Explain : Translocation of mineral ions.

Explanation

After the ions have reached xylem through active or passive uptake, or a combination of the two, their further transport up the stem to all parts of the plant is through the transpiration stream.
Transport route / pathway :
The chief sinks for the mineral elements are the growing regions of the plant, such as (1) apical (2) lateral meristems tissue (3) young leaves (4) developing flowers (5) fruits and seeds and the storage organs.

Unloading of mineral ions occurs at the fine vein endings through diffusion and active uptake by these cells.
Mineral ions are frequently remobilised, particularly from older, senescing parts.
Older dying leaves export much of their mineral content to younger leaves.
Similarly before leaf fall in decidous plants, minerals are removed to other parts.
Dying leaves `overset"mineral elements"to` New leaves
Falling trees/leaves `overset"mineral elements"to` Other parts
`{:("Most readily"),("mobilised ions"):}}` Phosphorus , Sulphur , Nitrogen , Potassium
`{:("Structural substances"),("which do not remobilised "):}}` Calcium
An analysis of the xylem exudates shows that,
Though some of the nitrogen travels as inorganic ions, much of it is carried in the organic form as amino acids and related compounds.
Similarly, small amounts of P and S are carried as organic compounds.
In addition, small amount of exchange of materials does take place between xylem and phloem.
Hence, it is not that we can clearly make a distinction and say categorically that xylem
transports only inorganic nutrients while phloem transports only organic materials.