[kingakim]

So just to clarify, this network is used primarily for transferring nutrients, chemicals and the like? Not signals(data). Does the fact that plants respond differently to differing stimuli imply that they have some information processing mechanism?

[icegreentea]

Chemicals are signals. For example, a hormone is pretty much by definition a signaling chemical.

Plants most definitely have information processing. The entire process of 20th century computation reveals that you can get 'intelligence' from really stupid things (NAND gates) - conversing that we can have computation (and all that implies) from a variety of different substrates (neurons, mechanical relays, semi conductors, quantum bits, etc). People tend to get panicky and start delineating things so that they can restrict plants from 'having thought' but its all pretty silly.

[kingakim]

I see, I understand that fundamentally chemicals are signals. I guess what I meant was: could they use this basic "computation model" to pass complex messages? For example, provided a plant is aware of it's distance from another nearby connected plant, could it indicate via chemical signals that the soil is richer here, grow your roots in this direction, conversely, the soil is toxic here, grow your roots in the opposite direction?

[jameshart]

That kind of interplant communication is subject to a prisoners'-dilemma-like payoff matrix though. Yes, a plant species evolving a co-operative strategy like that will do well, in aggregate, but individual plants which 'defect' and advertise to other plants that the nutritious soil they have found is poisonous and that other plants should keep away will outcompete its peers - so defector genes will prosper in the population - except in the face of plants which ignore their peers' chemical signals.

Overall, seems likely to be selected against as a strategy for individual organisms.

[icegreentea]

I think that the effectiveness of the strategy will depend on the specific plant's pollination/seed dispersal mechanism. And it gets really weird when you consider that you can have plants that over multiple seedling generations (years really) that have a mix of clonal colonies and sexually reproduced offspring dispersed around them.

To the original question, one obvious difficulty is considering how a mechanism encoding directionality in a chemical signal can evolve. It's certainly possible that these fungal networks are weakly directional, and it's also possible for a plant to evolve some sort of gradient sensing mechanism if its root network is sufficiently wide, but it -seems- unlikely. I would totally love to see if we can find an example of it though - it would be sooo cool.

[deciplex]

What about a population of 100 such plants where the defector gene is very unlikely to surface for whatever reason, and the plants are able to cooperate and that population becomes stronger for it, versus a population of 100 similar plants except the defector gene might be rather likely to show up, making the population weaker.

Couldn't the population without the defector gene, eventually outcompete and extinguish the population where it can appear?

[jarin]

Different species of bacteria have been shown to "communicate" via chemical signals, too. It's obviously not cognitive communication, but mating/threat displays between lower order animals can be considered to be just responses to stimuli as well.

Communication between plants may not be cognitive, but it's still the transfer of information.

[jdimov]

What's obvious about it? And what exactly do you mean by "cognitive communication"?

[jarin]

I mean communication between two organisms capable of cognition, i.e. language, mating displays, or other forms of communication that require a brain capable of interpretation.

[a-priori]

They're referring to chemical signalling of some kind when they use the word 'signal'.

Chemical signalling of various kinds is very common in all kingdoms of life; examples in animals are hormones (circulated in the bloodstream for communication between organs), pheromones (circulated in the air for signalling between organisms), and neurotransmitters (emitted in the gap between synapses and dendrites for signalling activation of a neuron).

[lowglow]

The fact that they feed and use the chemistry from their metabolic pathways to drive things like plant locomotion and tropism is a clear indicator for "information" processing. The information in this case is chemistry as a result of their surrounding, and processing is the metabolic pathway and beyond.