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In-Depth Information
Casparian
strip
Xylem with heavy
secondary walls
Cellular pathway
(symplastic and
transmembrane)
Phloem
Cortex
Root hair
Epidermis
Endodermis
Stele
Apoplast pathway
Casparian strip
Figure 6.3
Possible pathways of water conduction in the root tip (Ehlers and Goss,
2003
). Reproduced with permission of CAB International, Wallingford, UK.
allowed compared to loam and sand, as the macro pores in unsaturated clay are able
to transport large amounts of air.
Plants living under submerged conditions have adapted to the limited oxygen sup-
ply from the soil system. In these plants, parenchymatic cells in the shoot and root tis-
sue are only sparsely packed, leaving large air-illed spaces in between. This special
tissue is called aerenchyma and serves the internal oxygen transport to the roots by
diffusion. For instance, rice and reed are plants with effective aerating tissues. Wheat
is better adapted to conditions of waterlogging than barley, as wheat can develop
more porous root tissue in the event of looding (Ehlers and Goss,
2003
).
6.2.4 Modelling of Root Water Uptake
Root water uptake will be affected by atmospheric (potential transpiration rate),
plant (root density, wilting point, radial and axial root resistances) and soil (retention
function, hydraulic conductivity function) properties. Microscopic models intend to
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