What Makes Some Plants Carnivorous?

Triphophyllum pelatatum, an African liana that’s a part-time carnivore (Photo by Denis Barthel assumed (based on copyright claims). https://commons.wikimedia.org/w/index.php?curid=137455

Dear Readers, I am taking my nose out of my books for five minutes to talk about this very remarkable plant. I’ve long had a fascination with carnivorous plants (not entirely fuelled by Audrey the man-eating plant in ‘Little Shop of Horrors’) and in particular with those who seem to be on the edge of making the transition between purely photosynthetic and insect-eating. Recently, I read a study that suggested that teasel plants grew better when there were insects trapped in the little ‘baskets’ made by the juncture where their leaves meet the stems, and the scientific theory for a long time has been that when plants grow in nutrient-poor habitats, such as bogs they may turn to eating invertebrates to get what they need. 

The ‘pool’ at the base of teasel leaves

Now, surprisingly enough the soils in rainforests are often thin and poor (one reason why many tropical trees have such wide-spreading roots), and so there are a number of carnivorous plants there too, such as pitcher plants. But how about this liana, Triphyophyllum peltatum? What is interesting is that it puts out sticky leaves which entrap small insects, in the same way that the much smaller sundew does (to which it is distantly related). However, this plant only produces them in certain circumstances, with some plants happily getting on without them. Scientist Traud Winklemann of the Leipniz University, Hannover,  managed the difficult task of propagating the plant, and set out to see what it needed, and in which situations the carnivorous leaves appeared.

Bets were largely on nitrogen deficiency, as this is something that is a limiting factor in many environments. However, it turned out that what made the plant change its behaviour was a lack of phosphorous in the soil. Winklemann hypothesises that this is because phosphorous is one of the elements that is most depleted following the equatorial monsoon rains in September in West Africa, where the plant grows. Furthermore, as it grows on hillsides, the nutrients are regularly washed down the hill, away from the area where the plant lives. You can see how being able to access an alternative source of nutrients would be useful, although this would require the plant to use considerable resources in order to generate the ‘glue’. You can read the whole article here.

The ‘trap’ leaves of Triphophyllum peltatum – Photo by Traud Winklemann

I am always amazed at the adaptability of plants, and the many ways that they are able to use what’s available in their environment in order to survive. The fact that this plant is able to change its behaviour according to whether there’s enough phosphorous around or not is very impressive, and I anticipate a whole slew of future research on how exactly the plant manages it, and how it ‘decides’ that it’s time to produce a ‘trap’ leaf instead of a normal leaf or a leaf that enables it to climb through the undergrowth (this species also produces a leaf with hooks so that it can grapple its way up towards the sunlight). It often seems in science that every question that you answer opens the door for another dozen questions, but what fun to be continually learning!

I’ve revised growth hormones and cell membranes today, and my brain is so stuffed that I feel like those little guys from Mars Attacks!, a very strange film by Tim Burton. By the time that my first exam arrives I will be more than ready to let fly with some of those facts. Four more days to go!


3 thoughts on “What Makes Some Plants Carnivorous?

  1. Anne

    If our passports and UK visas arrive in time, I have eight days before flying out of Africa for a few weeks. I hope you do well in your examinations.

  2. Adrienne Rowe

    Thank you for taking the time to write this very interesting article.
    Wishing you the best of luck in your exam x


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