Sudden changes in the rate of photosynthetic oxygen evolution and chlorophyll fluorescence in intact isolated chloroplasts: the role of orthophosphate.

Simultaneous "ripples" (sudden changes in rate) in CO2 dependent O2 evolution and associated chlorophyll a fluorescence were followed in isolated, largely intact, spinach chloroplasts. These ripples could only be observed under conditions in which the supply of inorganic phosphate was limiting. This limitation was achieved either by 1) omission of phosphate in the assay medium, 2) use of inhibitors of the phosphate translocator, or 3) the addition of triose phosphate, a competitive inhibitor of Pi for the same translocator.The possible relation of these ripples to the dampening oscillations that can be observed in leaves, leaf pieces, isolated cells and protoplasts, is discussed.