Departamento de Ecología e Hidrología. Facultad de Biología, Universidad de Murcia, Campus de Espinardo, Murcia, Spain.
Departamento de Ecología, Pabellón 13, Universidad de Alicante, Alicante, Spain.
PLoS One. 2018 Nov 16;13(11):e0207345. doi: 10.1371/journal.pone.0207345. eCollection 2018.
The seagrass Posidonia oceanica is considered one of the oldest and largest living organisms on Earth. Notwithstanding, given the difficulty of monitoring its fruits and seeds in the field, the development of P. oceanica during its sexual recruitment is not completely understood. We studied the stages of development of P. oceanica seeds from their dispersion in the fruit interior to their settlement in sediment through histological, ultrastructural and mesocosm experiments. P. oceanica sexual recruitment can be divided into three main stages that focus on maximising photosynthesis and anchoring the seedlings to the sediment. In the first stage (fruit dispersion), seeds perform photosynthesis while being transported inside the fruit along the sea surface. In the second stage (seed adhesion), seeds develop adhesive microscopic hairs that cover the primary and secondary roots and favour seed adhesion to the substrate. In the last stage (seedling anchorage), roots attach the seedlings to the substrate by orienting them towards the direction of light to maximise photosynthesis. The adaptations observed in P. oceanica are similar to those in other seagrasses with non-dormant seeds and fruits with membranous pericarps, such as Thalassia sp. and Enhalus sp. These common strategies suggest a convergent evolution in such seagrasses in terms of sexual recruitment. Understanding the sexual recruitment of habitat-forming species such as seagrasses is necessary to adequately manage the ecosystems that they inhabit.
海草波西多尼亚海草被认为是地球上最古老和最大的生物之一。尽管如此，由于在野外监测其果实和种子存在困难，因此对其有性繁殖过程的了解并不完全。我们通过组织学、超微结构和中观实验研究了波西多尼亚海草种子从内部果实散布到在沉积物中定居的发育阶段。波西多尼亚海草的有性繁殖可以分为三个主要阶段，重点是最大限度地提高光合作用并将幼苗固定在沉积物中。在第一阶段（果实散布），种子在果实内部沿着海面进行光合作用的同时被运输。在第二阶段（种子附着），种子发育出微小的粘性毛，覆盖主根和次生根，并有利于种子附着在基质上。在最后一个阶段（幼苗锚固），通过朝向光源的方向引导根，使幼苗附着在基质上，从而最大限度地提高光合作用。在波西多尼亚海草中观察到的适应与其他具有非休眠种子和膜质种皮的海草，如马尾藻属和巨藻属，是相似的。这些共同的策略表明，这些海草在有性繁殖方面存在趋同进化。了解海草等栖息地形成物种的有性繁殖对于充分管理它们所栖息的生态系统是必要的。
