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Friday, 27 April 2012


Sundews (Drosera sp.) are insect-eating plants, found in swamps and marshes in much of Australia. Their leaves have sticky hairs that hold drops of protein-dissolving enzymes.

When an insect sticks to a leaf, the enzymes break the insect's protein down to amino acids, and this stimulates the leaf to curl over, slowly, bringing more hairs into contact with the insect, holding it better and dissolving it more.

The process generally takes several hours, so this would be a good case for time-lapse photography.

Gentle people can try feeding a sundew on tiny bits of cheese or meat, but if you are growing a sundew in a pot, you need to grow it in very pure sand, and never add any fertiliser, because these plants won't produce the sticky 'dew' if they can get enough nitrogen and phosphorus from the soil. Don't overfeed them.

Sounds like a science project? I thought so as well.  Congratulations on having such an excellent idea!

There are three other genera in the family Droseraceae: the Drosophyllum of the western Mediterranean, Dionaea, from the Carolinas (USA) and Aldrovanda, described in one of my reference books as "widespread in the Old World".

Here are some things to explore:

  • Do the plants 'react' faster in a warmer temperature? 
  • Do sundews like sugar?
  • How would you find out? 
  • How do different species compare? 
  • There is less protein in cheese: does this produce a slower reaction? 
  • Do they react to small pieces of metal or glass?

Just a note in passing: be careful how you speak. At one stage, I was teaching a bunch of teen-agers who were a bit wild.  We got on fairly well, because I used to be a wild teen-ager myself (more in thought than in deed, if the truth be known, but I understand the mind-set).

Anyhow, one day, I told them I had found some carnivorous plants in the school grounds, and that we were going to leave the classroom to go and see them.

Off we went, and one of the wildest and most switched-off ones was amazingly excited and animated.  It took a while to learn that he thought we were going to visit some cannabis plants!  The good news: he took just as excitedly to the carnivorous plants, finding them food and going back to check them.

There's one thing I haven't worked out yet: why are the leaves often red? Is it some response to its own enzymes, or a defence against them?

Here are some pictures of a few different species.  I need to take some more time to photograph them, but mainly, I need to go out, equipped with a ground-sheet to lie on, given that these things are always in swampy country!

The coin in the first shot is an Australian $2 coin: it is 2cm (0.8") across.

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