Carnivorous Plants Story
Copyright (c) 2013-2017 by Makoto Honda.
All Rights Reserved.
There are well over 200 species of bladderworts found in various parts of the world. Some bladderworts are aquatic, typically floating just below the water surface, while many others grow on the wet surface of marshes and swamps. Twenty or so species of bladderworts are known in North America.
Bladderwort blossoms are quite showy, especially when ponds and lakes are covered with them. A flower blooms at the top of a slender flower stem protruding out of the water surface. Yellow is the dominant flower color of the bladderworts though purple color is also common.
Let us examine the complex structure of the bladderwort trap. Each bladder has some antenna-like hairs growing on one end of the trap. These hairs are probably intended to attract tiny water animals to the trap. The entrance of the trap is located just below these hairs. A small door at the entrance, which opens only inwardly, rests on the ridge of the opening, and the door is sealed water-tight. On the outer surface of the door are four tiny stiff bristles called the trigger levers. When the trap is set, the inside pressure is lower than the outside because the water is constantly being pumped out of the trap interior. As a result of this pressure difference, the side walls of the trap look somewhat sucked in.
Bladders of bladderwort plants (Utricularia) are sophisticated underwater traps capable of catching small water animals quite efficiently. Each trap has a door on one side, that opens only inwardly. The water pressure is constantly kept low in the trap. When a potential prey touches a trigger lever growing on the door, the lock is released and the door snaps open, swallowing the prey into the trap.
Suppose a tiny animal approaches the trap, probably seeking a shelter in the bladderwort jungle, or merely passing by. The unwary visitor swims closer and closer to the trap entrance. The moment the water animal touches one of the trigger levers attached to the door, a delicate door lock is broken. Now the door free to open, the high water pressure outside causes a rush of water to flow into the trap with enormous force and speed, sweeping the prey with it. The door closes immediately, imprisoning the prey inside. All this happens in a fraction of a second. Once trapped, there is no hope left for the prey.
The water is constantly being pumped out of the trap. As a result , the trap is warped inward. The trap door is locked water-tight, so no water can get into the trap. When a potential prey disturbs a trigger lever growing on the door surface, a delicate door lock is broken, and the door swings open inward, giving in to the outside water pressure. This causes water to rush into the bladder, sweeping the prey with it. The door shuts back instantly once again, trapping the hapless victim inside.
Over a period of 15 to 30 minutes, the trap is automatically reset and the same bladder is ready again for another catch. This resetting happens because the water is constantly being removed from the trap interior. It is not unusual for a single bladder to capture several tiny creatures in animal-rich waters.
While this trapping spree is continuing, the animals captured in the bladder slowly begin to decompose. The dissolved nutrients of the digested prey are quickly absorbed through the trap walls and are carried to other parts of the plant. The digestion process continues for a week or so, depending on the size and amount of prey. As the digestion progresses, the color of the bladder often turns dark purple.
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