Does Wound-Induced Xylem Peroxide Contribute to the Post-Harvest Loss of Hydraulic Conductivity in Stems?

The hydraulic conductivity of cut flower stems decreases 4-8 h after cutting, possibly because of up-regulation of L-phenylalanine ammonia-lyase (PAL). To get more insight into the processes linking wounding with the increase in enzyme activity we explored the movement of reactive oxygen species (principally H2O2) in the xylem of Arabidopsis. Following wounding there is a rapid rise in the production of H2O2. The peroxide persists for a long time in the xylem, making feasible its role as a long distance signalling molecule. The link between wound-induced H2O2 in the xylem, up-regulation of PAL activity and decreases in hydraulic conductance postharvest needs further exploratio