ALDROVANDA /ældrəˈvændə/ is a genus of carnivorous plants
encompassing one extant species (
* 1 Description
* 1.1 Trap mechanism
* 2 Extinct relatives * 3 Evolution * 4 Species * 5 References
The waterwheel is a small, free floating and rootless aquatic plant, with a length of about 1.5 to 20 cm (9⁄16 to 7 7⁄8 in), and whorls of about 1 to 2 cm (3⁄8 to 13⁄16 in) in diameter. At every 3 to 4 cm (1 3⁄16 to 1 9⁄16 in) the plant branches, sometimes forming offshoots. An average of 12 to 19 whorls spans the length of the plant, each with about 5 to 9 leaves, each up to 11 mm (7⁄16 in) long. The growth is faster than terrestrial carnivorous plants, sometimes growing about 4 to 9 mm (3⁄16 to 3⁄8 in) a day.
In temperate regions the plant goes dormant in the winter, forming turions of about 4–6 mm (3⁄16–1⁄4 in) and sinking to the bottom. In tropical regions, the plant grows all year long without forming turions. The plant flourishes and produces seeds only in these warmer regions, with temperatures higher than 25 °C (77 °F), and produces only one flower, white or light pink, that arises above the surface. In temperate regions, the plant reproduces mostly via asexual means, producing inviable seeds or no flower at all.
The leaf structure is very similar to the Dionaea, the main difference being air chambers present in the "stem". The traps, at the end of the leaf, contains up to 6 bristles, analog to the Dionaea teeths, that prevents debris from activating the trap. Each trap contains additional 60–80 smaller "teeth", and circa 30–40 trigger hairs inside. The speed of closing is about 0.01 to 0.02 seconds.
The trap mechanism is akin to that present in Dionaea - Darwin even named it "the miniature aquatic Dionaea". The mechanism by which the trap snaps shut involves a complex interaction between elasticity , turgor and growth. In the open, untripped state, the lobes are convex (bent outwards), but in the closed state, the lobes are concave (forming a cavity). It is the rapid flipping of this bistable state that closes the trap, but the mechanism by which this occurs is still poorly understood. When the trigger hairs are stimulated, an action potential (mostly involving calcium ions—see calcium in biology ) is generated, which propagates across the lobes and stimulates cells in the lobes and in the midrib between them.
The extinct species are known only from fossil pollen and seeds ,
with the exception of A. inopinata, which is also known from
fossilised laminae .
The organ of carnivory in
Several undescribed species are also known.
The distinctions between the various named species have been criticised, although SEM analysis of the seed structures seems to confirm the existence of different species.
* ^ A B Kew World Checklist of Selected
* v * t * e
Carnivorous and protocarnivorous plants
Carnivorous genera († extinct)