Solution

In green plants, the site of photosynthesis is chloroplast. The chloroplast is double membrane bound organelles. The chloroplast has an internal membrane system made up of thylakoid membranes. Some of the thylakoid membranes are stacked one above the other and are called as grana. They are embedded in a viscous ground substance called stroma. The stroma contains enzymes of Calvin cycle, hence dark reaction occurs in the stroma, whereas thylakoid membranes carry on light reaction.