Write a short note on the uptake of mineral ions.

(N/A) $\Rightarrow$ Plants obtain their carbon and most of their oxygen from $CO_{2}$ in the atmosphere.
$\Rightarrow$ However,their remaining nutritional requirements are obtained from minerals and water (for hydrogen) in the soil.
Unlike water,all minerals cannot be passively absorbed by the roots.
$\Rightarrow$ Two factors account for this:
$(i)$ Minerals are present in the soil as charged particles (ions) which cannot move across cell membranes.
$(ii)$ The concentration of minerals in the soil is usually lower than the concentration of minerals in the root.
Therefore,most minerals must enter the root by active absorption into the cytoplasm of epidermal cells.
This process requires energy in the form of $ATP$.
$\Rightarrow$ The active uptake of ions is partly responsible for the water potential gradient in roots and,therefore,for the uptake of water by osmosis. Some ions also move into the epidermal cells passively.
$\Rightarrow$ Specific proteins in the membranes of root hair cells actively pump ions from the soil into the cytoplasm of the epidermal cells.
$\Rightarrow$ Like all cells,the endodermal cells have many transport proteins embedded in their plasma membrane.
$\Rightarrow$ They allow some solutes to cross the membrane,but not others.
$\Rightarrow$ Transport proteins of endodermal cells act as control points,where a plant adjusts the quantity and types of solutes that reach the xylem.