To study the effects of bottle gourd rootstock-grafting on the contents of ions and endogenous hormones in different parts of watermelon seedlings under NaCl stress,we used the salt-sensitive watermelon cultivar ‘Xiuli’ as the scion,the salt-tolerant bottle gourd cultivar ‘Chaofeng Kangshengwang’ as the rootstock in this study.The self-grafted watermelon seedlings were used to be the references to avoid the procedural errors induced by grafting.Results showed that:(1)Most Na⁺ was accumulated in the shoots of self-grafted seedlings while most of Na⁺ was stored in the roots of bottle gourd in rootstock-grafted seedling under NaCl stress.The contents of K⁺ and the ratio of K⁺/Na⁺ were significantly decreased under salt stress in both self-grafted and rootstock-grafted seedlings.However,rootstock-grafted seedling had much higher K⁺ contents and the ratio of K⁺/Na⁺ as compared with self-grafted seedling under salt stress.(2)The content of indole-3-acetic acid (IAA) and the total contents of zeatin and zeatin riboside (Z+ZR) were significantly increased in the roots and the shoots of the scion,while they were significantly decreased in the leaves of self-grafted seedlings under salt stress.The content of gibberellins (GA₃) was kept in the same level or enhanced by salt stress in self-grafted seedlings under salt stress.As regard to the rootstock-grafted seedlings,the contents of IAA and (Z+ZR) were increased under salt stress in all the organs while the content of GA₃ was reduced under salt stress in all the organs except the leaves.(3)The content of abscisic acid (ABA) was significantly decreased in the roots and shoots while it was remarkable increased in the leaves of self-grafted and rootstock-grafted seedling under salt stress.(4)The ratio of IAA/(Z+ZR) in the roots and the shoots of the scions were significantly increased while it was decreased in the leaves in both self-grafted and rootstock-grafted seedlings under salt stress.However,the increased and decreased extents induced by salt stress in rootstock-grafted seedling were much higher than those in the self-grafted seedlings.These results described above demonstrated that the roots of bottle gourd could play a role of trapping the Na⁺ under salt stress and then stopped the most Na⁺ flowing into the shoots,especially in the leaves of the watermelon scions.This might play an important role in stopping from the occurrence of the ion toxic in the rootstock-grafted seedlings under NaCl stress.On the other hand,the bottle gourd rootstock-grafted seedlings could maintain a much higher content of K⁺ and a higher ratio of K⁺/Na⁺ in all the organs as compared with self-grafted seedlings.This could do the favor to maintain the ion homeostasis for a plant exposed to the salt stress.Furthermore,bottle gourd rootstock-grafted seedlings had much higher contents of IAA and (Z+ZR) and a much higher ratio of IAA/(Z+ZR) in all the organs than those of self-grafted seedling under salt stress.This might also take part in the salt adaptation of grafted-watermelon seedlings under NaCl stress.