Monterey Bay Aquarium Research Institute
Marine Botany

Ulva title imageMorphology   

Structure       Function       Mechanical Properties  


Every cell in Ulva species contains photosynthetic pigments, including the reproductive cells. The chloroplasts are large and cup-shaped, located toward the exterior of each cell. All cells are also capable of reproduction, and there are no distinct reproductive structures.Ulva contain no intercellular connections (plamodesmata), and are essentially little more than complex colonies.

A surface view, showing the chloroplasts

A single rhizoid cell can generate a whole new alga, and blade cells of U. mutabilis can form new algae with a different morphology (vesicular thalli one cell thick). Interestingly, if any Ulva are grown without bacteria present, they lose their normal morphology and develop into pincushion-like colonies.

Ulva are pseudo-perennial: the holdfast portions are perennial and proliferate new blades each spring. The lower cells of the thallus produce rhizoids (long slender filaments), which grow down between the two cell layers then outward to form the holdfast.

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 ©Anna Kirby 2001  

Last updated: Feb. 05, 2009