Rhizosphere Engineering An innovative approach of modifying soil - - PowerPoint PPT Presentation

Rhizosphere Engineering – An innovative approach

• f modifying soil biophysical properties to

influence plant-microbiome-soil interactions.

S.J. Kostka1, K. Ahamadi3, M. Zarebanadkouki2, M.A. Ahmed2,

• Y. Kuzyakov3, and A. Carminati2

What is the rhizosphere?

The rhizosphere is the zone of soil surrounding a plant root where the biology and chemistry of the soil are influenced by the root.

• a few mm wide.
• an area of intense biological and chemical activity influenced by compounds

exuded by the root (mucilage), and by microorganisms

• communication between the plant and the microbiome

Mucilage

Photo credit: Phillipott et al, Nature Rev Microbiol, 2013.

Root

Mucilage - The hydraulic bridge between soil and roots

Relevant processes:

• Root hairs increase the root surface,

decreasing the solute concentration per unit root surface area

• Mucilage keeps the region between root

hairs wet.

• Mucilage and root hairs maintain the

hydraulic contact between roots.

Courtesy of M. McCully Carminati et al, 2016

Day 3 -Drying More water near roots

dist to root θ

Carminati and Vetterlein, 2013

5 cm 0.4 0.01

θ

Neutron radiography of water distribution near roots

Lupine

Day 3 -Drying Day 5 -1 hour after rewetting More water near roots Less water near roots

dist to root θ dist to root θ

Carminati and Vetterlein, 2013

5 cm 0.4 0.01

θ

Neutron radiography of water distribution near roots

Lupine

Soil water content (v:v)

What happens in corn?

Ahmed et al, 2017

What’s going on in the rhizosphere?

Moradi et al, 2012 Carminati et al, 2014 Carminati et al, 2016

Source: Water percolation through the rhizosphere - effect of heterogeneous pore scale wettability Pascal Benard, Zarebanadkouki Mohsen, Carminati Andrea Soil Physics, University of Bayreuth

Mucilage in pore spaces

Mucilage secreted by roots and EPS produced by microorganisms alter the physical properties of the soil solution and impact water dynamics in the rhizosphere. High viscosity mucilage and EPS form thin filaments and interconnected thin lamellae that span throughout the soil matrix.

Benard et al, Vadose Zone J, 2017

• Rhizoligand treatment - Cross-linked the mucilage

biopolymer results in:

• Increased speed of rhizosphere rewetting after drying
• Reduced mucilage expansion and total water content

in mucilage

• Limited diffusion of mucilage resulting in better root-

soil contact

Untreated “Rhizoligand” (50 ppm)

Can the rhizosphere be engineered?

Carminati et al, 2016 Ahmed et al, 2017

Lupine

• Modified plant transpiration rate
• Delaying onset of wilting (up to 2 days) in moncots and dicots.

Carminati et al, 2016 Ahmed et al, 2017

Water Rhizoligand

Rhizoligand Water

Tall fescue

• Rhizosheaths increased significantly (up to 1.6-fold)

Lupine

Ahmed et al, 2017 Ahmadi et al, 2017 Ahmadi et al , in press

Photo credit: K Ahmadi

Rhizoligand Water

• Increased root mass
• Increased rhizosheath C

Ahmed et al, 2017 Ahmadi et al, 2017 Ahmadi et al , in press

• Increased microbial biomass

• Rhizoligand treatment influenced

plant and rhizobiome enzymes

• Soil health
• Plant health

Ahmadi et al, 2017; Ahmadi et al , in press

Lupine Corn

Conclusions:

• Rhizosphere stabilization - Cross-linking of mucilage resulting in:
• Increased speed of rhizosphere rewetting after drying
• Reduce mucilage expansion and total water content
• Limited diffusion of mucilage resulting in better root-soil contact
• Modified plant transpiration rate, delaying onset of wilting (up to 2 days)
• Increased rhizosheaths significantly (up to 1.6-fold in monocots)
• Increased root mass (monocts and dicots)
• Increased soil enzymes related to soil and plant health - chitinase, sulfatase, and β-glucosidase
• Positive rhizobiome effects – Microbial biomass increased (+57%)

Untreated “Rhizoligand” (50 ppm)

Carminati et al, 2016 Ahmed et al, 2017 Ahmadi et al, 2017 Ahmadi et al , in press

Rhizosphere Engineering

Roots play an essential role in the acquisition of water and minerals from soils. Modifications to roots result in higher yield and increased stress tolerance. Strategies to manipulate the rhizosphere and the rhizobiome will enhance soil and plant health, and crop productivity.

Stan Kostka

stan.kostka@gmail.com

Photo: Dept of Plant Science - PSU