Microbial activity in the rhizosphere in relation to the iron nutrition of plants

Información del proyecto

Identificador del acuerdo de subvención: CI1*930006

Proyecto cerrado

Fecha de inicio 1 Enero 1994

Fecha de finalización 31 Diciembre 1996

Financiado con arreglo a

• Activity (Euratom, EEC) on cooperation in science and technology, 1984-

Coste total

Sin datos

Aportación de la UE

Sin datos

Coordinado por

UNIVERSITAET HOHENHEIM
Germany

Objetivo

- The overall goal of this project is to study the utilisation of different Fe siderophores and phytosiderophores by higher plants in short- and long-term experiments with particular consideration of the rhizosphere and root apoplasmic space.
- Hydroxamate siderophores are the most abundant siderophores in calcareous soils under agricultural cultivation. Beside an easily water extractable pool of siderophores firmly bound siderophores to the soil matrix can be determined. Hydroxamates of both pools are enriched in the rhizosphere compared with the bulk soil. A slow transformation between both pools can be detected.
- By short term uptake studies it could be shown that the microbial siderophore rhizoferrin can be easily used by dicots (strategy I plants) and by grasses (strategy II plants). Dicots utilise Fe rhizoferrin via the Fe deficiency-induced reductase system and grasses via the phytosiderophore system.
- The mechanism of utilisation involves the process of an exchange chelation between Fe rhizoferrin and phytosiderophores as shown by in-vitro and in-vivo experiments. Studies on the kinetics have shown a reaction time of t1/2 = 0.5 h. The presence of isolated cell walls (root apoplast) had no further stimulating effect.
- It could be demonstrated that in grasses plant-borne phytosiderophores can efficiently utilise apoplasmic bound Fe and also Fe in the root-soil interface (rhizosphere) of a calcareous soil.
- Maize and barley have the same rate of synthesis of phylosiderophores. However, in contrast to barley, maize and also sorghum do not store phytosiderophores in roots for the short-term release during a few hours once per day, but release phytosiderophore continuously at a constant rate over the whole day. Obviously, maize and sorghum do not have the typical vesicles as found in barley. Beside the maize mutant ys1/ys1 that is defect in the specific Fe phytosiderophore transporter, we have characterised another maize mutant ys3/ys3. This mutant is defect in the secretion mechanism for phytosiderophores.
- A transport of Fe through mycorrhiza hyphae into roots could be proofed by use of special techniques with separated hyphae compartments.

In conclusion, the results so far indicate that siderophores contribute decisively to Fe nutrition of crop plants in agricultural soils. However, the Fe siderophores will be not utilised directly via a specific transport system in the plasma membrane of root cells but by indirect mechanisms such as exchange chelation or reductive chelate splitting.
The following studies have been performed within the joint project :
- Extraction, characterisation and quantification of microbial siderophores in different calcareous soils;
- Uptake of different Fe siderophores and Fe phytosiderophores by dicot plants and grasses in short term experiments;
- Utilisation of Fe siderophores by graminaceous plant roots after exchange chelation with plant-born phytosiderophores;
- Importance of the root apoplasm as transient iron storage for Fe acquisition in general and in particular for exchange chelation;
- Diurnal rhythm in biosynthesis and release of phytosiderophores in sorghum and different maize mutants in comparison with barley;
- Possible transport of Fe through mycorrhiza hyphae into higher plants.

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Programa(s)

• IC-ISC C - Activity (Euratom, EEC) on cooperation in science and technology, 1984-

Tema(s)

Datos no disponibles

Convocatoria de propuestas

Datos no disponibles

Régimen de financiación

CSC - Cost-sharing contracts

Coordinador

UNIVERSITAET HOHENHEIM

• Aportación de la UE: Sin datos
• Dirección: Fruwirthstr.20 ; 70593 STUTTGART ; Alemania
• Coste total: Sin datos