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Title: Cytokinins in pollutant-treated forest trees and associated fungi
Author: Collier, M.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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Coniferous tree species growing on sites exposed to aerial pollution exhibit an altered pattern of vegetative development compared to those on unpolluted sites and contain higher needle cytokinin contents. This study aimed to determine which pollutants promoted the enhanced cytokinin status by analysing the needle cytokinin content of Sitka spruce (Picea sitchensis (Bong) Carr) trees sprayed with individual components of aerial pollution. Only needles of neutral N treated trees contained significantly higher isoprenoid cytokinin contents than that of control trees sprayed with water. In contrast, needles of trees treated with acid-mists containing S and N contained significantly lower levels of cytokinin than controls, indicating that S pollutants, or low pH, or both, significantly suppress the nitrogen-mediated stimulation of cytokinin levels. Changes in cytokinin metabolism were also recorded. Several aromatic cytokinins were detected in the needles of Sitka spruce for the first time. In contrast to the isoprenoid cytokinins, the aromatic cytokinin content was significantly reduced in needles from N treated trees. The function of this enigmatic group is unknown, although possible roles for these cytokinins in Sitka spruce are discussed. Beech seedlings (Fagus sylvatica L.) fumigated with NH3 also contained significantly higher cytokinin contents in the roots compared to controls fumigated with charcoal-filtered air. Changes in cytokinin metabolism were also detected. Defoliation and needle yellowing are common symptoms of trees growing on polluted sites. Sitka spruce seedlings were partially defoliated with the aim of characterising the changes in cytokinins resulting specifically from needle loss. Needles of defoliated plants contained significantly higher levels of O-glucosyl isoprenoid cytokinins, a 'diagnostic' by which the influence of defoliation might be recognised in the field.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available