My teacher ask this question, and I answered 7 to 7.4, but she said it's wrong. I read a lot and found the same answer (wikipedia) I'm here asking for confirmation of this and the pH inside & outside of the tilakoidal membrane.
- The optimum cytoplasmic pH for performing physiological activities in plant cells is a neutral pH of around 7.2 to 7.4.
- The pH of apoplastic space outside plasma membrane and vacuolar pH is acidic ranging between 5 to 7.
- The thylakoid lumen is more fluctuating which varies during light / dark cycles and is highly acidic.
- The mitochondrial compartment and chloroplast maintains a basic conditions of about pH 8 for optimization of biochemical reactions occurring in these two particular compartments.