Into the realm of carnivorous plants

Nature is teeming with marvels, marvels such as plants with a preferential palate for proteins.

But why and how do these killer plants have such an unorthodox way of living?

Myth vs fact

It was Satyajit Roy's 'Septopuser Khide' which first introduced me to carnivorous plants. In the story a hunter narrated killing man-eating plants raised by an unconventional horticulturist.  Many literary works and movies depicted tentacular leafy creatures and their grim ways of devouring animals and humans. However, the truth is far from these fictitious portrayals. 

In reality, you are quite safe from these unique plants. Carnivorous plants are always small and delicate. The largest prey these plants can consume are rats, and that too by the largest species. 

An insight into taxonomy

Carnivorous plants can be minute. But, they are diverse and often belong to common plant groups. Carnivory can be seen in the group of sunflowers and daisies, among carnations, and even in certain grass and pineapple species. 

However, carnivorous plants also have their own groups: the sundews and pitcher plants. 

Carnivory evolved independently in five different groups of flowering plants. They are represented by more than a dozen genera and a staggering 583 species. These plants are truly carnivores, meaning they actively lure, trap, and kill prey to absorb nutrients.

Additionally, there are over 300 other plant species which show a taste in flesh secondarily. We call them proto-carnivorous plants.

Where are they?

Except for Antarctica, there are at least one or two proteinaceous plants in every continent. The species diversity most flourished in South America and Asia. 

The hunt

The idea is simple. Draw an unsuspecting prey – be it a fly or a mosquito – trap it in a sealed enclosure, liquify it and absorb the nutrient-rich juice. 

Five major clans can be observed using this style of hunting. 

Peril in pitfalls

The users of the pitfall traps are perhaps the best-known carnivorous plants. The pitcher plants are the most diverse group, proliferated in the Malay Archipelago. These trappers don a pitcher-shaped growth holding an internal chamber with only one opening. 

Through the secretion that feigns nectar, they lure insects into the chamber of death. Once the prey is secure, the secretion rapidly changes to digestive juice. And, slowly, the poor prey is transformed into a gooey substance. 'The pitchers can be likened to an individual stomach.' – as termed by Charles Darwin in his paramount work Insectivorous Plants.

Flypaper users

We all know about glue traps to catch pests. Well, the Sundews are the pioneers of this technique. While the luring strategy are the same for them as well, these plants secure food in a different manner. 

Studded with mucous-secreting glands, the oval surface of sundews are equipped with tentacles. Initially, these tentacles lure insects. Once the fly lands on the fleshy pad, the sticky secretion sets in with an admixture of protein-breaking enzymes. And, in less than a minute, the pad curls and secures the meal. 

The gin trappers

The iconic and the most-famous carnivorous plants to use this trapping method are the Venus Flytraps and the Waterwheel plant. Their trapping mechanism has been described as a 'mouse trap', 'bear trap' or 'man trap', based on their shape and rapid movement.

These traps are leaves whose terminal section is divided into two lobes, hinged along the midrib. Trigger hairs inside trap lobes are sensitive to touch. When a trigger hair is bent, the lobes start to furl in. Osmosis regulates the inside pressures. To make the trap work even more efficiently, the lobes are embossed with long, hard setae, similar to studs of actual gin traps.

With a vacuum-pump

As the name implies, these plants hunt with vacuum forces. Seen only in one group – the Bladderworts – the bladder has a small opening, and is sealed by a hinged door. 

It draws water with rapid force once the trigger at the opening is activated. The bladderworts are aquatic, and, this way, aided with numerous bladders. It is said that a waterbody rich in bladderworts will never experience a bloom.

Hunting with Chai

Yes. There are plant traps that work exactly like a fish/prawn trap. Locally known as 'Chai', the trap, made of bamboo, has a chamber which is easy to enter but the exit is topsy-turvy, either puzzling or obstructed by inward-pointed thorns. 

The Chai mechanism is used exclusively by the corkscrew plant from the genus Genlisea.  A Y-shaped modified leaf allows prey to enter but not exit. Inward-pointing hairs force the prey to move in a particular direction. Prey entering the entrance that coils around the upper two arms of the Y are forced to move inexorably towards a stomach in the lower arm of the Y, where they are digested.

Why do they do it?

You are probably now wondering why they do it. Well, it is relatively easy to answer. All the carnivorous plants originated in deficient soils. Soils that are particularly poor in nitrogenous substances. These plants still need sunlight but they, with the help of protein-breaking enzymes and symbiotic flesh-eating bacteria, suck on prey to substitute nitrates. 

Well-lit bogs, acidic soil with clogged or running water, and fen formations are the places where you are likely to encounter one of these species.

Are there any in Bangladesh?

There are two recorded species in Bangladesh so far: A Sundew from Drosera and a Bladderwort from Utricularia. The latter one is pretty common, and can even be found in Dhanmondi Lake. Being an aquarist with a knack to know about unique species, I collected a few stems of this aquatic species. 

Regarding the former, the tuber-bearing seasonal Drosera is not identified to the species level. But it is distributed in north-eastern Bangladesh, likely in hill tracts too. One such place is Borshijora Eco-park of Moulvibazaar, discovered by eminent citizen-scientist Late Tania Khan. 

More plants are speculated to be in the region. The waterwheel plant of genus Aldrovendra is one of them. A free-floating aquatic species and user of snap-traps, Aldrovendra is known to occur along all the major routes of migratory ducks. 

Our haor basin is a hotspot for migratory birds, Aldrovendra is likely to be there, awaiting discovery.

Of the other kinds, the range of several pitcher plants overlaps the forests of Sylhet and Chittagong. ''There is an old record from Sylhet,'' stressed Dr Monirul H Khan, an ardent naturalist and professor of zoology at Jahangirnagar University when I asked him about the whereabouts of the pitchers of Bangladesh. 

Hearing the response, checking the maps, and the number of pitcher plants occurring in the adjacent Garo and Mizo Hills, I have gone into a trance imagining the moments of one such discovery.

Before our hilly eastern forests and her uncut gems are long gone, if this piece interests you, embark into the search for carnivorous plants. You can even keep them as a pet, you can  get one from many nurseries who sell varieties of nepenthes and Venus' fly traps.