Chemical treatment
All experiments were performed using a commercial, water-soluble
chitosan formulation, known as ChitoPlant (ChiPro GmbH, Bremen, Germany)
(Romanazzi et al., 2013, Younes et al., 2014). ChitoPlant, referred to
as chitosan latterly, was freshly prepared in water to the specific
concentrations (please see figure legends for details). Treatments were
performed by foliar spraying of chitosan solution (with 0.01% Tween20)
directly onto leaves.