Salicylic acid and hydrogen peroxide in abiotic stress signaling in plants

During the 1990's, much evidence has suggested roles for salicylic acid and H2O2 in responses of plants to pathogens. This article reviews recent inte rnational research suggesting that these compounds are also involved in res ponses to abiotic stresses such as extreme temperatures, ozone pollution or UV irradiation. We recently discovered that salicylate applied at low conc entrations (1-100 mu M) could protect seedlings or cultured microplants aga inst heat-shock. Endogenous levels of salicylic acid and its glucoside have been shown to increase in plants subjected to heat, ozone or UV. Salicylic acid and H2O2 appear to influence each other's levels in plant tissues. In creases in H2O2 occur in plants subjected to many abiotic stresses, but it has not been established to what extent this H2O2 is a symptom or a signal of abiotic stress. Consistent with a signaling role for this compound, some reports have shown that treatment with H2O2 can protect plants against col d- or heat-stress, and can induce stress-response genes.