Answer:
Yes, plants need to
adjust the type and quantity of solutes that reach the xylem. Thetransport
proteins of end dermal cell help in maintaining and adjusting solute movement.
As the minerals
are" present in soil as charged particles with a very low concentration as
compared of roots, they, all cannot be completely passively transported across
cell membranes of root hairs.
Thus,
minerals are transported both by active and passive processes, to the xylem.
Uponreaching xylem, they are further transported, i.e., upwards to sinks
through transpirationstream. At the sink regions mineral ions are unloaded
through diffusion and active uptake byreceptor cells.
Some of the
mineral ions moving frequently through xylem are
(i) Nitrogen
travels in plants as inorganic ions.
and
but much of the
nitrogen moves in the form of amino acids and related organic compounds.
(ii)Sulphur
and Phosphorus small amount of these two nutrients are carried in organic
forms.
(iii)
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.
Elements
most readily mobilised are phosphorus, sulphur, nitrogen and potassium.
Someelements that are structural components like calcium are not remobilised.
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