Figure 4.

Analysis of Soluble ROS Defense Metabolites and Oxidative Stress Products.

From three biological replicates, significant genotypic effects were identified by Student’s t test and are indicated with one, two, or three asterisks (corresponding to P value < 0.05, P value < 0.01, or P value < 0.001, respectively).

(A) Cell stains for O₂⁻ and H₂O₂ in response to 5× light stress. Leaves were stained either with nitroblue tetrazolium, which develops a blue precipitate in the presence of superoxide (left-hand panels), or with diaminobenzidine, which develops a brown precipitate in the presence of hydrogen peroxide (right-hand panels). wt, the wild type.

(B) Total levels of ascorbate and glutathione equivalents were measured by absorption spectroscopy as described (Luwe et al., 1993) before and after 5× light stress. Error bars indicate the sd of four biological replicates. Levels of oxidized product are <5% in all pools (data not shown). FW, fresh weight.

(C) Elevated accumulation of β-carotene oxidation products was found in k1 k3 in rosette tissue in response to the 5× light stress treatment. Oxidation products were collected from tissue samples 10 h into the photoperiod on 0, 1, and 3 d of 5× light stress, as well as 5 h into the photoperiod of the first day of light stress. Data points are normalized to fresh weight. Error bars indicate the sd of three biological replicates.