Developmental and Structural Section
Kitin, Peter , Robert, Elisabeth M.R. , Ntamwira, Niranda , Van den Bulcke, Jan , Takata, Katsuhiko , Beeckman, Hans , Lachenbruch, Barbara .
Three-Dimensional Structure of Stems formed by Successive Cambia.
Plant stems formed by successive cambia contain alternating layers of xylem and phloem, embedded in conjunctive tissue. The three-dimensional structure and the functional significance of the stem architecture with alternating vascular bands are little known. In Salacia reticulata, and Sericostachys scandens, successive cambia and new vascular increments were initiated from parenchyma cells at the outer side of the recently-formed phloem. Radial transport within a vascular increment may occur through the frequent tangential-wall pitting at the xylem/cambium interface. Radial transport between vascular increments may occur through rays and also along stem axis as successive vascular increments were inter-connected at different vertical positions along the stem. Moreover, S. scandens contained large vascular rays with vascular bundles, each initiating from an inner xylem increment and ending in the outer bark. Such 3-D network of subsequent vascular increments would confer an improved safety for the long-distance vascular transport in the case of injury or dysfunction of portions of the vasculature. In Avicennia, one of the main mangrove genera, the amount of internal phloem as well as the complexity of its reticulate structure inside the stem is found to change with changing environmental conditions. In more stressful conditions such as higher salinity levels, an increased proportion of internal phloem as well as a more complex internal structure can be observed suggesting an ecological advantage from the internal phloem in harsh environmental conditions by water storage and embolism repair. A database analysis showed 84.9% of the woody shrub and tree species with concentric internal phloem occur in either dry or saline environments. Other functional attributes that may result from this stem structure include allowing stems to flex and twist with less damage to the vasculature, and providing abundant and close phloem and conjunctive tissues for the xylem that could serve for carbohydrate storage, wound repairs and defenses against pathogens, as well as for meeting local demands for growth and maintenance.
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1 - Akita Prefectural University, Institute of Wood Technology, Noshiro-shi, Japan
2 - Vrije Universiteit Brussel (VUB), Laboratory for Plant Biology and Nature Management (APNA), Brussels, Belgium
3 - Official University of Bukavu, DP Congo
4 - Ghent University, Faculty of Bioscience Engineering, Laboratory of Wood Technology, Gent, 9000, Belgium
5 - Royal Museum for Central Africa, Laboratory for Wood Biology, Tervuren, 3080, Belgium
6 - DEPT WOOD SCI & ENGIN, 119 Richardson Hall, Oregon State University, Corvallis, OR, 97331, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Waterman Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 9:15 AM