Cross-tolerance to environmental stresses is a common phenomenon
in plants, whereby exposure to one type of stress confers
a general increase in resistance to a range of different stresses
(Pastori and Foyer, 2002; Suzuki et al., 2012). Cross-tolerance
occurs because of synergistic co-activation of non-specific stressresponsive
pathways that cross biotic–abiotic stress boundaries
(Bostock, 2005). Cross-tolerance phenomena are frequently linked
to the enhanced production of reactive oxygen species (ROS) such
as H2O2, oxidative signalling and the associated regulation of gene
expression through the redox signalling hub, as illustrated in Fig. 1.