Stimulative effect induced by low-concentration Cadmium in Lonicera japonica Thunb.

A hydroponics experiment was carried out to study the stimulative effect in Lonicera japonica Thunb. induced by cadmium (Cd). The results showed that the plants did not show any visual symptoms at low concentrations of Cd after 2 weeks exposure. Furthermore, roots elongation and contents of photosynthetic pigments displayed a biphasic curve with the increase of added Cd in nutrient medium, indicating plant growth was stimulated at low doses of Cd and inhibited at high doses of Cd. In roots, low-concentration Cd (5 to 25 μmol/L) reduced the content of malondialdehyde (MDA), superoxide anion radical () production decreased to 13.07 and 21.39% compare with the control, respectively. The activities of superoxide dismutase (SOD) and guaiacol peroxidase (POD) was slightly declined at 5 and 25 μmol/L of Cd, respectively and then significantly increased at higher Cd (> 100 μmol/L) treatments in roots. Low Cd led to a slight increase in the activity of catalase (CAT) after 2 week in roots, but lipid peroxidation was not higher than in the control. According to these results, low-concentration Cd (< 100 μmol/L) did not induce oxidative stress and even alleviated the oxidative stress in roots of L. japonica., which might be a mechanism of the stimulative effect in plants.   Key words: Cadmium, stimulative effect, oxidative stress, lipid peroxidation and Lonicera japonica Thunb.