In this study,we tested the response of black locust (Robinia pseudoacacia L.) with instantaneous and continuous mechanical damage to the arbuscular mycorrhizal (AM) fungi,and using three-partments system tested the role of common mycorrhizal networks (CMNs) in transmitting mechanical damage related signal between black locust seedlings.We set seedlings with a leaf cut and with a leaf cut every 3 days as the instantaneous and continuous mechanical damaged treatments,respectively,and tested the POD,PAL activities at 0-138 h and growth of the seedlings.Meanwhile,we used three-partments system with 25 μm nylon net to test POD and PAL activities of receptor plants after the donor plants suffered the instantaneous and continuous mechanical damage.The results showed that AM fungi can promote root growth and improve the ratio of transplanting survival of the seedlings with continuous mechanical damages.Suffering from instantaneous mechanical damage,the activities of L-phenylalanin ammo-nialyase (PAL) and peroxidase (POD) increased for 90 h and then decreased.Also,the PAL and POD activities of mycorrhizal seedlings were significantly higher than that of the non-mycorrhizal seedlings.And CMNs can transmit signals relating to mechanical damage,resulting in alteration of PAL and POD activities of donor plants.