In which form do plants store energy?

The form of which plants store energy is cellulose.

Celluose. That's the "food product" of photosynthesis.

Spores are a method of reproduction, hormones are chemicals that cause changes or maintain something within an organism (i. e. estrogen is a hormone). Carbon dioxide is the gas that is necessary for photosynthesis, processed into oxygen. So CO2 comes in and goes out just as quickly.