College of Life Sciences, Wuhan University, Wuhan, 430072, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
BMC Plant Biol. 2022 Mar 12;22(1):113. doi: 10.1186/s12870-022-03494-z.
Many seed plants produce winged diaspores that use wind to disperse their seeds. The morphology of these diaspores is directly related to the seed dispersal potential. The majority of winged diaspores have flat wings and only seeds; however, some angiosperms, such as Firmiana produce winged fruit with a different morphology, whose seed dispersal mechanisms are not yet fully understood. In this study, we observed the fruit development of F. simplex and determined the morphological characteristics of mature fruit and their effects on the flight performance of the fruit.
We found that the pericarp of F. simplex dehisced early and continued to unfold and expand during fruit development until ripening, finally formed a spoon-shaped wing with multiple alternate seeds on each edge. The wing caused mature fruit to spin stably during descent to provide a low terminal velocity, which was correlated with the wing loading and the distribution of seeds on the pericarp. When the curvature distribution of the pericarp surface substantially changed, the aerodynamic characteristics of fruit during descent altered, resulting in the inability of the fruit to spin.
Our results suggest that the curved shape and alternate seed distribution are necessary for the winged diaspore of F. simplex to stabilize spinning during wind dispersal. These unique morphological characteristics are related to the early cracking of fruits during development, which may be an adaptation for the wind dispersal of seeds.
许多种子植物产生带翼的种子，利用风来传播它们的种子。这些种子的形态与种子传播潜力直接相关。大多数带翼的种子具有扁平的翅膀和只有种子；然而，一些被子植物，如 Firmiana，产生具有不同形态的带翼果实，其种子传播机制尚未完全理解。在本研究中，我们观察了 F. simplex 的果实发育，并确定了成熟果实的形态特征及其对果实飞行性能的影响。
我们发现，F. simplex 的果皮早期开裂，并在果实发育过程中继续展开和扩展，直到成熟，最终形成一个带有多个交替种子的勺形翅膀。翅膀使成熟的果实在下降过程中稳定旋转，提供较低的终端速度，这与翅膀载荷和果皮上种子的分布有关。当果皮表面的曲率分布发生显著变化时，果实在下降过程中的空气动力特性发生改变，导致果实无法旋转。
我们的结果表明，F. simplex 的带翼种子在风传播过程中稳定旋转需要弯曲的形状和交替的种子分布。这些独特的形态特征与果实发育过程中早期开裂有关，这可能是适应种子风传播的结果。
