Enzymatic kinetics and microbial growth in the rhizosphere of maize: visualization and quantification of the functions

<p>Biochemical processes in the rhizosphere are distributed heterogeneously and depend on biotic and abiotic factors such as root morphology and physiology which affect the allocation of substrates, nutrients and water availability. In the frame of Priority Program &#8216;Rhizosphere Spatiotemporal Organisation &#8211; a Key to Rhizosphere Functions &#8217; we aim to visualize and quantify enzymatic activity related to C, N and P turnover in order to link them with microbial functional traits in space and time. To do that, we apply a time-lapse zymography of hydrolytic and oxidative enzymes coupled to micro-sampling of rhizosphere hotspots for enzymatic kinetics determination at the early vegetation stage of maize. Kinetic parameters of microbial growth will be estimated by micro-calorimetry. Traditional approaches of rhizosphere sampling will be compared with novel methodology at the level of individual soil aggregates. Specific strategies of two plant genotypes (wild type and root hair deficient mutant) in response to limiting conditions of water and nutrients content will be tested on two soil substrates of contrasting texture (loam and sand). Field experiments in a long-term maize monoculture will help disclose the interactions between rhizosphere and detritusphere from decaying roots of previous years.</p>