Diagram of stomata

Massive amounts of gaseous exchange takes place in the leaves through tiny pores called stomata for the purpose of photosynthesis. The opening and closing of stomatal pores is controlled by the guard cells, when water flows into the guard cells, they swell, become curved and cause the pore to open whereas when the guard cells lose water, they shrink, become straight and close the stomatal pore.

Apart from carbon dioxide and water, nitrogen, phosphorus, iron and magnesium are needed by the plants. Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants. Other materials like nitrogen, phosphorus, iron and magnesium are taken up from the soil. Nitrogen is an essential element used in the synthesis of proteins and other compounds which is taken up in the form of inorganic nitrates or nitrites or is taken up as organic compounds prepared by bacteria from atmospheric nitrogen.