Descending from terrestrial plants, seagrasses have evolved adaptations to survive in marine environments.

Saltwater

Seagrasses are well adapted to saltwater. Photo courtesy NOAA
Seagrasses are well adapted to saltwater. Photo courtesy NOAA

The adaptation to saltwater is most important since most land plants cannot tolerate even small amounts of salt. This salinity tolerance differs among species of seagrasses, resulting in zonation patterns.

Wave Energy

Seagrasses have flexible blades that bend with little resistance to water movement. Photo courtesy NOAA
Seagrasses have flexible blades that bend with little resistance to water movement. Photo courtesy NOAA

In response to high wave energy environments, seagrasses evolved well-developed horizontal stems, referred to as rhizomes. Blades grow directly from the rhizome or from branches originating at the rhizome. Roots extending from the rhizome also assist in anchoring and taking up dissolved nutrients.

The ribbon-shaped grass blades are flexible, bending with any water movement. Air spaces extending through the blades, rhizomes, and roots provide flotation and repiration mechanisms.


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