The timing of methyl jasmonate, hydrogen peroxide and ascorbate accumulation during water deficit and subsequent recovery in the Mediterranean shrub Cistus albidus L.

Here we examined the contribution of methyl jasmonate (MeJA) to the acclimation of a Mediterranean shrub, Cistus albidus L., to water stress under natural climatic conditions. For this purpose, changes in MeJA, hydrogen peroxide (H2O2), ascorbate (AA) and the maximum efficiency of PSII photochemistry (Fv/Fm ratio) and lipid peroxidation were monitored in young leaves of two sets of plants: well-watered plants and plants exposed to water stress and then re-watered. We also estimated plant water relations and plant growth. MeJA accumulation in water-stressed plants showed a maximum increase after 11 weeks of water stress and a second increase after the re-watering, which was performed in week 17 of the experiment. Like MeJA, H2O2 variations showed a biphasic time course, reaching the first peak under mild water stress and the second peak during plant recovery. H2O2 accumulation was not associated with oxidative damage, and in addition to showing intact cell ultratructure, water-stressed plants showed lower lipid peroxidation than well-watered plants. Furthermore, the Fv/Fm ratio remained above 0.75 throughout the experiment in both sets of plants. AA concentrations began to increase at the beginning of water stress, before the increase in MeJA. AA reached a steady maximum, which was maintained during water stress, and returned to initial values when plants were re-watered. On the basis of these results, we conclude that MeJA, H2O2 and AA are involved in the mechanisms of plant resistance to water stress as follows: MeJA arrests the growth of young leaves and AA prevents oxidative damage.