Figure 3.

A, Activities of SOD, APX, and GR measured from the first trifoliate leaves of bean plants after 2 weeks of growth in the presence of 0.3 μm Cu²⁺ (control plants; white bars), 4 μm Cu²⁺ (hatched bars), or 15 μm Cu²⁺ (black bars). B, The coefficient of nonphotochemical (q_N, circles) and photochemical (q_Q, squares) quenching of Chl fluorescence in leaves of control beans (white symbols) and leaves of bean plants grown in the presence of 4 μm Cu²⁺ (black symbols). Fluorescence was measured with a PAM fluorometer after 5 min of illumination at each PPFD, and far-red illumination was used to measure F₀ ' after each white light illumination period. Each data point shows the mean of four independent experiments, and the error bars show se.