Explain the mechanism of absorption of elements by plants.

(N/A) $\Rightarrow$ The studies on the mechanism of absorption of elements by plants have been carried out in isolated cells,tissues,or organs.
$\Rightarrow$ In the first phase,an initial rapid uptake of ions into the 'free space' or 'outer space' of cells,known as the apoplast,is passive.
$\Rightarrow$ In the second phase of uptake,the ions are taken in slowly into the inner space,the symplast of the cells.
$\Rightarrow$ The passive movement of ions into the apoplast usually occurs through ion-channels,which are transmembrane proteins that function as selective pores.
$\Rightarrow$ On the other hand,the entry or exit of ions to and from the symplast requires the expenditure of metabolic energy,which is an active process.
$\Rightarrow$ The movement of ions is usually called flux.
$\Rightarrow$ The inward movement into the cells is called influx,and the outward movement is called efflux.