Plant nutrient uptake
Plants uptake essential elements from the soil through their roots and from the air (mainly consisting of nitrogen and oxygen) through their leaves.
Plant nutrition is the study of the chemical elements that is necessary for plant growth. Nutrition can be defined as the process by which an organism obtains food, which is used to provide energy and materials for its life sustaining activities.
Plants use inorganic minerals for nutrition, whether grown in the field or in a container in solutions of fertilizer minerals in the absence of soil. A good soil supplies the plants with the mineral elements they use.
Nutrient uptake in the soil is achieved by cation exchange, wherein root hairs pump hydrogen ions (H+) into the soil through proton pumps. These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen. The carbon dioxide molecules are used as the carbon source in photosynthesis.
Complex interactions involving weathering of rock minerals, decaying organic matter, animals, and microbes take place to form inorganic minerals in soil. Roots absorb mineral nutrients as ions in soil water.
For example, plants acquire nitrogen in the form of nitrate ions (NO3−). Many factors influence nutrient uptake for plants. Ions can be readily available to roots or could be "tied up" by other elements or the soil itself. Soil too high in pH (alkaline) or too low (acid) makes minerals unavailable to plants.