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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?

Sklivvz
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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. –  Jul 22 '12 at 10:41
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    I have never doubted the [carnivorous intentions of tomatoes](http://killertomatoes.com/main.asp). – Flimzy Jul 22 '12 at 23:08
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    @Flimzy - I, for one, welcome our new carnivorous tomato overlords. –  Jul 23 '12 at 10:40
  • @Flimzy hehe! "Attack of the Killer Tomatoes?" was the original title of this question :) –  Jul 23 '12 at 14:06
  • I think the term would be omnivorous at best unless the claim is that they get no nutrients from decaying plant matter. – Chad Jul 23 '12 at 14:10
  • @woodchips I agree. But apparently the researchers and the media think otherwise. The subheading for the linked article reads: "Garden vegetables such as tomatoes and potatoes have been found to be **deadly killers on a par with Venus fly traps**, according to research." –  Jul 23 '12 at 14:12
  • And you believe the media? A subhead like that has a goal of getting you to read the article, no different than something you would see in a supermarket tabloid. Yes, it is fun and easy to add anthrpomorphic intent, even I did it above when I said that evolution finds a solution. There is no murder here though, at most omnivorous bug-slaughter. –  Jul 23 '12 at 14:28
  • Sure. But the researchers go on to echo the same sentiment in the main body. At any rate, I'm curious about the submitted paper - these reports usually never follow things up. –  Jul 23 '12 at 14:31
  • @Chad: But plants don't eat plants, so they aren't herbivores, either. Most plants "make their own food," making them, eh... *avores* (those which don't eat)? So a plant that eats animals would not be a *carnivore* + *herbivore* = *ominvore* (one which eats anything), but a *carnivore* + *avore*. 1+0=1, so I'd say *carnivore* is the proper term here. But of course more to the point, [carnivorous plants](http://en.wikipedia.org/wiki/Carnivorous_plants#Lobster-pot_traps) is already a well-accepted term. – Flimzy Jul 23 '12 at 19:39
  • @Flimzy - nonavores? Those plants actively trap and digest though. The tomato at best has a passive digestion process, in that it allows its food to decay and then intakes the nutrients it provides the soil. But it makes use of both plant and animal remains, making it omnivorous over carnivorous... though I agree they do not eat so that can not be either. – Chad Jul 23 '12 at 19:47
  • Some trap and digest... others are more passive, and are considered *proto-* or *sub-carnivorous* by some. The point is, in no case are they *herbivorous*, so calling them *omnivorous* isn't helping the situation. It does sound like tomato plants would clearly fall into the *pronto-carnivorous* category, at best, if anything does. – Flimzy Jul 23 '12 at 19:57
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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
  • @Flimzy - They spread their leaves choking off the sunlight to other plants causing them to die then absorb the nutrients after they decay... Though I agree with self Fertilizing is a more apt descriptor – Chad Jul 24 '12 at 14:26
  • @Simon: "Self-fertilising" is a term used in the article as well: _"the plants are carnivorous predators who kill insects in order to "self-fertilise" themselves."_ –  Jul 25 '12 at 19:16
  • Does anybody have access to [Agora](http://www.aginternetwork.org/en/)? It should provide (free) access to the journal in question. –  Jul 25 '12 at 19:18

1 Answers1

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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.

Oddthinking
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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. –  Jul 25 '12 at 19:15
  • Thanks for your research. It has made for interesting reading! –  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 01:14
  • 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 01:16
  • I have been following up on some of the material in the linked papers, and I came across [this entry](http://en.wikipedia.org/wiki/Protocarnivorous_plant) in WP hiding in plain sight. While it too alludes to the difficulty of defining these carnivores, there appear to be two definitions, a strict one and a broad one. The latter requires _"active attraction, capture, and/or digestion of prey"_. Both require _"adsorption of the digested nutrients"_. The apparent modus operandi of the tomato satisfies neither set of criteria. –  Jul 26 '12 at 17:36
  • @Oddthinking Looks like there's nobody with Agora access. If you can incorporate the details from the WP link on the known classifications of protocarnivorous plants, I'll be happy to accept this answer. Thanks again :) –  Jul 31 '12 at 06:51