Calcium-dependent storage/retrieval of environmental signals in plant development

Natural stimuli (e.g. wind, rain, touching, wounding) have the potential to affect plant morphogenesis, usually by inhibiting growth. We show here, to our knowledge for the first time that very mild, non-injurious environmental stimuli induce a signal responsible for initiation of meristem formation in the hypocotyl epidermis of intact flax seedlings. This signal can be recorded and stored in the plant without being expressed until recalled by a second signal resulting from calcium depletion. A 4-day separation between signals does not result in an apparent loss in the magnitude of the response. Information storage might be the basal mechanism allowing a plant to integrate the large set of environmental stimuli received under natural conditions, thus making it possible to optimize its developmental responses to these stimuli.