What is the connecting substance between light reaction and dark reaction? (AS1)

The process of photosynthesis is divided into two steps namely light and dark reaction. In the light reaction, photosystem I and II (present in thylakoid membrane) harness the sunlight through series of steps to form NADPH and ATP. This NADPH and ATP is pumped in reactions catalyzed by the enzymes involved in dark reaction to form sucrose. Therefore, ATP and NADPH are connecting link between light and dark reaction (Fig 2).

Fig 2 shows the connecting link between light and dark reaction of photosynthesis