Abstract: Extracellular ATP (eATP) has been considered as a mediating signal in several physiological processes of plants. In this article we showed that eATP can affect the copper-induced cell death and hydrogen peroxide (H_{2}O_{2}) production. CuCl_{2} at concentrations from 100 to 700 textit{mu }molL caused a
significant increase of cell death in tobacco (textit{Nicotiana tabacum} L) suspension cultures, and this increase of cell death level was followed with increases of both intracellular and extracellular H_{2}O_{2} production. The cells exposed to 300 textit{mu }molL CuCl_{2} were chosen to investigate the mechanisms for the copper-induced increases of cell death and H_{2}O_{2} production and the effect on this process. The results showed that the treatment_{ }with CuCl_{2 } at this concentration increased the activity of NADPH oxidase, and addition of DPI (diphenylene iodonium, an inhibitor of NADPH oxidase)alleviated the CuCl_{2}-induced increases of cell death and H_{2}O_{2} production, indicating that the CuCl_{2}-induced increases of cell death and H_{2}O_{2} production were related to an increase of the activity of NADPH oxidase. Addition of exogenous ATP at 50 textit{mu }molL into the CuCl_{2}-stressed cells further enhanced the levels of cell death,H_{2}O_{2} production, and NADPH oxidase activity. However, in the presence of DPI, exogenous ATP failed to do so. These observations indicated that eATP can affect the copper-induced changes of cell viability and H_{2}O_{2} production bystimulating NADPH oxidase

Key words: cell death;Cu^{2+ }ions;quad extracellular ATP, H_{2}O_{2;