New research shows that [tomatoes] capture and kill small insects with sticky hairs on their stems and then absorb nutrients through their roots when the animals decay and fall to the ground.

It is thought that the technique was developed in the wild in order to supplement the nutrients in poor quality soil – but even domestic varieties grown in your vegetable patch retain the ability.

So go the findings of research carried out at the Royal Botanical Gardens, Kew. Furthermore, their conclusions also contend that potatoes and other plants are also similarly "carnivorous", and that a number of other plant species exhibit such behaviour.

I am sceptical about the whole business and believe that these researchers are attributing too much importance (and murderous intent!) to insects getting caught in the sticky hairs, dying, decaying, falling to the ground, decaying further into the soil and being absorbed as nutrients by the plant.

How reliable is this research? How was the paper (which was submitted to the Botanical Journal of the Linnean Society) received?

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    My guess is that this is like many other aspects of any plant that must evolve under pressure from hungry insects. If some hair deters/kills off a few insects, thereby preventing them from damaging the plant, then it is a good thing that will help the species survive, and so will be retained in the genome. If the dead insects also add just a bit of nutrient value to the soil then it is even better. But there is no true anthropomorphic INTENT involved here. It is merely evolution finding a solution that benefits the plant in several subtle ways. – user3344 Jul 22 '12 at 10:41
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    I have never doubted the carnivorous intentions of tomatoes. – Flimzy Jul 22 '12 at 23:08
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    @Flimzy - I, for one, welcome our new carnivorous tomato overlords. – user3344 Jul 23 '12 at 10:40
  • @Flimzy hehe! "Attack of the Killer Tomatoes?" was the original title of this question :) – user7920 Jul 23 '12 at 14:06
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    Rather than calling them "carnivores", I would describe this alleged activity as "self-fertilizing". Also note that all of the species listed (except Shepherd's Purse) are members of the nightshade family, Solanaceae. – Simon Jul 23 '12 at 21:51

Here is the paper in question:

From the abstract, we can see this isn't an experimental paper, but just an overview. Tomatoes (i.e. Solanum lycopersicum) do not appear in the article's abstract, unlike in the newspaper article where they feature heavily.

The article does talk about the difficulty of classification into "carnivorous"

Mechanisms for capture and digestion of prey vary greatly among the six (or more) lineages of flowering plants that have well-developed carnivory, and some are much more active than others. Passive carnivory is common in some groups [...] There is no clear way to discriminate between cases of passive and active carnivory and between non-carnivorous and carnivorous plants – all intermediates exist. Here, we document the various angiosperm clades in which carnivory has evolved and the degree to which these plants have become ‘complete carnivores’. We also discuss the problems with definition of the terms used to describe carnivorous plants.

It strikes me that the reporter has played with the classification difficulty to enable him to have a hook - that tomatoes and potatoes can be classified as carnivorous - despite it not being a key feature of the paper. Looking closely at what the researcher says, he suggests carnivorousness is not a key feature of the domesticated tomato.

As to how it was received, it is necessary to look at the citations, to see if it is relied upon as a legitimate source, or argued against in the literature.

It has been cited at least 18 times (Ref), most prominently by 'Quite a few reasons for calling carnivores ‘the most wonderful plants in the world’' which draws on it approvingly several times. It is also cited approvingly here and here.

Of the freely available citations, none seemed to attack or contradict any of the findings - however, none referenced tomatoes.

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    So in conclusion... The newspaper article made a mountain out of a molehill. Shocking. "Nothing to see here, move along folks." – Flimzy Jul 24 '12 at 20:12
  • A 27-page paper seems a little long for an overview. None of the referenced literature cites tomatoes or potatoes. None of them mention sticky stems or hairs to trap insects. Furthermore, the sections about passive carnivory involve the secretion of a digestive enzyme coating, and so on, which really isn't applicable to the case of the tomato. As for the domesticated tomato, the article states: "they are getting plenty of food through the roots from us so don’t get much benefit from trapping insects". This, to my ears, does not mean that the domesticated tomato does not trap insects. – user7920 Jul 25 '12 at 19:15
  • Thanks for your research. It has made for interesting reading! – user7920 Jul 25 '12 at 19:15
  • @coleopterist: By "overview" I meant there is apparently no experiment here; it is research that has been done in a library, not in a lab or the field. It doesn't look like they were cutting open tomatoes. – Oddthinking Jul 26 '12 at 1:14
  • Not sure I understood your other points. It seems the definition of carnivory is problematic, and can be extended across a range of behaviours, but that doesn't tell us about tomatoes; it tells us about our language. Unless we get a copy of the original paper, it is hard to know if it mentions even tomatoes at all. – Oddthinking Jul 26 '12 at 1:16

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