Figure 1.

Electron transport of well-stacked and destacked spinach thylakoid membranes illuminated with photosystem I-specific far-red light (>715 nm at 20°C for 130 min) in the presence of externally added photosystem I electron donors. Electron transport rates were assayed using an oxygen electrode. Error bars indicate sd with n = 2 to 3. For stacked thylakoids 100% activity was −111 μmol O₂ and 140 μmol O₂ (mg chlorophyll) ⁻¹ h⁻¹ for photosystem I and photosystem II, respectively, and for destacked thylakoids 100% activity was −103 μmol O₂ and 200 μmol O₂ (mg chlorophyll) ⁻¹ h⁻¹ for photosystem I and photosystem II, respectively.