Glycogen is a complex carbohydrate that is used as a primary energy storage molecule in animals, fungi, and bacteria. Plants, on the other hand, use starch as their primary energy storage molecule.

Here's why:

* Starch: Plants produce and store starch in their leaves, stems, and roots. It is a complex carbohydrate composed of glucose units linked together in a long chain. When plants need energy, they break down starch into glucose, which is then used in cellular respiration.

* Glycogen: Glycogen is not found in plants. It is a branched polymer of glucose that is stored primarily in the liver and muscles of animals.

Therefore, plants do not use glycogen for energy storage. They use starch as their primary energy storage molecule.