Department of Biology, Botany, University of Osnabrück, Barbarastraße 11, D-49076, Osnabrück, Germany.
School of Biological Sciences, Plant Molecular Science and Centre for Systems and Synthetic Biology, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK.
Nat Commun. 2017 Nov 30;8(1):1868. doi: 10.1038/s41467-017-02051-9.
The biomechanical and ecophysiological properties of plant seed/fruit structures are fundamental to survival in distinct environments. Dispersal of fruits with hard pericarps (fruit coats) encasing seeds has evolved many times independently within taxa that have seed dispersal as their default strategy. The mechanisms by which the constraint of a hard pericarp determines germination timing in response to the environment are currently unknown. Here, we show that the hard pericarp of Lepidium didymum controls germination solely by a biomechanical mechanism. Mechanical dormancy is conferred by preventing full phase-II water uptake of the encased non-dormant seed. The lignified endocarp has biomechanically and morphologically distinct regions that serve as predetermined breaking zones. This pericarp-imposed mechanical dormancy is released by the activity of common fungi, which weaken these zones by degrading non-lignified pericarp cells. We propose that the hard pericarp with this biomechanical mechanism contributed to the global distribution of this species in distinct environments.
植物种子/果实结构的生物力学和生态生理学特性是其在不同环境中生存的基础。具有坚硬种皮（果皮）的果实的传播在具有种子传播默认策略的分类群中多次独立进化。目前尚不清楚坚硬种皮的约束如何根据环境确定发芽时间的机制。在这里，我们表明， Lepidium didymum 的坚硬种皮仅通过生物力学机制来控制发芽。机械休眠是通过阻止包裹的非休眠种子完全进入第二阶段吸水来实现的。木质化的内果皮具有在生物力学和形态上不同的区域，作为预定的断裂区。这种由种皮施加的机械休眠是由常见真菌的活动释放的，真菌通过降解无木质化的种皮细胞来削弱这些区域。我们提出，具有这种生物力学机制的坚硬种皮有助于该物种在不同环境中的全球分布。
