Principal Component Analysis and distribution of normalised expression ratios for the total of genes analyzed. (A) PCA was performed to reduce the dimensions of expression data to 4 components. Components 1 to 4 explained respectively 43.84%, 11.24%, 10.58% and 8.54% of variation in the data. The first and second components were used as the X and Y axes to plot values from the 16 conditions in this study. Ag10, Ag20, Ag40, Ag80 and AgN represent the addition of Ag-NPs of 10-, 20-, 40- and 80-nm diameter or AgNO3 bulk material, respectively. Ti10, Ti20, Ti40 and TiO the addition of TiO2-NPs of 10-, 20-, 40-nm diameter and TiO2 bulk material. CNT and CNT+ indicate COOH-MWCNTs added to non-supplemented or ABA-supplemented plants. (B) Box plot of the expression ratios for the 26,184 genes analysed with the AtV4 microarrays. Boxes represent 10th and 90th percentiles, with the median (Q2) in the middle line of the box. Minimum and maximum values (snapped to Q1-1.5 x IQR and Q3 + 1.5 x IQR, IQR = Interquartile Range) are shown by the end of the vertical lines (whiskers) and upper or lower outliers by red diamonds.