External and internal lowest observed effect concentrations (LOECs) for Ba in bean plants (Phaseolus vulgaris) were established using a nutrient solution culture system where BaSO4 precipitation in the growth medium was avoided. This was achieved by alternating every 24 h with a nutrient solution containing Ba (0, 50, 500, or 5000 μM) and all essential elements except S, with another containing S and all other nutrients but no Ba. The external LOEC for acute toxicity symptoms in the form of leaf withering and leaf growth inhibition was 481 μM of free Ba2+. This was also the LOEC for the complete inhibition of elongation of secondary roots, while for the elongation of the primary root the external LOEC was 4,821 μM. Barium interfered with both the sulfate transport from roots to shoots and the import of Ca into leaves. However, K was the most Ba-sensitive nutrient. External LOEC for reduced leaf K concentrations was 48 μM free Ba2+; the corresponding internal LOECs for primary and trifoliolate leaves were 700 and 460 mg kg-1 DW, respectively.
|Journal||Archives of Environmental Contamination and Toxicology|
|Publication status||Published - 4 Dec 2000|