UPPER CRITICAL LEVELS OF TOXIC ELEMENTS IN PLANTS .2. CRITICAL LEVELS OF COPPER IN YOUNG BARLEY, WHEAT, RAPE, LETTUCE AND RYEGRASS, AND OF NICKEL AND ZINC IN YOUNG BARLEY AND RYEGRASS

Though the concentration of Cu, Ni or Zn in the tissue of young (five‐leaf) spring barley grown in a nutrient solution containing one of these elements varies considerably with the growing conditions, the minimum concentrations of Cu, Ni or Zn in plant tissue (Cu 19, Ni 12, Zn 210 ppm dry wt) necessary to cause toxic reactions are relatively independent of the growing conditions. The values for ryegrass S.23 are very similar (Cu 21, Ni 14, and Zn 221 ppm), as are the Cu values for lettuce, rape and what (21, 16 and 18 ppm respectively). At higher concentrations of these elements in plant tissue yield is reduced approximately in proportion to log (tissue concentration). The application of these observations to a procedure for monitoring environmental pollution, outlined in an earlier paper, is further developed. Copyright © 1978, Wiley Blackwell. All rights reserved