Minerals are present in the soil in sufficient amounts.

Yes, plants need to adjust the type and quantity of solutes that reach the xylem. The transport proteins of end dermal cell help in maintaining and adjusting solute

movement. 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 deciduous plants, minerals are removed to other parts. Elements most readily mobilised are phosphorus, sulphur, nitrogen and potassium.

Some elements that are structural components like calcium are not remobilised.