One of the most amazing feat of plants regarding information processing is the way the leaves optimize the gas exchange process. They do this by opening and closing small gates known as stomata [0].

Each stoma integrate their local state with the current atmospheric conditions and the state of their neighbors, behaving as the cells of a cellular automaton [1].

Plant leaves literally compute.

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[0] http://en.wikipedia.org/wiki/Stoma

[1] http://www.pnas.org/content/101/4/918.full