To understand the general response of APX and SOD activities under the limitation of photosynthesis, the APX and SOD activities were measured in the Rubisco-sense and antisense plants (Figure S3a) (Makino et al., 2000; Suzuki et al., 2007). Under the control-Pi conditions, the Rubisco-antisense plants showed significantly higher total and chloroplastic APX activities than the WT and Rubisco-sense plants, although the cytosolic APX activity was similar among them (Figure S3b, c). Under 3.0 mM Pi conditions, the chloroplastic APX activities in WT and Rubisco-sense plants were activated compared to the control-Pi conditions, and showed similar values to that in Rubisco-antisense plants (Figure S3b, c). The total- and Cu/Zn-SOD activities were higher in the Rubisco-antisense plants than in the WT and Rubisco-sense plants under the control-Pi conditions (Figure S3d). However, under 3.0 mM-Pi conditions, the Cu/Zn-SOD activities in the Rubisco-antisense plants were suppressed similar to those in the WT and Rubisco-sense plants. These results indicated that the P toxicity-mediated suppression of photosynthesis triggers an increase in APX activity as similar to the results of the Rubisco-antisense plants, but the Cu/Zn-SOD activity showed different responses between excessive Pi treatments and a decrease in the Rubisco content, even though both situations limit photosynthesis.