Step 1: Know what suberin is.
Suberin is a waxy, water-repelling substance found in certain plant cell walls. Because it blocks water, it controls where water can move in the plant.
Step 2: Recall the root layers.
Inside a root, going inward, we cross the epidermis, the cortex, then the endodermis, and finally the inner tissues with xylem.
Step 3: Find the special waterproof band.
The endodermis has a band called the Casparian strip, and this strip is made of suberin.
Step 4: See why this matters.
Because the Casparian strip is waterproof, water cannot leak between cells here. It is forced to pass through the living cell membranes, which lets the plant control mineral uptake.
Step 5: Rule out the others.
The epidermis, cortex, and xylem do not have this suberin band as their key feature. Only the endodermis is defined by it.
Step 6: Conclude.
So the waxy material suberin is deposited mainly in the endodermis.
\[ \boxed{\text{Endodermis}} \]