Creating an explosion: how growth and tension interact in explosive fruit

种子传播是一个物理过程，其中种子从一个位置移动到另一个位置。进化已经为植物传播种子形成了许多巧妙的适应性。从机械的角度来看，也许最有趣的是水果产生自己的爆炸力来喷射种子。我们研究这一特点的爆炸性种子传播的拟南芥相对，碎米荠。在这个项目中，我们解决如何在C中产生爆炸所需的张力。毛果我们以前表明，张力产生的差异收缩的组织在果实瓣。一个活跃的外层组织层收缩，而一个不可伸展的内层，由木质素硬化，不收缩。外果皮组织层中的细胞利用膨压通过在其他维度上扩张而在长度上收缩。我们使用有限元建模表明，外果皮细胞的形状和各向异性是很重要的这种反应。该项目第一阶段解决的具体问题是外果皮细胞如何通过生长获得这些特性？利用活细胞成像和形态动力学方法，我们定量的皮质微管的取向以及细胞生长的数量，方向和持续时间在外果皮层的C。毛果我们的研究结果揭示了一种独特的细胞生长模式，其基础是皮质微管的预测性重新定向，将定向生长分为两个发育阶段。外果皮中完全各向异性生长的后期阶段，产生收缩所需的细胞形状和各向异性。通过将这些信息整合到生长细胞的三维模型中，我们可以模拟在C.多毛。在第二阶段，我们将利用这些方法和发现，以进一步了解皮质微管的作用，指导产生和释放的张力，在爆炸性卷曲和扭曲的C。多毛果裂爿。

Seed dispersal is a physical process in which seeds are moved from one location to another. And evolution has shaped a multitude of ingenious adaptations for plants to disperse their seeds. Perhaps most intriguing from a mechanical perspective, are the fruits that generate their own explosive force to eject their seeds. We study this trait of explosive seed dispersal in the Arabidopsis relative, Cardamine hirsuta. In this project, we address how the tension required for explosion is produced in C. hirsuta fruit. We previously showed that tension is generated by differential contraction of tissues in the fruit valve. An active, outer tissue layer contracts while an inextensible inner layer, stiffened by lignin, does not. Cells in the outer exocarp tissue layer use turgor pressure to contract in length by expanding in other dimensions. We used finite element modelling to show that exocarp cell shape and anisotropy are important for this response. The specific question addressed in phase one of this project was how do exocarp cells acquire these properties through growth? Using live cell imaging and a morphodynamics approach, we quantified cortical microtubule orientations together with the amount, direction and duration of cellular growth in the exocarp layer of C. hirsuta fruit. Our findings revealed a distinctive pattern of cellular growth, underpinned by predictive reorientations of cortical microtubules, that partitions directional growth into two developmental phases. A late phase of exclusively anisotropic growth in the exocarp, produces the cell shape and anisotropy required for contraction. By incorporating this information into a 3-D model of growing cells, we could mimic the differential contraction found in explosive fruit of C. hirsuta. In phase two, we will capitalize on these methodologies and findings to further understand the role of cortical microtubules in directing the generation and release of tension in explosive coiling and twisting of C. hirsuta fruit valves.