Seed Germination and Seedling Physiological Characteristics of Cardamine hupingshanensis K.M. Liu et al. (Brassicaceae) under Cadmium Stress

Abstract

Cadmium is a naturally occurring element that can seriously harm food safety and human health with strong biological toxicity. Thus it is necessary to investigate the plants that can be used for phytoremediation of the metal. Therefore, the physiological mechanism of Cardamine hupingshanensis K.M. Liu et al. tolerance to cadmium for phytoremediation technology was conducted. The results showed that: [1] the germination potential, germination rate, germination index, and activity index of C. hupingshanensis increased at first and then decreased along with the increase of cadmium concentration; [2] with the increase of cadmium concentration, the root length, plant height, number of leaves, and weight per plant increased at first and then decreased, i.e. when the cadmium concentration is 1 mg/L, the chlorophyll content is slightly higher than the control, and when the cadmium concentration is greater than 1 mg/L, the chlorophyll content gradually decreases; [3] the relative conductivity and malondialhehyde of C. hupingshanensis increased gradually with the increase of cadmium concentration, and both were significantly higher than the control when the cadmium concentration was greater than 50 mg/L; the activities of superoxide dismutase, peroxidase, and catalase were stimulated; the glutathione peroxidase was significantly higher than the control at cadmium concentrations of 100 and 200 mg/L; [4] the absorption coefficient of C. hupingshanensis gradually decreases with the increase of cadmium concentration, whereas the transport coefficient is slightly affected by the increase of cadmium concentration. The average value of the ratio of cadmium concentration in the aboveground part to that in the underground part is 1.17. This shows that C. hupingshanensis is a plant with a super enrichment capacity for cadmium.