If you grew a plant with labeled atoms of carbon, nitrogen, hydrogen, and oxygen, which of these sources would dominate the mass of the plant? see section 36.1 (page 749).

Labeled carbon and oxygen, coming from carbon dioxide as source

Plants are autotrophs, which means that they capable of producing their own "food" from inorganic substances using energy from light or chemical reactions. Plants produce their food mainly by photosynthesis, which utilizes energy in the form of sunlight to convert carbon dioxide in the atmosphere to complex organic molecules as source of food.