Physiological response of Perilla frutescens (L.) Britt. to cadimium

Hydroponic culture experiments were conducted to study physiological characteristics of Perilla frutescens (L.) Britt. under cadmium stress. The paper analyzed P. frutescens growth, cadmium accumulation and protective enzyme activities in leaf at Cd²⁺ concentrations of 0 mg·L^-1, 2.0 mg·L^-1, 5.0 mg·L^-1 and 10.0 mg·L^-1, respectively. The study showed that the per plant biomass of P. frutescens under cadmium stress dropped by 28.4%, 42.4% and 66.0% compared with control (0 mg·L^-1 Cd²⁺), respectively. Extremely significant differences were noted among the different treatments. Per plant cadmium accumulation capacities under the cadmium treatments were 462.4 μg, 705.0 μg and 609.7 μg, with enrichment coefficients of 91.9, 70.0 and 51.1, respectively. This showed the superior ability of P. frutescens to accumulate cadmium or resist cadmium stress. Tests for SOD, POD and CAT enzyme activities further showed significant increases in SOD activity and MDA content in P. frutescens leaves under cadmium treatments. On the other hand, POD and CAT activities significantly dropped with increasing cadmium concentration. High cadmium concentration destructed protective enzyme balance, which restrained growth of P. frutescens.