Sodium chloride alleviates cadmium toxicity by reducing nitric oxide accumulation in tobacco

Nitric oxide (NO) is involved in regulating the response of plants to Cd toxicity. In this study, we examined possible involvement of NO in the alleviation of Cd toxicity by NaCl in tobacco plants. Two independent experiments were conducted to investigate the changes of NO accumulation and Cd concentration in tobacco plants after the addition of a NO donor, sodium nitroprusside dehydrate (SNP), or a NO inhibitor, nitro-l-arginine methyl ester (l-NAME) in the solution containing NaCl and Cd. NO accumulation in tobacco roots was enhanced when plants were exposed to Cd, but reduced in the treatments of NaCl or l-NAME. NO production was not enhanced even when SNP (NO donor) was added to the solution containing Cd and NaCl. Root number was reduced in plants exposed to Cd, and increased by the addition of NaCl and reduced by the addition of SNP. Addition of NaCl or l-NAME to the Cd-containing solution reduced Cd concentration in plant tissues, with l-NAME having a more dramatic effect. It can be concluded that alleviation of Cd toxicity by NaCl contributed to reduction of NO accumulation in plants.