Plants manufacture their own food through the process of photosynthesis.A commonly used equation for photosynthesis is, 6CO, 6H2O Light energy CH0+ 60, (Carbon IV oxide) (Water) chlorophyll (Carbohydrate i.e. glucose) + Oxygen They have chlorophyll which traps light energy from the sun.The general equation is as follows; (Glucose) (Oxygen) 2 CHO + 0 6CO + HO + 38ATP (Carbon IV oxide) (Water) (Energy)During this process oxygen is given off as a by-product.