Monterey Bay Aquarium Research Institute
Marine Botany

Morphology

Holdfast

holdfast on rock

Through the mixed winter waters, a holdfast is visible (above) at the base of the giant kelp.  A giant kelp holdfast does just that, it holds fast to the rocky floor.  In appearance, it looks similar to roots.  However, these roots due not uptake nutrients and water as terrestial plants do.  The holdfast maintains the kelps position.  The holdfast of giant kelp is perennial, and will last one to seven years (Connor and Baxter 1989).

As the holdfast grows, new branches grow over the old, inner ones into new cracks and crevices.  Over time, this produces a large conical shape for the holdfast.  Pictured above is Macrocystis integrifolia, the intertidal relative of the giant kelp.  Giant kelp's holdfast can grow many tiimes larger than its intertidal relative.

holdfast

Over time, resident animalss of the kelp forest eat the older, inner layers of the holdfast, pictured above.  This hollowed out cone gives refuge to many members of the kelp forest community.  As the giant kelp fast holdfast ages, it may lose its grip on the ocean floor, especially during strong winter storms, and end up as beach rack or on the ocean floor in deeper water (Connor and Baxter 1989).

Copyright 2001:  James Lopez

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