Vegetation: Transport Processes Inside and Outside of Plants - Transport in the Atmosphere-Vegetation-Soil Continuum - page 203

Stele

Cortex

Pericycle

Cortical cells

Lateral root
primordium

Epidermis or rhizodermis

Emerging lateral root

Root hair zone

Fully grown root hair

Mature vessel

Endodermal cells differentiate

First vessel begins to differentiate

Root hair
appears
Elongation
zone

Maximum rate of cell elongation

First sieve tube matures

First sieve tube begins to differentiate

Cell division ceases in most layers

Meristematic
zone

Pattern of future vascular cylinder
becomes recognizable

Maximum rate of cell division

Apical
meristem

Quiescent centre

Root cap

Figure 6.1 Longitudinal section of a root tip (Ehlers and Goss, 2003 ). Reproduced
with permission of CAB International, Wallingford, UK.

older part of the branched root system, where the root epidermis has been formed.
When the root tissue starts to decay, the colour turns to dark brown.
Depending on the species, the root tip may extend to several centimetres in length.
The tip can be subdivided into four sections: the root cap, the meristematic zone, the
zone of elongation and the root hair zone ( Figure 6.1 ). The starting point of growth is
the meristematic zone , which produces new cells by division. The cells at the bottom
form the root cap . The cap is the protection shield of the growth tissue. It excretes a
mucilage, lowering considerably the friction between the root cap and the surrounding