The carbon and oxygen for the plant is available from the carbon-dioxide present in the atmosphere. The hydrogen for the plants is obtained from the water and the mineral nutrients are obtained from the soil.
The plant roots cannot absorb mineral nutrients in the passive manner from the soil unlike they take up water. Minerals cannot be taken passively by the plants as they are present as ions or charged particles in the soil. These charged particles cannot get transported across cell membranes. The mineral concentration in the soil is found to be lower compared to that of root. Hence, the minerals have to enter into the epidermal cells of the root through active absorption which means energy in the form of ATP is essential for the entry of minerals into the plant. The gradient of water potential in roots is caused by the active uptake of ions. Osmotic intake of water is also done by the active process. The charged ions also move into the epidermal cells in the passive manner.
The ions are absorbed from the soil through both the active as well as passive transport. The proteins present in the membrane of the root hair cells pump the ions from the soil into the epidermal cell cytoplasm. The endodermal plasma cell membrane consists of transport proteins that are usually present in all other cells. Some of the solutes cross the membrane transport proteins of the endodermal cells while some solutes are not transported. The screening of solute types that enter into the xylem and the quantity of them is monitored by the endodermal cells. The single direction active transport of ions occurs due to the suberin layer of the root endodermis.