Salt addition after insect herbivory does not increase PPO and TPI levels more than that from herbivory alone
Salt was added to plants subjected to prior insect herbivory. There was no significant interaction between salt and herbivory on PPO and TPI levels (all P > 0.05). Furthermore, salt application did not affect PPO levels regardless of insect herbivory (F(1,21) = 0.0038, P > 0.05). However, PPO levels were significantly higher in herbivory tissue than in no herbivory tissue, regardless of the salt application (Figure 7A; F (1, 21) = 83.17, P < 0.0001). Salt application showed a significant main effect for TPI levels (Figure 7B; F(1, 12) = 8.261, P = 0.0140). TPI levels were significantly higher in herbivory tissue than no herbivory tissue, regardless of salt application (Figure 7B; F (1, 8) = 53.94, P < 0.0001). Salt addition after insect herbivory does not increase PPO and TPI levels more than that by insect herbivory alone.