Little green flesh-eaters

by Geetha Ramaswami

 

We are all too familiar with the mundane chore of gathering food from our environment to fuel our bodies, i.e., eating from the fridge. Now pretend that you are a plant, rooted to one spot, how would you manage? Sure, you can make your own food, but your roots have to toil very hard to collect other things like nitrogen, phosphorus and minerals that help you make and use your food. All is fine when the soil around you has these things in abundant supply. But what if this is not the case?

Plants have devised clever ways to make up for deficiencies in their diets. Some plants rope in rather unspectacular creatures such as fungi and bacteria to collect missing nutrients. Some fungi share the plant’s food in exchange for making nitrogen available. Plants like the humble groundnut harbour bacteria in special root nodules that convert nitrogen into a form that the plant can use. The fungi and bacteria are like the tellers at an exchange office in a foreign country who convert your rupees into usable foreign currency. A handful of plants have gone beyond these subtle gives-and-takes and developed tactics that can only be described as dramatic. Enter: carnivorous (meaning “flesh eating”) plants.

Predators with roots

Carnivorous plants collect nitrogen, phosphorus and other nutrients by hunting other creatures. These sit-and-wait predators have a plethora of trapping mechanisms that seem straight out of a sci-fi movie — from suction traps (like bladderworts) and sticky hair (like sundews) to long pot-like chambers with slippery edges filled with digestive juices (like pitcher plants). Carnivorous plants hunt a variety of animals from tiny zooplankton to large insects and sometimes even lizards or frogs!

Bladderworts live underwater and have bag-like structures with mouths that are covered with sensitive hair. A bladderwort’s bag is normally collapsed, like a partly deflated balloon. But the touch of a tinyDaphnia passing by triggers the bag to suddenly expand and the prey gets sucked in. This happens so fast that even high-speed cameras cannot capture the whole process clearly!

Venus Flytraps have a ‘snaptrap’- a hinged, toothed leaf that waits for an unsuspecting insect to fly into it before snapping shut and pouring digestive juices over it. Insects get attracted to the shiny droplets of sugary stuff on the Sundew plant, thinking it is food, but instead find themselves entangled in a sticky mess of hair and get slowly digested. Insects that land on the slimy lips of a Pitcher Plant find themselves slipping into a pot-like structure full of digestive juices. A few enterprising pitcher species have even stuck up a friendship with cooperative bacteria that do the digesting for them, saving the plants the trouble of spending lots of energy in making digestive juices! The digested prey thus provides precious nitrogen and phosphorus to the plants.

Isn’t it incredible to see the mundane leaves of a plant crafted into such fine traps? I think it is quite marvellous that we share our beautiful planet with these bizarre and intriguing creatures!

 


Fungi that help plants in return for food are called mycorrhyzal fungi and bacteria that convert molecular nitrogen into absorbable compounds are called nitrogen-fixing bacteria (such as Rhizobium ).

Zooplanktons are tiny aquatic animals. They are transparent and come in a variety of shapes and sizes. They mostly feed on bacteria and other zooplankton that are smaller in size.

The traps of carnivorous plants are actually modified leaves. They not only photosynthesise as other leaves do, but also trap insects and absorb nutrients from them. Talk about multi-tasking!

 

This article appeared in the Hindu in School on 21 January 2015.

Illustration: Yummy! An underwater bladderwort about to suck in a Daphnia for breakfast.
Credit: Geetha Ramaswami