Fig. 9.

The proposed mechanism of Al induced cross-resistance of potato to P. infestans, in which moderate Al stress triggered changes in short-term biochemical imprint in distal potato leaves, facilitating effective defense responses against a subsequent pathogen attack. First, plant pretreatment with Al at the root level provoked redox imbalance manifested in H₂O₂ overproduction and diminished NO synthesis. These local changes might create a redox background for distal NO and SA-dependent signal generation. The complex regulatory networks facilitated systemic activation of Al stress responses engaged in the biochemical imprint linked to the coding of NO message in reversible SNO storage. Finally, signal amplification leading to potato resistance manifested in distal leaves of Al-treated plants was related to expression of SA-mediated defense genes (PRs and PAL) early after contact with a challenging pathogen and to subsequent disease limitation