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Thread: Primitive carnivory analyzed

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    Primitive carnivory analyzed

    Take a close look at photos of plants having sticky defensive glands such as Stylidium. Captured insects are stuck on the glands and not even in contact with the leaf surface.
    There is a prevalent misconception about such sticky glands. The retentive glands of pseudo-carnivorous plants resemble those of Byblis and Pinguicula. Unlike in Drosera, the retentive glands of these plants only secrete glue and do not absorb. Absorption in Byblis and Pinguicula is carried out by the leaf surface through the digestive fluid secreted there.
    Carnivory in Byblis linifolia is rather primitive. I have observed while growing the plant that there is no secretion of digestive fluid from the leaf surface unless the plant is in high humidity. Also note that the majority of the retentive glands are too long stalked and insects caught on them will be suspended well above the leaf surface and so unavailable for digestion. I suspect that these excessively tall retentive glands are primarily defensive. It seems to me that carnivory in this species is more of a side benefit of the plantís defensive weaponry.

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    Interesting idea. It seems like the plants evolved from having using hairs as defense to using hairs to acquire more nutrients through capturing prey. Pinguicula are most closely related to Utricularia and Genlisea though, so maybe something different happened with those.

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    Quote Originally Posted by Tanukimo View Post
    Interesting idea. It seems like the plants evolved from having using hairs as defense to using hairs to acquire more nutrients through capturing prey. Pinguicula are most closely related to Utricularia and Genlisea though, so maybe something different happened with those.
    Thanks. Yes, the glandular hairs surly started out deterring plant eaters in both Byblis and Pinguicula. Although, these two probably do not have a common ancestor: Parallel Evolution. Note that butterworts have glandular hairs on their flowers stalks also which are not for carnivory.

    I am studying a Monkey Flower (Mimulus sp.) found here in Southern California which intriguingly has another carnivorous characteristic. In addition to glandular hairs which capture insects, this plant is also able to take nutrition from them. The leaves (not the glandular hairs) secrete something analogous to digestive fluid. As in Byblis, this fluid is only secreted during high humidity. The fluid is from guttation which forms the morning dew so often seen on plants. Most curious though, the fluid does seem to digest. I am thinking this might be another defense mechanism. And if so, this is a case of carnivory only by accident; which is the most primitive level. Quasi (or seemingly) Carnivorous is a fitting term.

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    Hmm, I wonder if that plant is closer to being carnivorous than Ibicella or Proboscidea, which also have a reputation as being quasi-carnivorous. I also wonder why the plants only secrete those fluids in high humidity. It doesn't seem like they live in places which get very humid.

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    Good point; they do not. Perhaps a better term for those plants might be Pretend Carnivorous?

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