Is there a plant that eats animals? And if I were to eat that plant will I…

Is there a plant that eats animals? And if I were to eat that plant will I become a non-vegetarian, albeit once removed? After all, such a plant is technically a non-vegetarian!

This question is not just coffee-table chatter. There are insect-eating plants in nature. The Venus fly trap is an often-quoted example. Now comes the startling information about a member of the pitcher plant family, which has a particular preference for termites, and eats thousands of them at one go. Drs. Marlis and Dennis Merbach and their associates from Germany report on such a plant in the 3rd January issue of Nature.

Our general opinion about plants is that they are truly ascetic, demanding little from other life forms. Much of what they need comes from whatever there is in the ground below, sunlight, some water, and air. They make carbohydrates out of this spartan set of ingredients and store them in their bodies. Animals like us pluck these and feed ourselves.

Many of us humans pride ourselves by declaring that we eat nothing but plants and that we do not eat meat since that amounts to harming animals. The truth is plants are life forms too; furthermore, such interdependence and “big fish eat small fish” is an inescapable part of existence. The wanton hurting of other life forms is what we should not be practising.

The relation between insects and plants has always been intimate and mutually beneficial. Many plants need insects such as bees to help in propagation. For this purpose, they have put in elaborate structures in their flowers, which entice the bee. The colour attracts the insect while the nectar offers a meal. For its part, the insect carries the pollen across to another plant, helping the latter to propagate through such dispersal. In many instances, this mutualism has become so one-to-one as to be finicky or specific. For example, it is a particular legume plant alone that the insect called psyllid (or the jumping plant lice) will go to and none other – an example of “made for each other”.

It is all very well, as long as it is the flower and the nectar that the insect is interested in. But if the insect were to start eating any other part of the plant, say the leaf or the seed, it has had it! The plant puts up a strong reaction. Its defence or self-protection can be pretty offensive. The plant releases chemicals that can stun or even kill the insect. The neem tree is an example. It synthesizes and stores a chemical called azadirachtin. When the insect takes a bite at the plant, the released chemical kills all further desire in the insect to take any more bites. As a result, the insect dies a slow death of starvation. Azadirachtin is therefore called an insect antifeedant. Other plants use other strategies aimed at the same defensive purpose. For example, why are all fruits two-faced?

The pulp in them is entirely tasty and nutritious. But the kernel and seed are at best indigestible (they actually can give you a stomach upset), and at worst poisonous (recall the desperate poor tribals of Orissa who suffered eating mango kernels). The pulp is the enticement, the come-hither. The seed should not be destroyed but simply dispersed, so that the next generation plant can grow.

We know that all plants are not passive bystanders in the theatre of life. Several of them are activists that seek out their food and nutrition beyond air, water, soil, and sunlight. There is a whole bunch of tropical plants that are carnivorous, yes, they gobble up insects for food! The Venus Fly Trap mentioned above is the famous one. Its leaf has two lobes, edged with interlocking "teeth". On the surface, they have many trigger hairs. When a hapless insect were to disturb these hairs, the leaf snaps shut. Upon this, the plant secretes some digestive juice into the enclosure, which dissolves much of the insect. The food so mashed up into a puree or soup is absorbed by the plant. The chitinous outer layer of the insect is all that is left, which is discarded later. Here is a twist – the leaf of the plant holds its stomach!

What Dr. Merbach and co-workers found in the Southeast Asian country Brunei was an even more striking example of a non-veg plant. Called "Monkey's Rice Pot" in West Australia, it is technically known as Nepenthes albomarginata. The family Nepenthes has many subspecies. The name is Greek in origin and means banisher of sorrow. One account has it that the plant was used by the ancient Greeks to banish sorrow and induce restful sleep. Obviously, its nectar or some other component has a sedative influence. (Parenthetically, Dr. Dennis Merbach writes to me that he doubts this since not even Alexander the Great came far enough east to find this plant).

The genus Nepenthes is found in Southeast Asia, Seychelles and Madagascar, and Australia, but N. albomarginata is abundant in Peninsular Malaysia, Sumatra, Borneo, and Brunei. The German work was done in Brunei. Albomarginata literally means white border and is so named because the pitcher that it presents at its leaf tips is rimmed with white hair-like protrusions. It is a slender, heat-loving plant that has attractive pitchers rimmed white and does very well in a stove house or heated frames.

N. albomarginata is quite different from its cousins of the pitcher plant genus Nepenthes. Others are not choosy about their prey. They catch any insect that is careless enough to step on their slippery, toothy appendage. Monkey's Rice Pot or N. albomarginata is picky – it loves to eat termites! In order to do so, it presents its pitcher to the prey, luring them with its colour and distinctive smell. The white hairs that fringe the rim of the pitcher are edible. Termites seem to love the hair and come to it in hordes. The scientists usually found not one or ten, but thousands of termites trapped in a single pitcher!

All the termites they found in one pitcher belonged to the same species and were in the same state of decomposition. This led the researchers to conclude that a whole battalion was caught over a short period of time. The termites caught and gobbled up were largely from no more than three genera, with one particular genus called Hospitalitermes predominating. It thus seems that these fellows are picky about N. albomarginata, and the latter returns the compliment. In fact, the plant pretty much starves when termites are not around. Over the six-month lifespan of the pitcher, it gets by with a few dozen ants, beetles or flies (while neighbouring pitcher plants of other provenance, not being so picky, get along much better). For its part, the termite genus mentioned above gets by usually with live fungi and algae, but upon sensing the plant it forages in massive columns and meets its death by the thousands at the teeth of the pitcher plant. Extraordinary, till death do they part!

It is the white hair that the termites go for. Pitchers with no hair are ignored. When the researchers placed near a termite marching column both pitchers with hair and pitchers shaven off, the lead termite sensed the white hair, went back and called his mates for the forage. They came in numbers, started gobbling up the edible hairs and making food pellets out of them to carry home. In the process, they fell into the pitcher and could not escape. The fall-in rate was one every three seconds (could be even faster with a bigger marching band). After an hour, when all the hairs were gone, the pitcher was no longer of any interest to the termites. What is in the hairs that attract the termite is not clear yet. It could be some volatile molecule, but the researchers could not detect any smell in their study. As of now, it appears that contact happens by chance. To date, N. albomarginata appears to be the only known plant that offers up its own tissue as bait and the only one too that specialises on a single prey.

Reading the article, it occurred to me that there is a clean and green way to rid your house of termites – plant a hedge of N. albomarginata around your house, and it will do the rest. Alas, when I raised this point, Dr. Merbach disappointed me with his e-mail message, stating that this group of termites does not feed on wood since they feed over the ground. The wood-eater termites feed underground, while the plant presents its pitchers above. There goes another of my brilliant solutions!

I wonder whether N. albomarginata is seen in India since there are other members of Nepenthes that grow in our subcontinent. It will also be interesting to check whether some of these are pest-gobblers. One plant, called N. khasiana, is found in the Khasi hills of Assam, but its termite-preference has not been tested so far, to the best of my knowledge. This pitcher plant is an undemanding highland species that grows slowly to a height of about two feet. It is able to tolerate low humidity and temperatures and thus should be cultivable in other chosen areas of India. And it better be soon, since this plant is already on the endangered list because of encroachment by farmers who have cleared up land in that area for agriculture.

According to the passage, which of the following is facing the threat of extinction?