ABSTRACT
Salinity is considered a major factor in limiting plant growth and production. Being the major common abiotic stress, high exogenous salt concentrations cause an imbalance of the cellular ions resulting in a sort of physiological and biochemical changes such as ion toxicity, osmotic stress and production of activated oxygen species, and disrupt the integrity of cellular membranes, the activities of the various enzymes, function of photosynthetic apparatus and many other processes. Plant cells have developed an array of enzymatic and non-enzymatic mechanism for scavenging these toxic components to protect cellular and subcellular systems from the cytotoxic eects of these oxygen species (AOS), including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX), glutathione reductase (GR), polyphenol oxidase (PPO) and non-enzymatic ascorbate and glutathione. SOD removes superoxide anion free radicals accompanying with formation of hydrogen peroxide (H2O2), which is then detoxified by CAT and POD. In the ascorbate-glutathione cycle, APOX reduces H2O2 using ascorbate as an electron donor. Oxidized ascorbate is then reduced by GSH generated from GSSG catalyzed by GR at the expense of NADPH. There are many reports about eects of salt stress on plant growth and antioxidant system. The plants involved include lentil (Ebru Bandeoğlu and Füsun Eyidogan, 2004), wheat (R.K. Sairam et al., 2005), olive, Cassia angustifolia (S. Agarwal and V. Pandey, 2004) and so on. However, no information is available on the eects of salt stress on the AOS metabolism and antioxidant system in dierent shoots of snow lotus (Saussurea involucrata Kar.et Kir.). Snow lotus is an endangered medicinal plant distributed in the Tianshan and Kunlun mountain ranges of China, and is very sensitive to salinity. Studies of antioxidant mechanism on snow lotus seedlings under
* Corresponding author :Ye Jian, Tel:+86-10-66269548, E-mail:yejian77@126.com.
