Abstract: Effects of exogenous calcium on the growth of lotus flower, physiological and biochemical indices and expression of Ca²⁺-related genes under salt stress were studied, which could provide theoretical guidance for further study on molecular mechanism of salt tolerance in lotus and the improvement of salt tolerance of lotus resources by molecular-assisted breeding. Pot experiment was carried out with Fengwu, Fenmeiren, Honglou, Xianjiao, Chunhong and Shuijingfen No. 7, five salt concentration gradients were set, and salt damage index was used to screen salt sensitive varieties and salt-resistant varieties. After treatment with exogenous calcium, effects of calcium on the physiological process of lotus growth and the expression of NnCIPK6 gene under salt stress (100 mmol·L^-1)were studied. The results showed that 150 and 200 mmol·L^-1 NaCl significantly inhibited the growth of lotus. Under salt stress, physiological indices of lotus seedlings showed a trend of rising first and then decreasing with the increase of Ca²⁺ amount, and chlorophyll content of lotus was significantly reduced, and the decline of salt-sensitive variety Fenmeiren was more obvious. Under the treatment of 10,15 mmol·L^-1CaCl₂, antioxidant enzyme superoxide dismutase(SOD) activity and active oxygen scavenging ability were increased, and soluble substance proline accumulation increased,which indicated that the appropriate concentration of exogenous calcium could alleviate lotus salt damage. Under the salt stress treatment, the expression levels of NnCIPK6 genes in Fanmeiren and Jingfenfen No. 7 showed a significant increase trend, and the salt-sensitive variety Fanmeiren showed the most significant change.The variation of the sensitive variety Fenmeiren was the most significant. Treatment with 10 mmol·L^-1 CaCl₂ had a better effect on salt stress, which was beneficial to improve the growth and development of lotus.

Key words: lotus, exogenous calcium, salt damage, chlorophyll, superoxide dismutase, NnCIPK6 gene