Cotyledons are the seed leaves of a plant embryo, and they serve as a food source for the developing seedling. Starch is a complex carbohydrate that provides energy for the seedling to grow and develop until it can produce its own food through photosynthesis.

While starch is the most abundant food substance, cotyledons may also contain other nutrients such as:

* Proteins: Provide amino acids necessary for growth.

* Lipids (fats): Provide energy and support cell structure.

* Vitamins and minerals: Essential for various metabolic processes.

The exact composition of food substances in cotyledons varies depending on the plant species.