Which is an important difference between light-dependent (L-D) and light-independent (L-IND) reactions in photosynthesis? The L-D reactions need CO2 and light energy, and the L-IND reactions needs water and O2. The L-D reactions require light energy and water, and the L-IND reactions require ATP, NADPH, and CO2. The L-D reactions can only occur during daylight, and the L-IND reactions can only occur during the night. The L-D reactions need water and CO2, and the L-IND reactions need CO2 and light.