Common Bladderwort (Utricularia macrorhiza)


Common Bladderwort Detail

The Common Bladderwort (Utricularia macrorhiza or Utricularia vulgaris) is of the order Lamiales and Bladderwort Family (Lentibulariaceae) and is a carnivorous plant common in French Hill Pond. The specimen shown in the photographs on this page was removed from French Hill Pond for study in July 2010. All members of this genus are carnivorous.

Common Bladderworts do not have roots but obtain their nutrients directly from the water like algae. However, they are much more sophisticated than algae. The stems of bladderworts are called stolons. The leaves of the bladderwort in which photosynthesis takes place are attached to the stolons. Scattered throughout the plant are tiny bladders that trap food. The genus name, Utricularia, comes from the Latin, utriculus, that translates to "leather bag." The bladders of a bladderwort do look like tiny leather bags. These bladders are ingenious applications of physical principles. Water in the bladders is constantly being forced out through the bladder's walls by osmosis as the plant is moved about in the water. A partial vacuum is generated causing the bladder to crush inward. The opening of the bladder during this process is closed and sealed by the difference in water pressure, the pressure being higher outside than inside. This process is limited by the osmotic pressure generated by the passage of water through the bladder walls. The bladder mouth or opening is surrounded by tiny hairs. The bladder remains closed until these hairs are disturbed, thereby breaking the vacuum and sucking the prey into the bladder. The prey is digested as the process is repeated.

The Common Bladderworts of French Hill Pond are large enough to capture and digest tiny insects as well as microorganisms. The bladders are the dark or black parts of the plant in the photograph above. Note that the bladders are scattered in the leaves, which is one of the distinguishing characteristics of the Common Bladderwort. The leaves are filament-like, branched and finely divided. They are arranged on the stolon in an offset, alternate pattern. As this bladderwort grows, the new leaves are a bit greener than the old and the newest bladders are almost transparent. The new bladders turn tan and eventually black as the plant grows. These transitions can be seen in the photograph below. The newer part of the plant is at the upper left.

The flower of the Common Bladderwort resembles a yellow snapdragon. The Common Bladderwort reproduces by winter buds and segments of the plant that survive winter. This plant flowers June to August.

Common Bladderwort


Common Bladderworts may be seen suspended in the pond water frequently near hair algae. If the plant is removed from the water, it will collapse into what appears to be grass with black dots. Placed back in water, the Common Bladderwort will return to the form shown in the photographs above. The Common Bladderwort can survive on the ground during droughts. It is a very adaptable and ingenious plant. WARNING: This plant has tiny hairs containing an acid that can irritate skin.


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