Autotrophic nutrition is the type of nutrition in which the organisms can produce their food by themselves. Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide (CO2), water (H2O), chlorophyll pigment, and sunlight are the necessary conditions required for autotrophic nutrition. Carbohydrates (food) and O2 are the by-products of photosynthesis.
The whole process can be demonstrated as -
6CO2 + 12H2O --------------------> C6H12O6 + 6O2 + 6H2O + Energy.