[paul.fr]

I know who my sisters are, although i get their names mixed up. now i assume that plants have brothers and sisters too, lots of seeds from one pod for example, would make them related. But does a plant know the others are his/her relatives and is it able to recognise them?

[Karen W.]

What a good Question..Interesting!

[dentstudent]

Yes they do, yes they can, and I don't know yet.

There was an experiment recently on the response of roots to competition from different species, same but non-related species, and same and related species. I'm going to have to check up on the results, but the upshot was that siblings could "recognise" each other, and their growth adjusted accordingly.

There are many instances of intra-species recognition - during insect attack for example, the affected trees let out a chemical signature which tells other trees that they are being attacked. The response is to do something to counteract the potential attack, by releasing tannins for example to make the tree less palatable.
There is also allelopathy, which again involves the release of compounds, but which are designed to restrict the growth of other species in the proximity of that plant.

[Karen W.]

That is really cool to know! I like the idea that life is life.. You know what I mean?