Which structure anchors seaweeds to the substrate?

• A. Holdfast
• B. Gas Bladder
• C. Frustule
• D. Mangrove

Answer: (A)

Seaweeds stay in place in dynamic coastal waters thanks to a specialized attachment structure that anchors them to the substratum. This holdfast acts like a root-like grip, gripping rocks or other surfaces so the seaweed can resist wave action and currents. It keeps the thallus in place while nutrients diffuse through the rest of the plant, but it doesn’t conduct water or nutrients the way a true root would in a land plant.

Gas bladders, or pneumatocysts, provide buoyancy to keep the blades near the surface where light is available, not anchorage. The frustule is the silica cell wall of diatoms, microscopic and not involved in anchoring seaweeds. Mangroves are terrestrial or coastal trees with true roots and not part of seaweed anatomy.