CALCIUM AND THE GENERATION OF PLANT FORM

The involvement of mechanical signals (tension and compression) in the determination of the form of living organisms has been speculated upo n for many years. These mechanical signals (both environmental and tho se generated within the plant itself) have significant effects on plan t development and thus morphology. Plants respond to externally applie d mechanical signals (touch and wind) by an immediate elevation of cyt osolic calcium concentration ([Ca2+](cyt)) in stimulated cells. This r esponse requires the movement of plant tissues to cause tension and co mpression. Some of the more longer-term responses to mechanical signal s, e.g. TCH gene expression and reduction in hypocotyl growth, show a calcium-dependency. It seems likely, therefore, that the effects of me chanical signals on plant development are mediated by the second messe nger, calcium. This raises the exciting possibility that this simple i on plays a central role in the determination of plant form itself.