The overall effect of photosynthesis is to increase the concentration of oxygen in the Earth's atmosphere. This stage also requires energy, which is supplied by the ATP made by the light reactions.

During the light, provided the rate of photosynthesis is sufficiently high ... The hydrogen is needed for the second stage of reactions and the oxygen is released by the plant as a waste product.

Photosynthesis is a light-activated catalytic reaction that ... "By freezing these species in the gas phase, we can access potential reactive intermediates in chemical reactions that would be ...