“Single … of Cu and Cd (0.4 μM Cu2 and 0.45 μM Cd2+) to the culture medium induced the production of short-chained phytochelatins ((γ-Glu-Cys)n-Gly where n = 2–5), whereas a single addition of Zn (2.2 μM Zn2+) did not stimulate phytochelatin production.”