Carbon Dioxide: Land plants obtain it from atmosphere while aquatic plants absorb the same from water. Atmosphere contains over 0-038% carbon dioxide. It enters the leaves through stomata. However, the open stomata also become sites for loss of water in transpiration.

Water: Land plants absorb water from soil through their roots. The absorbed water is transported to photosynthetic areas through xylem. Minerals are also transported along with water. They are used in synthesis of different organic substances like sulphur in proteins, phosphorus in nucleic acids, magnesium in chlorophyll, etc. 99% of absorbed water is lost through transpiration. Only a small quantity of water is used in photosynthesis as hydrogen donor. For this, water splits into its components with the help of light energy. The phenomenon is called photolysis of water. Oxygen is evolved.