If Calvin cycle happens in the stroma ,the splitting of water happens with the help of light energy that has been captured from the sun by the chlorophyll which is present in the thylakoid membranes.
Explanation:
The photosynthesis is a process that is made up of both light and dark reactions, the light reactions take place in the thylakoid. This is because of the presence of chlorophyll that traps the sunlight and gets the light energy in order to fuel the energy reactions in a plant.