Fig. 5
Pearson correlation analysis of SiO2-NPs treatment and variable trait relationship in damask under control and different drought conditions. The heat map of the Pearson correlation coefficient (r) values of variable traits, where the colored scale indicates the positive (blue) or negative (red) correlation and the ‘r’ coefficient values (r = − 1.0 to 1.0). The tested variables included carotenoids (CARs), Chl a, Chl b, ChlT, relative water content (RWC), membrane stability index (MSI), maximum PSII (Fv/Fm), protein (Pro), maximal fluorescence from dark-adapted leaf (Fm), variable fluorescence (Fv), malondialdehyde (MDA), hydrogen peroxidase (H2O2), proline (Pro), peroxidase (POD), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and catalase (CAT)