Departamento de Biologia, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901, Ribeirão Preto, SP, Brazil.
Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, s/n, 14040-903, Ribeirão Preto, SP, Brazil.
Am J Bot. 2019 Mar;106(3):489-506. doi: 10.1002/ajb2.1254. Epub 2019 Mar 15.
This study details the unusual synorganization of the staminate flower in wind-pollinated urticalean rosids to add the missing pieces that complete the puzzle of the explosive mechanism of pollen release in this group.
Flower buds and flowers were analyzed using light and scanning electron microscopy.
The pistillode, stamens, and sepals form a floral apparatus that explosively releases pollen to be carried by the wind. The anthers dehisce when the stamens are still inflexed on the floral bud and are enveloped by the sepals and supported by an inflated pistillode. The distension of the filaments presses the pistillode, which decreases the pressure exerted on the anthers by releasing the air accumulated internally through its apical orifice. The extended filaments and the dehiscent free anthers move rapidly outward from the center of the flower. This movement of the filaments is then blocked by the robust basally united sepals, which causes a rapid inversion of the anther position, thus hurling the pollen grains far from the flower. The pollen grains are released grouped by the mucilage produced in high quantity in the cells found in all floral organs.
The anatomical structure of the pistillode and the finding of mucilaginous cells are the main features that help in the understanding the explosive mechanism of pollen release in urticalean rosids. The pistillode can be considered an exaptation because it was evolved later to provide a new role in the plant, optimizing male fitness.
本研究详细描述了风媒荨麻目杨柳科雄性花的异常同步组织，以补充该类群花粉释放爆炸机制拼图中缺失的部分。
使用光镜和扫描电子显微镜对花蕾和花朵进行分析。
雌蕊、雄蕊和萼片形成一个花器官，可将花粉爆炸性释放，随风传播。当雄蕊仍在花蕾上弯曲且被萼片包裹并由膨胀的雌蕊支撑时，花药开裂。花丝的膨胀将雌蕊向下压，从而通过其顶端孔释放内部积累的空气，从而减少对花药施加的压力。伸展的花丝和开裂的自由花药从花朵的中心迅速向外移动。然后，花丝的这种运动被基部联合的强壮萼片阻挡，导致花药位置迅速反转，从而将花粉粒远远抛出花朵。花粉粒通过在所有花器官中发现的大量细胞产生的粘液释放时成团。
雌蕊的解剖结构和粘液细胞的发现是帮助理解荨麻目杨柳科花粉释放爆炸机制的主要特征。雌蕊可以被认为是一种适应，因为它是后来进化而来的，为植物提供了一个新的角色，优化了雄性的适应性。
