass, and twig unit mass. In general, the effect of the mistletoe was to decrease the annual allocation of carbon to infected tissues. This is what is predicted by the model.
The concentration of starch in infected tissues was found to be as much as 15 times that found in comparable uninfected tissues. This seems to be contradictory to the proposed model.
In terms of carbon budgets for branches, the proposed model was found to be inaccurate. Although the amount of carbon being allocated for biomass decreased, the concentration of starch in infected host tissues increased. However, in terms of the accuracy of the model for the entire tree, more work needs to be done. Work on whole tree biomass allocation has shown decreasing trends, however, no work has yet been done on entire tree starch concentrations.
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Broshot, Nancy Ellen, "The Effect of Dwarf Mistletoe (Arceuthobium americanum) Upon a Portion of the Carbon Budget of Lodgepole Pine (Pinus contorta)" (1982). Dissertations and Theses. Paper 3138.