Abstract:

[Objective] The aim of the present study was to explore the responses of antioxidant capacity of different parts of alfalfa to the exogenous selenium priming duration, and to provide references for the production of selenium-rich alfalfa grass products by seed priming technology. [Method] Alfalfa seeds were subjected to priming treatment with 0.5 mmol/L sodium selenite solution for 0, 3, 6, 9, and 12 h, respectively. The activities of superoxide dismutase （SOD）, catalase （CAT）, ascorbate peroxidase （APX） and glutathione reductase （GR） as well as the content of malondialdehyde （MDA） in the whole plant, cotyledon, and radicle of the alfalfa seedlings treated for different priming durations were determined and statistically compared. [Result] With the prolongation of selenium priming duration, the activities of SOD, CAT, APX, and GR of the whole plant, cotyledon, and radicle of the alfalfa seedlings all increased, whereas their content of MDA increased first and then decreased. For the whole plant, cotyledon, and radicle, significantly （P<0.05） lower and significantly （P<0.05） higher activities of both SOD and CAT were observed at 0 h and 12 h priming compared with the other priming durations, respectively. The APX activity of cotyledon was significantly （P<0.05） reduced at both 0 h and 3 h priming, and was significantly （P<0.05） elevated at 12 h priming. The significantly （P<0.05） lowest and the significantly （P<0.05） highest APX activity of both radicle and whole plant were observed at 0 h and 12 h priming, respectively. The whole plant, cotyledon, and radicle had the significantly （P<0.05） lowest GR activity at 0 h priming. Their GR activity all reached to the peak at 12 h priming, with a statistically significant （P<0.05） difference observed in the whole plant. The lowest MDA content of cotyledon was observed at 12 h priming, which exhibited statistically significant （P<0.05） differences compared with that at 0 h and 3 h priming. The MDA content of the whole plant peaked at 3 h priming, declined at 6 h priming, and decreased to the lowest level at 12 h priming, showing statistically significant （P<0.05） differences compared with that at 0 h, 3 h, and 6 h priming. The MDA content of the radicle peaked at 3 h priming, declined at 6 h priming, and decreased to the lowest level at 12 h priming, showing statistically significant （P<0.05） differences compared with the other priming durations. Under the same priming duration, the activities of SOD, CAT, APX, GR and the content of MDA in the radicle were all significantly （P<0.05） higher than those in the cotyledon and whole plant, with radicle being the highest followed by the whole plant and cotyledon. [Conclusion] The effects of selenium priming on the antioxidant capacity depended on the parts of the alfalfa seedlings and priming duration. The antioxidant enzyme activities of the whole plant, cotyledon and radicle of the alfalfa seedlings increased with the prolongation of selenium priming duration, while the change trend of MDA content was the opposite. Selenium priming had limited affects on the cotyledon and had great affects on the radicle. For the alfalfa seedlings, selenium priming concentration at 0.5 mmol/L (sodium selenite solution) and priming for 12 h were the optimal conditions.

Key words: selenium, seed priming, priming duration, alfalfa, antioxidant enzyme