Which of these parts of an illuminated plant cell would you expect to have the lowest ph?

The answer is thylakoid space. The thylakoid space is the space inside of the thylakoid which is well-defined by the individual membrane of the thylakoid. The mainstream of the light dependent responses happens in the thylakoid membrane and not the thylakoid space. There is a constituent named lumen in the thylakoid space that mostly supports to offer assembly and to construct up a concentration incline of protons throughout photosynthesis.