Plant Development / Développement des plantes (CBA/ABC)
Yin, Xiaofeng , Lacroix, Christian , Barabé, Denis .
Analysis of phyllotactic pattern transition in seedlings of Thuja occidentalis.
Phyllotaxis (phyllotaxy) is central to the study of plant morphogenesis. It deals with the arrangement of plant organs such as leaves, bracts, branches, petals, florets, and scales during their early stages of development as primordia. The most commonly observed phyllotactic patterns are spiral and whorled. In some plants, the phyllotactic pattern will undergo transitions during early stages of development. During these transitions, some important phyllotactic parameters (apex volume, divergence angle and plastochrone ratio) undergo corresponding changes. The objectives of this study are (1) to describe the developmental morphology of seedlings of T. occidentalis; (2) to establish the mathematical basis of different phyllotactic patterns in T. occidentalis and (3) to document the pattern transition of T. occidentalis. Young seedlings aged from 12 to 24 months were used to collect quantitative data. To describe the developmental morphology of the plant, shoot tips were dissected and examined using scanning electron microscopy (SEM). The volume of the shoot apex was measured using 3D reconstruction software. Divergence angles and the plastochrone ratio were determined by using cross sections of the shoot tip. Before the development of the first branch on the seedling, the main stem undergoes a transition from a whorl of 4 to a whorl of 3 pattern (sometimes from a whorl of 4 to a whorl of 2 pattern). Eventhough all side branches have a decussate phyllotactic pattern characteristic of mature shoots, the main stem can still exhibit a whorl of 3 pattern. If the main stem has made the transition to decussate phyllotaxis before the first branching event, this pattern will be maintained throughout. The ranges in values of the parameters measured at different stages during the phyllotactic transition overlap and don’t form distinct categories.
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1 - University of Prince Edward Island, Department of Biology, 550 University Avenue, Charlottetown, PE, C1A 4P3, Canada
2 - Jardin botanique de Montréal, Institut de recherche en biologie végétale, 4101 Sherbrooke Est., Montréal, QC, H1X 2B2, Canada
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM