Roots adhesion processes in the Mediterranean seagrass Posidonia oceanica

This doctoral thesis investigates root and root hair adhesion in Posidonia oceanica seedlings and its relevance for restoration. This endemic Mediterranean seagrass delivers key ecosystem services, including carbon sequestration, sediment stabilization, and biodiversity support, yet its meadows have declined due to multiple stressors. Restoration remains limited by slow growth and poor understanding of early anchorage. The study aims to clarify the morpho-functional and biomechanical traits driving seedling adhesion to hard substrates, with emphasis on root hairs. An interdisciplinary approach combining experiments, microscopy, biomechanical testing, numerical modelling, and substrate characterization was used to analyze the hierarchical anchorage strategy. Anchorage operates across three interconnected scales: the seed scale (cm), where seeds lodge in crevices; the root scale (mm), where roots penetrate interstices; and the root hair scale (µm), where dense hairs adhere to micro-rough surfaces. Root hairs show marked plasticity, forming adhesive pads that maximize contact. Peel tests identified optimal adhesion at substrate roughness between 3 and 26 µm. Electron microscopy revealed branching hairs and a glue-like substance at the interface, indicating a dual mechanism of mechanical interlocking and biochemical adhesion. Numerical simulations further described contact dynamics under different roughness conditions. The thesis also proposes custom seedling holders that replicate ideal microsites to enhance early establishment. Produced from biodegradable materials or via 3D printing, these devices enable sustainable and scalable restoration. Overall, this research advances understanding of P. oceanica seedling anchorage and provides a biologically informed framework for Mediterranean seagrass restoration.

 

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