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Soil Physics

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Mutez Ali Ahmed: Theses offered



Bachelor's Theses offered
The impact of root exudates on the physical properties of soil and root water uptake

Introduction:

Global population is increasing and projected consumption is placing unprecedented demand on agriculture for food production. Securing food availability is a major challenge, since global water shortage and degradation are already limiting crop yield today and this limitation, will further intensify as agricultural activities expand to less fertile areas. The rhizosphere, the interface between plant roots and soil, is rich in provides a unique environment for large and diverse types of substances like microbes, including plant growth-promoting rhizobacteria (PGPR) and root exudates. Investigations on the mechanisms by which these substances mediate plant drought tolerance have largely focused on -root/plant interactions and related plant responses to bacteria types. Comparatively, much less is known about the role of root exudates in altering the physiochemical and hydrological properties of the rhizospheric soil that may affect plant drought stress tolerance.

Hypotheses:

This project is aiming on testing the following hypotheses:

1. Root exudates change the pore space of soils and improve the soil hydraulic properties (both wetting and drying), resulting in material that can hold more water and increase residents time of solutes in the rhizosphere

2. Root exudates may improve crop yields, especially in coarse (sandy) to medium (loamy) texture soils, due to either increase in available water in the rhizosphere, and/or due to prolonging the contact of roots with the soil matrix and consequently higher root water uptake and nutrient uptake.

Methods:

Laboratory work on the estimation of soil hydraulic properties for materials treated with different concentrations of root exudates for both wetting and drying processes. In case of a master thesis, the thesis will include quantification of the SHPS based on pore scale considerations or quantification of root water uptake with a numerical model. In both cases, model results will be compared against the lab measurements.



Contact: Efstathios (Stathis) Diamantopoulos, Mutez Ali Ahmed


Master's Theses offered
The impact of root exudates on the physical properties of soil and root water uptake

Introduction:

Global population is increasing and projected consumption is placing unprecedented demand on agriculture for food production. Securing food availability is a major challenge, since global water shortage and degradation are already limiting crop yield today and this limitation, will further intensify as agricultural activities expand to less fertile areas. The rhizosphere, the interface between plant roots and soil, is rich in provides a unique environment for large and diverse types of substances like microbes, including plant growth-promoting rhizobacteria (PGPR) and root exudates. Investigations on the mechanisms by which these substances mediate plant drought tolerance have largely focused on -root/plant interactions and related plant responses to bacteria types. Comparatively, much less is known about the role of root exudates in altering the physiochemical and hydrological properties of the rhizospheric soil that may affect plant drought stress tolerance.

Hypotheses:

This project is aiming on testing the following hypotheses:

1. Root exudates change the pore space of soils and improve the soil hydraulic properties (both wetting and drying), resulting in material that can hold more water and increase residents time of solutes in the rhizosphere

2. Root exudates may improve crop yields, especially in coarse (sandy) to medium (loamy) texture soils, due to either increase in available water in the rhizosphere, and/or due to prolonging the contact of roots with the soil matrix and consequently higher root water uptake and nutrient uptake.

Methods:

Laboratory work on the estimation of soil hydraulic properties for materials treated with different concentrations of root exudates for both wetting and drying processes. In case of a master thesis, the thesis will include quantification of the SHPS based on pore scale considerations or quantification of root water uptake with a numerical model. In both cases, model results will be compared against the lab measurements.



Contact: Efstathios (Stathis) Diamantopoulos, Mutez Ali Ahmed
The role of arbuscular mycorrhiza fungi in plant water status

Introduction: Water scarcity in soil and atmosphere escalates stress on vegetation and threatens future agricultural production and forest survival, especially in the face of climate change. Recent literature has identified soil drying as a primary cause of transpiration reduction globally. Thus, detailed knowledge of water flow processes, particularly belowground, is required to fully understand and predict plant behavior under drought episodes and future climate conditions.

Although Arbuscular Mycorrhiza Fungi (AMF) are assumed to play a pivotal role in plant response to soil drying, studies investigating the impact of AMF on plant water status and soil-plant hydraulic conductance are limited.

Hypotheses: This project aims to test the following hypotheses:

  1. AMF limit the drop in matric potential across the rhizosphere, especially during soil drying. The underlying mechanism is that AMF extend the effective root radius and hence reduce the water fluxes at the root-soil interface.
  2. The follow-up hypothesis is that AMF enhance soil-plant hydraulic conductance and plant water status during soil drying.

Methods: Measuring transpiration and leaf water potential during soil drying of two maize genotypes; a mutant that suppresses AMF colonization and the corresponding wild-type. The plants will be grown in a walk-in climate-controlled chamber and placed on automated wireless balances. The latter will record the weight every 10 minutes to obtain gravimetric transpiration rate. Complementary measurements will be done to assess soil dryness after the last irrigation.



Contact: Mohanned Abdalla Ali, Mutez Ali Ahmed, Efstathios (Stathis) Diamantopoulos
A hairy matter: The influence of root hairs on root water uptake

Root hairs play an important role in the uptake of immobile elements (e.g. phophorous) but our understanding of their role in root water uptake is still unsatisfying.

 

In the course of your master thesis, you will assist in supervising a field experiment at the experimental research station Bad Lauchstaedt by installing and maintaining different soil and plant sensors. The collected data, comprising of soil parameters like soil water potential as well as plant parameters e.g. leaf water potential and sap flow, will serve as a basis for your thesis. Comparing the data of two maize genotypes differing in the property of building root hairs, you will investigate the effect of root hairs on transpiration and leaf water potential over an entire cropping cycle.
Furthermore, maize plants will be grown in two different soil textures (sand and loam), which allows the investigation of the impact of these soil textures on the different genotypes.

 

The field experiment in Bad Lauchstaedt is part of a DFG-funded priority programme (SPP 2089) which aims at the identification of spatiotemporal patterns in the rhizosphere and at the explanation of the underlying processes. Our measurements started in 2019 and the period of your master thesis will cover the second growing season.

 

A driving license for reaching the field experiment is needed. All your travel costs to Bad Lauchstaedt and your corresponding expenses will be reimbursed by the Department of Soil Physics.



Contact: Andrea Carminati, Mutez Ali Ahmed, Patrick Duddek
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