Plant Stems: Functional Design and Mechanics
Plant stems are one of nature's most impressive mechanical constructs. Their sophisticated hierarchical structure and multifunctionality allow trees to grow more than 100 m tall. This review highlights the advanced mechanical design of plant stems from the integral level of stem structures down to the fiber-reinforced-composite character of the cell walls. Thereby we intend not only to provide insight into structure-function relationships at the individual levels of hierarchy but to further discuss how growth forms and habits of plant stems are closely interrelated with the peculiarities of their tissue and cell structure and mechanics. This concept is extended to a further key feature of plants, namely, adaptive growth as a reaction to mechanical perturbation and/or changing environmental conditions. These mechanical design principles of plant stems can serve as concept generators for advanced biomimetic materials and may inspire materials and engineering sciences research.
Available from: Moacyr Bernardino Dias-Filho
- "This is commonly observed in studies of forest tree species under restricted light conditions   . According to these studies, stem diameter is commonly measured, because its development is essential for growth, ensuring plant survival in the field under environmental stress and is also important for wood formation  . "
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ABSTRACT: Variations in light intensity can lead to important anatomical and morphophysiological changes in plants. Aiming to increase knowledge about the Amazonian tree species, this study examines the influence of shade on the cambial activity and development of Parkia gigantocarpa Ducke and Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby seedlings. Seedlings of the two species were grown in a nursery under four shade intensities (treatments): full sun, low, moderate, and high shade (resp., 0%, 23%, 67%, and 73% of shade, or 2000, 1540, 660, and 540 í µí¼mol⋅m −2 ⋅s −1) obtained with polyethylene screens. We measured plant height, stem diameter, biomass production, stomatal conductance (í µí± í µí±), transpiration (E), photosynthesis (A), and cambial activity (CA) (xylem, cambium, and phloem). Also, we calculated the Dickson Quality Index (DQI). The highest values of biomass production, í µí± í µí± , E, A, and DQI, were found under full sun, in P. gigantocarpa, and under low shade intensity in S. parahyba. In both species high shade intensity reduced CA. We concluded that the CA and the physiological and morphological attributes work together, explaining the radial growth and increasing seedlings quality, which optimized efficient seedling production under full sun, in P. gigantocarpa, and under low shade intensity in S. parahyba.
Available from: Khoi Anh Nguyen
- "all the nodes at the bottom surface of the model were set to be fully fixed), without branches but with foliage. The cocowood form and complex hierarchical structure at integral level (Speck and Burgert 2011, Knippers and Speck 2012) shaped in the FE model by the fibrovascular bundle orientations and the density distribution were derived from previous findings by the authors (Gonzalez et al. 2014b, Gonzalez 2015). Specifically, the characteristic 25 m cocowood stem shape was mapped in the FE model using the representative palm stem radius R max (in mm) given as: "
Available from: Xiaoqing Wang
- "Plants have adopted different growth strategies to form numerous types of stem structure with specific functional anatomy and excellent mechanical properties to fulfil a multiplicity of functions, such as mechanical support and water transport to ensure survival and competitiveness in their respective habitats (Speck and Burgert, 2011; Niklas and Spatz, 2012). The monocotyledonous bamboos grow fast in length but do not show secondary thickening to add cells to their periphery, and the final diameter of the stem is determined in the initial growth phase, which results in a slender stem with a hollow structure. "
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ABSTRACT: Background and Aims Bamboo is well known for its fast growth and excellent mechanical performance, but the underlying relationships between its
structure and properties are only partially known. Since it lacks secondary thickening, bamboo cannot use adaptive growth
in the same way as a tree would in order to modify the geometry of the stem and increase its moment of inertia to cope with
bending stresses caused by wind loads. Consequently, mechanical adaptation can only be achieved at the tissue level, and this
study aims to examine how this is achieved by comparison with a softwood tree species at the tissue, fibre and cell wall levels.
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