Abstract

Nitric oxide (NO) is a bioactive and a multifunctional gaseous molecule signal playing a central role and mediating variety of physiological processes in plants. In this study, the protective effect against chilling stress of exogenously applied sodium nitroprusside (SNP, a NO donor) in Cucumis sativus L. cv ZND407 and cv ZND461 was investigated. The SNP was sprayed over cucumber seedlings using different doses at 4°C. The results indicated that malondehyde (MDA) content was decreased however, soluble sugar and chlorophyll content increased upon treatment with 1.0 mmoll^-1 SNP. Further investigations showed that treatment with NO donor stimulated the activities of various enzymes such as, superoxide dismutase (SOD, EC1.15.1.1), glutathione reducatse (GR, EC1.6.4.2), peroxidase (POD, EC.1.11.1.7) and catalase (CAT, EC.1.15.11). However, the soluble protein content did not change significantly under the NO treatment. The study indicated that exogenous NO at 1.0 mmoll^-1 SNP enhanced chilling stress tolerance. In comparison with cvZND 461, cvZND407 had higher tolerance ability to chilling stress.

Key words: Antioxidative enzymes, chilling stress, cucumber, nitric oxide (NO) osmotic adjustment; reactive oxygen species (ROS).