The cytogenetic activity of humic acids extracted from brown coals and thei
r effect on both the germination of corn seeds and the yield of barley and
wheat were studied. They induce no chromosomal aberrations in plants when a
pplied at concentrations of 4.03 to 160 mg/l. The biological activity of hu
mic acids depends on the treatment of coal, the relative content of constit
uents with a molecular weight over 10000, the content of carboxyl and pheno
lic OH groups, and macromolecule charges.