WOUND-INDUCED HYDRAULIC SIGNALS - SURVEY OF OCCURRENCE IN A RANGE OF SPECIES

Localized wounding induces rapid systemic responses in many plants. These responses include change in surface electrical potential in various species and induction of proteinase inhibitor genes in tomato and potato. The nature of the signalling system which co-ordinates such responses is not known, but recently, a role for wound-induced hydraulic signals was proposed. Such signals have been reported only from seedlings of wheat and tomato. If they are of any general importance, they must also occur in other species. Here, displacement transducers are used to test for the occurrence of wound-induced hydraulic signals in a wide range of species. A method is also presented for assessing the transmission rate in vivo, of the slower component of the wound-induced hydraulic signal (a xylem-borne mass flow of water and solutes released at the wound site). This component could be important in the systemic distribution of elicitors from sites of localized wounding. It is proposed that hydraulic signals could form part of a widespread mechanism for co-ordination of the plant response to localized stress.