THE EFFECTS OF ZINC ON CELL VIABILITY AND ON MITOCHONDRIAL STRUCTURE IN CONTRASTING CULTIVARS OF FESTUCA-RUBRA L - A RAPID TEST FOR ZINC TOLERANCE

A 20-min exposure to 5.0 mu g Zn cm(-3) reduced the percentage of viable root meristematic cells in three cultivars of Festuca rubra L.: Merlin (Zn-tolerant), Hawk (salt-tolerant but with a degree of zn tolerance) and S59 (Zn-sensitive). The Zn-induced cell mortality in S59 was approximately twice that of the tolerant cultivars. The mean area of mitochondrial profiles in root meristematic cells of Zn-untreated roots was similar in S59 and Merlin but that of Hawk was smaller. A 4-day exposure to 0.2 mu g Zn cm(-3) resulted in mitochondrial swelling in the Zn-sensitive cultivar; there was a 25% increase in the mean area of mitochondrial profiles in this cultivar, but no significant increase occurred in Hawk or Merlin. Zn treatment caused a collapse of the cristae and a localized condensation of the mitochondrial matrix in S59, but not in Hawk or Merlin. The marked increase in cell mortality after only a 20-min Zn exposure and the relative simplicity of the technique, indicates that this procedure could be used as a rapid and independent measure of Zn tolerance.