An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture
Populus tremuloides Michx. (trembling aspen) is a tree species native to much of North America, characterized by an excurrent crown with horizontal to ascending branches and a dominant terminal leader. An unusual clone of trembling aspen was discovered in the 1940s near Hafford, Saskatchewan. This...
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ndltd-LACETR-oai-collectionscanada.gc.ca-MWU.1993-2232014-03-29T03:40:57Z An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture Linden, Ashley Wade Remphrey, William R (Plant Science) Stasolla, Claudio (Plant Science) Renault, Sylvie (Botany) Populus tremuloides crooked clone shoot branch architecture biomechanics shoot anatomy phloem fibres reaction wood L-system Populus tremuloides Michx. (trembling aspen) is a tree species native to much of North America, characterized by an excurrent crown with horizontal to ascending branches and a dominant terminal leader. An unusual clone of trembling aspen was discovered in the 1940s near Hafford, Saskatchewan. This clone demonstrates abnormal crown morphology, in which vigorous shoots bend down, ultimately leading to an overall twisted or crooked appearance. The objectives of the present study were to investigate the mechanism of shoot bending by (1) characterizing the process and timing of bending, (2) evaluating structural aspects of developing wild-type and crooked aspen shoots, and (3) comparing anatomical features of bending shoots with wild-type shoots. L-system reconstruction models of 3-D digitized shoot development revealed dramatic bending midway through the growing season. Morphological analyses revealed that crooked aspen shoots had greater taper compared to the wild-type, typically known to create shoots resist deflection and bending. However, preliminary strength analyses indicated that crooked aspen shoots were less rigid, with smaller values of Young’s modulus compared to wild-type shoots. Anatomical investigations revealed differences in several structural tissues between developing wild-type and crooked aspen shoots, and differences within crooked aspen shoots. Primary phloem fibres on the upper side of bending shoots maintained relatively large lumens while those on the lower side were fully lignified, similar to those of mature vertically oriented wild-type leader shoots. These differences may result in differential extension growth early in development, and/or uneven mechanical support later on, ultimately resulting in bending due to self-weight. Gelatinous fibres (G-fibres), characteristic of tension wood (TW), were found throughout older wild-type and vertically oriented crooked aspen shoots; however, G-fibres were only found on the lower side of crooked aspen shoots. These lateral differences could have contributed to shoot bending by actively bending shoots downwards, or lack of TW on the upper side may not have prevented biomechanical bending from self weight. Nevertheless, shoot bending stops at the end of the growing season, suggesting that the mechanisms involved in creating bent shoots are only functional during the first growing season. 2006-03-28T13:19:35Z 2006-03-28T13:19:35Z 2006-03-28T13:19:35Z Electronic Thesis or Dissertation http://hdl.handle.net/1993/223 en_US |
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en_US |
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Populus tremuloides crooked clone shoot branch architecture biomechanics shoot anatomy phloem fibres reaction wood L-system |
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Populus tremuloides crooked clone shoot branch architecture biomechanics shoot anatomy phloem fibres reaction wood L-system Linden, Ashley Wade An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture |
description |
Populus tremuloides Michx. (trembling aspen) is a tree species native to much of North America, characterized by an excurrent crown with horizontal to ascending branches and a dominant terminal leader. An unusual clone of trembling aspen was discovered in the 1940s near Hafford, Saskatchewan. This clone demonstrates abnormal crown morphology, in which vigorous shoots bend down, ultimately leading to an overall twisted or crooked appearance. The objectives of the present study were to investigate the mechanism of shoot bending by (1) characterizing the process and timing of bending, (2) evaluating structural aspects of developing wild-type and crooked aspen shoots, and (3) comparing anatomical features of bending shoots with wild-type shoots. L-system reconstruction models of 3-D digitized shoot development revealed dramatic bending midway through the growing season. Morphological analyses revealed that crooked aspen shoots had greater taper compared to the wild-type, typically known to create shoots resist deflection and bending. However, preliminary strength analyses indicated that crooked aspen shoots were less rigid, with smaller values of Young’s modulus compared to wild-type shoots. Anatomical investigations revealed differences in several structural tissues between developing wild-type and crooked aspen shoots, and differences within crooked aspen shoots. Primary phloem fibres on the upper side of bending shoots maintained relatively large lumens while those on the lower side were fully lignified, similar to those of mature vertically oriented wild-type leader shoots. These differences may result in differential extension growth early in development, and/or uneven mechanical support later on, ultimately resulting in bending due to self-weight. Gelatinous fibres (G-fibres), characteristic of tension wood (TW), were found throughout older wild-type and vertically oriented crooked aspen shoots; however, G-fibres were only found on the lower side of crooked aspen shoots. These lateral differences could have contributed to shoot bending by actively bending shoots downwards, or lack of TW on the upper side may not have prevented biomechanical bending from self weight. Nevertheless, shoot bending stops at the end of the growing season, suggesting that the mechanisms involved in creating bent shoots are only functional during the first growing season. |
author2 |
Remphrey, William R (Plant Science) |
author_facet |
Remphrey, William R (Plant Science) Linden, Ashley Wade |
author |
Linden, Ashley Wade |
author_sort |
Linden, Ashley Wade |
title |
An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture |
title_short |
An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture |
title_full |
An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture |
title_fullStr |
An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture |
title_full_unstemmed |
An investigation into mechanisms of shoot bending in a clone of Populus tremuloides exhibiting 'crooked' architecture |
title_sort |
investigation into mechanisms of shoot bending in a clone of populus tremuloides exhibiting 'crooked' architecture |
publishDate |
2006 |
url |
http://hdl.handle.net/1993/223 |
work_keys_str_mv |
AT lindenashleywade aninvestigationintomechanismsofshootbendinginacloneofpopulustremuloidesexhibitingcrookedarchitecture AT lindenashleywade investigationintomechanismsofshootbendinginacloneofpopulustremuloidesexhibitingcrookedarchitecture |
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1716657140176781312 |