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| Titel |
How the soil-root interface affects water availability to plants |
| VerfasserIn |
Andrea Carminati, Ahmad Moradi |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041051
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| Zusammenfassung |
| Water supply to roots is essential for plant life. To sustain the root water uptake,
a continuous liquid phase has to be maintained at the interface between soil and
roots. Gaps between soil and roots may interrupt the liquid-phase continuity across
the soil-root interface, acting as capillary barriers for the water flow. Additionally,
due to the radial geometry of the flow to roots and the non-linearity of the soil
hydraulic conductivity, a drop in water potential and consequently of water content is
expected to occur next to the roots, in particular when soil dries and transpiration
demand is high. Such a drop in water content may limit water and nutrient uptake by
roots.
How plants can overcome these mechanical and hydraulic flow resistances at the root-soil
interface?
Recent experiments with neutron radiography showed that during transpiration the water
content next to roots was larger than in the bulk soil. Immediately after rewetting, the picture
reversed and the soil next to roots remained markedly dry. During the following days
the water content next to roots increased, exceeding that of the bulk soil. These
water dynamics cannot be described by models assuming homogeneous soil around
roots.
Our hypothesis is that the observed moisture dynamics at the soil-root interface were caused
by mucilage exuded by roots. Mucilage is mainly composed of polymeric substances and has
a high water holding capacity. Mucilage is known to be exuded by roots but its effect on
water uptake is not known.
By calculating the water flux to roots we demonstrate that mucilage weakens the
drop in water potential at the root-soil interface, increasing the conductivity of the
flow path across soil and roots and reducing the energy needed to take up water.
Additionally, mucilage improves the mechanical contact between soil and roots, avoiding
formation of gaps as roots shrink in response to high transpiration demand or drought
stress.
In conclusion, mucilage works as hydraulic and mechanical connector between soil
and roots, favoring water availability to plants. However, under severe drought
conditions, mucilage becomes dehydrated and reduces the wettability of the soil next
to roots. Such a temporary low wettability may have harmful consequences for
the water storage in the root zone and should be taken into account in irrigation
policy. |
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