Full Idea
Variable secretions of auxin account for a plant's behaviour in following the sun, without any extra hypothesis of purpose, teleology, or intentionality.
Gist of Idea
Chemistry entirely explains plant behaviour
Source
John Searle (The Rediscovery of the Mind [1992], Ch.10.II)
Book Reference
Searle,John R.: 'The Rediscovery of the Mind' [MIT 1999], p.229