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dc.contributor.advisorHolbrook, Noel Michele
dc.contributor.authorHuggett, Brett Andrew
dc.date.accessioned2013-09-27T21:09:24Z
dash.embargo.terms2015-06-07en_US
dash.embargo.terms2015-06-07
dc.date.issued2013-09-27
dc.date.submitted2013
dc.identifier.citationHuggett, Brett Andrew. 2013. The Plant Vascular System: Structure, Function, and Responses to Environmental Stress. Doctoral dissertation, Harvard University.en_US
dc.identifier.otherhttp://dissertations.umi.com/gsas.harvard:10913en
dc.identifier.urihttp://nrs.harvard.edu/urn-3:HUL.InstRepos:11124830
dc.description.abstractEnvironmental stressors such as nutrient deficiency and insect infestation can significantly impact tree health. Despite much research on the ecological effect on forests in the northeastern United States due to calcium depletion and hemlock woolly adelgid infestation, little is known regarding the physiological mechanisms altered by these stress factors. I tested the hypothesis that calcium depletion, associated with sugar maple decline, compromises water transport processes as a result of calcium-related reductions in cell growth and stabilization. A survey of forest-grown sugar maples from a long-term replicated calcium-manipulation study showed no significant impact of calcium deficiency on wood density, stem hydraulic conductivity (Ks), or vulnerability to cavitation (VC). In vitro removal of xylem-bound calcium showed no impact on VC or air seeding thresholds (Pt). Results suggest that sugar maple decline is not caused by compromises in xylem function due to calcium deficiency. I also tested the hypothesis that hemlock woolly adelgid (Adelges tsugae Annand) (HWA) infestations impact water transport processes and nutrient partitioning in eastern hemlock trees. HWA infestation resulted in higher Ks due to an increase in average tracheid lumen area associated with the proliferation of false rings. HWA-infested trees exhibited higher rates of net photosynthesis and significant changes in foliar nutrient partitioning. These results are the first to demonstrate increases in Ks and alterations in foliar cation levels in response to HWA infestation. In two additional studies, I investigated methods for evaluating the structure and function of xylem networks. Using sequential sectioning of aerial roots of epiphytic aroids, I directly quantified the topographic relation of vessels in a single organ with measurements of vessel length, diameter, vessel end overlap length, and vessel stelar orientation. In a separate study, I explored the relationship between vessel length and measurements of Pt. In establishing guidelines for estimating whole-stem cavitation with the use of single vessel air injection, I demonstrate that calculations of Pt are influenced by stem length measured and removal of native emboli prior to testing. Improvements in tools to quantify xylem structure and function will enhance our ability to understand the responses of forest trees to environmental stress.en_US
dc.language.isoen_USen_US
dash.licenseLAA
dc.subjectPlant biologyen_US
dc.subjectair seedingen_US
dc.subjectcavitationen_US
dc.subjecteastern hemlocken_US
dc.subjecthemlock woolly adelgiden_US
dc.subjectsugar mapleen_US
dc.subjectxylemen_US
dc.titleThe Plant Vascular System: Structure, Function, and Responses to Environmental Stressen_US
dc.typeThesis or Dissertationen_US
dash.depositing.authorHuggett, Brett Andrew
dash.embargo.until2019-06-07en_US
dc.date.available2015-06-08T07:30:30Z
thesis.degree.date2013en_US
thesis.degree.disciplineBiologyen_US
thesis.degree.grantorHarvard Universityen_US
thesis.degree.leveldoctoralen_US
thesis.degree.namePh.D.en_US
dc.contributor.committeeMemberPfister, Donalden_US
dc.contributor.committeeMemberKramer, Elenaen_US
dash.contributor.affiliatedHuggett, Brett


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