Abstract: To destroy Ca²⁺ signal system,the detached leaves of Capsicum annuum were pretreated with EGTA,a commonly used Ca²⁺ chelator,or La³⁺ ,an ion which competitively inhibits Ca²⁺ movement through plasma membrane channels.The induction of sesquiterpene cyclase gene expression in the pretreated pepper leaves under the treatments of CuCl₂,HgCl₂ and UV was conducted in this paper.The result showed that no hindrance of sesquiterpene cyclase enzyme activity was detected in the EGTA or LaCl₃ pretreated leaves,compared to the controls treated with CuCl₂,HgCl₂,and UV without the pretreatment,while the pretreatment with EGTA enhanced the inductivity of the above exogenous abiotic elicitors on the enzyme activity.The sesquiterpene cyclase activity was also detected in leaves treated with EGTA only,and the result of Northen Blot analysis indicated that the enhancement of EGTA on the enzyme activity was due to the induction of EGTA on the gene transcription.It is suggested that there might exist other signal pipelines,in addition to the Ca²⁺ signal system in sesquiterpene cyclase gene expression in pepper leaves,and the mechanism of induction of abiotic elicitors on sesquiterpene cyclase in C.annuum differed from that of biotic elicitors.