PREMISE Lianas are intriguing forest components in the tropics worldwide. They are characterized by thin and flexible stems, which have been related to a unique stem anatomy. Here, we hypothesized that the anatomical diversity of lianas, varying in shapes, proportions, and dimensions of tissues and cell types, would result in different stem bending stiffnesses across species. To test this hypothesis, we chose four abundant liana species of central Amazonia belonging to the monophyletic tribe Bignonieae (Bignoniaceae) and compared their basal stems for their anatomical architectures and bending properties. METHODS Measurements of anatomical architecture and bending stiffness (structural Young's modulus) included light microscopy observations and three-point bending tests, which were performed on basal stems of eight individuals from four Bignonieae species. All analyses, including comparisons among species and relationships between stem stiffness and anatomical architecture, were performed using linear models. RESULTS Although the anatomical architecture of each species consists of different qualitative and quantitative combinations of both tissues and cell types in basal stems, all species analyzed showed similarly lower bending stiffnesses. This similarity was shown to be directly related to high bark contribution to the second moment of area, vessel area and ray width. CONCLUSIONS Similar values of stem bending stiffness were encountered in four liana species analyzed despite their variable anatomical architectures. This pattern provides new evidence of how different quantitative combinations of tissue and cell types in the basal stems of lianas can generate similarly low levels of stiffness in a group of closely related species.

中文翻译：

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种间解剖学差异导致紫杉科藤本植物的茎具有相似的高度柔韧度

前提 藤本植物是全球热带地区引人入胜的森林组成部分。它们的特点是茎细而灵活，这与独特的茎解剖结构有关。在这里，我们假设藤本植物的解剖多​​样性，在组织和细胞类型的形状、比例和尺寸方面不同，将导致不同物种的茎弯曲刚度不同。为了验证这一假设，我们选择了属于单系部落 Bignonieae (Bignoniaceae) 的四种丰富的亚马逊中部藤本植物，并比较了它们基部茎的解剖结构和弯曲特性。方法解剖结构和弯曲刚度（结构杨氏模量）的测量包括光学显微镜观察和三点弯曲试验，这是在来自四种紫杉科物种的八个个体的基部茎上进行的。所有分析，包括物种之间的比较以及茎刚度和解剖结构之间的关系，都是使用线性模型进行的。结果 虽然每个物种的解剖结构由基部茎中组织和细胞类型的不同定性和定量组合组成，但所有分析的物种都显示出类似的较低的弯曲刚度。这种相似性被证明与高树皮对面积二阶矩、血管面积和射线宽度的贡献直接相关。结论 尽管四种藤本植物的解剖结构不同，但在分析的四种藤本植物中遇到了类似的茎弯曲刚度值。