2.14. Statistical analysis

The experiment was conducted using a completely randomized block design with three replicates. All the parameters described above were measured at six weeks after the plants were subjected to soil Pb treatments. The data for Miscanthus sinensis exposed to Pb1000 treatment are not shown in the study because this plant could not survive under these severe Pb stress conditions. The SPSS 18.0 statistical software package (SPSS) was used to perform the statistical analyses. The mean with standard deviation (±SD) is shown for each treatment in the tables and figures. The parameters were analyzed by one‐/two‐way analysis of variance (ANOVA) followed by Duncan's multiple range test at p < .05. Figures 1,​, 2 2 and ​and33 were performed with the help of Origin 9.0 software (Origin Lab). The heatmap in Figure 4 was constructed by R 3.6.1 (Bell Laboratories).

Effects of Pb treatment on chlorophyll a (a), chlorophyll b (b), chlorophyll a + b (c), and chlorophyll a/b (d) in leaves of Hemerocallis fulva, Iris germanica L., Canna generalis, Pennisetum clandestinum, and Miscanthus sinensis. Vertical bars represent ± SD of the mean (n = 3); different letters on the SD bars indicate significant differences among the Pd treatments (p < .05). Pb, Pb treatment; PS, plant species. **Significant differences at p < .01

Effects of Pb treatment on leaf net photosynthetic rate (a) and root activity (b) of Hemerocallis fulva, Iris germanica L., Canna generalis, Pennisetum clandestinum, and Miscanthus sinensis. Vertical bars represent ± SD of the mean (n = 3); different letters on the SD bars indicate significant differences among the Pd treatments (p < .05). Pb, Pb treatment; PS, plant species. **Significant differences at p < .01

Effects of Pb treatment on proline (a), soluble sugar (b) and membrane stability index (c) in leaves of Hemerocallis fulva, Iris germanica L., Canna generalis, Pennisetum clandestinum, and Miscanthus sinensis. Vertical bars represent ± SD of the mean (n = 3); different letters on the SD bars indicate significant differences among the Pd treatments (p < .05). Pb, Pb treatment; PS, plant species. **Significant differences at p < .01

Heatmap based on the Spearman correlation matrix of the 17 variables (plant physiological and biochemical parameters) in different Pb‐treated ornamental plants. AB, above biomass of plant; Chl a + b, chlorophyll a + chlorophyll b; Chl a/b, chlorophyll a/chlorophyll b; Chla, chlorophyll a; Chlb, chlorophyll b; GB, gross biomass of plant; LA, leaf area; LN, leaf number per plant; MTI, membrane thermostability index; PH, plant height; P _n, net photosynthetic rate; Pro, proline; R/S, root biomass/aboveground biomass; RA, root activity; RB, root biomass of plant; SS, soluble sugar; TN, tiller number per plant