From all the points discussed above regarding the interaction between Q. robur and E. alphitoides, it can be concluded that (1) the activities of APX, DHAR, MDHAR, and GR; (2) the levels of ascorbate and glutathione, which are involved in promoting effective plant defence responses, were increased with increasing infection severity; and (3) elemental components such as Mn, Ni, Fe, Zn, and Mg, which accumulate to different degrees in infected leaves, may be key to the development of plant defence. Here, APEX1 is linked to infection.