AP BIOLOGY

Detailed explanation-1: -Stroma is the fluid-filled internal space of the chloroplasts which encircle the grana and the thylakoids. It contains chloroplast DNA, starch and ribosomes along with enzymes needed for the Calvin cycle.

Detailed explanation-2: -Stroma is the fluid filling up the inner space of the chloroplasts which encircle the grana and the thylakoids. In addition to providing support to the pigment thylakoids, the stroma are now known to contain chloroplast DNA, starch and ribosomes along with enzymes needed for Calvin cycle.

Detailed explanation-3: -So, the correct answer is ‘the central fluid-filled space of the chloroplast’.

Detailed explanation-4: -The function of the stroma is to provide volume around the different structures inside the chloroplast for protection. The stroma is where the light-independent reaction process of photosynthesis, also called the carbon cycle, takes place.