Answer:
In photosynthesis, photolysis of water at photo-system II provides high energy electrons as well as protons to the system.
Thus, the main source of protons in the electron transport chain of photosynthesis is water.
In addition, protons from the stromal side are also pumped into the lumen in order to develop a proton gradient.
In the electron transport chain of respiration, energy provided by NADH and FADH₂ is used by the complexes ( associated with ETC) to pump the protons present in the mitochondrial matrix into the inter-membrane space.
