Instant Notes: Plant Biology

120 Section I – Plants, water and mineral nutrients

Lower uptake of

water. Suberinization

of endodermis

Rapid uptake of

water. Root hairs,

xylem, little

suberinization

Lower uptake of

water. No root

hairs, xylem

or suberin

Endodermis

becomes suberinized

Cortex

Endodermis

Stele

Xylem

Suberin

(Casparian strip)

Root hair zone

First xylem forms

Meristem

Root cap

CortexStele

VAC 2 VACUOLE VAC

1

(^32)
3
(a)
(b)
(c)
Fig. 4. Key features of water transport in a primary root. (a) Root hairs increase root surface area in contact with films of
water around soil particles. The suberinized endodermis of older tissue restricts water uptake. (b) Illustrates the position
of the endodermis between the cortex and vascular tissue. (c) Shows the possible pathways of transport through root
cells: (1) apoplastic; (2) symplastic through plasmodesmata; and (3) symplastic (transmembrane).