Abstract

The effects of exogenous NaCl and silicon on activities of antioxidative enzymes in the root, shoot and leaf of two alfalfa cultivars were investigated in two alfalfa (Medicago sativa L.) cultivars: the high salt tolerant Zhongmu No. 1 and the low salt tolerant Defor. Both cultivars were grown in a hydroponics system with control (no NaCl and no Si added), Si treatment (1 mM Si), NaCl treatment (120 mM NaCl), and Si and NaCl treatment (120 mM NaCl + 1 mM Si). After 15 days of the NaCl and Si treatments, four plants of the cultivars were removed and divided into root, shoot and leaf parts for activity of antioxidative enzyme measurements. Salinity changed the antioxidative enzyme activity to different extents in the root and shoot of both cultivars when Si was not applied. Applying Si to both cultivars under NaCl stress significantly increased ascorbate peroxidase (APX) activity in root, shoot and leaves, and catalase (CAT) activity in leaves, and peroxidase (POD) activity in shoots of both cultivars, but decreased the superoxide dismutase (SOD) activity in shoots of Zhongmu No.1 and roots of both cultivars under salt stress. It is concluded that the changes of antioxidative enzymes activity varied in different organs of alfalfa plant after salt stress, while silicon could alter the activity of antioxidative enzyme of one or several organs of plants to improve the salt tolerance.

Key words: Medicago sativa L., antioxidative enzymes, silicon, salt stress.

Abbreviation

Abbreviations: AOS, Active oxygen species; MDA, malondialdehyde; SOD,superoxide dismutase; CAT, catalase; APX, ascorbate peroxidise; GR, glutathione reductase; Si, silicon; EDTA, ethylenediaminetetraacetic acid; PVP,polyvinylpyrolidone; NBT, nitro-blue tetrazolium.