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Questions:

  1. What type of plant movement is shown by each of Sundew, Venus Flytrap and Pitcher Plant? What is the mechanism of the movement?
  2. Can a movement be both Chemonastic and Thigmonastic? If yes, so any plant in Question 1 show both?
  3. Give example(s) of exclusively chemonastic and exclusively thigmonastic movement.

Description:

Sundew (Drosera sp.), Venus Flytrap (Dionaea sp.), Pitcher Plant (Nepenthes sp.) are 3 examples of Carnivorous Plants.

These plants use rapid movements to capture their prey and then digest them to fulfill their Nitrogen requirement as they grow in Nitrogen deficient soil.

My Attempts:

I have found different answers according to different sources.

  1. According to one source, tentacles of both Sundew and Venus flytrap curve in response to soluble proteins placed in the centre of the leaf. So, both of them are Chemonastic.
  2. According to another, Chemonasty is exhibited by long peripheral tentacles of sundew. Closing/Bending of glandular hairs of sundew in response to nitrogenous compounds.
  3. According to Wikipedia, Sundew and Venus Flytrap shows thigmonasty.
  4. Interestingly, none of the above sources mention Pitcher Plant. According to a friend, Pitcher Plant shows free movement (moves its leaves at its own will). Is that true?
  5. Finally, according to me, all three should be thigmonastic. Because all three trap the insect once the insect touches it. So, it is influenced by touch, thus, thigmonastic. Maybe some of them are chemonastic as well (I don't know which ones).
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  • $\begingroup$ Hi everyone! Sorry for making the question too big. For a smaller version, just read the Question: part. $\endgroup$ Nov 6 '21 at 5:19
  • $\begingroup$ Also, in our school, a T/F question was: Chemonastic movement is noticed in Pitcher Plant. This is a reason that I am asking this question. $\endgroup$ Nov 6 '21 at 5:28
  • $\begingroup$ So, I studied abo them a little more, and came to a conclusion, which I am adding as answer. $\endgroup$ Nov 6 '21 at 5:57
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Answers:

  1. Sundew and Venus Flytrap show both Chemonastic and Thigmonastic movements. Pitcher plant doesn't move at all. Reasons in Description.
  2. Yes, Sundew and Venus Flytrap show both Chemonastic and Thigmonastic movements.
  3. Mimosa pudica, bunchberry and mulberry plants show exclusively thigmonastic movement. Still didn't find any plant that shows exclusive chemonastic movement.

Description:

  1. In Sundew and Venus Flytrap, trigger hairs contain some proteins that sense touch. Although the in response to nitrogenous compounds part is hoax (since even if you put a stone in the trap and move it a little, then it will shut. After a day, it will spit that stone out.)

  2. In a Pitcher Plant, no movement occurs. Rather, a slippery substance on its opening lid makes the prey slip in. Watch this video.

Trigger hairs in Venus Flytrap

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  • $\begingroup$ I still didn't find any exclusively chemonastic movement, and also still don't know for sure if the mechanism in venus flytrap and sundew invokve something chemical (not exclusively thigmonastic) since according to Wikipedia, Venus flytrap shuts its leaves even if a non-living thing falls in. $\endgroup$ Nov 6 '21 at 6:35

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