Figure 4.

Extractable catalase activity from leaves. Leaves were exposed to 500 µmol quanta m⁻² s⁻¹ at 10°C for the indicated time. 100% activity corresponds to the activity measured in the absence of 10 mM DTT divided by the activity measured in the presence of DTT. The samples were treated with DTT to determine the proportion of catalase activity that is sensitive to reduction. Closed squares, S44; open squares, M44; open triangles, M81. Data are mean ± s.e. of seven to eight measurements. The significance levels (*p < 0.05 and **p < 0.005) are indicated.