Cd-Uptake of Perilla frutescens (L.)Britt as Affected by Cultivation Conditions

Effects of planting density, fertilization and other cultivation conditions on the Cd uptake of Perilla frutescens(L.) Britt was studied under a randomized block field experiment. Both density and starting from sowed seeds or transplanted seedlings of the planting practices were found to significantly affect the uptake and accumulation in parts of the plant.Fertilization exerted a significant effect on the uptake in the seeds. A high content of Cd was found in the entire plant when P. frutescens was started by transplanting seedlings (P1) with a low planting density (i.e., at row and plant spacings of 30 cm×20 cm) (D1), and in the seeds by applying organic fertilizer (F1). The Cd translocation factor (TF) and bioconcentration factors (BCF) of the plants decreased as the planting density increased. They were higher for the transplanted than the seeded P. frutescens. Thus, the maximum Cd content (i.e., 4.57-5.08 mg·kg^-1), TF(i.e., 1.43-1.75) and BCF(2.08-2.24) of P. frutescens were observed when the plants were transplanted from seedlings and allowed adequate space to grow. The Cd accumulation did not differ significantly between D1 and planting spacing of 20 cm×20 cm(D3). However, both D1 and D3 yielded plants with significantly higher Cd than if the spacing was 25 cm×20 cm (D2). Cd in the above-ground stems and leave saccounted for 83.11% of the entire plant and was higher than the under-ground roots, while the seeds had the least.It appeared that organic fertilizer promoted Cd uptake in the seeded plants, while compound fertilizer benefited the Cd translocating to the above-ground plant parts, and appropriate planting density facilitated the phytoremediation of Cd-contaminated soil.