Light. That's the chemical equation for photosynthesis
In gilled mushrooms, gills are used to maximize spore production. Gills of some mushrooms are folded and crowded to obtain maximum spore production. Other gills, spread towards the outer cap which gives way to new gill growth in between gills which is called partial gill. Some of the mushrooms grow gills in layers too.
Without any photosynthesis, there would be no plants which would lead to the many of the civilians of Earth starving to death. In the likely scenario where photosynthesis does not occur the world would most likely go into an apocalyptic way with the human race as well as many other mammals dying. The organisms that would survive might be used as a food source but the population would drastically decrease
