The mystery of root exudation 2 – How do environmental changes affect root exudation?

• Applicant: Dr. Eva Oburger
• Subject Area: Soil Sciences
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 403803214

Roots release a large diversity of soluble or volatile organic molecules (i.e. root exudates) as well as cell debris and sloughed-off root cap cells as they forage for water and nutrients. Despite our awareness about the functional importance of root exudates in driving belowground interactions between plant roots, soil microbes and the soil matrix, studies investigating exudate quality and quantity under natural growth conditions are still relatively scarce and even less information is available on how root exudation is altered upon environmental changes. In phase 1, we characterized maize root exudation under the standardized experimental conditions in the two, DFG priority program (PP) 2089 specific, experimental platforms (soil column experiment & soil plot experiment) and evaluated the effect of different sampling strategies. Building on what we have learned, we now set out to reveal the effect of soil environmental changes on maize (Zea mays WT & rth3) root exudation with particular focus on drought and changes in soil structural properties, which have both been identified as major factors driving rhizosphere pattern formation. In joint laboratory experiments with several other PP 2089 partners focusing on different plant and soil parameters, we will reveal how root exudation of the two maize lines (WT, rth3) is altered upon moderate short-term as well as more severe long-term drought stress. We will also investigate seasonal differences in exudation in the field and evaluate a potential soil legacy effect induced by several years of maize monoculture. In addition, we will study modifications in maize exudation patterns upon soil structural changes, including soil compaction and changes in number of root-soil particle contact points, again under controlled conditions in the laboratory. Like in phase 1, we will focus on soil-based exudation sampling approaches and combine these ecological meaningful sampling techniques with non-targeted metabolomic analysis by UHPLC-QTOFMS and GC-QTOFMS to uncover the entire diversity of exudates released. Our results will provide important mechanistic insights on how root exudation is altered under changing environmental conditions. Furthermore, we will deliver key information for all exudation-driven rhizosphere processes that will be investigated by other participants within the PP 2098 und significantly contribute to merge individual parameter patterns and holistically decipher the spatiotemporal interplay of rhizosphere processes.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2089: Rhizosphere Spatiotemporal Organisation - a Key to Rhizosphere Functions
• International Connection: Austria
• Cooperation Partner: Professor Dr. Stephan Hann