鎘對孔雀草生理反應之研究

Abstract

Tagetes patula, a common landscape plant, is a newly discovered cadmium(Cd)-hyperaccumulator with the advantages of strong adaptablilty, large biomass, and high accumulating capability of Cd. To investigate the physiological changes and antioxidative responses to Cd, hydroponic culture system was developed. Fourteen days after CdCl2 (10 μM) treatment, Cd more than 400 mg kg-1 was accumulated in shoot tissue. No significant changes could be observed in biomass, chlorophyll content, root cell viability and H2O2 content between control and 10 μM CdCl2 treatment. In contrast, higher CdCl2 concentration (more than 10 μM) increased the formation of reactive oxygen species (ROS), O2 •- and H2O2 and reactive nitrogen species (RNS), NO in Tagetes patula. Thus, excess Cd exerts its effect on growth inhibition, chlorosis, lateral root shortening, and root cell death. Analysis of antioxidative defense system showed that the activity of ascorbate peroxidase (APX), superoxide dismutase (SOD) and the content of phytochelatins (PCs) were enhanced in leaf tissue. On the other hand, the content of ascorbate (AsA) and PCs were enhanced in root tissue with the increase of Cd concentration. Our results also showed that exogenous application of AsA, the specific electron donor of APX, alleviated Cd toxicity and increased the accumulation of Cd in shoot tissue. These results demonstrated that the activities of APX and SOD, and the content of PCs and AsA are involved in modulating Cd tolerance of Tagetes patula.