What tropism does the bladderwort exhibit?

Question

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Answer 1

Bladder-wort ( Utricularia) is an insectivorous plant that belongs to Lentibulariaceae family of Angiosperms or the flowering plants .

It is not an ally or relative of Ferns at all.

It is an aquatic plant that remains submerged in water .

Its roots show geotropism and the shoot shows phototropism.

Even though it is photosynthetic and Autotrophic plant ; it catches insects in its bladders ( Some modified leaves for that purpose) for its protein/aminoacids supply.

Which tropism YOU have in mind is not clear from the question.


The following information is reproduced thanks to Wikipedia--:

Physical description of the trap Or the Bladder

Authorities agree that the vacuum-driven bladders of Utricularia are the most sophisticated carnivorous trapping mechanism to be found anywhere in the Kingdom of Plants.

The bladders are usually shaped similarly to broad beans and are to be found attached to the submerged stolons by slender stalks.

The bladder walls are very thin and transparent, but are sufficiently inflexible to maintain the bladder's shape despite the vacuum created within.

The entrance, or 'mouth', of the trap is a circular or oval flap whose upper half is joined to the body of the trap by very flexible, yielding cells which form an effective hinge.

The door rests on a platform formed by the thickening of the bladder wall immediately underneath.

A soft but substantial membrane called the velum stretches in a curve around the middle of this platform, and helps seal the door.

A second band of springy cells cross the door just above its lower edge, and provide the flexibility for the bottom of the door to become a bendable 'lip' which can make a perfect seal with the velum.


The outer cells of the whole trap excrete a mucilage (gummy substance) and under the door this is produced in greater quantities and contains sugars.

The mucilage certainly contributes towards the seal, and the sugars may help to attract prey.

Terrestrial species generally have tiny traps (sometimes as small as 0.25 mm) with a broad beak-like structure extending and curving down over the entrance; this forms a passageway to the trapdoor and may help prevent the trapping and ingestion of inorganic particles.

Aquatic species tend to have larger bladders (up to 10 mm as those of Utricularia hamiltonii), and the mouth of the trap is usually surrounded not by a beak but by branching antennae, which serve both to guide prey animals to the trap entrance and to fend the trap mouth away from larger bodies which might trigger the mechanism needlessly.

Epiphytic species have unbranching antennae which curve in front of the mouth and probably serve the same purpose, although it has been observed that they are also capable of holding a pocket of water in front of the mouth by capillary action, and that this assists with the trapping action

Trapping mechanism
The trapping mechanism of Utricularia is purely mechanical: no reaction from the plant (irritability) is required in the presence of prey, in contrast with the triggered mechanisms employed by Venus Flytraps (Dionaea), waterwheels (Aldrovanda), and many sundews (Drosera).

The only active mechanism involved is the constant pumping out of water through the bladder walls by active transport.


.As water is pumped out, the bladder's walls are sucked inwards by the vacuum created, and any dissolved material inside the bladder will become more concentrated. The sides of the bladder bend inwards, storing potential energy like a spring. Eventually, no more water can be extracted, and the bladder trap is 'fully set' (technically, osmotic pressure rather than physical pressure is the limiting factor).

Extending outwards from the bottom of the trapdoor are several long bristle-stiff protuberances that are sometimes referred to as trigger hairs but which have no similarity to the sensitive triggers found in Dionaea and Aldrovanda. In fact, these bristles are simply levers. The suction force exerted by the primed bladder on the door is resisted by the adhesion of its flexible bottom against the soft-sealing velum. The equilibrium depends quite literally on a hair trigger, and the slightest touch to one of the lever hairs will deform the flexible door lip enough to create a tiny gap, breaking the seal.

Once the seal is disturbed, the bladder walls instantly spring back to a more rounded shape; the door flies open and a column of water is sucked into the bladder. The animal which touched the lever is inevitably drawn in, and as soon as the trap is filled, the door resumes its closed position—the whole operation being completed in as little as one-hundredth of a second.

Once inside, the prey will be dissolved by digestive secretions. This generally occurs within a few hours, although some protozoa appear to be highly resistant and have been observed to live for several days inside the trap. All the time, the trap walls continue to pump out water, and the bladder can be ready for its next capture in as little as fifteen minutes.


Lloyd's experiments--

In the 1940s F.E Lloyd conducted extensive experiments with carnivorous plants, including Utricularia, and settled many points which had previously been the subject of conjecture. He proved that the mechanism of the trap was purely mechanical by both killing the trigger hairs with iodine and subsequently showing that the response was unaffected, and by demonstrating that the trap could be made ready to spring a second (or third) time immediately after being set off if the bladder's excretion of water were helped by a gentle squeeze; in other words, the delay of at least fifteen minutes between trap springings is due solely to the time needed to excrete water, and the triggers need no time to recover irritability (unlike the reactive trigger hairs of Venus Flytraps, for example) .

He tested the role of the velum by showing that the trap will never set if small cuts are made to it; and showed that the excretion of water can be continued under all conditions likely to be found in the natural environment, but can be prevented by driving the osmotic pressure in the trap beyond normal limits by the introduction of glycerine .

To see abeautiful photo of the plant, just on the blue link below-

http://images.google.co.in/imgres?imgurl=http://www.juzaphoto.com/eng/galleries/photos2/001484-utricularia_vulgaris-common_bladderwort.jpg&imgrefurl=http://www.juzaphoto.com/eng/galleries/utricularia_vulgaris-common_bladderwort.htm&h=427&w=640&sz=93&hl=en&start=25&tbnid=syKvmbNLEJO8YM:&tbnh=91&tbnw=137&prev=/images%3Fq%3DBladderwort%26start%3D20%26gbv%3D2%26ndsp%3D20%26svnum%3D10%26hl%3Den%26sa%3DN

Answer 2

Tropism is attraction.

So, geotropism (geo = earth) is attraction to the earth (this is what roots show--they grow downwards). Bladderworts are fern allies, and cannot grow in an upwards direction because they have no vascular tissue to give them strength against gravity. They are either geotropic or hydro (water) tropic, because they require water to reproduce (spread their spores).