Plastic, inquisitive roots and intelligent plants in the light of some new vistas in plant biology

Abstract

Metaphors, such as those used in the title of this article, are often useful for the comprehension of specialised topics in plant biology. A brief attempt is made to elucidate one of these metaphors, plant “intelligence”, as it relates to the plastic responses of roots and root systems to their environment. Tropisms and nastic movements of root apices are two expressions of an inherent plasticity of form exhibited by roots. In soil, roots are exposed to multiple stimuli, many of which can potentially elicit such movements. Hence, a key question is how roots respond to and process the different stimuli which simultaneously reach their surfaces. Assuming that roots always use the same site along their length to express their movement responses, and that they also use an auxin‐based information‐transduction pathway, the most evident choices for the processing of stimuli are that roots either prioritise the various incoming stimuli and respond only to the strongest or they amalgamate stimuli and mount an averaged compromise response to all of them. The proposal that plants may be “intelligent”, especially in respect to their plastic growth responses, is one that draws upon knowledge of this faculty from animal biology. Also implied is that plants and animals are sufficiently similar to share usage of this term “intelligence”. But an alternative view is that plants and animals are sufficiently different and so intelligence is an unfitting term. Following the line of enquiry into creative evolution initiated by Henri Bergson, plants can be viewed differently to animals. The tendency of plants is towards instinctive behaviour rather than intelligent behaviour.

Keywords:

• Bergson
• determinism instinct
• memory
• plant intelligence
• plasticity
• root apices
• root systems
• tropisms

Acknowledgements

The author is grateful for comments received from Prof František Baluška, Dr Jacqueline Lück and Prof Elizabeth van Volkenburg. To the many authors whose works could not be mentioned here due to limitations of space, apologies are extended.

Notes

1. Intelligence – two definitions from the Oxford English Dictionary are: “The faculty of understanding”; “The action or fact of mentally apprehending something; understanding, knowledge, comprehension (of something)”. Or put more simply, as in the Reader’s Digest Universal Dictionary: “The capacity to acquire and apply knowledge”; “The faculty of thought and reason”.