Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia.
Present address: Queensland Herbarium, Mt Coot-tha Road, Toowong, Queensland 4066, Australia.
New Phytol. 2012 Jan;193(1):137-149. doi: 10.1111/j.1469-8137.2011.03887.x. Epub 2011 Oct 14.
• Wind is a key mechanical stress for woody plants, so how do shoot traits affect performance in wind? • We used a vehicle mounted apparatus to measure drag, streamlining and mechanical safety in 127 vertical lead-shoots, 1.2 m long, across 39 species in tropical Australia. • Shoot dimensions and stem tissue properties were closely coupled so that shoots with low stem specific gravity or larger projected area had thicker stems. Thicker stems provide larger second moment of area (I), which increased shoot safety and bending stiffness but impeded shoot reconfiguration in strong winds, including frontal area reduction. Nonetheless, increasing I also improved streamlining. Streamlining was unrelated to traits except I. Stem tissue material properties only had small effects. Higher modulus of rupture increased shoot safety and higher Young's modulus impeded shoot reconfiguration. • We found no conflict between bending stiffness and streamlining for woody shoots. Stiffness might help streamlining by increasing damping and stability, thereby reducing flagging in wind. Tissue-level traits did influence shoot-level mechanical safety and behaviour, but shoot geometry was much more important. Variable shoot and stem traits, which all influenced shoot biomechanics, were integrated in shoots to yield a relatively narrow range of outcomes in wind.
• 风是木本植物的主要机械应力，那么芽的特性如何影响其在风中的表现呢？ • 我们使用车载设备测量了 39 种澳大利亚热带地区 127 根 1.2 米长的垂直导状芽的阻力、流线型和机械安全性。 • 芽的尺寸和茎组织特性密切相关，因此比叶重或投影面积较小的芽具有较粗的茎。较粗的茎提供了更大的惯性矩（I），这增加了芽的安全性和弯曲刚度，但阻碍了强风中的芽重新配置，包括减少迎风面积。尽管如此，增加 I 也改善了流线型。流线型与除 I 以外的特征无关。茎组织材料特性的影响很小。断裂伸长率增加会提高芽的安全性，而杨氏模量增加会阻碍芽的重新配置。 • 我们发现木质芽的弯曲刚度和流线型之间没有冲突。刚度可能通过增加阻尼和稳定性来帮助流线型，从而减少风中的摆动。组织水平的特征确实会影响芽水平的机械安全性和行为，但芽的几何形状更为重要。影响芽生物力学的可变芽和茎特征在芽中进行了整合，从而在风中产生了相对较窄的结果范围。
