Portland State University. Department of Biology
Clyde L. Calvin
Term of Graduation
Date of Publication
Master of Science (M.S.) in Biology
Chlorophyll -- Synthesis, Mistletoes
1 online resource (2, iv, 42 pages)
The aerial shoot pigments of three epiphytic mistletoes and their hosts were examined and the results were found to concur with earlier reports. Emphasis was placed on the mistletoe Phoradendron juniperinum. Absorbance spectroscopy indicated a very similar ratio of pigments in both the aerial tissue of the mistletoe and its juniper host. Spectroscopic examination found the presence of chlorophyll in the endophytic tissue of the genus Phoradendron for the first time. Total chlorophyll concentrations of the endophytic tissue of Phoradendron juniperinum were found to be approximately 10% that of aerial shoots. However, chlorophyll a/b ratios of endophytic tissue were 40% of those in aerial tissue. The dwarf mistletoe Arceuthobium tsugense was found to have about 1/3 the chi content of its host and of the two Phoradendron species examined. However, the endophytic concentrations of chlorophyll of A. tsugense were 250% higher than those found in compatible Phoradendron tissue.
Ultrastructural inspection of Phoradendron juniperinum revealed chloroplasts of the aerial shoots to be typical of C3 plants, yet they were small and contained little relative stroma lamella. This is characteristic of plants with unequal complement of the two photosystems. Examination of the endophytic system indicated that the most likely source of the chlorophyll to be plastids with enlarged thylakoid channels. These plastids were termed endophytic-chloroplasts.
Experiments were performed to establish whether the synthesis of the chlorophyll within the endophytic system was via a light-independent pathway or by means of light penetration into mistletoe tissue and stimulation of the typical angiosperm light-dependent pathway. However, results as to the biosynthesis of chlorophyll were inconclusive. These experiments did indicate that chlorophyll was still present in endophytic tissue of Phoradendron juniperinwn after 11 months without aerial shoots, whether enclosed in complete darkness or not. Microscopic examination of tissue did not revile the presence of any light conductive tissues in either the parasite or its host.
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Dubbs, Wesley Emanuel, "Chlorophyll Characterization of Three Mistletoes and the Chloroplast Ultrastructure within Aerial and Endophytic Tissues of Phoradendron Juniperinum" (1994). Dissertations and Theses. Paper 4747.