Question

Minerals are present in the soil in sufficient amounts. Do plants need to adjust the types of solutes that reach the xylem? Which molecules help to adjust this? How do plants regulate the type and quantity of solutes that reach xylem?

Answer 1

Types of solute

Yes, the plants need to adjust the types of solute that reach the xylem.

Regulatory molecules

The molecules that regulate the ion content in the plant are transmembrane proteins present in the plasma membrane of the root hair cells and the endodermis.

Proteins in the plasma membrane of root hair cell

* The uptake of the mineral ions are regulated by the membrane proteins present in the plasma membrane of the root hair cells.

* ATP is required to transport these mineral ions selectively through ion pumps across the membrane of the root cells against the concentration gradient. This is called active transport.


Proteins in the plasma membrane of endodermis

The endodermal cells contain an impermeable suberin layer that prevents passive transport of the ions. Therefore it contains transport proteins that regulate the type and quantity of solutes that pass into the xylem vessels. Large solute particles cannot pass through these proteins.