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

Abstract

summary 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.

Simultaneous recording of xylem pressure and trans‐root potential in roots of intact glycophytes using a novel xylem pressure probe technique

“…Several hypotheses are currently considered in the literature (Malone & Alarcon 1995): phloem transport of proteinase-inhibitor inducing factors (PIIF; Pearce et al 1991), hydraulic dispersal of PIIF chemicals by mass flow in the xylem (Malone 1993(Malone , 1994, and electrical transmission (Williams & Pickard 1972;Roblin & Bonnemain 1979, 1985Satter 1990;Fromm 1991;Sibaoka 1991;Wildon et al 1992). Our results suggest that (1) an intricate relationship between electrical and hydraulic signals frequently exists (see also Malone & Stankovic 1991;Stahlberg & Cosgrove 1997) and that (2) other mechanisms for transmission of electrical signals must be taken into consideration.…”

Variation potential in higher plants: Mechanisms of generation and propagation

“…3,11,13 A combination of hydraulic and chemical signals is also proposed in some studies. 59 The hydraulic hypothesis maintains 4,7 that damage increases hydraulic pressure in the stimulated zone that induces a hydraulic wave that is propagated through the plant body. A number of experimental data support this hypothesis.…”

“…6,47,50,81 As a result, an alternative mechanism of wound substance transmission was suggested. According to Malone,59 local damage increases hydraulic pressure in the stimulated zone; in turn, this pressure growth induces acropetal and basipetal water flows in xylem, which transfers wound substances ('hydraulic dispersion'). Another possible way of wound substance propagation was suggested previously.…”

“…47,56 Both mechanisms of wound substance propagation (hydraulic dispersion and turbulent diffusion) suppose that this propagation can be intensified by damage-induced changes in hydraulic pressure (hydraulic wave transmission), i.e., the chemical and hydraulic mechanisms cooperate during VP propagation. 47,59 Mechanisms of variation potential generation Both potential mechanisms of VP propagation rely on damage-induced signals that influence ion transporters in plant cell plasma membranes, which are ligand-dependent (chemical mechanism) or mechano-sensitive (hydraulic mechanism). Therefore, discerning the nature of these transporters is key to understanding VP generation mechanisms.…”

Is membrane potential involved in calmodulin gene expression after external stimulation in plants?

“…This VP (or SW) is not a genuine electrical signal in so far as its method of propagation is still unknown. It appears to be the consequence of the prior passage of a hydraulic signal [9,12,30]. Thus, it is a VP rather than an AP that evokes calmodulin transcript accumulation at a distance followed by the inhibition of growth in Bidens.…”