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Environmental Influences on Wood Structure and Water Transport in the Model Tree Populus Open Access


Other title
plant water transport
plant water relations
hydraulic conductivity
Type of item
Degree grantor
University of Alberta
Author or creator
Plavcová, Lenka
Supervisor and department
Hacke, Uwe (Renewable Resources)
Examining committee member and department
Lieffers, Victor (Renewable Resources)
Hacke, Uwe (Renewable Resources)
Strelkov, Stephen (Agricultural, Food & Nutritional Science)
Flanagan, Larry (Biological Sciences Department, University of Lethbridge)
Deyholos, Michael (Department of Biological Sciences)
Department of Renewable Resources
Forest Biology and Management
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Variation in xylem structure and function has been extensively studied across different species with a wide taxonomic, geographical and ecological coverage. In contrast, our understanding of how xylem of a single species can adjust to different growing conditions remains limited. In this thesis, I studied phenotypic plasticity in xylem traits in hybrid poplar (Populus trichocarpa × deltoides). Clonally propagated saplings were grown under experimental drought, nitrogen fertilization and shade for >30 days. The hydraulic and anatomical traits of secondary xylem were subsequently examined. Substantial variation in the dimensions of xylem cells and wood density was observed. The changes in xylem structure were paralleled by differences in xylem hydraulic conductivity and vulnerability to drought-induced cavitation. In order to gain insights into the molecular underpinnings of different xylem phenotypes, I conducted a microarray analysis of gene expression in the developing xylem of plants receiving high versus low nitrogen (N) supply. I found 388 genes differentially expressed (fold change ±1.5, P ≤ 0.05), including a number of genes putatively involved in nitrogen and carbohydrate metabolism and various aspects of xylem cell differentiation. The results of this study provide us with gene candidates potentially affecting xylem hydraulic and structural traits. Furthermore, the results presented in this thesis enhance our knowledge of the mechanisms underlying xylem vulnerability to drought-induced cavitation. Using scanning and transmission electron microscopy, I studied the structure and chemical composition of pit membranes in saplings grown under shade and control light conditions. I found that pit membranes in shade plants were thinner and showed an increased tendency for pore enlargement during membrane dehydration compared to control plants. This difference in pit membrane structure is consistent with greater xylem vulnerability in shade plants. I furthermore showed that pectic homogalacturonans are not abundant in the intervessel pit membranes of hybrid poplar. In a follow-up study, I corroborated this surprising result. Using immunolabeling and two specialized histological methods, I demonstrated that homogalacturonans and calcium are restricted only to a limited region around the edges of the membrane in four angiosperm species including poplar. This finding has important implications for our understanding of pit membranes.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Plavcová L, Hacke UG, Almeida-Rodriguez AM, Li Eryang & Douglas CJ (2012). Gene expression patterns underlying changes in xylem structure and function in response to increased nitrogen availability in hybrid poplar. Plant, Cell & Environment. DOI: 10.1111/j.1365-3040.2012.02566.xPlavcová L, Hacke UG & Sperry JS (2011). Linking irradiance-induced changes in pit membrane ultrastructure with xylem vulnerability to cavitation. Plant, Cell & Environment. 34:501-513.Plavcová L & Hacke UG (2011). Heterogeneous distribution of pectin epitopes and calcium in different pit types of four angiosperm species. New Phytologist. 192: 885-897.

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