FIGURE 2.

Photoinhibition assays on wt and PTOX⁺ thylakoids in low and high light. Freshly shocked thylakoids were incubated: (A) at low light (120 μmol quanta m⁻² s⁻¹), wt with ferricyanide (○), and DCBQ (▵), and PTOX⁺ with ferricyanide (●), and DCBQ (▴); B, same as A but at high light (1500 μmol quanta m⁻² s⁻¹); C, high light (1500 μmol quanta m⁻² s⁻¹) in the presence of SOD, wt with ferricyanide (□), and DCBQ (▿), and PTOX⁺ with ferricyanide (■), and DCBQ (▾). 50 μg SOD/ml were added prior to the photoinhibitory illumination. The dotted line is the same as the lower line in panel B, and the difference between it and the solid line shows the protective effect of SOD. The maximum activity was between 270–290 μmol of O₂ mg Chl⁻¹ h⁻¹ for both wt and PTOX⁺ thylakoids in the presence of ferricyanide and 400–425 μmol O₂ mg Chl⁻¹ h⁻¹ in the presence of DCBQ as electron acceptor. Error bars represent S.D. (3–4 independent experiments).