The Amazing Pitcher Plant

THE AMAZING PITCHER PLANT

The pitcher plant is one of Nature's most amazing creations. It is one type, among at least 580 species of flora, that grows in places lacking nutrients-particularly nitrogen-that plants need to remain healthy. In order to compensate for this deficiency, these plants have evolved to become carnivorous, catching insects and other arthropods and digesting them for their nutrients. Some species of carnivorous plant rely on glue traps to catch their prey, such as the sundew, so named because its leaves are covered in little red stalks whose tips are dabbed with what looks like a dewdrop on the end, but which is in fact a sticky substance waiting to trap any insect that is lured by the promise of nectar. Some species of carnivorous plant have evolved active traps, such as the venus' flytrap, which grows what looks just like a miniature mantrap. On the inside of this plant, which is coloured to resemble meat, there are three 'trigger' hairs and when an insect brushes past these hairs, that springs the trap and the jaws rapidly close around the victim.

As for the pitcher plant, its very name provides a clue as to how it goes about catching its prey. These plants resemble drinking vessels, particularly champagne flutes. Some species of pitcher plants-the genus 'nepenthes'-grow their traps on the end of tendrils sprouting from ordinary leaves. Others, such as the genus Sarracenia, are ground-dwelling herbs whose entire leaf is the trap. Whether it grows its trap on the end of a tendril or rising up from the ground, they all work in more or less the same way. The pitcher secretes a subtle perfume which is all but irresistible to insects. This scent, along with a seductive colour pattern, entices prey toward the top of the pitcher, where they are seemingly rewarded with nectar secreted by a leaf that grows over the pitcher (thereby resembling a little umbrella, and in fact it is there to prevent the pitcher from becoming overfilled with rainwater). However, the closer they get to the lip of the pitcher, the more in danger they are, for it is treacherously slippy and covered with downward-facing hairs that make it exceedingly difficult to climb back up. Any insect that happens to walk on the lip is almost certain to fall into the pitcher itself, inside which is a pool of water waiting to drown the unfortunate creature.

(Image from wikimedia)

Now, you would be forgiven for thinking that I describe the pitcher plant as 'amazing' because it is carnivorous. After all, we are used to thinking of plants as passive things that sit at the bottom of any food chain and it seems like quite the role-reversal to find some that are predators rather than prey. But, actually, the amazing aspect of the pitcher plant lies not just in the fact that it kills small creatures for their nutrients but in how it digests them.

The pitcher plant itself produces no digestive enzymes with which to break down the organic material of its prey. Instead, it produces something all leaves come equipped with, which is oxygen-producing chlorophyll. The inside of the pitcher contains more of these chlorophyll than the outside, and the cells are further specialised to secrete oxygen directly into the pool of water in the pitcher's interior.

Now, why would the pitcher plant want to keep that water oxygenated? The reason why this water must remain fresh and not become fetid as standing water has a tendency to do, is because the pool is home to a rich variety of maggots and other creatures that live nowhere else but inside these plants. They provide the jaws and the digestive systems required to devour and decompose the prey, and the plant itself subsists on the resulting excretory products, which is absorbed through the pitcher's lining.

(Image from wikimedia)

So what we have here is an example of co-evolution. The maggots and other creatures that dwell exclusively inside the pitcher plant have adapted to become the digestive mechanisms for this carnivorous plant, for which services they are rewarded with a safe place to call home, and the pitcher plant has evolved to keep those creatures' pool a hospitable place to be, for which service it is rewarded with nutrients enabling it to thrive where other plants could not.

That's pretty cool:)

REFERENCES

Wikipedia entry on carnivorous plants and pitcher plants

'Climbing Mount Improbable' by Richard Dawkins