Isnard S, Speck T, Rowe N P
Botanique et Bioinformatique de l'Architecture des Plantes, UMR 5120 CNRS, TA40/PS2, Boulevard de la Lironde, 34398 Montpellier, France.
Plant Biomechanics Group, Institute for Biology II, Botanical Garden of the Albert-Ludwigs-Universität, Schänzlestrasse 1, D-79104 Freiburg, Germany.
New Phytol. 2003 Jun;158(3):543-559. doi: 10.1046/j.1469-8137.2003.00771.x.
• Mechanical architectures of two Clematis species, the herbaceous perennial Clematis recta and the woody liana, Clematis vitalba, were investigated and compared with the woody rhizomatous sand dune plant Clematis flammula var. maritima. • Bending mechanical properties of stems from various developmental stages were compared and related to stem geometry and relative proportions of tissues during development. • Clematis vitalba and C. flammula var. maritima showed mechanical architectures with reductions in structural Young's modulus of the stem during ontogeny. Irreversible loss of stem rigidity was mediated by disruption, separation and eventual loss of primary phloem fibres via secondary growth of the periderm and cambial activity. Each species showed variations of non-self-supporting mechanical architecture relating to specific habitat preferences. In aerial stems of C. recta the structural Young's modulus remained approximately constant during ontogeny, a mechanical signal characteristic for semi-self-supporting architectures. • Woody aerial plant stems are extremely rare in the Ranunculaceae and seldom, if ever, show self-supporting characteristics. Growth form evolution in the group may have been canalised by evolution of rhizomatous geophytic growth forms with secondary growth confined to underground stems specialized for water conduction, storage and perennation. Variation of this ground plan includes climbing, straggling or rhizomatous architectures but not self-supporting shrubs or trees with secondary growth generating requisite self-supporting mechanical properties. Certain body plan organisations appear to have inbuilt mechanical constraints which may have profound effects on the subsequent evolution of growth forms.
• 对两种铁线莲属植物的机械结构进行了研究，这两种植物分别是多年生草本植物直立铁线莲和木质藤本植物欧铁线莲，并与木质根茎沙丘植物滨海铁线莲变种进行了比较。
• 比较了不同发育阶段茎的弯曲力学性能，并将其与发育过程中茎的几何形状和组织相对比例相关联。
• 欧铁线莲和滨海铁线莲变种在个体发育过程中，茎的结构杨氏模量降低，表现出机械结构特点。茎刚性的不可逆丧失是由周皮的次生生长和形成层活动导致的初生韧皮部纤维的破坏、分离以及最终丧失所介导的。每个物种都表现出与特定栖息地偏好相关的非自支撑机械结构变化。在直立铁线莲的气生茎中，结构杨氏模量在个体发育过程中大致保持恒定，这是半自支撑结构的一个力学信号特征。
• 毛茛科中的木质气生植物茎极为罕见，很少（如果有的话）表现出自支撑特征。该类群的生长形式进化可能已通过根茎状地生生长形式的进化而被限定，次生生长局限于专门用于水分传导、储存和多年生的地下茎。这种基本结构的变化包括攀缘、蔓生或根茎状结构，但不包括具有次生生长以产生必要自支撑力学性能的自支撑灌木或树木。某些身体结构组织似乎具有内在的机械限制，这可能对生长形式的后续进化产生深远影响。
