 The chloroplast stroma varies from being slightly acidic in the dark to more alkaline in the light.Therefore, in the dark, more FNRs would be recruited and bound to the thylakoid membrane, and in the light, more FNRs would dissociate from the membrane and be free in the stroma.Ferredoxin NADP reductases are present in many organisms, including plants, bacteria, and the mitochondria of eukaryotes.