Exogenous jasmonic acid decreased Cu accumulation by alfalfa and improved its photosynthetic pigments and antioxidant system.

Jasmonic acid (JA) is an important phytohormone, which among others may be involved in the regulation of plant accumulating heavy metal. This experiment was designed to explore the effects of exogenous JA on the responses of alfalfa to Cu stress (100 µM) in Hoagland solution. When 1, 5 or 10 mM JA was added to the treatment with Cu addition, Cu concentrations in roots and leaves of alfalfa were significantly decreased (p < 0.05) to some extents compared to the treatment without JA addition. The biomasses of roots and leaves of alfalfa in treatments of JA additions were significantly increased (p < 0.05) compared to the Cu stress treatment. Similarly, the concentrations of Chlorophyll, antioxidant enzyme activities, MDA and H2O2 were improved accordingly. But these factors of JA were not improved further when its concentration added in media was the highest (10 mM), indicating its improvement roles were limited. These results suggested that there were positive roles of exogenous JA on alfalfa decreased its Cu accumulation and toxicities might via reduced oxidative stress.

Selenium spiked in soil promoted zinc accumulation of Chinese cabbage and improved its antioxidant system and lipid peroxidation.

Selenium (Se) and zinc (Zn) are necessary mineral nutrients for human body but millions of people have an inadequate intake of them, and eat food enriched with Se and Zn may minimize these problems. Chinese cabbage is an important food in people's daily life. The aim of this study was to evaluate the effects of single Se, Zn and their combination treatment in soil on their accumulation, antioxidant system and lipid peroxidation in roots and leaves of Chinese cabbage using soil pot culture experiment. When 0.5 mg kg-1 Se +30 mg kg-1 Zn and 1.0 mg kg-1 Se +30 mg kg-1 Zn were spiked in soils, Zn concentrations in roots and leaves of Chinese cabbage were significantly increased (p < 0.05) by 20.2%, 37.8% and 17.9%, 34.1% respectively compared to the treatment of 30 mg kg-1 Zn added, and the latter was significantly higher (p < 0.05) than that of former, indicating Se significantly promoted Zn accumulation. Almost all physiological indexes including POD, SOD, CAT, APX, GR, Chlorophyll a, Chlorophyll b, Carotenoids, MDA and Free proline in the treatments of Se or Zn spiked were significantly improved (p < 0.05) or basically unaffected compared to the control without Se or Zn added. The biomass change trends were similar with these indexes either. These results showed that the addition in soil of Se and Zn significantly increased their accumulation in Chinese cabbage without affected its formal growth. Particularly, the addition of Se promoted Zn accumulation. The conclusions were more important reference for the production practice of cash crop enriched of Se and Zn either.

The difference in antioxidant capacity of four alfalfa cultivars in response to Zn.

The aim of this study was to evaluate antioxidative responses in roots, stem and leaves of four alfalfa cultivars to different concentrations of zinc (Zn) (0, 300, 600 and 900 µM) for 23 days. Among the four cultivars, Aohan displayed the highest Zn concentrations in tissues and the largest Zn amount in aerial parts. Zn stress induced the production of H2O2 and increased the content of free proline and activities of antioxidative enzymes in roots, stem and leaves of Aohan. Based on the above results, we concluded that Aohan is superior to other three cultivars for Zn phyto-remediation, which indicated that Aohan is a novel Zn accumulator and able to tolerate Zn-induced toxicity by activating the antioxidative defense system.

Effects of Se on the growth, tolerance, and antioxidative systems of three alfalfa cultivars.

The aim of this study was to evaluate the selenium (Se) tolerance and exploit the physiological mechanisms in roots, stem, and leaves of three alfalfa cultivars to different concentrations of Se for 60 days. Among three cultivars, Medicago sativa ssp. displayed the highest Se concentrations in tissues, the largest Se amount in aerial parts, the highest bioconcentration factor (BCF) in aerial parts, and translocation factor (TF) under Se stress. Under Se stress, induced O2•- production in roots and leaves and increases in free proline and activities of antioxidative enzymes were observed in M. sativa ssp. Based on the above results, it is concluded that M. sativa ssp. is superior to the other two cultivars for Se phytoremediation, and its well-coordinated physiological changes under Se stress confer the great Se tolerance of this cultivar.