(a) How do plants obtain food? (b) Why do plants need nitrogen? How do plants obtain nitrogen?

(a) Plants obtain food by the process of photosynthesis. Photosynthesis is a process in which green plants use sunlight to make their own food. Photosynthesis requires sunlight, chlorophyll, water, and carbon dioxide gas.

(b) Plants need nitrogen because it is the major component of amino acid and is also building blocks of protein. Plants obtain nitrogen from the soil by inorganic salts like nitrites or nitrates in the form of organic compounds produced by bacteria using the atmospheric nitrogen. Plants also obtain nitrogen from the NPK fertilizer.