Wound-induced hydraulic signals and stimulus transmission in Mimosa pudica L

The mechanism of wound signalling in Mimosa is discussed with a brief historical survey. It is demonstrated that strong wound-induced hydraulic signals occur in Mimosa pudica L., as in many other plants, and that the basipetal mass flows associated with these events could disperse solutes from the wound site at rates of at least 15 mm s^-1 and possibly up to 300 mms^-1 . When such wound-induced 'hydraulic dispersal' is taken into account, Ricca's theory of chemical signalling can explain long-distance transmission in Mimosa. The pattern of long-distance wound signalling in Mimosa is shown to be consistent with such a model. Implications for theories of electrical signalling in Mimosa are discussed and it is concluded, in agreement with some previous workers, that systemic wound-induced electrical phenomena in Mimosa are not travelling signals, but are local responses to the travelling chemical messengers.