The process directly used by autotrophs to store energy in glucose is photosynthesis.

Here's why:

* Autotrophs are organisms that can produce their own food. They use energy from sunlight, water, and carbon dioxide to create glucose (a sugar) through photosynthesis.

* Photosynthesis is the process where light energy is converted into chemical energy stored in the bonds of glucose molecules.

Let me know if you'd like to know more about photosynthesis!