Interesting Plants in New Mexico
left and middle Brother
Alfred Brousseau © 1995 Saint Mary's College of California, right
© 2004 Robert Sivinski
The Uncommon Bladderwort
In the hidden realm of shallow pools and tranquil streams dwells
an ogre of the plant kingdom. Armed with an underwater flotilla
of pear-shaped bladders or "utricles," it engulfs myriad unsuspecting
minute passers by. This ogre, the common bladderwort Utricularia
macrorhiza Le Conte, has evolved an ingenious adaptation to
survive in a nitrogen-deficient environment.
A member of the bladderwort family (Lentibulariaceae), the common
bladderwort is a rootless (some say ruthless) perennial aquatic
herb and the only native carnivorous plant in our state. The generic
name, Utricularia, is derived from "utriculus," the Latin
diminutive of "bag". The numerous small bladders are modified hollow
leaves with sensitive bristles on "trap door" entrances. When the
primary prey (Lilliputian crustaceans and insect larvae) trigger
the bristles, the door opens inward, expanding the bladder. The
force of this expansion sucks the prey in and the trap door shuts
within 1/35th of a second. The prey then dies and its decaying remains
An unoccupied trap is somewhat flattened and curves inward because
of water tension. Water pressure is lower inside the bladder than
in the surrounding water. After the trap has been triggered, it
can take 30 minutes for the excess water to pass to the exterior
of the bladder, restoring the water tension and resetting the trap.
There may be hundreds of tiny bladders on a single plant, attached
to submerged leaves by short slender stalks. These bladders measure
just a few millimeters wide.
Being aquatic and devoid of roots would pose nutritional problems
if it were not for the numerous bladders digesting a nitrogen-rich
supply of aquatic animals. Biologists are uncertain whether digestion
occurs through enzymes secreted by the bladders or by bacterial
breakdown. It is presumed that the decomposed nutrients are absorbed
through the cells of the bladders.
In July, attractive flowers rise completely above water level,
effecting insect pollination. The yellow bilabiate flowers resemble
those of the figwort family (Scrophulariaceae) from which the bladderworts
are derived. The capsules bear numerous small seeds and germination
takes place in the water.
Methods of capturing prey reach some of the greatest heights of
specialization in bladderworts. A carnivorous lifestyle is present
in more than 500 species of flowering plants worldwide, all bearing
modified leaf structures for the capture and digestion of animal
prey. Our fascination with these botanical ogres increases as we
learn more about their unusual tactics in nature's "Little Shop
© 2001 Jane Mygatt.