Sc. Sheppard et al., A PLANT LIFE-CYCLE BIOASSAY FOR CONTAMINATED SOIL, WITH COMPARISON TOOTHER BIOASSAYS - MERCURY AND ZINC, Archives of environmental contamination and toxicology, 25(1), 1993, pp. 27-35
Bioassays using rapid-cycling plants allow measurement of multiple end
points and assessment of impacts on both growth and reproduction. Sele
ctions of Brassica rapa develop rapidly in a broad range of soils and
are very consistent in production of flower and seed. Their sensitivit
y to variation in growth conditions was investigated to define the var
iables that most affect performance. Yield differences between soils w
ere substantial, indicating the need for careful selection and use of
control treatments. The sensitivity to contaminants was investigated w
ith applications of mercury (Hg) and zinc (Zn) to three soils. In a sa
nd soil, bloom initiation was slowed by < 10 mg Hg kg-1 soil and < 50
mg Zn kg-1 soil. In contrast, lettuce emergence and earthworm survival
were less sensitive to these metals in this soil. Survival of Daphnia
magna and the Microtox(R) assay in soil extracts were more sensitive
to Hg than bloom initiation, but less sensitive to Zn. A similar relat
ionship among the bioassays was observed for two finer-textured soils,
although for these, effects were usually apparent only at soil metal
concentrations > 200 mg kg-1. Enzyme assays were included for comparis
on, but were not sensitive to Hg contamination. Rapid-cycling B. rapa
selections are suitable for routine bioassays, and are representative
of several widely distributed and utilized species.